brakes pulling to one side

[sixpipe98]

Hi All,
I've recently started to push it a bit more in my 911t and have started to notice that under particularly hard braking it pulls slightly to the right. I've recently fitted a new master cylinder as the pedal went straight to the floor post its winter hibernation, that's now sorted. I do remember it pulling to the right slightly before the new master cylinder so don't think its anything to do with that. I didn't pay much attention to it before but now that i'm starting to push the car a bit i'd like to sort it. Also any good brake pad recommendations would be great, the car currently has EBC yellow stuff (apparently these are only for track us though ??) and i believe brake calipers off a 911s.
cheers
Sam

[hot66]

Could be a sticking calliper or collapsing flexi. Buy a cheap infrared temp gun and see how the two front discs compare after some long hard braking, might give you an idea if one side has less temp in it.

[911hillclimber]

I'm sure James is right.
Why not simply re-seal all 4 calipers?
Not too difficult and certainly cheap to get the parts, fresh hoses takes away any other doubt at the same time, just do the whole system at the same time.?
You have done the awkward expensive bit with the Master.

As to pads, I have never had a good response with Green Stuff etc products.
The subject is very subjective just like "what is the best oil" etc.

It is hard to get an early car to stop well and you need good brakes in today's world.
My opinion is to buy 'Carbone' and fit new discs at the same time to get the very best out of the system.

They can be a bit noisy in use, but do work well from cold, mighty expensive though.

The whole refresh is not cheap, but you will have the best brakes possible with 'stock' parts and cheaper than specialist calipers.

Let us know how you get on.

[sixpipe98]

Great, thanks for the advice. Do you mind just explaining a bit more what you mean by resealing the calipers. As in is that simply replacing the brake lines feeding them or rebuilding the actual caliper ?

[Ashley James]

Overhaul the calipers and replace the seals. The pistons will be sticking, which is a common fault with older cars. My Healey does it all time so much so that I’m considering fitting more modern calipers.

[sixpipe98]

Having thought about i think I'll just get all 4 calipers professionally rebuilt. Does anyone know any good places for this ?

[911hillclimber]

Google is your best friend.
A set fully done by a pro will be around £800 but more if you have aluminium S callipers on the front.
As Ashley says, if not used regularly any one or more can corrode, I've done mine about 5 times in 28 years, dry miles only on the car. I even have a car set of seals in stock!
There is a company specialising in Porsche callipers, and they will refurbish your actual units for you.

Any reasonable garage can do all this refresh, nothing special needed though bleeding can be a pain.

[sixpipe98]

Ok understood. Cheers

[Ashley James]

We use Past Parts who re-line the calipers with stainless steel to stop it happening again. http://www.pastparts.co.uk

Otherwise it’s easy to do yourself.

[Gary71]

I’ve previously fixed a strong pull to one side with a new set of pads (callipers had already been refurbished)

For whatever reason one pad had worn unevenly (wedge shape) and a new set (OE) fixed it and it’s never happened again.

Maybe worth trying that (along with pushing the pistons in and out during the pad change) before spending heavily on calliper refurb.

[jevvy]

Can we not be a bit more logical here - callipers may actually be fine!

If you have time / inclination you can do some simple tests to try to narrow down the problem a bit. I'd start with:

Get the car in the air with wheels off (all four or one end at a time) then get someone to stand on the brake pedal. Try turning each hub (use a wooden lever if needed in between the wheel studs) to check that the calliper is clamping the disc correctly. You can also try wiggling the pads as any stuck calliper pistons will not force the pad against the disc so you will notice some play.

While your helper is still standing on the brake pedal inspect each of the flexi hoses for any bulges.

If you find a sticky piston remove that pad and replace it with a thinner than a pad lever and work the piston in and out a few times while someone presses the brake pedal - keep your fingers out the way though.

If you find a bulge in the flexi get it replaced.

If you find nothing then its something else and refurbed callipers wont fix it.

Yes yellow stuff are fast road / track orientated - how new are they? Have they been properly bedded in?

What is your alignment like? Squiffy corner weight / ride heights can create some interesting braking characteristics if its a long way out. Tyre pressures? Tyre age?

Lots to look at before throwing new parts at it.

Good luck.

[fetuhoe]

The tandem master cylinder on an early 911 is 'split' to the front and rear not side to side so it will not produce any uneven braking from side to side so it is most likely the caliper.

Bad hoses tend to cause brakes to pull when there is an internal restriction.

If the hose is bulging so badly that it uses all of the fluid volume that the cylinder can displace you will also have a 'long' pedal which feels very different to a sticking caliper.

Uneven pad wear can often be caused by a pad sticking on the guide pin and this can also result in the brakes pulling slightly.

I wouldn't really worry about sleeving a brake caliper as the 911 calipers all use a seal groove at the leading edge of the cylinder so the seal locates against the piston and the condition of the bore is relatively unimportant.

Early Dunlop Callipers use pistons with a seal fitted to the base of the piston and in this case the seal is made to work in the bore and it is common practice to sleeve the caliper 'pod' which unbolts from the carriers.

Many of the commercial caliper rebuilders use a short cut when refurbishing early 911 calipers and remove the 'anti-knock back' pins and bushes and fit a later style of piston and I have never been enthusiastic about this idea and prefer to retain the original design features of the caliper.

EBC pads are an interesting topic in themselves and IMHO the best thing to do with them is leave them in the box.

[911hillclimber]

We all appreciate brakes are important and in the busy places where I live having poor brakes can be heart stopping.
Early 911 brakes are poor and everything needs to be as good as possible to minimise the weaknesses, so fresh discs with fresh pads.
Fresh pads on groovy discs...

Caliper seals are dirt cheap, simple to fit and in doing so you can check for corrosion that no seal will protect you from, and make a decision looking at the key parts.
With all that apart, may as well change the hoses for fresh, again, not expensive.

Bleed the whole lot through with fresh fluid and the car is sound and ready for some good pads.

And, as Chris says, the EBC pads, in my 2 x experiences, are best left on the shelf and look further, but there are many answers to that question.

Only with the whole system as good as it can be will you get the best from the pads.

If the car's geo is out the car might pull or other ways move without braking. If this is so, then that needs sorting.

Simply, the car needs to be sorted as best as possible in all departments.
IMHO, if one caliper (say) is a bit iffy, then the others will not be far behind. May as well do the lot and bleed once.

Costs:
Fr discs and ATE pads £95 (ATE pads as bad as EBC but cheaper in my experience)
Rr 106
Flex hoses, set 40
Seals, car set 30
(refurb calipers, £100 each, non S calipers)
Nipples, car set 24
Fluids 10

Thus £381 inc VAT and packing (ref: Type911 web site)

In parts that is very cheap to overhaul the whole system?
Garage time? Possibly 8 hours?

[gridgway]

Is changing the seals a simple task? I've done loads of fford ones, just wondered if there are any nuances in the Porsche ones?

I'd do the checks on the brake system suggested and unless the fault is found, I'd also get the Geo checked. It would be frustrating to chat it through the brake system only to find it's a geo or even suspension bush problem.

Graham

[911hillclimber]

I've done my A type and M rear callipers several times over 30 years and they are simple.
Remove the dust seals and the spring C rings and drown the exposed piston with WD40, you may need all the help you can get!
I blow the pistons out carefully using a foot pump and an adaptor to go into the brake line threaded port.
Slowly you can get both pistons on the edge of popping the cylinder seals and ease them out mechanically from there. I use a variety of wood blocks to get the pistons to advance out evenly under pressure. The block stops just one piston coming right out on its own, it is sandwiched between the pistons
Always wear safety glasses as when the pistons pop surplus fluid ejects all over the place, messy, and I simply hate the feel of brake fluid...esp in the eyes.

The pistons must be replaced in the right orientation to allow the anti squeal shim to sit correctly in the recess. Very easy to get this wrong and the piston will thrust out of alignment if not done right.
All this is easy to check before the calliper goes back on the car.

The seals are just simple 'square' section seals and the dust seals are a thin and readily torn if you are clumsy, be warned.
Good amounts of red brake grease helps in the reassembly as well as a light wetting with fluid.

The worst task in all this is bleeding the bloody system.....