Ae Pedal Box

[Boosted]

In my continuing bid to circumvent the AE series diagonal braking and aid in the installation of a Hydraulic handbrake, I've been investigating twin master cylinder pedal boxes with a balance bar.

The fabrication shouldn't be a problem and it looks like you can get pre-fabbed balance bars off e-bay for reasonable dollars, so it's all down to pedal lengths, pivot points and actual master cylinder sizes.

The standard bore on an AE92 m/cyl is 15/16" (23.8mm) and consulting the TRD bible on AE's, they claim to be using a 7/8" (22.2mm) for the front and a 13/16" (20.6mm) for the rear. And this is some of what isn't making sense to me at the moment. The Grp A Corolla's were using some pretty big 4 piston stuff up front and some nice 2 pots at the rear, but they're using a smaller dia. cylinder than stock and then I presume they're moving the brake pushrod point closer to the pedal pivot to compensate for the loss of the booster, which says to me they must have had alot of brake pedal travel, which doesn't sound good.

My rolla's got the larger front disc brakes (off the GTI ?) and is disc at the rear, so looking for advice from people who have gone this way already, mostly about what size cylinders and pedal lengths you've used and what the pedal travel, feel is like.

[Boosted]

Just updating the thread with where I'm at for people seeking in the future. Yet to plumb the system in and give it a trial.

After talking to some mates who have built/installed adjustable pedal boxes and doing a bit of research, a 5/8" Front M/Cyl and 3/4" Rear M/Cyl were chosen. I would have liked a 0.7" rear but as I was buying some pretty cheap m/cyl's with integrated reservoir, I didn't have that option. Pedal ratio is 6:1, measured from the centre of the pedal. Standard is under 5:1, so needed to mod the pedal and when I looked at modding the standard pedal box to clear the balance bar, decided it was all too hard and made a new pedal box as well. Think I might have made some measurement errors when I built the box and modded the pedal though as the brake pedal now sits lower than the clutch and the original intention was to have them at the same level. Having said that, can't remember how they were to begin with.

Chose a Rally Design balance bar with cable adjuster. I wanted something a bit nicer, like Tilton or AP, but the price difference is just staggering. In Aus, the Tilton balance bar is $200 on it's own with the adjuster adding another $120 or so. Could have got them out of the states cheaper and that was a real consideration until the americans I chose wanted to slug me $90 to ship the damn thing when it's only a small package. Went weeks without getting answers from anyone I was emailing (including Rally Design) and in the end bit the bullet and just ordered one. With adjuster from Rally Design ended up being ~$80 to my door, so can't complain about the price. Quality is a little, meh, but adequate for the role and more than enough for the price. The billet adjuster is nowhere near as nice as the Tilton/AP options, and the adjuster has a huge gap between the nut and the back of the adjuster where it's meant to mount thru the panel. Will obviously need something to thicken things up before mounting in the plastic trim. Look's like it's designed to screw into 16 plate :laff:

Haven't bothered plumbing in a pressure adjusting device to the rear as a friend had said he'd had trouble getting enough rear bias with the setup I'm running (though that was in a RWD escort).

There are some relatively cheap options around for a complete pedal box that looks like it could be bolted to the end of the booster and retain standard pedal and all of that. The strut brace and engine (supercharged) in my beast made that a no go unfortunately. Otherwise they can be had from Comp Brake for ~$250 incl Cylinders.

Because I didn't want to remove the dash and spend a lot of time getting the pedal box right, it has turned out a bit ghetto looking, though I'm sure it will be fine in operation.

I also had the self imposed restriction of not wanting to weld plates into the firewall or modify the vehicle substantially to fit it all in (if I trash the shell, everything needs to bolt off), so I did end up with the m/cyl's a little further from the balance bar than I would have liked. The longest pushrod you can buy off the shelf for a Girling style m/cyl is 4-3/4", whereas with my setup I really need 5-1/4". Works better for angularity into the cylinders, but also means I've gotta knock up a custom slightly heavier pushrod to cope with it all.

Btw; Rally Design trunnions are threaded 5/16" UNF (one of the questions I didn't get answered till they rocked up) with most pushrods at my local brake shop being M8 thread (and they were still too short anyway).

 

Anyway, will post back when I've got it all rolling and let you know the final outcome. I've since learned from another guy that he just re-plumbed the AE system to the Hydraulic handbrake with a standard front rear circuit (rather than the AE's diagonal setup) and claims the car stops fine (Gravel rally car though). I still feel the adjustable pedal box is worth the effort for the purist though.

 

(The car is to be used for closed course competitions and is not road legal)