i had a question about the use of crash bolts for added camber. i'm aware of what they do and how you use them, but i'm now curious about their integrity and longevity. i recently installed swapped 96+ hats, with reinforcement plates, on my 95 LTW and i only came up with 2.0 negative camber. not that 2.0 is necessarily bad, but i had read posts where most people wound up with something close to, or right at, 3.0 neg. camber. i run H&R sport springs also. so, first i'm curious why i only wound up with 2.0 neg., and second, i'd like to hear more about the use of crash bolts.

how much additional camber can i expect to gain with the crash bolts. does anyone have a P/N? with the bolts being thinner, has anyone had any problems with them failing? i ran an autox this past weekend (the LTW is a BSP car) and i could use just a bit more camber. i'll probably move to camber plates for next season, but for now i'd just like to be able to use shims/crash bolts. would be interested in hearing any info. thanks.

I don't think I'd worry too much about the bolts breaking (I don't think they are significantly smaller than stock), but under hard cornering loads the camber is going to want to revert back to the most positive setting that the bolt will allow. I know you can really wrench the bolt tight, but I can't help but wonder what a few trips over the rumble strips would do to your camber sittings.

OTOH, I've never used them, so for all I know they'll stay put forever:).

Instead of using crash bolts, why don't you just shim the bottom of the strut? I believe that a .072" shim under each of the bolts will give almost exactly -1 degree of camber. Watch the clearance between the strut and tire, though this method will keep the strut *very slightly* further from the strut than using crash bolts (iow, it's better:)). This is how I got the last degree of camber on my LTW, and the guys at GC said that you can go up to a .250" shim (if memory serves) before needing longer bolts. That's almost 3.5 degrees if you've got the strut/tire clearance.

Chris

Edit - Just checked my math, and a .072" shim between the bottom of the strut and the spindle will indeed give 1 more degree negative (+/- .01 degree).

I agree with Cannon. I used a flat washer between the lower mounting flange on the strut housings and the steering arms. I believe the washers were about .1" and added a little over 1 degree negative. No worries about settings changing. You do loose clearance between the top of the tire and the spring perch on the strut housing though. I'm running 18x8.5", 38mm, 235/40-18 Pirelli P7000SS with 5mm spacers in front. Pretty tight.

The crash bolts are prone to movement which changes your settings.

Jay

thanks guys. i was actually interested in using 'shims' before the crash bolts, but then i was seeing more mention of the crash bolts. based on your thoughts, and a bit more research this morning on crash bolts, i think i'm definitely back to shims for the added camber.

since you're both using them on your cars, did you have any trouble getting the lower 2 bolts to line up, once the shims/washers were in place? it would seem that it wouldn't take much for the holes, on both parts, to go out of alignment with eachother, by increasing the angle. hopefully, a small shim, the size you guys referenced, won't make that kind of difference. what did you use for your shims, cannon? washers? where did you find/buy the correct thickness/grade?

thanks for all the info, guys. quite helpful.

It's an easy deal. Loosen the top bolt and remove the bottom bolts. Slip the washers/shims in and re-insert the bottom bolts. Not necessary to disassemble anything. I just used hardware store flat washers. I bought a bunch and then measured them to get 4 alike. If you use shims, you can probably get them in different thicknesses and I've heard of some being hardened. Be sure to reset your toe afterwards. It'll change. Also, be careful of clearance at top.

Jay

Originally posted by LUNI2NZ
It's an easy deal. Loosen the top bolt and remove the bottom bolts. Slip the washers/shims in and re-insert the bottom bolts. Not necessary to disassemble anything. I just used hardware store flat washers. I bought a bunch and then measured them to get 4 alike. If you use shims, you can probably get them in different thicknesses and I've heard of some being hardened. Be sure to reset your toe afterwards. It'll change. Also, be careful of clearance at top.

Jay

yep, no problem with the install, just curious how you found the appropriate shim/washer. i think i'll try to find a hardened washer, if i can. where did you guys find what dimension/thickness gave what camber improvement? are you doing a measurement ratio from the pivot point and then calculating the change? with chris "checking his math" it has me thinking he might be. thanks for the clearance warning, but with 15mm spacers, i've got plenty of room up there. :D thanks again guys. i think this is going to be just what i need.

one more thing, have either of you noticed, at any time, these bolts loosening? if i remember right, torque on those bolts is like 90ft/lb., that should be enough. just curious again.

guys, what size washer would you need?

Originally posted by MPHATIC


yep, no problem with the install, just curious how you found the appropriate shim/washer. i think i'll try to find a hardened washer, if i can. where did you guys find what dimension/thickness gave what camber improvement? are you doing a measurement ratio from the pivot point and then calculating the change? with chris "checking his math" it has me thinking he might be. thanks for the clearance warning, but with 15mm spacers, i've got plenty of room up there. :D thanks again guys. i think this is going to be just what i need.

one more thing, have either of you noticed, at any time, these bolts loosening? if i remember right, torque on those bolts is like 90ft/lb., that should be enough. just curious again.

I just used washers that I had lying around my garage. I mic'd them (mine were ~.065) and installed them. I've since gone to one track event and will check the torque before I hit the track again. At some point I will probably go to hardened washers, since I honestly have no idea how hard these are.

I just measured the distance between the upper (where your crash bolt would've gone) and lower strut attach points. It was 4.125" according to my super accurate ruler (I measured my stock struts which aren't in the car). With that distance and either the opposite angle or shim thickness known, you can account for the remaining number.

To get the camber change from a given washer thickness:

Inverse Tangent of (shim thickness/4.125) = degrees of camber change

Inverse Tangent of (.072/4.125) and you get:

Inverse Tangent of (.017454545). If I push the correct buttons on my calculator I come up with .99997 degrees.

To go the other way (if you want to know the shim size for a given angle) here's the calculation:

Given: 1 degree more neg camber wanted, and 4.125 distance between strut mounts.

(Tangent of 1) x 4.125 = shim size needed
(.017455065) x 4.125 = .072" shim.

Another example: We want 1/2 degree more neg camber:
(Tan of .5) x 4.125 = Shim size
(.008726868) x 4.125 = .036" more shim

Edit - NOTE:
Now, after all that, the actual camber change will be less than what we've figured above. The reason is that as you shim the bottom strut attach points, the strut actually moves *very slightly* more vertical, and the spindle assembly will move slightly as well. This will offset some of the camber change, somewhere in the neighborhood of a 1/4 degree (iow, you will need a thicker shim than the calc above would suggest), but this amount changes depending on how much the strut is compressed or extended. I haven't measured this number at my ride height, so I just guessed 17" from the strut hat to the lower mounting bolts. Factoring this in (the calcs are the same, just use 17" or whatever that distance is instead of the 4.125), it looks like you'd need a .094" shim to really get 1 degree more camber.

Inv Tan(.094/4.125) = 1.305 degree -camber change, but the strut will move more vertically, so we have to subtract the 'strut effect'.

Inv Tan(.094/17) = .317 degree +camber change from the strut movement.

1.305-.317=.99 degrees overall change.

Remember, YMMV.

Hope this helps. I had nightmares of High School when I was trying to remember how this stuff works..

Chris

Yeah....what Cannon said. Jay

Originally posted by MPHATIC
i recently installed swapped 96+ hats, with reinforcement plates, on my 95 LTW and i only came up with 2.0 negative camber. not that 2.0 is necessarily bad, but i had read posts where most people wound up with something close to, or right at, 3.0 neg. camber.

Just an FYI Rich, I had about 2.5 degrees neg. camber when I had the hats swapped on the M3.

Jim

Guys, it's really not that hard. I'm a freaking business major (7 years ago at that) and it's been almost 10 years since my last true math class, and I managed to figure it out.

Here's the idiot's guide to figuring out camber changes (meaning: for guys like me):):

If you want 1 more degree of camber, get out your calculator.

1. Press the number 1.
2. Press the Tangent button.
3. Press the X (multiply) button.
4. Type in 4.125 (the distance between the strut attach points).
5. Hit '='
You should see something close to .072002143.
This is the shim size you'd need if the strut didn't move.

Now lets find out how much the strut movement is going to affect us (it will negate some of the 1 degree change).

1. Type in .072002143 (your answer from step 1 above).
2. Press the 'divide' button.
3. Type in 17 (or the actual number of inches between the top of the strut and the lower attach bolts - 17 was just a guess).
4. Press '='
5. Press the INV button.
6. Press the TAN button.
You should have something close to .24267025 degrees.

Now subtract .24267025 from 1 and you get a net result of .75732975 degrees of camber change for a .072" shim.

Repeat this process until you get the result you want.

It's not too hard, but you've got to do it once or twice.

Chris

I think 0.02" shims gave me .3 degress of camber, if IIRC.

Originally posted by Cannon
Now lets find out how much the strut movement is going to affect us (it will negate some of the 1 degree change).

1. Type in .072002143 (your answer from step 1 above).
2. Press the 'divide' button.
3. Type in 17 (or the actual number of inches between the top of the strut and the lower attach bolts - 17 was just a guess).
4. Press '='
5. Press the INV button.
6. Press the TAN button.
You should have something close to .24267025 degrees.

Now subtract .24267025 from 1 and you get a net result of .75732975 degrees of camber change for a .072" shim.

Repeat this process until you get the result you want.

It's not too hard, but you've got to do it once or twice.

Chris



Or set it up in a spreadsheet once and theoretically shim away!

///badmonkey

Already been done!

Chris

the shims/washers worked great. i put them in on saturday and ran an SCCA autox on sunday. from my calculations, i should be in the -2.9 degree neighborhood on both sides, now with 1/16" total toe out. i haven't taken any 'accurate' camber measurements yet (although i have checked it a few times on various surfaces, including my garage), but it should be close. i have a camber gauge, i just haven't gotten to a flat/level spot to try to take a clear reading yet. visually, it looks good. i took my pyrometer with me on sunday, but i got lazy and didn't take any readings. the heats went very quick. the car hooked up much better in the front though (i also move my front sway bar setting to 'soft') and i was able to take 1st place in BSP.

Awesome! Were you able to follow the math above?

I'm curious as to how close my calcs are to the actual results. I still haven't measured my strut length to ensure that the second calculation pans out...

Chris
Man I hate math

Originally posted by Cannon
Awesome! Were you able to follow the math above?


yes, i was a math/eng. major myself, for a while. :D i just never thought to apply it to camber adjustments. i will let you know just what i came up with, when i get some solid/reliable camber measurements.