S3 Callipers

[ScottD3]

I got a set of S3 brakes to convert my brakes from 288mm to 312mm.

Will the S3 callipers fit?

 

[olds_kool]

i asked the same question and the answer is yes but aragorn said they use a smaller piston than the a4 ones
so as long as you have ate calipers in good working order already there's no point it would just be more work bleeding brakes

i am curious as to what difference a couple of mm in piston size makes, never heard of s3 owners swapping to a4 calipers

 

[Bradderz_1988]

I dont think they do scott as they have straight screw in fitting on the calliper where as ours iirc have a small brake pipe and a union fitting wear the pad wear indicator connector is if you got some custom brakelines then id say they probably may fit but i just used the existing caliper as tgere almost identical.

 

[aragorn]

Yeh, the stock calipers have 57mm pistons, whereas the S3/TT ones have 54mm, so you'd actually reduce your braking effort.

As bradders says the brake pipe fittings etc are a bit different.

Just keep the stock A4 caliper and use the S3 carrier.

You can then stick the A4 carrier on with the S3 calipers and put them back on ebay as standard 288mm A3/golf brakes

 

[ScottD3]

i asked the same question and the answer is yes but aragorn said they use a smaller piston than the a4 ones
so as long as you have ate calipers in good working order already there's no point it would just be more work bleeding brakes

i am curious as to what difference a couple of mm in piston size makes, never heard of s3 owners swapping to a4 calipers

I'm not worried about bleeding. I'm replacing the fluid.

The size difference on the pistons will effect peddle travel but can't see how it will effect the braking effects.

I'll check these callipers and mine and I'll stick with the best set or even rebuild a set, I got enough time.

Which pads do you I order?
I don't want to order normal 288mm pads cause they won't use the full disc surface, do I order S3 pads?

 

[Bradderz_1988]

The 288mm pads use the same disc surface as the 312mm ones, heres a pic of a caliper and you can see what i mean by the fitting on our caliper.

 

[aragorn]

Simple physics.

Force = pressure x area.

Pressure is related to the force your leg would apply to the pedal.

Area is the size of the piston on the caliper.

given area = pi x r^2, going from 54mm to 57mm is about 10% reduction in braking force for a given pedal pressure.

going from 288 to 312mm disks only gains you about 8%.

You dont really want to be using the S3 calipers.

 

[ScottD3]

The 288mm pads use the same disc surface as the 312mm ones

I'm only questioning it cause when I looked at these S3 brakes the pads covered the whole surface of the disc.
When ever I've seen any one do a 288-312mm conversion there pads never use all the surface of the disc.

I'll try and find some pics.

 

[ScottD3]

Simple physics.

Force = pressure x area.

Pressure is related to the force your leg would apply to the pedal.

Area is the size of the piston on the caliper.

given area = pi x r^2, going from 54mm to 57mm is about 10% reduction in braking force for a given pedal pressure.

going from 288 to 312mm disks only gains you about 8%.

You dont really want to be using the S3 calipers.

Got it.
I wont.

 

[aragorn]

Scott: the pad surface area is the same, it just sits further out from the centre with a bigger ventilation gap.

 

[Broken Byzan]

You probably have 280's on there scott dont you?

 

[ScottD3]

Scott: the pad surface area is the same, it just sits further out from the centre with a bigger ventilation gap.

From Jason.S build thread.

Unless I'm missing something, I don't think thats a 288mm pad.

 

[ScottD3]

You probably have 280's on there scott dont you?

288mm, I checked it a couple of times.

 

[aragorn]

110 TDi's got 288's.

It is a 288 pad.

On the 288 disks theres not as large a gap between the central hub, and the pad surface:

 

[ScottD3]

110 TDi's got 288's.

It is a 288 pad.

On the 288 disks theres not as large a gap between the central hub, and the pad surface:

Ahh ok.
That makes sense.
Ta.