brake prop valve adusting, any experience doing this? Options

[Trekkor]

I still have the stock proportioning valve in the car.

I think the brakes favor the fronts a little too much.

I smoke the fronts, never the rears.

I'd like to put on some junk tires and see if I can get to the point where when I apply max brake pressure, the rears lock just after the fronts. (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)

Anybody try this experiment?


KT

[brant]

The tires comment is absolutely correct.
you want to do this test with the tires/brakes/all variables just like you intend to run it.

there is a lengthy article on the stock valve.
the article says that the adjusting bolt is not long enough to cause the change that you are looking for.

It is theorized that you could remove the adjusting bolt completely and buy one that is 1/8th longer and then get more than is possible from stock.

However... before you go to that extreme. I agree with paul, you should buy a different valve. The only reason for not buying a different valve would be some rules classification.

I know the local pca chapter would not allow an aftermarket valve in the stock class, and that would be the only time I would even consider fiddling with the stock valve.

Instead, buy it from james. His price is as good or better than anyones, and he will sell you the correct bubble flare convesion fittings you are going to need and won't be able to find anywhere else. I know this because when doing the new car I bought a valve somewhere else and then months later when I realized I needed those conversion fittings I went to james anyways.

Now onto testing.
for a ROUGH estimate of setting the new valve.
take a ride in the country on a dirt road....
you can easily judge lock up that way.
even better to have a friend stand outside the car and watch for wheel lock up.

this will not take into account weight transfer.
but it will give you a rough estimate.

seat time, practice (settup) sessions, and a private track rental will get you the rest of the way.

brant