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#16
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I don't know how other MBs are, but on a 108/109/111/112, if improper torque caused warping of rotors, the hub would also become warped. They are bolted together quite well.
Also, if improper torque caused rotor warping, wouldn't it also cause the WHEEL ITSELF to warp as well? They're mated flat and tight against each other with a LOT of force. If one warps, the other will have to warp as well.
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Current: 2021 Charger Scat Pack Widebody "Sinabee" 2024 CR-V Hybrid Previous: 1972 280SE 4.5 2018 Durango R/T, 2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi" 1999 Chrysler 300M - RIP @ 221k |
#17
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Quote:
Tom, you make a good point; If the wheel or hub were distorted by improper torque, then perhaps you would experience the same 'shudder' without application of the brakes. Of course if the runout is minor, then the elasticity of the tire may mask it. Regardless I am yet to be convinced that improper torque will deform a rotor. Anyone? Mark |
#18
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Quote:
The rears take longer to 'fix' as they don't do much braking.. hence why the rear discs on MBs corrode first. As far as the sandpaper goes- MB has made special tools for years that are basically brake pads with sandpaper on them to 'surface' rotors- far as I can tell, it is regular sandpaper like you would get at Home Depot. I guess every one missed my point- tightening them to the wrong torque wouldn't warp the discs, but tightening them wrong WOULD!! Your father was right, if you tightened the wheel like that and had wrong torque on each bolt- no problem with warpage- however, very few do it like that any more, so you get the scenario I described. |
#19
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if you look, when tightening a steel wheel you will see that the parts around the bolts indeed does flex a bit. because of the shape of the wheel, with the rim being such a large mass, if the center is warped a bit here and there the flexibility of the overall wheel will absorb the differences and no effect will noticable.
now with an aluminum wheel because of the mass of metal around the hub area, the flexing is a lot less noticalbe, but it will be there too. you know, "if you drop a feather on an anvil, it will deflect....it will be hard to measure though". tom w
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual. ![]() ..I also have a 427 Cobra replica with an aluminum chassis. |
#20
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I have a 95 E320 and there is an issue with my 7k old rotors (call it "warped" or not) they make a pulsating sound. My MB mechanic says my calipers are fine, but the lug nuts were too tight and he said it was the lug nuts being too tight.
My MB mechanic has over 30 years of experience so he appears to be an authority to me on the subject. What else am I to think? Calipers are operating fine so I need to chagne teh rotors again and torque the lugs equally to the required spec. |
#21
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As far as the tire shops using torque wrenches versus impact wrenches, that is mostly due to protecting the alloy rims, which CAN warp if improperly torqued.
Using torque wrenches to eliminate warped rotor complaints may only serve to placate customers. I don't buy the warped rotor theory either...I'm more inclined to believe that a bad caliper or pad can create issues that would appear that the rotor is warped (i.e., high vs low spots measurable with a caliper), but I believe visible damage such as scoring would be present.
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#22
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Well, I have no degrees in any field but I do know that uneven torque on the lug nuts where some are TOO tight and some are TOO loose will cause the rotors to warp. It is not immigrant but takes 3 or 4 weeks of normal driving to happen. A trip to the mountains and getting the rotors extremal hot will cause it to happen sooner. We replaced the pads and turned the rotors for a gentleman and all was good. He later had a new set of tires installed at a tire shop. About a month latter, he came back to us with a pulsating brake peddle. We took care of the problem. About 2 months later he returned with the pulsations again. Again we took care of the problem. Another 2 months later, same problem. This time we ask a few questions. Have you had your tires rotated or anything? Well, he got a lifetime rotation with the new tires. We ask that the next time he had his tires rotated if he would come by ASAP and let us torque the lug nuts correctly. He did, and had no problems for the next 6 months. We lost so much money so we could keep a customer. He then believed what we were saying about the torque being very important that he took all the receipts we have given him (we make a receipt for our files and for the customers files even if it was free) to the tire place and demanded that they pay us a fair amount for all the work we had done that they had caused. Believe it or not, they paid us the labor for 5 brake jobs and one set of rotors. What we learned from all of this is that lug nut torque is very critical and needs to be the same on each lug nut and applied in a star pattern. This is only one of many stories about this problem we have had.
science and education may disagree, but real life tell a different story. Did you know that science says it is impossible for a bumble bee to fly but the bumble bee proves them wrong every day. Paul
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