Brake rotors

[1200images]

When I apply the brakes I get front wheel shutter. I assume it's a warped rotor.
Do I need a new one, or could turning the rotors cure the problem.

Thanks for any help.

Gary

[yelcab1]

Turn them until you can't turn them no more.

[m110]

At $46.75 from our host, assuming this is for your SC, I would just buy new ones.

Pelican Parts - Product Information: 477-405-083A-M359

[tonythetarga]

What kind of pads are you using? It is not easy to warp a Porsche rotor and it likely has pad material transfer. Try using a different or maybe slightly more aggressive pad and do a series of progressively harder stops to clean the rotor.
I agree that turning the rotor is a bad idea, just replace it. Turning it gives you less mass and a decreased ability to dissipate heat and that WILL be a cause for the rotor to warp or for you to have brake fade from overheating your pads and fluid beyond their specified heat range.

[RichardNew]

Here are a couple of articles I've written about brake rotors - or more correctly brake discs. Often times you will get a brake shudder after switching pads. Too many people diagnose it as a bad rotor. What is really happening is that the new pad material is interacting with the old pad material. The two types of material simply don't work well together.

You really have to clean your old brake discs if you're installing a new brand of brake pad.

Poke around my site for the 2nd article on brake rotors. I also just finished a 3rd article that is now in Vintage Motorsport magazine.

Richard Newton

[porschenut]

Had exactly the same problem on a car I used to have. Had the rotors turned and the problem was gone.

[Tidybuoy]

Might also check to be sure your wheel bearings are not too loose. I'm not sure if that affects brake shudder but I thought I'd suggest.

[Craig]

Try using a different or maybe slightly more aggressive pad and do a series of progressively harder stops to clean the rotor.

I second what TonytheTarga said. I have tried this on mine when there was some shudder, and it fixed it. An article I read said it is almost like re-bedding in your brakes. There was mention to try and not let your hot brake pads sit against the rotor for any length of time while doing this, ie. at a stop sign or somethnig. I have a four mile stretch of road I do this on. I progressively stop harder for the first 1-2 miles, then just drive normally for the last 2 miles to allow some cooling on the brakes.

Craig

[redridge]

bedding the pads will cure the shudder, do not lock up your brakes though. Keep the wheels rolling... warped rotors are very rare.

[NICE 69 S]

Why not buy a small dial indicator with a magnetic base and check the rotor. First try and rock the rotor in and out at the point your dial indicator touches the rotor (somewhere close to the last 10mm of wear surface on the perimeter) to see if you need to tighten the wheel bearing nuts. Next rotate the rotor to see if there is any variation in the reading with a complete 360 turn of the rotor. Not sure what would be acceptable, but anything more than 10 or 15 thou. probably is not good.
Bob B

[db_cooper]

Originally Posted by 1200images

When I apply the brakes I get front wheel shutter. I assume it's a warped rotor.
Do I need a new one, or could turning the rotors cure the problem.

Thanks for any help.

Gary

Gary, assuming the shutter has just become noticeable and no brake work has been done recently..chances are your rotors (discs) are warped.

It was fashionable at one time to always turn the rotors whenever you replaced the brake pads..some shops still do. It runs up the shop labor charges and costs "slightly" less than brand new rotors, especially on the front.

Once the 911 rotors have been turned they will warp eventually..you might get one or two pad "slaps"..then the rotors are a shuttering

Getting a magnetic dial gauge from Harbor Freight..jack up the front of the car...good time to check the front wheel bearings (see if the front wheel(s) have much movement grasping the top and bottom of the tire....pull the wheels (insert usual lawyer disclaimer here) install the dial gauge and check the rotors for run-out..

If your steering wheel is shuttering when braking..its the front discs..if the car shutters..then its likely the rear discs.

I have seen the rear rotors get turned more often than the fronts..probably because of the parts expense..that's when they will warp eventually too.

If your front wheel bearings are sound..just bit the bullet and replace the rotors.

911 brakes are a DIY job..unless your just not handy with tools.

If the rotors are original or old enough to vote..change the rotors, repack the front wheel bearings..pads..sensors..rubber brake lines and check the caliper boots..they get torn.

My winter project coming up..I can't wait:

[rgoodrich]

I put Porterfield C4's and aluminum slotted rotors on my 84 Carrera. Stops like a race car and no shuddering. Not to hijack, but now I have squealing when the brakes are worn. I have these same pads on my 81 SC with no noise. We've chamfered the pads and roughen the rotors a little. Some improvement, but still unacceptable. Any ideas?

[RichardNew]

Here's a 3rd article about brake rotors. Did I mention that I really like brake rotors? Maybe I need a life.

Richard Newton

[GH85Carrera]

Originally Posted by 1200images

When I apply the brakes I get front wheel shutter. I assume it's a warped rotor.
Do I need a new one, or could turning the rotors cure the problem.

Thanks for any help.

Gary

I hope you did not intend to ever just replace one rotor. Always work on both sides and work hard to keep them equal.

[zippy_gg]

Originally Posted by GH85Carrera

I hope you did not intend to ever just replace one rotor. Always work on both sides and work hard to keep them equal.

+1 And install new pads when installing new rotors.

[RichardNew]

I have to giggle about the brake noise question. An engineer at one of the brake companies once told me that racing pads are the easiest pad to design. The only thing that matters is stopping and lasting for 500 miles. "If you're worried about brake dust and squealing you ain't a racer."

Richard Newton