Brake Disc 420sel

[SCOTTFISH]

I have this feeling when braking that the car is coming and going like maybe the discs are warped. Could this be the feeling I am experiencing? If so, is there anyway to keep discs from warping? Also, what about vented discs, are they a good idea or not? I just replace my front pads about 5k ago. If I replace the discs, will I need to purchase new pads again? Any help would be appreciated.

[psfred]

If I remember correctly, you already have vented disks on a 420.

Take a look at the rotors -- is there a distinct lip at the outer edge where the pads don't complete cover? If so, they are too thin and needed to be replaced when you did the pads.

I suppose you could re-use the pads, but unless they show very little wear, the $35 or so spent on new ones would be a good investment. New rotor will last longer with new pads, the wear is more even at the beginning.

Peter

[SCOTTFISH]

What would you say is an average life of a disc? When the disc gets thin, this of course, would cause there to be more heat. Would this cause the discs to warp? Do you think changing the discs every other pad change would be a measure or will they last longer than that?

[neileg]

Disc wear depends on how and where you drive. From the stuff on this site, US drivers get much higher mileage from their brakes that we do in the UK. I guess it's down to longer, straighter roads!

A rule of thumb is new discs every three sets of pads.

Warping is due to heat. Main factors are
1) Heavy braking generates lots of heat
2) Worn discs can't dissipate the heat and warp easier than new discs.
3) Poor quality discs will warp before good quality ones. This is largely down to quality of materials and heat treatment of the disc during manufacture to relieve stress.

[psfred]

Well, so far in seven years of driving my MBs I've not yet had to replace the pads twice (all except the 300D had terrible brakes when purchased). One set on the Volvo in 50,000 miles.

I expect around 30,000 or so on a set of pads, that means around 100,000 on rotors for me.

I do almost exclusively "open road" driving at moderate speeds and rarely have to brake hard. If you drive in heavy city traffic with lots of hard stops, expect considerably less. If you do almost all interstate, expect more.

Peter

[Cigar Havana]

Will drilled rotors last longer? What is the advantage to drilled rotors? When installing drilled rotors, should you put them on all 4 wheels or can they just be put on the front or rear?

[manny]

1. No.
2. They look cool.
3. You don't have to " match " them front/rear.

[SCOTTFISH]

What kind of brake disc do you recommend? I have gotten a pretty good price quote for ATE discs. Any suggestions?

[manny]

You can't go wrong with Ate.
There are others like Balo, Zimmerman, etc.
As long as you stay with a known brand, and follow the break-in procedure that comes with them.

[psfred]

Brake rotors are drilled to reduce weight in racing applications, where more braking isn't an issue (just use larger rotors and pads). Might also be some minor effect on cooling, too, but not much. Lifetime isn't an issue, they are usually shot by the end of the race and won't be reused anyway -- safety hazard!. Ditto for pads.

They have very little effect other than looks in normal street use. I have my suspicions about wheels with thin enough spokes to show the rotors anyway, but the holes are only there for looks, nothing else.

Be trendy or die!!!!! That's why I drive the last W108 chassis in Evansville.

Peter