Primoz

Yesterday I drove my 71 to the MOT and guess what, the car pulls to the left when braking.
It is almost 30% difference in braking power from left to right front brake caliper.
The brakes are all redone with o-rings and new pistons etc. Although I didn't bleed them yet in 2017.
Will the front wilwood calipers solve that issue?
The ones that installed the wilwood calipers what were the things you noticed when upgrading?
Better stopping power? No pulling to one side?

Domobomb

Did you replace the brake hoses also? Collapsed hose can cause that.

I have the Wilwood replacement brakes. Haven't driven with them yet. Only real benefit I expect is the unsprung weight reduction.

terrys6t8roadster

A D-8 calipher either aluminum or iron has the same braking capability. T

Fredric Björnefält

You will need to bleed them !

Primoz

All hoses are new! Rubber not stainless!

jb78L-82

A wilwood aluminum 4 piston caliper which is the same size caliper as the OEM GM iron caliper, using the same size brake pad, clamping the same size 12 inch rotor will show NO improvement in brake performance over the OEM delco caliper. A wilwood 6 piston front caliper, clamping a 13/14 inch rotor, but using the same size brake pad will show slightly better brake performance due to slightly higher clamping force from the larger brake rotor and more consistent linear brake pressure across the 6 pistons in the caliper versus 4 pistons. The only real advantage of the wilwood system is less unsprung weight of the aluminum caliper and better heat rejection from the aluminum versus cast iron.

Sounds like you need to rebleed your system. I have VBP SS calipers (GM type lip seals, NOT Oring seals..no oring calipers in 1985) all around on the car since 1985 with SS flex hoses at each wheel with performance friction pads (since 2001) and the brakes are simply terrific and amazing even today since the brake system was designed and used on the C2's starting in 1965!

Only my 10 C6Z06 with 14 inch 6 piston fixed calipers in front and 4 piston 13 inch rear rotors are better. My 08 Chrysler 300 which I upgraded myself to the Hemi brake system with 14 inch front rotors and massive dual piston front caliper (giant front brake pad) with 12 inch vented single piston rear caliper/rotor are about equal to my C3.

Primoz

My motive bleeder will come in handy once again. I will measure the rotors for run out and see if that is the issue. Last year after bleeding the driver side brake was still putting out around 10% more braking than the passenger side according to measurements at the MOT! Does the proportioning valve has anything to do with that? My setup is all original!

bashcraft

There is no proportioning valve.

What is the "MOT"?

Primoz

No proportioning valve in 71? It is called proportioning valve but it may serve only to split the tubes.
The MOT test (Ministry of Transport, or simply MOT) is an annual test of vehicle safety, roadworthiness aspects and exhaust emissions.
We in Europe have to take it every year! That is for classic cars! In classic cars they test brakes and lights. They also can test the loudness of the exhaust but they are not so strict on that front.

Big2Bird

Check the run out and the caliper bracket for square. My pass side was out .030" last time I checked. A little sedge hammer action squared it up.
The front brackets are a weak point.

jb78L-82

You should have a brake proportioning valve and it controls the front to rear brake bias, not side to side brake proportion. The brake bias front to rear on a C3 is about 65-70% front: 30-35% rear, with the fronts doing most of the braking mainly due to the rear weight bias of the C3 small block engines. My 78 C3 weight distribution is 52% rear:48% front. The heavy front brake bias is to prevent snap oversteer for the uninformed driver who hits the brakes hard in a turn. Most C3's will lock the fronts way before the rears. This brake distribution is also why the front caliper 4 pistons are slightly larger than the 4 pistons in the rear caliper...more brake force in the front versus the rears.

bashcraft

It's not a proportioning valve on a '71. Though 74-82 is different and I can't speak for them.

Primoz

I have changed the front brackets! They are brand new!

jb78L-82

https://www.ebay.com/p/?iid=30231928...pItem=1&chn=ps

http://www.zip-corvette.com/68-82-c3...ng-valves.html

bashcraft

I don't care what people call it. It's not a proportioning valve. If you take one apart you'll see.

The front to rear bias was accomplished by the sizing of the caliper pistons.

jim2527

OK...don't mean to be a stickler here but I thought front bias was primarily due to weight transfer under braking. Balance shifts forward therefore front brakes can handle much more of the work.

But yes I agree on the locking of fronts before rear to prevent snap oversteer.

jb78L-82

That is correct but without a brake proportioning valve to reduce rear brake pressure to the rear calipers, the rear wheels would lock prematurely when the weight is naturally transferred to the front axle under hard braking which is why all cars have brake proportioning valves. FWd cars with most of the weight over the front wheels are especially susceptible to rear wheel lockup without a brake proportioning valve.

I recently had to replace the brake proportioning valve on my daughters FWD Pontiac grand prix since it was leaking.....

Easy Mike

FWIW: it's a pressure differential switch and not an actual proportioning valve. The J56 heavy duty brake package had a proportioning valve in addition to the pressure differential switch.

jb78L-82

http://www.zip-corvette.com/68-82-c3...ng-valves.html

Primoz

OK! But to summarize it all do the wilwood calipers remove that brake pulling to one side?