metric control arm mounts

I read a few articles on removing and lowering the upper control arm mounts to optimise the front end geometry.  Anyone ever try it?  How much is too much?  Everything I ever read on set ups has left out the actual numbers.  I realise every car is a little different and every set up is different but my car and set up is not the only one of its kind out of all the millions of metric racers out there.  Give me a starting point please!!!  3/8 oval 3300 lb car  

better check your rules to see if you can do this first, most street stock classes wont let you do this  

next season our class is getting a make over. Its not quite going to be an all out sportsman but definatly not a street stock any more.  This was one of the things i wanted to play around with over the winter to see if it helps the car turn.  

We put ours flat by just lowering front hole to same as rear . Best thing we ever did as a big pay back in lap times  

I feel your pain on the metric upper control arm mount locations. I have been trying to figure this one out for myself. Once I read in circle track that they don't give out specific set-ups because every car/condition is different. Well that's bull in my opinion. I have read many times over that the factory geometry is junk, but cannot get help with the mount placement to figure it out. If it is so bad there has to be a minimum amount that will be better than factory for everyone regardless of all other factors. Sure an asphalt can might need more or less than a dirt car, but give us a clue as to what would help and what would be way too much. Just give me a safe middle of the road location and a ride height for a new baseline and I could work it from there.

   If you want to rune a car beyond belief just go hacking on the mount with out a plan. You need to know what you are doing before you cut that mount off or you will have much bigger issues that extreme camber changes to worry about. Things like unwanted bump steer and anti-dive isses and that is assuming you get the camber and caster close enough that they can be aligned back in. I want to know where it is suppose to go before hand.

   Even when I get the figures I think I need I still plan on making myself a simple jig to be able to reposition the mount back to factory location if all else fails. This will also give me a point of reference for the new mount location after the old one has been cut off.  

As far as lowering the frount a-arm mount hole to match the height of the rear mount hole I have heard that this use to work very well on the right front of the mid 70's Camaro. I had not heard of anyone doing this on a metric chassis (before now). Lowering just one side of the control arm effects more than just chamber gain. It will also change caster as the suspension travels.

I cannot say if this is a good or bad thing for handling of a metric chassis, but this should be looked at as two changes and not just as one. It may very well be the degree change in anti-dive is what helped and not the small change in control arm mount height. Also lowering only one side of the mount will net you only 1/2 the distance lowered. So say you lowered front 1/2 inch then it would have the chamber change effect as if you had done both mounts holes just 1/4 inch, but with the side effect of changing caster as the suspension travels. The caster change will change the feel at the steering wheel. The difference in anti dive will also change the loading under braking effecting corner entry.

Here is a some info on anti dive. It talks a little about the brake loading effects of anti dive and/or lack of.

http://www.circletrack.com/techarticles/antidive_suspension_tech_parameters/index.html