Spacing Crossmembers Effect on Steering

[PRIMRK]

Hey All,

For my engine conversion i may need to space down the cross member no more than an inch but just want to know if there is anything i will have to watch for when doing this?

[Sam-Q]

It's the oppersite of putting roll center adjusters in. What thickness adjusters and wheel diameter are you running now?

[Gunner]

can I ask why you feel the need to space it down?

[PRIMRK]

Im not sure that i will have to but it would make it sit a bit lower allowing ITB's or twin plenum depending what i fancy doing later on.

Ill have a look at the roll centers tomoz but the wheels are 15"

[Sam-Q]

if your running 15" then you can run something like 50 or 60mm roll center adjusters. I want to get some thicker ones myself.

Also if your running an OEM style outer tie rod ends then Dave from AJPS has some that don't have the bulky dust cover and grease nipple but instead a more slim line housing alowing for more room and hence a thicker spacer.

[fantapants]

dry sump it over dropping the crossmemebr....

if you have a "problem" allways try and find a solution that imrpoves other aspects of the car, rather than creating another set of problems that need adressing.

i realise cost to performance doesnt match here, but it provides benefits over and above what are looking for, and doesnt introduce aggressive geometry issues.

[PRIMRK]

but there is the cost that it introduces....

[fantapants]

hence the last line of my comment.... i know it costs a bomb, BUT its moving forward not sideways as lowering the crossmember and then fixing all the associated problems would be

[KurtHS]

Think the engine as two steps forward and the geometry changes one step back, you may as well have just gone one (cheaper) step forward in the overall scheme of things.

[Gunner]

Personally, I think you are better of modifying the bonnet. Yeah it may not be "correct" in alot of peoples eyes. But it is the one thing that will not hamper performance, of any component.

[PRIMRK]

if i was to mod the bonnet id let some of my american muscle roots show and stick a shaker scoop on it...

By the way I've read into this if i use larger roll center adjuster if i have to space it that will bring every thing back into line.

True or False?

[Sam-Q]

now that I think about it your castor rods will be on slightly more of an angle, I seriously doubt this would have an effect though

[kaibeecee]

what motor are you putting in?

and moreso, what are you using to space it with?

spacing them should really be a last resort thing. depending on things, you might be able to get away with cutting a rib out of the bonnet and spacing the bonnet up a bit.

[fantapants]

1uz i believe?

also think about the relationship of your front to rear roll centres. as while you may bring the front back to a standard platform, or near, that platform is now "out" compared to the rear pickup and pivot points

[Skylar]

Here's some rough numbers.

Lower inner pivot at 140mm and lower outer at 140mm(~507mm guard to ground on AE71), the roll centre was at +24mm. Change lower inner to 100 and changes to -84mm. That's with 40mm RCA and XT130 LCA.

I had another spreadsheet which showed the effect of moving roll centres on total lateral load transfer distribution but I can't find that one. That'll tell you more in terms of what the car will behave like after spacing crossmember down. In theory, all you'll have to do is increase the front springs rate to increase to bring roll rate back up to what it was before with the downside being increased ride rate. Then you gots to deal with the steering stuffs, which is not a problem for you since you're doing cut steering arms. or did you buy T3?

[PRIMRK]

i got t3