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evanbottcher · Posted: Sun Nov 28, 2004 11:20 pm Post subject: Uneven Sud brakes

Hi All,

My Sud is running again after a few years in storage and I've adjusted up the front brakes and have a nice firm pedal. However I get a bit of an inconsistent pedal travel - sometimes it travels a bit further than other times. It feels a bit uneven front -> rear also - I mean different between different braking applications. I also get a loud 'clack clack' sound coming from the rear when I hit the brakes sometime, only after driving along for a bit (i.e. it doesn't repeat if I'm sitting still).

One thing occurred to me this morning thinking about it... the rear hubs are quite loose. Could run out on the discs be pushing the rear pads/pistons back into the calipers and causing a bit of extra pedal travel? The clack clack sound could be the pads being banged against the discs.

Any other ideas? Master cylinder?
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'77 Alfasud Ti
'69 1750 GTV

evanbottcher · Posted: Tue Nov 30, 2004 2:16 pm Post subject:

I've been told that it's likely to be the proportioning valve, dunno why it would make a clacking sound - but I'm not going to strap myself under there while someone goes for a drive to find out.

Thinking of removing the valve completely and fitting an adjustable one, probably under the bonnet (less plumbing). Any thoughts/suggestions?
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http://www.trofeoalfasud.com
'77 Alfasud Ti
'69 1750 GTV

GaryUK · Guest

Surely you want the proportioning vavle in the cabin so you can adjust it for the number of people/load in the car. You just need to run a new pipe from the master cylinder into the cabin then back out to the rear spiltter. Only one pipe (in two sections) to make up, a piece of piss. Using known weights of balast you will be able to calibrate the valve for easy use.

alexj · Posted: Fri Dec 03, 2004 8:38 am Post subject:

Since your car seems to be a race car, there are a number of considerations...

1) what are the class restrictions - do the rules prevent you having an in-cockpit brake proportioning valve? If it's allowed, that's probably the best place, as suggested in post above.

2) is it also a road car? - if so, do the road rules in your country/state prevent the use of an in-cockpit brake proportioning valve?

There are a number of areas that could be causing inconsistant braking. In my race car (now stolen - see the thread in aussie/nz section), I had the front inboard calipers rebuilt without the handbrake mechanisim and this helped a great deal.... but just a caliper rebuilt could help a lot. Sounds like it could be a sticking caliper.

However the rear proportioning valve doesn't last long, so most race cars have had these removed/replaced long ago.

If you have a lot of float in the rear hubs, you could be getting "knock back", where under cornering/suspension movement, the side movement in the disc rotors is pushing the pads back and in turn the caliper pistons back in the calipers... so next time you use the brakes there is too much pedal travel and you almost don't make the corner. However next time you brake the pistons are back to normal and you end up braking too soon. So you need to get any rear hub problems fixed too.

Inconsistant brakes are worse than just bad brakes, because with simply bad brakes you can adjust your driving style.... but with inconsistant brakes, it's very difficult to drive the car better if it's a different behaviour on each corner.

Just read your post again.... "few years in storage". Brake systems don't like years of storage. Caliper rebuilds might be needed.

Master cylinder test is constant pressure on pedal - does the pedal slowly sink to the floor? If so, that needs rebuild too. I got mine done by one of those places that resleeves with stainless steel. Bit expensive but should last.

Good luck.....
Lex

evanbottcher · Posted: Thu Dec 09, 2004 4:13 am Post subject:

Thanks Alex,

Taken a while to reply - have been distracted by the depressing state of the car's sills, is going to cost a wedge to be put right. *sigh* Am considering re-shelling the car if I can find a decent series 1 body.

1) class restrictions - I'm running in a modified class of which 1 of the available modifications is braking, so I can do whatever I want including a proportioning valve, even fitting outboard ventilated discs from a 33 if I wanted to.

2) road car - yes the Sud is going to be run on the road occasionally, so I need to look into that thanks. Here in Victoria we only have to have a single 'roadworthy' test when re-registering the car, not annually, so I'll probably just modify it once the car is back on the road. Did I say that out loud???

I've never been happy with the handbrake adjusters - last time I drove the car I pretty much didn't ever touch the handbrake as the calipers would go out of adjustment when it was used. So the adjustment mechanism is likely to be clagged. I don't really understand how it works actually - will have to pull a caliper apart at some stage to work it out. Rebuilding the calipers without the adjusters sounds like an excellent idea - a club member here suggested the same thing. What's involved?

I think the master cylinder is okay, I also suspect 'knock back' from the rear hubs - when I get a chance I'll tighten them up and see what difference that makes.

Firmly agree with your comment regarding inconsistent brakes being worse than cr*p brakes. At the moment I have no confidence in what the brakes are going to do at any particular time.

thanks again,
Evan.
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http://www.trofeoalfasud.com
'77 Alfasud Ti
'69 1750 GTV

Eddie W · Posted: Fri Dec 10, 2004 8:59 pm Post subject:

One of the first jobs after having a car in storage for a while would be to replace the brake fluid as it absorbs moisture over time. Old fluid can contribute to inconsistant braking. Dot 4 minimum.
Regards Eddie
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