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Neil-h

Impreza WRX brakes

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I'm just wondering, has anyone ever fitted the brakes from a new-age (00-07)  Impreza WRX to a GT86? The reason i ask is i've got a set sat in the loft of the garage (from a previous car) and i've seen talk previously about fitting the Brembos from the same year STi. I figure with the Godspeed 335mm disc kit, it could be a fairly cost effective way of going for a (notionally) big brake setup. So any thoughts?

https://www.godspeedbrakes.co.uk/impreza-ver-4-onwards-type-r/97-impreza-335mm-4-pot-caliper-big-brake-conversion.html

 

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A few people run them, however they are less effiecent than the stock brake's and move the brake bias substantially towards the rear (that's with the 294mm standard WRX disc's), so not ideal. However I don't know what effect the larger disc's would have. 

The important question is why do you want to change the calipers?

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Rears dont fit you need hatch sti calipers and discs.

Anything pre hatch back does not fit on the rear of gt86/brz

I have some that will be fitted next week although I already have a front bbk

20190701_175011.jpg

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1 hour ago, will300 said:

A few people run them, however they are less effiecent than the stock brake's and move the brake bias substantially towards the rear (that's with the 294mm standard WRX disc's), so not ideal. However I don't know what effect the larger disc's would have. 

The important question is why do you want to change the calipers?

Yeah I’ve never been able to get my head around the change in brake bias. Assuming the only thing that’s changed is the callipers, you’re going from a single piston sliding calliper to a 4 pot with slightly larger pads, so I’d have expected the brake bias to move forward slightly if anything.

As for why, in all honesty it’s a bit of a “because I can”. The callipers are sat in the loft at the moment and they aren’t worth a vast amount, so if they’re an improvement on the GT86 then that’s got to be a better used.

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@Neil-h - Right if you run the calipers with the standard size discs there is a 12% loss in performance (braking power) & a 3% change in brake bias to the rear over the standard calipers, this is due to a reduced size piston (WRX = 40mm vs OEM = 42.8mm).

However with the WRX calipers and godspeed 335mm disc's you are changing the total surface area the pad can work against, this actually returns the performance & brake bias to that of the OEM setup (within 1% so negligible difference). 

In that case it wouldn't actually be a bad swap. My only concern would be sourcing replacement brake pads as the Godspeed kit uses a modified Aston Martin pad.

(Hope that helps) 

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Yeah it's the bit about piston area that i don't follow. By my maths the WRX 4 pots give you significantly more piston area, even if i'm being generous and assuming the OEM calipers act as a 2 pot (rather than a sliding single).

1 piston WRX = Pi x 20^2 = 1256.6mm^2      So 4 pistons = 4 x 1256.6 = 5026.5mm^2

GT86 OEM = Pi x 21.4 = 1438.7mm^2    So 2 pistons = 2 x 1438.7 = 2877.4mm^2

 

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Iirc the stock front calipers are a 2pot sliding so should be calculated as 4pot. There is a wealth of information on this on the American forums. I tried to work it out but gave myself a headache so decided to stick with OEM and will wait till I can find / get a performance pack setup

Sent from my LYA-L29 using Tapatalk

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I'm not sure if the godspeed kit will also allow you to swap the bleeder over from trailing caliper to leading caliper on the 86. For aesthetics I'd say why not. Alot of the american guys run cadillac brembos because they want big brakes for looks. Depends on the uses of your car. 

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Don’t think you actually need to. Pretty sure the pistons are all the same diameter, so I can’t see any reason why you shouldn’t be able to just swap them across the axle.

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26 minutes ago, Neil-h said:

Don’t think you actually need to. Pretty sure the pistons are all the same diameter, so I can’t see any reason why you shouldn’t be able to just swap them across the axle.

Actually your right they don't need swapping, it's the sti brembos that do. 

If you use the bigger discs then it will balance the brakes correctly, but how easy would it be to source the right pads? I've seen this a few times pop up on USA forums: https://www.fastwrx.com/products/subaru-four-pot-two-pot-full-brake-upgrade-frs-brz

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