23 replies to this topic

[pikey7]

Is there some way I can modify or replace the FAM7821 to allow me to have an adjustable brake bias?

I know I can fit an extra prop valve inline in the rear system (away from the drivers seat), but if I can do it one unit.....

[Jammy]

I've heard you can modify the FAM valve to make it adjustable as well, although not sure on the method?

[Dan]

The FAM7821 valve is tricky. No-one actually knows exactly what it does. I was intending to fully test one but I never got round to it. I think it's actually a delay valve rather than a brake bias valve, it doesn't appear to do any biasing in the normal sense in that is messes up all the calculations that you do when working out line pressures based on cylinder sizes.

I've never heard of a way to alter it but there may be a way that some people use.

[miniboo]

is the valve you are talking about the T piece on the rear subframe?

[Dan]

No, the large two circuit brake valve on the bulkhead. The tee-piece is just a tee-piece usually.

[biggav]

i had one that didn't work once.... was fine as long as you didn't use the last 1/2" of brake travel or it would lock the rear end up.. never replaced it because it was actually good fun when you got used to it. this is why most junctions in witney still have a black figure 11 painted on them..

[pikey7]

it just comes apart with that big nut on the end right? I have a spare I may have a play with to see what it does. Its only £30 of ebay junk anyway.....

I had a feeling it wouldn't be as simple as just tapping a hole and adding a bolt though. Nothing is ever that easy.....

[Dan]

I think all the important bits are under the crimped on cap at the other end. Since there's no re-build kit for these though I've never had reason to open one up so far so who knows what's inside it?

[pikey7]

I guess we'll find out tomorrow then! I'll take the camera......

[miniboo]

thank god it is only a t piece because i gave a spare one i had to a mate to use on his kit car.

[Wil_h]

Actually the earlier single line systems had a 'biasing' T-piece on the rear subframe, like this:

http://www.minispare....aspx?pid=36159

It's these that can be modified to be adjustable.

[Jammy]

Ahh, I see, cheers Wil, don't suppose you know how to modify them do ya?

Also have a spare FAM7821....

Edit: Thought I'd have a quick look on Claver's Corner on MiniSpares. Found this.

[Dan]

You have to make sure you're modifying the right one if you are working on the rear bias valve. The very early Cooper had a brake intensifier at the rear rather than a biasing valve which had some form of additional cylinder inside it. Modifying that can give nasty results.

But in the vast majority of Mini's it's just a tee-piece.

Edited by Dan, 12 April 2006 - 10:35 AM.

[pikey7]

Sorry guys, no pics today (I had a little problem with the turbo on the Porsche.... As in blew it up! ) Will get on it tomorrow (plus it gives this thread a little bump if anyone else has a bright idea on how to do it!)

[Jammy]

This was posted on 16VMC in a similar thread.