Is Rotor Turning/Resurfacing a Scam?
08-27-07, 11:59 PM
#31
yup, but ya gotta be careful with that... if you are not 100% sure of the vehicles service history specifically...
On one specific occasion, I had a vehicle towed in for brake issues, and upon inspection, the obvious problem was that the pistons in the front two calipers had cracked because they were overextended... I've seen similar issues with people who drive on metal to metal brakes for extended periods of time, but upon closer inspection, there was still a small amount of brake pad left (not much, maybe 15%), then I checked the rotors against minimum specs stamped on them - they were above spec... weird I thought... that shouldn't happen if the rotors are above their minimum and there is still some pad left... After a couple closer looks, everything appeared to be in place and in working order (minus the cracked pistons)... Searching for an answer, I grabbed our brake spec book, and low and behold, the minimum spec in the brake book was over a half inch thicker than what was on the front of this vehicle... turns out someone had previously done brakes, and purchased the wrong rotors for the car... (maybe the rears?) and obviously when this happened it caused catastrophic failure of the calipers...
not that this is common, but it's definitely something to be aware of...
On one specific occasion, I had a vehicle towed in for brake issues, and upon inspection, the obvious problem was that the pistons in the front two calipers had cracked because they were overextended... I've seen similar issues with people who drive on metal to metal brakes for extended periods of time, but upon closer inspection, there was still a small amount of brake pad left (not much, maybe 15%), then I checked the rotors against minimum specs stamped on them - they were above spec... weird I thought... that shouldn't happen if the rotors are above their minimum and there is still some pad left... After a couple closer looks, everything appeared to be in place and in working order (minus the cracked pistons)... Searching for an answer, I grabbed our brake spec book, and low and behold, the minimum spec in the brake book was over a half inch thicker than what was on the front of this vehicle... turns out someone had previously done brakes, and purchased the wrong rotors for the car... (maybe the rears?) and obviously when this happened it caused catastrophic failure of the calipers...
not that this is common, but it's definitely something to be aware of...
08-28-07, 12:39 AM
#34
Perhaps with a sledgehammer and a mill as the rear hub is considerably larger to accommodate the parking brakes and would not come close to going on the front just the same as every car I have messed with , thus why I am curious what car has interchangeable front rear rotors even if just close.
08-28-07, 12:55 AM
#35
Perhaps with a sledgehammer and a mill as the rear hub is considerably larger to accommodate the parking brakes and would not come close to going on the front just the same as every car I have messed with , thus why I am curious what car has interchangeable front rear rotors even if just close.
08-28-07, 01:02 AM
#36
I am fully aware of that, but again, even those rotors have a different offset making mounting on another axle difficult at best due to caliper clearance. Not saying it can't be done, just curious what kind of car it was so that when I drop by one of my stores I can check that out is all. have not heard of that before and curious minds want to know.
08-28-07, 05:56 AM
#37
I am fully aware of that, but again, even those rotors have a different offset making mounting on another axle difficult at best due to caliper clearance. Not saying it can't be done, just curious what kind of car it was so that when I drop by one of my stores I can check that out is all. have not heard of that before and curious minds want to know.
08-28-07, 12:00 PM
#38
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Thank you
Yes, thanks. Sorry for not specifying as based on reading the great posts here you probably would be able to quote me the specs on the M3.. ;-))
Yes, thanks for the specs on the RX300 rotors. I need to measure and see if the pad job I'm about to do also needs rotors to be replaced as well. I've done the 95 BMW E36 M3 rotors and pads many times and so this should be relatively easy I think.
Thank you,
Marc
06M3 (mine)
01RX300 (hers)
Yes, thanks for the specs on the RX300 rotors. I need to measure and see if the pad job I'm about to do also needs rotors to be replaced as well. I've done the 95 BMW E36 M3 rotors and pads many times and so this should be relatively easy I think.
Thank you,
Marc
06M3 (mine)
01RX300 (hers)
08-29-07, 09:34 PM
#39
Lexus Champion
JPI
08-29-07, 09:37 PM
#40
Lexus Champion
yup, but ya gotta be careful with that... if you are not 100% sure of the vehicles service history specifically...
On one specific occasion, I had a vehicle towed in for brake issues, and upon inspection, the obvious problem was that the pistons in the front two calipers had cracked because they were overextended... I've seen similar issues with people who drive on metal to metal brakes for extended periods of time, but upon closer inspection, there was still a small amount of brake pad left (not much, maybe 15%), then I checked the rotors against minimum specs stamped on them - they were above spec... weird I thought... that shouldn't happen if the rotors are above their minimum and there is still some pad left... After a couple closer looks, everything appeared to be in place and in working order (minus the cracked pistons)... Searching for an answer, I grabbed our brake spec book, and low and behold, the minimum spec in the brake book was over a half inch thicker than what was on the front of this vehicle... turns out someone had previously done brakes, and purchased the wrong rotors for the car... (maybe the rears?) and obviously when this happened it caused catastrophic failure of the calipers...
not that this is common, but it's definitely something to be aware of...
On one specific occasion, I had a vehicle towed in for brake issues, and upon inspection, the obvious problem was that the pistons in the front two calipers had cracked because they were overextended... I've seen similar issues with people who drive on metal to metal brakes for extended periods of time, but upon closer inspection, there was still a small amount of brake pad left (not much, maybe 15%), then I checked the rotors against minimum specs stamped on them - they were above spec... weird I thought... that shouldn't happen if the rotors are above their minimum and there is still some pad left... After a couple closer looks, everything appeared to be in place and in working order (minus the cracked pistons)... Searching for an answer, I grabbed our brake spec book, and low and behold, the minimum spec in the brake book was over a half inch thicker than what was on the front of this vehicle... turns out someone had previously done brakes, and purchased the wrong rotors for the car... (maybe the rears?) and obviously when this happened it caused catastrophic failure of the calipers...
not that this is common, but it's definitely something to be aware of...
JPI
08-29-07, 11:42 PM
#41
I don't see why it is so hard to imagine... many cars don't have rear integrated parking brakes like our Lexus do... all vehicles, for the most part have the same hub size and bolt pattern front to rear and similar rotor diameters (within an inch to half inch), the main difference being the thickness of the rotors... I see some truly ghetto rigged cars, this really didn't surprise me when I saw it....
08-30-07, 12:55 AM
#42
It could be possible the rotors were still front rotors,but for a different car or model. For example. One a certain Acura, the higher HP model had the same rotor size and hub, but 5mm thicker for one. I realize that 5mm is Not 0.5", but I've seen aftermarket rotor for that specific model be 2-3mm less thick at maximun that spec. For a car like this, if the lower HP cars rotors where used,it would be 5mm thinner at start. Plus, if one of those aftermarket thinner rotors were used, possibly it could be 7-8mm thinner right off the bat. Anyway, not saying this happened, just saying it is possible.
08-30-07, 01:00 AM
#43
It could be possible the rotors were still front rotors,but for a different car or model. For example. One a certain Acura, the higher HP model had the same rotor size and hub, but 5mm thicker for one. I realize that 5mm is Not 0.5", but I've seen aftermarket rotor for that specific model be 2-3mm less thick at maximun that spec. For a car like this, if the lower HP cars rotors where used,it would be 5mm thinner at start. Plus, if one of those aftermarket thinner rotors were used, possibly it could be 7-8mm thinner right off the bat. Anyway, not saying this happened, just saying it is possible.
05-11-08, 08:00 PM
#44
Racer
To answer the OP's question, as the attached article from Bendix indicates, there are definitely occasions where Turning/Resurfacing is not needed.
"Many technicians still turn rotors that should be left alone. Consider these facts: A typical modern rotor is noticeably lighter than its 1973 counterpart. It’s thinner, so there’s less metal available for removal by machining.
"Many used rotors don’t need to be turned, either. In fact, really good, un-machined used rotors are desirable. This is because during stops some friction material transfers from the pads to the rotor working surfaces. This form of conditioning is a part of the normal break-in process, and it improves a rotor’s friction coefficient. Good, used rotors are already conditioned this way. This can be especially significant with certain vehicles that tend to stop less than spectacularly when new brakes aren’t yet broken in. They’ll actually stop better during the break-in period with matched pairs of good, used rotors installed than with new or resurfaced ones.
"There are three standards a used rotor must meet before it can be put back into service as-is: Call them “SST.” Surface condition, Specifications and Trueness.
"Assaying surface condition starts with an eyeball check: Are they smooth or not? If you see roughness, machining is in order – assuming rotor thickness meets specifications. Some manufacturers even allow scoring up to .060” (1.5mm) wide or deep. (GM suggests a simple test: If the edge of a dime won’t fit into a surface groove it’s not wide enough to be a problem. What if the dime fits in? If you can see all of FDR’s hair, the scratch isn’t deep enough to worry about.)"
"Many technicians still turn rotors that should be left alone. Consider these facts: A typical modern rotor is noticeably lighter than its 1973 counterpart. It’s thinner, so there’s less metal available for removal by machining.
"Many used rotors don’t need to be turned, either. In fact, really good, un-machined used rotors are desirable. This is because during stops some friction material transfers from the pads to the rotor working surfaces. This form of conditioning is a part of the normal break-in process, and it improves a rotor’s friction coefficient. Good, used rotors are already conditioned this way. This can be especially significant with certain vehicles that tend to stop less than spectacularly when new brakes aren’t yet broken in. They’ll actually stop better during the break-in period with matched pairs of good, used rotors installed than with new or resurfaced ones.
"There are three standards a used rotor must meet before it can be put back into service as-is: Call them “SST.” Surface condition, Specifications and Trueness.
"Assaying surface condition starts with an eyeball check: Are they smooth or not? If you see roughness, machining is in order – assuming rotor thickness meets specifications. Some manufacturers even allow scoring up to .060” (1.5mm) wide or deep. (GM suggests a simple test: If the edge of a dime won’t fit into a surface groove it’s not wide enough to be a problem. What if the dime fits in? If you can see all of FDR’s hair, the scratch isn’t deep enough to worry about.)"
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