Firstfives.org

While I'm saving up to do a rear disc conversion, I need to get some more work out of the drum brakes on the back of the 520i. Since I've upgraded the fronts, the rears hardly do anything.

I was going to buy an adjustable brake pressure regulator to allow some more pressure through, but a mechanic (actually the CAMS inspector scruitineering my roll cage) told Dad that it wouldn't work with a split brake system. This doesn't make sense to me as it is just changing the maximum amount of pressure that goes through.

I know most of you guys have rear discs, but has anyone got some expereince to help me out?

Cheers

is there currently a pressure regulator in the system? If not, adding one won't increase rear pressure (regulator can't increase line pressure, it can only limit high pressure). If there is one present, and you replace it with one that is adjustable to a higher pressure, it could work.

There is one at the moment, which leads me to think the guy doesn't know his stuff. I was jsut wondering if anyone had installed an adjustable valve. Might ask the guys at e21.net. Their 4 cyl 3 series would have had drums.

Cheers

I'd be curious to see how much limitation the factory proportioning valve does. I'd be interested in grabbing one and doing some tests. I know wilwood and tilton both make nice simple, reasonably priced proportioning valves. You could feasibly replace the oe valve (which also serves as a Y in the rear brake line) with straight junction block and then put the wilwood valve somewhere more accessible if it is something that you would want to adjust periodically for various driving styles.

My 2 cents - seems like a lot of extra work. My only concern would be that the factory drum proportioning valve is not the same valving as the rear drum version. But a realoem.com part numbering lookup would resolve that for you.

Nice 520!!

Jason

We've got an rpm adjustable valve which is just a re-badges Tilton.

The valve is actually right below the booster and is an in-line connection. It'll be interesting to see the difference. Ours has a maximum of 57% presssure reduction. I hope it's enough.

Cheers