brake balance

[sawood12]

Just reading an article on brake balance where it said that manufacturers achieve the desired brake balance by the relative sizing of the calipers front to rear. Alot of people are running uprated brakes up front which would upset this balance and I was wondering if many people had noticed much of a difference when upgrading to bigger brakes up front. Or does the 944 have another method of achiving brake balance which means its not sentitive to the realive size of the calipers?

I have been considering upgrading my brakes using BoxterS/996 calipers which seem to be cheaper and more readily available than the big reds/blacks and wondered about replacing the calipers all round to maintain brake balance and the asthetics of having the same type of caliper on the rear - also you irradicate the caliperplate problem.

 

[Fen]

There's a balancing valve on top of the ABS unit in the offside front wheelarch (I imagine it's there on non-ABS cars, too). It's a fixed proportion, but a lot of people (Rick for example) use the 928GTS one when going to big reds/blacks on the front.

I have an adjustable one in my box of as-yet-unfitted parts, but to be honest my car felt fine with the original one, hence the laziness fitting it.

 

[eastendr]

Actually ...... I don't have one fitted because the bias feels pretty good as it is ... sorry []

 

[Fen]

Why did I think you had it then? Anyway, your finding matches mine at least.

 

[Indi9xx]

The less effective (more standard) the cars braking is, the more important brake bias front to rear becomes.

This is because as you increase the braking ability (such as fitting front big blacks or reds) the weight transfer off of the back axle during braking increases, which means you need more front bias and less rear bias..

The upshot of all this is, that if you fit big blacks or big reds, often the rear bias decreasing as a result is pretty close to whats called for anyway (isnt it nice when a mod kinda sorts itself out like this!)

So dont worry about it... You could fit the 928 bias valve, but its not really essential and may in some peoples eyes make it worse.

 

[Fen]

It's still my intention to fit the adjustable one I have and play with it - I agree with what you say Jon, but I imagine messing with the suspension and so altering the squat and dive characteristics of the car lessens the effect. I'd also like to experiment with making it slightly more nervous under braking, though that could be a route to getting very exciting very quickly.

 

[sawood12]

So in that case then it might not be a good idea to fit BoxterS/996 calipers alround then. I do feel I need more braking force at my disposal since I completed the installation of my Level 2 kit as the performance has really picked up and I find when I use it I'm being much harder on my brakes.

Just another quick brake related question - if you totally drain the braking system of fluid does it cause complications with filling and bleeding again? A friend has said that ABS systems often have an accumilator which if emptied is a real pain to refill and bleed. I've not read anything like this in relation to the 944 so wondered if it applied.

 

[Fen]

Actually I forgot, I have a set of 220 Turbo front calipers to go on the back which will get fitted sometime before the car is a runner again.

 

[chrisg]

Scott

having drained the system on my 88 Turbo S to refit a 'new' ABS pump last year, bleeding the system didn't take any longer or more difficulty than when I've taken calipers off.

C