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Sitting calipers do have a habit of seizing up, due to lack of use
We were recently schooled on warped rotors from some friends over at Baer Brakes (baer.com). First off, it’s exceedingly rare to actually warp a rotor. Instead, the cause of the shudder you feel through the pedal is an uneven buildup of brake pad material on the rotor itself.
Here’s how it works. Modern asbestos-free and nonmetallic brake pads contain different resins in addition to the actual brake material itself. Some of these resins and materials transfer themselves to the rotor face so that there will be adherent (sticky) braking in addition to abrasive braking. In a nutshell, when a brake system is properly bedded in, there’s a thin layer of pad material on the rotors. When you use the brakes hard, such as when coming down a steep grade, the heat buildup causes these resins to loosen. When you stop the vehicle completely, such as at a red light at the bottom of an off-ramp after that steep hill, you actually make an imprint of the brake pad on the rotor, creating a high spot. By the time you get gas or stop for lunch (or whatever) the rotors have had a chance to cool off, but that high spot is still there. As little as 0.0004 inch can be felt through the pedal, and 0.001 inch can be downright annoying. Repeated use just leaves more material on the high spots, making the shudder worse.
Now that you understand what’s going on, here’s what you can do to help combat it. If caught early, you can often eliminate the shudder by rebedding the brakes. To do this, find a safe area where you can make a series of hard slowdowns from 50 mph to about 10 mph. Don’t come to a full stop. Doing this several times will heat up the material on the rotors and help smear it evenly on the face of the rotors again. Then drive around for a little while without stopping much to let the brakes cool off.
3. Brake Rotors Warp
FALSE.
Rotors don’t warp.
Back in the 1970s, in what was probably a scene right out of the movie Dazed and Confused, someone came up with a theory about brake-rotor “warping,” and it totally stuck. Why? Probably because, in layman’s terms, it makes sense.
But then real life happens and this faulty explanation doesn’t hold up to scientific scrutiny.
What is often described as “warping” is actually the presence of two separate phenomena that can happen in isolation or in combination with each other, and neither has anything to do with warping.
These phenomena are:
BTV is a variation of torque across the rotor’s face which causes the rotor to slip and catch as the brake caliper is engaged. The differences in torque across the rotor may be caused by inconsistencies in the rotor’s finish or metallurgy.
- Brake torque variation (BTV), and
- Disc thickness variation (DTV)
BTV can be caused by uneven deposits of friction material. This might not cause a pulsation in pedal feel, but it will cause vehicle judder or vibration.
DTV, on the other hand, is the result of measuring the thickness of the rotor surface in multiple spots around the rotor. DTV measurement can be found simply by finding the difference between the thickest part of the rotor from the thinnest.
As the rotor’s variable thicknesses pass through the restricted caliper, the piston moves in and out, causing pulsations in the brake pedal while stopping.
If it was rotors causing the problem, wouldn't the brake pedal pulse ?? I have never had one that pulsed the brake pedal only the shimmy feel though the steering wheel sometimes so bad that I had to release pressure on the brake pedal.
So anyone who buys one of the VFs still sitting on dealer lots should be asking for a caliper service before delivery ?
An SSVR is an expensive performance machine and demands performance rotors, so if cheap easily warped crap is used, it can be argued they are not fit for purpose under ACL and as such must be replaced.
Can agree with lack of use being a contributor to seized caliber pistons but I would expect that over a much longer period with zero kilometres driven and doubt it would occur if 5000kms are being put on the car each year.
You mean the following critical part where it’s mentioned no abuse and a desire to push for a warranty fix?
Oh, and the reason I often mention ACL is because many retailers simply try to fob people off with some rubbish written on a legally irrelevant piece of paper they call a warranty and use that document to fool people into thinking its gospel. who have valid fault.
Obviously @Flying Scotsman is free to take or discard any comments I make but for you to continually be pushing an attitude that is unhelpful to him when he is looking for a warranty based solution is confusing. Seems you simply dislike anything ACL related.
To add to this, i reckon my rotors have a issue and need some help as well.
Light braking i get a small shake but under harder braking is smooth as silk.
From my knowledge, steering and rack perfectly fine, as is suspension.
Only happens on light braking, not firm.
I think material on pads. Thoughts?
Good to know that. We have a shimmy or pulse and i can't remember which now on the Outlander. I will take note now and tell the mech as rear pads are due, he said. Might have to get new rotors as not many places machine in Launceston.Warped rears will cause a pulse through the brake pedal....Warped fronts cause a shimmy through the steering wheel
Good to know that. We have a shimmy or pulse and i can't remember which now on the Outlander. I will take note now and tell the mech as rear pads are due, he said. Might have to get new rotors as not many places machine in Launceston.