Sub par brakes

[Ignatzcatz]

From my car sitting for so long the rubbers in the master cylinder had become non functioning so I got a new master and got a pair of braided lines for the front calipers. I bled the brakes in the usual fashion but I didn't get a very positive pedal. So I bled them again, same result, so I power bled them and got a slightly better feel with the pedal. I was a bit puzzled because I had recently fitted braided lines plus one new hard line onto my 911 and with one bleed got a brilliant hard pedal. Back with the 356 I wasn't too happy with all this so I bled the master cylinder then all the line junctions and only then got an improvement in pedal performance. I would really like the brakes to go full on within a couple of inches of pedal movement, like my 911, but for the time being I'm just going to drive the car and hope for some improvement. There is no way I could heel and toe due to the overlong pedal movement so if nothing improves I reckon a visit to Cridfords may have to be in the old dogs future.

[silverboydreamer]

I had similar problem and tracked it down to no gap between the pedal plunger and the master cylinder socket when at rest, from memory I think the workshop manual says there should be a gap of 1-2mm before the pedal starts to actuate the master cylinder, I assume it’s so the internals get past the fluid intake hole,

[alfacat]

Hi there
Have you replaced the old fluid, if not how old is the brake fluid?
I think I'd want to flush the system if the car had been sitting long enough for the 'rubbers' to perish.
Please excuse my 'teaching my Grandmother to suck eggs' if you've already done this...

All the best
Ian F.

[neilbardsley]

I had a similar problem in my A until I realised there are two bleed nipples on the front brakes however not your issue because I believe you have installed discs

Sent from my M2004J19C using Tapatalk

[KS]

Long brake pedal... What brake calipers and master cylinder do you have? Two things crossed my mind, thinking back to when I had Wilwood calipers on my race car. That also suffered from a long pedal, which wouldn't respond to bleeding. The solution was fitting residual pressure valves in the brake lines. They prevent the pads from retracting too far – a lot of the pedal travel is from moving the pads closer to the disc.

From Wilwood's website: "Wilwood's two, four and ten pound residual pressure valves retain a minimum brake line pressure to help eliminate excessive pedal travel in both disc and drum brake systems. The two pound valve is used in disc brake applications where the master cylinder is mounted below the horizontal plane of the calipers and fluid drain back occurs from gravity and vibration, thereby causing excessive caliper piston retraction and a longer brake pedal stroke. The minimal two pound residual pressure prevents fluid from flowing back without causing the brakes to drag. Four pound valves can be beneficial in high vibration brake systems such as off-road or dirt circle track racing."

The other thing is the master cylinder diameter. For example, changing my 914's 17mm m/c to a 911 19mm one reduced pedal travel by almost half, giving far more confidence. If you have a 19mm m/c then this is something that might possibly be worth checking?

[silverboydreamer]

The correct master cylinder must be used for drum brakes as it has a built in residual pressure valve thereby holding some pressure in the system to reduce slave cylinder piston travel, it is no good on cars with discs as the last thing you need is pressure in brake system when releasing the pedal because the pads will still be part clamped on.
If you have disc’s up front and drums at back you need a duel master cylinder with the front circuit ( discs) without pressure valve and the rear circuit ( usually nearest pedal ) with a PV for the drums.
Found this out the hard way!

[KS]

That’s the opposite of my experience and what Wilwood recommend. With disc brakes a RP valve is used to stop fluid flowing back into the master cylinder where the M/C is mounted lower than the callipers, as is the case on 911s and 356s, etc. It only needs to have a low rating (2psi) to get the job done.

[Ashley James]

Lots of bleeding can result in aerated fluid and a spongy pedal. Leaving the car for a couple of days and then bleed again being very gentle with the pedal as well as keeping the master cylinder topped up and with the lid on may do it.

[Peter Roberts]

You list that you have a 356B but say in your text" calipers". Have you got drum or disc brakes fitted as per 356C?

[Ignatzcatz]

Well it's a right old mix up really; the master cylinder is a L/H drive '70's 19mm VW piece with early 944 front calipers with single bleed nipple and pre '69 s/w/b 911 rear calipers with twin bleed nipples. I've made and re-tapped a new long nut to eliminate any additional play between the pedal and master cylinder and following 'Another' bleed around I now have a fairly decent pedal. It's not like the 911 which is like hit the pedal and - bang -you feel you are pushing onto a concrete wall, but I'm going to drive the car a bit and just see if I gain some improvement. I don't know if I mentioned it but I fitted braided hoses on the front also I'm seeking a pair of 944 turbo front calipers which should make the old girl stand on it's nose.

[Peter Roberts]

It’s rumoured that Porsche tended to underbrake their cars in the old days to stop the front wheels locking up and losing all control. With later ABS this problem disappeared. I would not want brakes that lock front wheels when you stand on them in earnest in an emergency stop. It does not help when your on skinny tyres. BEWARE

[roy mawbey]

That's a sensible reply Robert. My old A is still on Drums and they are in good condition. I have respect for the way they work and I do have to make sort of comparisons to my BMW discs with servo. The old 356 actually stops very well, in fact I feel it needs almost driver feel when the brakes are applied as the front is quiet light. I drive though with 75hp and not a fully updated uprated engine. So you sort of drive to the spec of the car and its much older design.

If the car were pushing out 50% more power it sort of changes things you probably need then the instant response of a modern system. Don't really want that, don't think I need it, as my driving style is different I guess from getting out of the BMW and getting in the 356. If the 356 could stop on a sixpence with prod of the brake at any time I would still need it to be very responsive to my foot pressure.

I would never have made a 356 racer !

Roy

[Peter Roberts]

I have a 356SC with disc brakes. During restoration i fitted proffesionally reconditioned calipers, new pads and new discs on the front. I had huge problems bleeding them to start with as i would get a good pedal then after a week of standing the pedal would go half way down. Turned out the new seals have a memory function which will pull the pistons back slightly. Got over it by removing pads and moving the pistons half way in then pushing them back just enough to squeeze the pads back in which sorted the problem of losing pedal. Having said that even now i do not have a brilliant pedal and to stop quickly have to stand on the brakes. You cannot compare them to modern BMW brakes as so many things have changed. Old days hard discs soft pads. Modern thinking soft discs and soft pads plus a servo to get better grip. Just remember disc brakes are better than drums in that they do nor fade when hot or under racing condition. They are not better when cold. These designs and the thinking behind them are over 60 years old so just be prepared to jump on them when you need to

[Peter Roberts]

Kust read through all the posts and note the change of master cylinder and calipers. If you use a smaller mastercylinder you will generate more pressure in the system for a given push. If you use a larger piston in the calipers you will increase the force exerted by the master cylinder pressure. That can be good but the downside is you have to displace more fluid to move the calipers hence you have a longer pedal travel which you cannot get rid of. Maybe this is your issue.

[silverboydreamer]

I fitted a CSP front disc brake kit to my T6 last year together with a duel circuit master cylinder ( for a disc and drum setup)and separate brake fluid tank (fitted in front trunk area), fitting was straight forward, however getting a solid pedal proved to be elusive. I finally solved the problem by leaving a 2mm gap between the pedal piston and the base of the master cylinder, as instructed by the workshop manual, whilst the feel of the pedal is good it doesn’t compare to a modern car.
After the fitting and using the brakes over the next month I experienced a heavy juddering from the disc brakes, several weeks of investigation narrowed the problem to ‘ heat judder’ , I contacted CSP and they sent me an alternative set of pads which when fitted solved the problem.
The other problem experienced was very hot discs even after short trips, this proved to be my fault as I had got the drum circuit connected to the discs and because the master cylinder has a device in the drum circuit that slowly releases the internal fluid pressure, the discs were dragging on the disc’s. When i changed over the circuits to the correct position, all was ok.
I cannot stress enough that any residual fluid pressure in a 356 disc brake setup will result in DRAG, resulting in friction that in turn produces heat, more wear on pads and disc’s and lower mpg.
The correct master cylinder for a drum and disc setup is one designed for that purpose therefore it has to be a duel circuit cylinder.
Since fitting the CSP kit and ironing out the above problems, the brakes have been much improved with better stopping power (compared to drums) with good pedal feel and I would recommend fitting the kit to your car, it’s not cheap but it’s well thought out and straight forward to fit by anyone with reasonably competent skills. Because your buying the complete kit rather than a ‘bitsa’ setup, if you have any problems you have the ability to contact the seller or manufacturer to solve them.