SAI Mod on MkII - Help!

[bwwooster]

So... I'm installing the Borden/Whitby SAI modification on my MkII and the UCA mounting points on my chassis have two sets of holes. The SAI kit's UCA mounting brackets are notched to clear the coilover lugs like they're supposed to fit on the inner set of mounting holes, which would require cutting away a 1.5" strip of material from the outer edge. Is this correct, or do I just bolt the brackets onto the outer sets of holes? I have standard (not pin-drive) length control arms.
http://i157.photobucket.com/albums/t47/johntennyson/IMG_0244.jpg (http://s157.photobucket.com/user/johntennyson/media/IMG_0244.jpg.html)

http://i157.photobucket.com/albums/t47/johntennyson/IMG_0243.jpg (http://s157.photobucket.com/user/johntennyson/media/IMG_0243.jpg.html)

The dark strip is where the UCA had been mounted.

Thanks!

John T.

[rich grsc]

You bolt it in the same set of holes as the upper control arms used.

[skullandbones]

Hi John T,

If you don't mind, could you describe your setup and why the SAI mod? I'm trying to make sense of this front suspension modification and it seems there is a lot of variations to the process. I saw one where they are actually putting the UCA on the same bracket but on the bottom instead of the top without the SAI angle bracket. So that's why I was wondering what spindle and other components you were using. Not trying to hijack just curious about the reasons for people making such changes in this critical aspect of the build. Thank you, WEK.

[bwwooster]

Yep, there are a lot of other threads about it and Dave Borden explains it best. As I understand it, and in a nutshell, the front wheels can be self-centering by either a) having the upper steering pivot point (balljoint) closer to the car's centerline than the bottom pivot point (Steering Axis Inclination) or b) having the top pivot point behind a point directly above the bottom pivot (caster) or a bit of both. FFR used more axis inclination to move the upper control arm inward to allow use of 15" wheels like the originals did.

The SAI kit moves the top pivot out and you increase the caster to improve stability. This new steering geometry is more conventional, like just about everything else you've driven. Moving the UCA out, away from the centerline apparently lowers the roll center to a point where it better matches the roll center of the rear suspension, giving a more equal 'pendulum' effect to both front and rear suspension action in a corner.

The effects everyone seems to notice are greater stability and less sensitive steering around center, especially at freeway speeds, and lighter steering effort.

Dave Borden, if you're reading this, please fix anything I've got wrong!

[skullandbones]

I was just reading several of the threads you suggested. I did a general search on line and it took me to 3 very good ffcar.com discussions which Dave Borden was involved in. I am trying to see how specific components adjust for the various changes in the steering geometry. That's why I asked for the components you were using. I realize that the SAI mod was designed to improve the geometry for racing and has the spin off benefits for the street driver as well. Thank you, WEK.

[bwwooster]

I'm using the 1994 SN95 uprights (spindles) and Fox lower control arms. I've also got 5" threaded tubes from Speedway to replace the front tubes on the kit UCAs to increase the caster.

HTH

[skullandbones]

bwwooster,

You got the better of the SN95 spindles. I was not educated on the difference between the 94-95 and the later models so I got 2000 ones (may cause more bump steer). If you get a chance, check out that Breeze setup on utube that utilizes the same spindles you have and the Breeze rack adaptors which lower the rack about .35 inches. I found it by typing: Breeze utube for front suspension setup. Thanks for sharing. WEK.