RF92 FF Question: Anti Dive

[Craig Henry]

RF90 - 92 owners,

Front lower rear control arm attachment to frame question: Utilize the upper or lower frame attachment point? I assume anti dive is not needed thus the lower attachment point.

Took the car apart long ago and didn't include the position in my notes or teardown images (getting older and dumber.)

Thanks in advance for the help.

Craig

[bassracer]

Craig
I recently had a thread containing a similar question for my RF95. I have been using anti-dive (front lower, rear upper) but after calculating roll centers with the radial tires questioned removing it (front upper, rear upper). Valuable feedback I received was that anti-dive can create understeer.
https://www.apexspeed.com/forums/sho...ters-axis-RF95

[Craig Henry]

Brandon,

Thanks for the input. I did read your thread (and all the others I could find) but they were all discussing FC chassis and had a few conflicting recommendations. Just trying to get a warmer feeling with respect to a FF. Like you, I didn't know the rear FC suspension is slightly different (explains why the used FC spare suspension parts I purchased were all slightly different.) Also, I'm not sure about the pre 94' FC cars but my FF bellhousing doesn't have any rear lower front control arm anti squat adjustment.

I've read/researched this a bit and I'm 99% sure I have the answer, but I'd like to confirm it with some FF owners.

Thanks again,

Craig

[billtebbutt]

I *think* we always use the top mounts, but will have to check
bt

[billtebbutt]

I *think* we always use the top mounts, but will have to check
bt

Yep - always the top mounts

bt

[Rick Kirchner]

so when I took out the anti-dive, I went front lower, rear lower.. Folks here are suggesting front upper, rear upper. What's the reasoning behind that?

[billtebbutt]

so when I took out the anti-dive, I went front lower, rear lower.. Folks here are suggesting front upper, rear upper. What's the reasoning behind that?

Rick, the original post was only wrt the rear suspension - just want to be clear that my comment only pertained to the rear. On my 90, there is only one mount on the front - IIRC there was only one year where there were two front mounts (92 I think).

best
bt

[DaveW]

We have found that front anti-dive and rear anti-squat both lead to a reduction in grip. My Citation has neither.

[Rick Kirchner]

sure you don't have those reversed? my 94 has front upper/lower, and rear upper/lower (two spots on the bell machined for a shear plate).

In the enclosed collage:

upper two are the two different locations for the forward leg of the lower rear A-arm
middle two are of the front mount of the lower front a-arm, the spacer busing is above the arm in the second pic
bottom two are the rear mounting points of the trailing arm of the lower front A-arm, spacer shown in the upper position in the second pic.

So my lower arm is mounted low. I suppose the difference in using the upper mount would be in lengthening the pushrod to raise the car an additional 1/2" to achieve the same ride ht, and raise the roll center.

[Craig Henry]

Bill,

Thank you for checking. I was talking about the front, and you did clear up some questions I had. After spending too much time reviewing RF90 - RF92 FF images I noticed some only had one position option in the front. It seems to be located where the upper location is on an upper/lower location option car. My car is a RF92 thus it has the front upper/lower option.

I just re-checked, and my bellhousing's rear lower front control arm attachment point casting was designed and machined for only one clevis position. Interesting your RF90 has an upper/lower option like the FC cars.

My car is a bit of an oddball. Prince converted the front mono shock to a top position dual shock before I purchased it and I add a rear EFM bell crank system to improve the motion ratio.

Thanks all for the help.

Craig

[Rick Kirchner]

Bill,

I add a rear EFM bell crank system to improve the motion ratio.

Thanks all for the help.

Craig

what did you do to make the bodywork fit?

i did a bunch of measurements with that set up . it looked like i'd have to make some big changes to the rear cover

[Craig Henry]

Rick,

Image (poor) of an RF90 FF front lower control arm rear frame single attachment point.

Craig

[Craig Henry]

Rick,

I purchased it off a RF90 FF (one season of autocross use.) He used the stock engine/tail cover without any modifications thus I'm not anticipating any clearance issues (my car is still apart.) Image is from when it was installed on his car. I utilize the short adjustable blade rear ARB system versus the stock chopsticks.

Craig

[billtebbutt]

Bill,

Thank you for checking. I was talking about the front, and you did clear up some questions I had. After spending too much time reviewing RF90 - RF92 FF images I noticed some only had one position option in the front. It seems to be located where the upper location is on an upper/lower location option car. My car is a RF92 thus it has the front upper/lower option.

I just re-checked, and my bellhousing's rear lower front control arm attachment point casting was designed and machined for only one clevis position. Interesting your RF90 has an upper/lower option like the FC cars.

My car is a bit of an oddball. Prince converted the front mono shock to a top position dual shock before I purchased it and I add a rear EFM bell crank system to improve the motion ratio.

Thanks all for the help.

Craig

Me bad - I misread the first post!!!! My apologies folks
bt

[Rick Kirchner]

Rick, He used the stock engine/tail cover without any modifications

Interesting. There must be some significant differences in the early tails vs the later. Here's my 94 (wide body) tail sitting on top of the EFM pieces.

Somewhere I had an extensive pile of photos downloaded from the RaceCars.com archive before it turned into the POS that it is now, that showed all the various VD configurations, but they seem to be gone now....