Help: Brake Balance?

k9handler · 12-20-2005, 07:55 AM

I managed to get my car back together and just in time for my annual inspection. Not good news on the inspectilon...the front right (passenger side) is not in balance with the front left so the car failed. And...the hand brake is not grabbing to the inspectors standards although the car is held firm by it.

So...without having a machine to test the car myself, how do I get the brakes in balance? Would simply replacing the pads and bleeding the brakes be a fix? Or...take the car to the stealership and have them fix it?

Any ideas will be much appreciated.

RESULTS:
FL: 2,34 kN FR: 1,53 kN diff (35 %)

RL: 2,56 kN RR: 2,56 kN diff (0 %)
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MotoSook · 12-20-2005, 07:59 AM

Rebuild the front caliper and flush the system Smitty.

Those are interesting numbers. How does the TUV (right?) test the brakes?

buster73 · buster73's Garage

Seems something is wrong with the front right brake. If rotors and pads are o.k. I would start with a full bleed job. If this does not help, it could be the caliper needs cleaning/rebuilding (always rebuild both sides at the same time). Could also be a brake line is damaged/blocked. If you have old rubber brake hoses they might be swollen, reducing the open diameter inside. Handbrake can most probably be adjusted. You can check and adjust the handbrake cable and the drum brake shoes inside the rear disks.

Good luck - reminds me what is awaiting me when I bring my car from California back to Germany next year. Lucky California - no TUEV here. Although it is certainly a good idea to have proper working brakes.

damian911 · 12-20-2005, 10:12 AM

i had the same headache and i rebuilt the calipers, bleed brakes and was about to change the lines. I then went ahead and removed both pads and replaced them with new one's thinking one side might have been oil'd soaked or something but that turned out to be wrong, but when i finally finished and looked at the pads as i sat down and relaxed i noticed that the idiot who did the brake job before i owned the car put two different styles/models on each side, one side was oem,the other was more racing applications......I was amazed,

k9handler · 12-20-2005, 10:29 AM

Souk...it's a drive on sled with 4 brake areas, the inspector drives onto the sled and then applies the brakes. The computer then produces a graph with the results.

thanks guys, will start with a bleed and new pads and go from there.

What is the best method to bleed them? LR, RR, LF, RF? Tricks?

boyt911sc · boyt911sc's Garage

H.D.,

The proper sequence in bleeding all four wheels is to start with the farthest wheel from the brake fluid reservoir. Meaning that the farthest wheel would have the longest brake line.

For SC/Carrera cars, it would be RR, LR, RF, and LF. This should be same for your car. Hope this helps.

TD

Thrasher · Thrasher's Garage

I agree with what's been posted so far - checking pads for contamination and calipers for leaks. It could be air in one caliper leading to a low reading (think gas/air = compressible, liquid/fluid not)

Always bleed from the corner furthest from the MC, so for a 911 RR, then LR, then RF, then LF. It wouldn't hurt to drive it a day or two and re-bleed either.

Get a helper to hold the pedal - there are a million writeups in the archives and I think a tech article. It's really easy with a helper and that method usually yields about the best results (as compared to pressure or vacuum bleeders )

For the testing, they probably used one of these: http://hunter.com/pub/product/braketester/4002T/index.htm

I used to work for that company and still have some buddies that let me run my 911 over one recently - mine were amazingly well balanced, I was happy to learn.

Wil Ferch · 12-20-2005, 10:48 AM

Another hint, Smitty....

rebuild the calipers to assure equal brake "puck "action....yes, use new rubber lines for the front...and here's a tip...get the front weights ( LF =RF) equal so that both sides lock up at about the same time.

A slighty light corner will lock first........

Wil

k9handler · 12-20-2005, 11:05 AM

thanks guys, great ideas from all of you. I have the 101 projects book in front of me and have been brushing up on my knowledge so I should be able to correct this. This is how I learn, so thanks for all yourr help with this matter. =o)

Thrasher · Thrasher's Garage

Good point about the weight balance, Wil.

If they really are using the Hunter brake tester, it may/should have corner balance scales built in. The one I was on did. Maybe you can get a "free" corner weighting out of this.

k9handler · 12-20-2005, 11:15 AM

that is a great idea, it does match axle data and such (the car passed this) as well as suspension. The test is free and it's the only way I know to test them as I conduct the repairs, so I may be going back a few times until it's right. =o)

k9handler · 07:17 AM

It all went well today and the brakes are fixed and in good working order. I replaced the pads and did a full bleed and checked the rotors. The inspection went well and the brakes were within 5% front and rear. I also tuned up the emergency brake so it holds much better now, but I thought it held well enough before.

So what was the issue? It turns out that the FR had air in the line (inside valve) so that was causing the loss in brake power. After a full bleed the numbers are damn close.

RESULTS:
FL: 2,55 kN FR: 2,56 kN diff (1 %)

RL: 2,56 kN RR: 2,56 kN diff (0 %)

The point of the story is my car passed the inspection.

Thanks guys for your help.

Bill Verburg · Bill Verburg's Garage

It's pretty impresssive that the Germans do so thorough an inspection. If it was done here I don't think we would need to worry about traffic jams.

k9handler · 12-22-2005, 11:40 AM

funny thing that you say that Bill...with the number of Americans in this part of Germany you still see a bunch of cars that make you wonder how they pass inspection. Not just the Americans either, there are quite a few locals with cars that could use a little TLC. No doubt the TUV is a tough test.