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By skinthespin : A picture and text write up showing all the work that is required to get these capliers fitted to a Mk2

First things first, the calipers are NOT a bolt on fit, the spacing of the bolts is different, also GT4 discs will not fit as they have a 100mm PCD as opposed to a 114.3mm of the MR2.

I used discs from a Lexus LS400 which have the right bolt spacing, disc height and a diameter of 313mm, which is plenty! they were also reasonably priced from www.brakesint.com.

The biggest issue is bolting the caliper to the hub. to do this I had some custom made brackets made, ths meant that the top lug on the hub machining off.

The strut mounting bolts are bolted straight into this bracket (machined from solid) as opposed to being held on with nuts. These bolts need replacing as they are 15mm as standard, which is not a recognised size, I am assuming Toyota used these bolts to stop people replacing them with lower grade bolts (they are torque'd to 255 Nm). I reamed the strut holes out to 16mm then used 16mm high tensile (12.9 grade) cap head bolts, I calculated you would need at least 10.9 grade bolts of 16mm to take this torque, 8.8 grade bolts would be marginal. The hubs also needed reaming out to 16mm in order for the new bolts to slide through.

As can be seen from the picture below the bracket is not that simple, with the strut holes not being planar with the hub face.

The lower mounting lug hole needed moving towards the centre of the axis by 6mm in order for the pad to sit correctly on the disc. I welded this hole up them machined a new hole, this can be seen below:

Please be aware that you should not cut lugs off either calliper or hub and re-weld as you do not know the correct specification of the material and therefore it isn't possible to be 100% confident that you are using the correct weld wire, plus assuming you are pulling 1G under braking then a quarter of the weight of the car may be going through each weld.

The caliper width forced me to space the wheels out 5mm, therefore I needed to use extende wheel studs, the old ones were pressed out and new one pressed in using a hydraulic ram.

The caliper mounted provisinally to the hub can be seen below:

Although the caliper has 'L' written on it it is used on the RHS of the car as it is mounted on the front of the disc on the GT4 and on the rear of the disc on the MR2, this is so the bleed nipple is on the top of the caliper and it can be bled properly. You can also see that the bracket I have made is under compression and there is virtually no chance of failure in that area.

The whole lot was offered up to the car, as you can see below the caliper is a substantial size!

The brake hose no longer reaches the caliper, at least not when you utilise the retaining bracket on the strut. I removed the retaining bracket on the strut and the anti-rotation feature on the hose banjo, when connected to the caliper the brake hose is well controlled and there is no risk of fouling on the wheel or any other component, this is all that is required for an MOT pass.

So there you have it, easy! All in cost was around '500 so not too bad for a big brake conversion, would I do it again' Probably not!

the pic below is the brakes on the car, I havent used it for a little while so the discs have gone rusty, although I assure you there brand new!

: Sat Jan 28, 2006 10:41 am [ KB ] Celica GT4 WRC 4 pot caliper conversion

[ Article updated...BenF ]

Category: Brakes
Type: Picture How-To

Article Name: Celica GT4 WRC 4 pot caliper conversion
Author: BenF
Description: By skinthespin : A picture and text write up showing all the work that is required to get these capliers fitted to a Mk2

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: Wed Apr 15, 2009 11:34 am

So Ben, thanks for the write up. I am considering something like this for my motor. What made you do this, what was the difference before and after etc...?

Thanks.

: Sat Jul 25, 2009 8:40 pm

Ben,
How much did it cost to get the brackets made up? What will it cost me if I wanted some?