Warped Rotors?

Hi Everyone!

Hope all is well. I've been pretty busy lately.

Brakes -

Anyhow, I was driving 55-60mph on the highway a couple days ago. (I rarely reach 55mph in my daily city driving.) I applied the brakes because other cars in front were braking. I felt a little vibration through the steering wheel. I took Beemie to the new mechs who said "Your front rotors are a tiny bit warped, but your breaks are still very new. We don't recommend replacing them now."

Do you have thoughts?

Are there risks associated with "letting things be"?

What if I needed to apply the brakes as hard as possible for rapid stopping?


Coolant Hoses-

I also noticed two little leaks of coolant. One is where the small hose connects at the radiator's upper left corner. Hose connects to the plastic coolant reservoir tank above the wheel well. The other leak is some where under the thermostat. I asked the new mechs to check both. The said that they pressure tested the radiator and just tightened the hose clamps. But that's all for now. I asked if him was sure that was all that was required. He said yes. And, yet I'm still wringing my hands. The ghost memory of the old mech lingers. Still, I think that Beemie must need some new hoses. What if one failed? I would be so so sad if Beemie had a melt down...

What to doooooo?


Please offer any mechanical or therapeutic suggestions.



Thanks, Kelly :-)

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Kelly
Hi Everyone!

Hope all is well. I've been pretty busy lately.

Brakes -

Anyhow, I was driving 55-60mph on the highway a couple days ago. (I rarely reach 55mph in my daily city driving.) I applied the brakes because other cars in front were braking. I felt a little vibration through the steering wheel. I took Beemie to the new mechs who said "Your front rotors are a tiny bit warped, but your breaks are still very new. We don't recommend replacing them now."

Do you have thoughts?

Are there risks associated with "letting things be"?

What if I needed to apply the brakes as hard as possible for rapid stopping?
...

Thanks, Kelly :-)

Just when we thought you had a real mechanic; he has to say something completely dumb like 'warped rotors'
No such animal, they don't exist and there is no physical proof that has ever been put forth to substantiate the myth.

Just the opposite, there are professional brake people who can prove that warped rotors don't exist.
Here is a little reading your mechanic might do well to read...
[www.stoptech.com]

As for the leak, just keep an eye on it...I seem to remember you replacing the hoses not long ago, no?


There are lots of things that can cause the brake pedal to pulsate; worn ball joints, worn tie rod bushings, worn control arm bushings, seized caliper pins, seized caliber pistons, worn wheel bearings, out of round wheels, tire problems and improperly torqued wheel lug nuts, just to name a few.

The Bentley manual says that a "warped" rotor is mainly caused by not having all the lug nuts torqued to the same amount of pressure. My experience is that the rotor really isn't the problem it is the caliper guide pins and piston. They have grease inside a rubber boot that tends to allow contaminants to compromise the functionality of the calipers themselves. What happens is they get stuck in one position and the caliper rubs against the rotor unevenly and causes the feeling of a warped rotor. This will heat up the rotor and cause the brakes to smoke and the grease melts and then the guide pins have no lube and the problem gets worse over time. The only way to really correct the problem is to get new guide pins, boots, grease, and if the problem has gone on too long rotors and pads. I would suggest drilled rotors if you replace them. As far as hard stopping is concerned if the mechanic says that the brakes look pretty new then I would not think that that is really an issue unless the rubber brake lines have cracks in them and they will also need replaced as they will explode under pressure and no brakey. As far as the coolant issue a leak around the stat is easy enough to repair, but it also could be the water pump. I would not be too concerned unless you are loosing a quart a week. I hate coolant leaks too, but it has to be major to warrant fixing this time of year. Your coolant light should alert you if you get too low and unless you have a major blow you won't even get hot this time of year. So much for my two cents!

Kelly, try doing a couple good long stops like he describes in his article. Find somewhere that you can get up to about 60+ mph and step on the brakes pretty hard but don't stop completely after. Do this a couple times. I generally get up to about 80 coming up to an exit ramp and do it there when no one is behind me every once in a while just to help keep deposits from forming to the rotors. A lot of times it is just some pad material left on the rotors that will come off doing this that causes that pulse.

As for the coolant leaks, like others have said, just watch it. I would go out and make sure there is no coolant in either of those places (use a rag, or just spray it off with water or brake clean if it is warm enough where you are). This way you know if anything shows up in the next few days that it is new and not left over from before he tightened them. If you find any signs of leaks after a couple days I would make sure it is indeed the hoses and replace them. They could very well be right that the clamps were just loose, but you can never be too safe. I took my jeep in one time because I had seen a puddle of coolant and smelled it when driving. The tech said it was fine and there was no sign of a leak. He said the power steering hose was leaking a little and was I sure it wasn't that...Anyway, I went back with him and insisted that it was coolant. Sure enough, he prodded around a little and pulled down on a plastic cover and coolant ran all over the floor!

Hey Kelly, I should have warned you on the warped rotor thing around here, but a simple dial indicator reading will tell you what you want to know. The hoses should be evaluated for age, cracks, hardness and changed out accordingly. Don't rely on quick fixes. It'd be a real bust to lose a motor over a simple cheap hose. If you feel it and it doesn't seem right, don't think about it, replace it!

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Kelly
Brakes - ...

What if I needed to apply the brakes as hard as possible for rapid stopping?

Read the article linked by Peter. It explains everything.

It's a good thing to use the brakes as hard as possible occasionally, as described in the article, to clean off any buildup on the rotors and properly bed the brake pads.

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Kelly
Coolant Hoses-

I also noticed two little leaks of coolant. One is where the small hose connects at the radiator's upper left corner. Hose connects to the plastic coolant reservoir tank above the wheel well.

That one always seems to come loose on my car too. Have to retighten the clamp every now and then. Just be careful not to overtighten that one too much, and to avoid pulling on the hose or overstressing that connection, because it's pretty easy to snap off the plastic nipple at the rad and that can't be fixed without replacing the whole radiator.

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Kelly
The other leak is some where under the thermostat. I asked the new mechs to check both. The said that they pressure tested the radiator and just tightened the hose clamps. But that's all for now. I asked if him was sure that was all that was required. He said yes. And, yet I'm still wringing my hands. The ghost memory of the old mech lingers. Still, I think that Beemie must need some new hoses. What if one failed? I would be so so sad if Beemie had a melt down...

It could well be that they fixed it by tightening another clamp. That would be good. Or it could be that the water pump is starting to leak. That would be less good, but not yet terminal.

Do you know when the timing belt was last replaced? You should really replace the water pump at the same time.

If a hose fails, splits or comes off, you'll notice it right away because all the coolant comes out very suddenly and makes a hell of mess. There'll be a big cloud of steam, you'll smell the coolant, and the low coolant light should come on in your overhead check panel. If for some reason you don't notice all that while driving, the temperature gauge will very soon thereafter start climbing into the red zone. If that ever happens to you, just shut the engine off before it overheats and it's a simple fix to replace the blown hose and refill the coolant system. Continuing to drive with no coolant will very quickly cause terminal damage to the engine though.

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Kelly
Please offer any mechanical or therapeutic suggestions.

Good for you for spotting the leaks in the first place. If you're still worried about it, just keep a close eye on the coolant level in the reservoir tank. Do NOT open it when it's hot! But you can open it when it's been sitting cold overnight to check the level of coolant.

There is a float switch with two wires attached to the reservoir cap, at least that's they way it's set up on my 1986 325. When the coolant level drops, the float sinks lower and opens the switch, causing the coolant warning light to come on in your overhead check panel. You can confirm whether that float switch is working properly by unscrewing the reservoir cap and lifting it out of the tank so the float drops, then turn your ignition key to the run position. The overhead check panel should then indicate a low coolant warning. It's nice to know for sure that this float switch actually still works.

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Ferdinand

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Kelly
Brakes - ...

What if I needed to apply the brakes as hard as possible for rapid stopping?

Read the article linked by Peter. It explains everything.

It's a good thing to use the brakes as hard as possible occasionally, as described in the article, to clean off any buildup on the rotors and properly bed the brake pads.

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Kelly
Coolant Hoses-

I also noticed two little leaks of coolant. One is where the small hose connects at the radiator's upper left corner. Hose connects to the plastic coolant reservoir tank above the wheel well.

That one always seems to come loose on my car too. Have to retighten the clamp every now and then. Just be careful not to overtighten that one too much, and to avoid pulling on the hose or overstressing that connection, because it's pretty easy to snap off the plastic nipple at the rad and that can't be fixed without replacing the whole radiator.

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Kelly
The other leak is some where under the thermostat. I asked the new mechs to check both. The said that they pressure tested the radiator and just tightened the hose clamps. But that's all for now. I asked if him was sure that was all that was required. He said yes. And, yet I'm still wringing my hands. The ghost memory of the old mech lingers. Still, I think that Beemie must need some new hoses. What if one failed? I would be so so sad if Beemie had a melt down...

It could well be that they fixed it by tightening another clamp. That would be good. Or it could be that the water pump is starting to leak. That would be less good, but not yet terminal.

Do you know when the timing belt was last replaced? You should really replace the water pump at the same time.

If a hose fails, splits or comes off, you'll notice it right away because all the coolant comes out very suddenly and makes a hell of mess. There'll be a big cloud of steam, you'll smell the coolant, and the low coolant light should come on in your overhead check panel. If for some reason you don't notice all that while driving, the temperature gauge will very soon thereafter start climbing into the red zone. If that ever happens to you, just shut the engine off before it overheats and it's a simple fix to replace the blown hose and refill the coolant system. Continuing to drive with no coolant will very quickly cause terminal damage to the engine though.

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Kelly
Please offer any mechanical or therapeutic suggestions.

Good for you for spotting the leaks in the first place. If you're still worried about it, just keep a close eye on the coolant level in the reservoir tank. Do NOT open it when it's hot! But you can open it when it's been sitting cold overnight to check the level of coolant.

There is a float switch with two wires attached to the reservoir cap, at least that's they way it's set up on my 1986 325. When the coolant level drops, the float sinks lower and opens the switch, causing the coolant warning light to come on in your overhead check panel. You can confirm whether that float switch is working properly by unscrewing the reservoir cap and lifting it out of the tank so the float drops, then turn your ignition key to the run position. The overhead check panel should then indicate a low coolant warning. It's nice to know for sure that this float switch actually still works.

Hi Everyone,


Thanks for all the fab advice. I will try to find a road appropriate for the brake cleaning procedure. I think my front brakes are two years old. I recall having them replaced when the control arms and bushings were replaced. I wanted to have all front wheel "things" done at the same time for efficiency's sake. I don't think that the tie rods were replaced however.

Beemie has brand new fuel lines and older coolant hoses. The timing belt and water pump were replaced a little over one year ago.

I noticed the coolant leaks when I removed the air filter housing this Sunday. I was able to replace its broken rubber mounting. Shortly, I will post a progress report (with some killer graphics from my dad - you will be astonished) in the Air Filter Housing Thread. It is very likely that I jostled the small coolant hose attached to the radiator's upper left corner when I removed an replaced the Air Filter Housing.

Ferd - thanks so much for the float value test. In fact, I intended to ask if such a test was possible. I will feel much better after testing the sensor.

Overall my plan is to watch for any more fluid from the 2 previously leaking areas. I probably will have some coolant hoses replaced before long.


10,000 Thanks, Kelly

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Kelly
...

I noticed the coolant leaks when I removed the air filter housing this Sunday. I was able to replace its broken rubber mounting. Shortly, I will post a progress report (with some killer graphics from my dad - you will be astonished) in the Air Filter Housing Thread. It is very likely that I jostled the small coolant hose attached to the radiator's upper left corner when I removed an replaced the Air Filter Housing.

Ferd - thanks so much for the float value test. In fact, I intended to ask if such a test was possible. I will feel much better after testing the sensor.

Overall my plan is to watch for any more fluid from the 2 previously leaking areas. I probably will have some coolant hoses replaced before long.


10,000 Thanks, Kelly

Congrats on getting the air filter box mount replaced...you'll be an E30 mechanic in no time

Ferd sez- If a hose fails, splits or comes off, you'll notice it right away because all the coolant comes out very suddenly and makes a hell of mess. There'll be a big cloud of steam, you'll smell the coolant, and the low coolant light should come on in your overhead check panel. If for some reason you don't notice all that while driving, the temperature gauge will very soon thereafter start climbing into the red zone. If that ever happens to you, just shut the engine off before it overheats and it's a simple fix to replace the blown hose and refill the coolant system. Continuing to drive with no coolant will very quickly cause terminal damage to the engine though.

Rick sez--- This might happen but it would probably be the one time you were not paying attention and the winds where wafting the smell away and the leak was making the car run hot that you would cook a motor or cause serious damage. These cars, any car with a fat Maserati style alloy head hates running low on coolant, even a small amount, if the motor is functioning right the cooling system will be tight and never even need a top up (well, almost never). For this reason I never mess around with older hoses if they're in question (once you retighten a hose clamp it just digs in to the hose making it more weak and suspect). Its a sad way to loose a motor or even a head...

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Archeo-peteriX


Congrats on getting the air filter box mount replaced...you'll be an E30 mechanic in no time

Hi Everyone,

Well, per Ferd's sugesstion I tested my coolant sensor which I believe has failed. I removed it from the reservour tank, cleaned the algee like film off the outside, and turned the key one click. The error light did NOT turn on. I tried moving the float tube and repositioning the sensor - vertical, horizontal, etc. Still no light. After, I unpluged the sensor and turned the key one click, then the light did turn on. The failed sensor would somewhat explain my overheating situation in November.

I could give you more details about the sensor test, but I'm in a rush. I can add more info later if you like.

Any reason that I should not order a new sensor ASAP?

As for the hoses which I think are bad - #13 is looking generally dicey, #18 and #19 are iffy. I can't find #12. Others are fine.
Engine Cooling on RealOEM


I think that everyone should test their sensors.

:-) Kelly

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Kelly
After, I unplugged the sensor and turned the key one click, then the light did turn on.

The coolant level sensor is a small reed switch held closed by a magnet in the float when the coolant level is high enough. If the coolant level drops too low, the float sinks, and the reed switch opens triggering the overhead warning light. Unplugging the connector causes the same open-circuit, triggering the warning light.

If the switch housing is cracked allowing fluid inside the switch, or the reed switch simply corrodes from old age, the switch will eventually fail, either causing a permament open-circuit triggering the warning light all the time, or a permanent closed-circuit with the terminals welded together in which case the warning light will never come on even if the coolant level drops.

When I first bought my car the low coolant warning light was always on. It bugged me, so I simply unplugged the connector from the coolant tank sensor and stuck a paper clip across the terminals of the connector, thereby keeping the circuit closed. No warning light ever. Perfect. Never had use for that annoying thing anyway. I always glance at the coolant level in the tank, and the washer fluid level, and brake fluid level, whenever I have the hood open. Don't need no lights.

Within the very same week my engine suddenly puked out all of its coolant. I happened to glance in my rearview mirror and saw a huge cloud of steam behind me! I was just rolling up to a red traffic light, stopped and saw a lake of green coolant flowing out from under the car. Luckily there was a service centre right there at that intersection, so I just drove straight in.

All of the rad hoses looked fine, no clamps missing anywhere. So we poured some water to the coolant tank and, oh dear, a gush of water came straight out the side of the engine block! That can't be good...

Turns out, the block heater fell out.

The car had a block heater like this, which is basically just a heating coil like you have in your tea kettle, but it's fitted into the cooling jacket through one of the core plugs in the engine block. I guess it wasn't in tight enough so it got spit out.


The mechanic had another block heater that fit, and refilled the system with fresh coolant. Simple fix. No harm done.

But, if that ever happened out on the highway somewhere, I'd have been stranded for sure. And if I hadn't noticed the big cloud of steam behind me, or been watching the gauges, the engine wouldn't have run much longer with no coolant in it.

I ordered a new coolant level sensor right away after that scare. Paper clips are not a smart fix. Our cars have these nifty sensors and warning lights. It's a good idea to keep them in working condition.

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Ferdinand
Our cars have these nifty sensors and warning lights. It's a good idea to keep them in working condition.

Wow Ferd! A close call indeed! Thanks for the story.

I just ordered the new sensor. It should arrive tomorrow.

Are there any other sensors that should be checked? My oil sensor does function correctly. (When I park on a hill, the light will appear.)

Brakes?

Reply at your lesuire. The Great Coolant Crisis of 2008/2009 is almost over - I hope. Well, still the hoses need changing.

:-) Kelly

The brake sensors are consumables. Just replace them with the pads. If you are worried, just take a look at the pads and make sure they are not down to the sensors yet. This will also give you a good idea of when to expect to see the brake light. ie. if there is a lot of material all the way around you know you won't see it come on for a while, but if it is getting close to the sensor, expect to see it in the next month or two...

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Kelly
My oil sensor does function correctly. (When I park on a hill, the light will appear.)

That's reassuring.

Before I replaced the leaky head gasket, my car used to have a slow but steady oil leak. The oil level warning on the overhead check panel used to come on when the engine oil level dropped below half way between the full and low mark on the dipstick. Then one day I checked the dipstick and there was no oil showing at all. Yikes! The oil level sensor had stopped working. Then, out of the blue, on another day it worked again like normal. Now I no longer trust it and always check the dipstick manually.

More critical is the oil pressure light in your instrument panel. When you first turn the ignition key to the run position, before cranking the engine, make sure the oil pressure light comes on to confirm the bulb hasn't burned out. Then, when you crank the engine to start, the oil pump should build enough oil pressure almost immediately and the light will go off. Train yourself to check and watch that oil pressure light going off each time you start the car to confirm that sensor is still working okay. That one is really the only vitally important one.

My car scared the crap out of me once when, in the middle of one of our all-night car rallies, the oil pressure warning light suddenly started flickering. No low oil level warning from the overhead check panel. Just the much more serious oil pressure warning light in the instrument panel. Yikes!

We stopped to check the dipstick first chance we could find a spot to safely pull over. Phew, big relief, there was plenty of oil in the engine. It turned out the single wire had come off the oil pressure sensor connector, low on the engine block under the exhaust manifold. On sharp right turns over bumps the dangling loose wire would touch against the engine block, shorting the wire to ground and triggering the oil pressure warning light. Otherwise the wire was just hanging loose, not attached to the sensor. That meant the oil pressure light could not have been coming on like normal when starting the engine, and I didn't remember the last time I'd actually seen it light up during startup.

Now I always check to ensure the oil pressure light comes on, as it should to confirm it's working, before starting the engine.

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Ferdinand
When you crank the engine to start, the oil pump should build enough oil pressure almost immediately and the light will go off. Train yourself to check and watch that oil pressure light going off each time you start the car to confirm that sensor is still working okay. That one is really the only vitally important one.

Now I always check to ensure the oil pressure light comes on, as it should to confirm it's working, before starting the engine.

Hi All,

Well the new coolant sensor is installed and working. WooHoo! Next the hoses. :-) Kelly - still busy as a beaver in an old growth forest.

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Ferdinand
The coolant level sensor is a small reed switch held closed by a magnet in the float when the coolant level is high enough. If the coolant level drops too low, the float sinks, and the reed switch opens triggering the overhead warning light. Unplugging the connector causes the same open-circuit, triggering the warning light.

Apologies for taking this a bit off-topic (and light years away from warped brake rotors!), but I just had a similar experience with my windscreen washer fluid warning light. After getting it back from the mechanic, this light would intermittently come on, despite a full tank of fluid.

Today I had a peek in the tank and discovered that the level sensor is little pivotting hinge that tries to float toward the top of the tank. Well, it does if it is installed at the correct angle. For some reason, the mechanic had turned the sensor sideways so it was not floating towards the top of the tank. I rotated it back and, presto, no more warning lights! (cos I removed the bulbs for all the others ).

So if you ever have "washer fluid" light come on wrongly, check it is not rotated before buying a new sensor!

Cheers,
Simon

OK, let me tell you something here. Rotors do warp. It creates steering wheel nibble and judder. Don't expect to be able to measure at home, it is in the order of µm (micrometer). Sometimes left and right phase out each other, sometimes they amplify each other, depending on the position of both wheels relative to each other. Wether you can feel them in your steering wheel depends on the amount of warping, the bushes on your suspension, on your steering rack, the play on your steering rack etc.
We do a lot of measurements on this at work and with some experience, you can estimate the amount of warpage by just braking the car.

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Michiel 318iS
OK, let me tell you something here. Rotors do warp. It creates steering wheel nibble and judder. Don't expect to be able to measure at home, it is in the order of µm (micrometer). Sometimes left and right phase out each other, sometimes they amplify each other, depending on the position of both wheels relative to each other. Wether you can feel them in your steering wheel depends on the amount of warping, the bushes on your suspension, on your steering rack, the play on your steering rack etc.
We do a lot of measurements on this at work and with some experience, you can estimate the amount of warpage by just braking the car.

Sorry...until we see documented proof of this mythical warping; it does not exist

We've been down this road spo many times it's not funny; and nobody has yet produce any proof of this non existent phenomenon.

There are many things that will cause the wheel 'nibble and judder' but none of them are from warped rotors.

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Archeo-peteriX

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Michiel 318iS
OK, let me tell you something here. Rotors do warp. It creates steering wheel nibble and judder. Don't expect to be able to measure at home, it is in the order of µm (micrometer). Sometimes left and right phase out each other, sometimes they amplify each other, depending on the position of both wheels relative to each other. Wether you can feel them in your steering wheel depends on the amount of warping, the bushes on your suspension, on your steering rack, the play on your steering rack etc.
We do a lot of measurements on this at work and with some experience, you can estimate the amount of warpage by just braking the car.

Sorry...until we see documented proof of this mythical warping; it does not exist

We've been down this road spo many times it's not funny; and nobody has yet produce any proof of this non existent phenomenon.

There are many things that will cause the wheel 'nibble and judder' but none of them are from warped rotors.

Yes, we've been down this road sooo many times I could puke, the fact is, if the rotors are out (just put a dial indicator on them for gods sake) then they're out! IT will make a steering wheel shake and cause all kinds of crappy behavior period.

Now

Uncle Pete has given us enough information on the subject (no, I'm not going to say the R or the W word!) that I'm more than willing to trust him and the info.

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Archeo-peteriX
Sorry...until we see documented proof of this mythical warping; it does not exist

That'll be more difficult, all the info I can get my hands on has this 'confidential' line in the bottom...
Maybe the term warping isn't 100 % correct, let me try to explain tomorrow, I'm a bit too feverish right now.



Edited 1 time(s). Last edit at 03/01/2009 11:47AM by Michiel 318iS.

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Michiel 318iS

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Archeo-peteriX
Sorry...until we see documented proof of this mythical warping; it does not exist

That'll be more difficult, all the info I can get my hands on has this 'confidential' line in the bottom...
Maybe the term warping isn't 100 % correct, let me try to explain tomorrow, I'm a bit too feverish right now.

I think you are right. The term might not be correct, but that is the basic idea. My rotors are F'ed right now, and that is exactly what it feels like. Whether that is what it actually is or not, is a different issue.





Edited 1 time(s). Last edit at 03/01/2009 01:18PM by daniel.

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Michiel 318iS

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Archeo-peteriX
Sorry...until we see documented proof of this mythical warping; it does not exist

That'll be more difficult, all the info I can get my hands on has this 'confidential' line in the bottom...
Maybe the term warping isn't 100 % correct, let me try to explain tomorrow, I'm a bit too feverish right now.

Hope you're not coming down with a bug

I'm sure that warping isn't what's happening or what you're measuring.

As rotors and break pads heat up, there can be an exchange of materials from on to the other; usually pads to rotors. Often what happens is the rotors and pads will be come extremely hot and if the wheels stop with the brakes pressed for more than a second; some of the pad material actually becomes transferred to the rotor and becomes part of it. What happens then is there will be a place or places on the surface of the rotor which are thicker than others. Next time the brakes are used there will be a pulsating in the break pedal and/or the steering wheel. This is what is most often incorrectly though to be warped rotors.

Another thing that comes closest to warped rotors is when wheels are reinstalled with incorrectly set air wrenches. The wrong torques can distort the wheel and rotor causing the pulsations. Since these symptoms will go away if the wheel lugs are loosened and retorqued to the proper specs; it can't be said that the rotors are actually warped.

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Archeo-peteriX
Often what happens is the rotors and pads will be come extremely hot and if the wheels stop with the brakes pressed for more than a second; some of the pad material actually becomes transferred to the rotor and becomes part of it.

Yup. It's for this reason that if you ever drive on the track you need to remember not to set the e-brake when you park it afterwards. The brakes get extremely hot, and if you clamp the pads down on a hot, stationary rotor, you'll fry the pad material right onto the rotor surface.

__________
Dave
'91 325iX

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Dave_G

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Archeo-peteriX
Often what happens is the rotors and pads will be come extremely hot and if the wheels stop with the brakes pressed for more than a second; some of the pad material actually becomes transferred to the rotor and becomes part of it.

Yup. It's for this reason that if you ever drive on the track you need to remember not to set the e-brake when you park it afterwards. The brakes get extremely hot, and if you clamp the pads down on a hot, stationary rotor, you'll fry the pad material right onto the rotor surface.

But Dave, our hand brakes are shoes that go against their own drum. Has nothing to do with the normal street brakes.

I learned something the other day about rotors, they can be off by someone dropping them in shipping, this info comes from my brake shop of many years.

Again, weather the metal on the rotor is bunching up from excessive heat or the pads are causing some infusion I don't know, and personally couldn't care less. If you run a dial indicator on the surface and its not within spec the rotor is trashed and NO amount of re tightening is going to bring it back, sorry Peter, but thats the truth of the matter.

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rkj

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Dave_G

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Archeo-peteriX
Often what happens is the rotors and pads will be come extremely hot and if the wheels stop with the brakes pressed for more than a second; some of the pad material actually becomes transferred to the rotor and becomes part of it.

Yup. It's for this reason that if you ever drive on the track you need to remember not to set the e-brake when you park it afterwards. The brakes get extremely hot, and if you clamp the pads down on a hot, stationary rotor, you'll fry the pad material right onto the rotor surface.

But Dave, our hand brakes are shoes that go against their own drum. Has nothing to do with the normal street brakes.

I learned something the other day about rotors, they can be off by someone dropping them in shipping, this info comes from my brake shop of many years.

Again, weather the metal on the rotor is bunching up from excessive heat or the pads are causing some infusion I don't know, and personally couldn't care less. If you run a dial indicator on the surface and its not within spec the rotor is trashed and NO amount of re tightening is going to bring it back, sorry Peter, but thats the truth of the matter.

No problem there...deposits will produce high and low spots on the face of the rotor. That's not warping.
Dropping a rotor from any height that's enough to physically damage or deform the rotor will also cause readings to be out of spec...that is also not warping.; that is klutz damage
If you think about it, you'll surely realize that it would take a pretty high drop to actually damage a rotor and then it is likely to crack it rather than deform it; these things are heat treated or tempered to be fairly hard or they wouldn't last too long.

See if your brake guys can come up with a warped rotor...might change your mind about the faith you put in them. There is a big difference between people who design and manufacture brake components and those who simply install them. The former will tell you warped rotors don't exist while the later almost always mistakenly repeat the myth without really understanding what is going on with the brakes.

As I said, there is any number of things that will cause the rotors to be out of spec but none of them are from warping.

This whole discussion is about the incorrect use of a single word. If we can't use language properly then we might as well speak in grunts

Nothing personal Rick, I will just continue to try and educate where possible...even though I am fully aware that once a myth is started, it can never be killed.

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rkj
But Dave, our hand brakes are shoes that go against their own drum. Has nothing to do with the normal street brakes.

Doh! Oh yeah. Forget I said that. But the idea is the same anyway.

__________
Dave
'91 325iX

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Dave_G

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rkj
But Dave, our hand brakes are shoes that go against their own drum. Has nothing to do with the normal street brakes.

Doh! Oh yeah. Forget I said that. But the idea is the same anyway.

Not totally irrelevant...during a hard driving/braking event, it is totally conceivable that the parking brake drums; which are an integral part of the rotor assembly; would reach the same temperatures as the rotors. Good advice just the same

Dear Friends,
I have had the some situation what Kelly had, but another reason. Braking at speed 80 km/h cause vibration through the steering wheel
In my case it is front wheel hub with bearing, I have not opportunity to change the complete hub with bearing, so I treat only bearing, and problem was over.
You can check the bearing of wheel very easily. Lift the car, shake the wheel, you will see if the bearing is good or bad.
Best regards
Chan.

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Archeo-peteriX
This whole discussion is about the incorrect use of a single word. If we can't use language properly then we might as well speak in grunts

And THAT is the reason I stay out of these arguments, because it's quite obviously a word definition that you are all arguing about, and not the actual state of the rotor.

[Diverges and is no longer directing his comments at Archeo, but is instead launching off into his own tirade]

Merrian Webster says that the word means "to turn or twist out of or as if out of shape ; especially : to twist or bend out of a plane". So Archeo is referring to a deforming of the material in order to cause an uneven plane, and obviously a build up of external material on the surface does not constitute as deforming of the original metal rotor material.

Now, that said, warped is a word used in a variety ways. When it comes to this topic, all of your opinions are a bit warped after so many years of discussion, and in fact the entire course of the conversation often times is warped. As a vessel is warped to a pier, these discussions need to be hauled back in, perhaps if you all just bought some yarn and went about warping it you'd find that put your mind at ease, or if you sat down and watched a little Star Trek, as they warp off to new frontiers. In any case, since humans have not yet found a way to effectively warp time, we should try and avoid conversations that revolve around English definitions of words, as the entire language is warped.

For a mechanic to not stick to the scientific meaning of the word as it applies to material objects does not sound strange to me, as the common english use of the word, as well as the theoretical use of the word, do not restrict themselves to quite the same bounds. I've never thought of my mechanic as a scientist ;-)
Perhaps if any of us are told by our mechanic that our rotors are warped, we should be asking "how?" or "In what way?" instead of losing faith in his/her ability to perform quality mechanical work.

G'Day

Or lift the wheel, spin it and feel if there's a vibration in your spring, that will tell if the bearing is broken as well.