Brakes seizing on the road - Resolved

[Jason_323i]

Got a servo I wipped of my track car herer if you need, been dry stored for a year, but 1st check is the 1-way valve
Jason

[rob0r]

Thanks Jason.

As an absolute curve ball, I have thought perhaps down the line using an E30 pedalbox and making use of the side bar linkage, storing the servo and MC where the glove box used to be. I've seen some E30 M60 V8s fitted up like this, certainly an interesting solution.
(Apparently this is using a skyline servo)

[e21-Mark]

Just how heavy would the brakes be if we bin the servo all together or is that just not viable?

[Jason_323i]

I Know some one working on it, ditch the servo and move the pivot point on the brake pedal to 6:1 and mount the master direct to the back of the pedal box

Jason

[nas80]

you can buy pedal boxes that dont need a booster dude - however you might want something with a ratio of like 9:1 - 6:1 might be struggle if your right leg isnt super human like Jasons lol

[rob0r]

I haven't heard great things about brake bias boxes in regards to durability and build quality, at least at the cheap end of the market . I have no idea at this stage if an E30 pedal box would be anywhere close to fitting in an E21, if it did it wouldn't cost much, I know the pedal boxes are good, and the accelerator pedal would be the same etc etc. I'd also say keeping a servo would be no bad thing, and how cool would it look under the dash!

All pie in the sky at the moment, I'll fix the E21 system... for now.

[nas80]

ive been looking at alternatives too - the stock system is good but tbh takes up far too much room in the engine bay. if you rid of that stuff - plenty of room for a turbo!

[Jason_323i]

I have pedal box in the e30 m3 and it is going back to servo and that is after spending a grand to to replace with a new pedal box and setup and fabrication to replace the orgian sh*t home made pedal box.

Also have a pedal box in the e21, DrJim has on in his e21. You have to balance leg input, master cylinder size, calpiper size, pedal travel, pedal feel. A lot of variables to get it right.

On track they are great because you hit set braking points.If you need to do an emergancy stop on track your are already probably going to run out of track or hit something anyway

On the road, driving my e30 on a wet cobled road in rush hour with a pedal box is scary as you do not have the same low speed braking power as a servo when other drivers cut you up.

On an e21 the servo is giving about 50% additionial force so by using the stock MC and a 6:1 pedal ratio you are close to normal braking, on any car with PAS retro fitting the e28/34 hydralic system would be my choice

Jason

[nas80]

I read this guide a while back from stop tech and thats as far as I wanted to go lol - as you say theres a lot you need to think about / work out never mind sticking all that lot in there!

http://www.stoptech.com/tech_info/Pedal ... -Guide.pdf

[drjim]

The other issue is that you can't get the pedals in the right place with a pedal box - unless you custom make it, and then the steering column etc is in the way as well, or you have to move the bulkhead. If I was doing it all again I'd try using the standard M/C with a modified pedal.

When I first tried the pedal box the brakes were rock solid, worked very well but no feel to the pedal. CHanging the fronts to 4 pot Wilwood made a huge difference in feel and usability - still not nice on the road though.

I reckon it'd be worth trying Wilwoods on the front with a standard M/C mounted directly on the pedal box, maybe change the rears a bit as well so that the hydraulic side of things is more in your favour. If it was still too heavy change the pedal pivot point a bit or get a different M/C.

[rob0r]

Hopefully I will have some progress tonight...

I still think I'm going to check out the E30 pedal box and servo under the dash at some point!

[rob0r]

Success! Last night I replaced the MC, servo, part of the servo piping and lubricated and worked the linkages. After bolting everything up I realised I had bolted up the original servo, whoops... I bled the brakes and took it for a drive, after 20miles of testing/thrashing the cars around local B-roads I'm satisfied the problem has gone. The two times the car locked up the first time was after 2 miles, the 2nd time after 6 miles, and the car was coasting with no signs of the brakes binding after 20...

[e21-Mark]

Good news!