Had somewhat of a shudder before when applying brakes to my 1993-240. Changed both front and rear pads yesterday and now shudder is pretty bad when stopping.

I think it is probably warped rotors. The question is, how do I tell if it's the front or rear rotors that need replacing?

Thanks

 

Generally, it is very obvious. Front rotors are felt strongly through the steering wheel while rear rotors are more obvious through the seat of the pants. If they are badly warped, high "hot" spots can often be seen on the rotors. Generally, front rotors warp more often as they do the majority of the braking. Be forewarned, Volvo rotors do not have much meat on them. The difference in thickness between brand new and thin enough they are garbage is not much. New rotors may be in your future. Check rockauto.com for some less painful prices. Also, improperly torqued wheel lugs can lead to rotors warping.

 

From what I understand how you brake has a lot to do with warping your rotors. My rotors are never warped I think because I don't let the car come to a complete stop on hot brakes. I work the car hard, but I let off the brakes so the car is still rolling a tiny bit before any complete stop. From what I've read, working your brake hard causes heat. When it's really hot and you stop dead on one spot on the rotor, the pads bake onto and hold heat on that part of the disc, where the rest can cool more easily. First, the pads glue onto the rotor and secondly, the difference in cooling rate is what warps them. So I always let the car roll to prevent this.

 

Heat buildup causes warping for sure but I've never heard your theory of the pad baking on to one spot. It would seem to me that would lead to one spot being substantially different in height and most rotors I see have several hot sots. The braking I have seen cause failure and supposedly lead to warpage is the long, moderate braking of descent...not only running down a mountain, but the long, slow sweeping descents of an interstate off ramp. Rather than ride the brakes and gradually slow the vehicle, I have a habit of stabbing the brakes and dumping speed and then letting off to allow cooling; repeat as necessary.
I think an important side note is that many brake rotors, particularly from Red China, are warped when new. They need to be turned straight out of the box. Making matters worse, many of the big names are having at least some of their rotors manufactured in China. We chuck all new rotors up in the brake machine and check for run out prior to installation...easier than taking it off later and redoing your work.
Regardless, heat is an obvious enemy of brakes, yet they generate heat as a by-product of their function so adaptive driving styles can and will help, IMO.
Over torqued wheels have been the suspect in many a warped rotor as well.

 

I agree and that is why you should always use a torque wrench instead of an impact wrench which is what most tire places use.

 

I always remove hub caps and center caps before I go to the tire shop. I let them gun the heck out of the wheels and then go home and torque them. Some places use those stupid torque sticks which, IMO, are one of the greatest frauds of all time! Worthless...

 

re: the baked on pad thing... the changes are not visible, just a few 1/1000ths of an inch can make the brakes shudder.

see -Warped- Brake Disc and Other Myths
for a decent discussion of how to heat cycle new pads and rotors to avert this.

 

Yeah, I think I read that somewhere else before. Good stuff. Yeah, prolonged braking is another good way to ruin brakes. I forgot to mention that. I think that the discs will look glazed if that is the case. The should appear fairly dull under normal circumstances.