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Old 04-03-2023, 05:45 AM   #4327
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Turn the steering wheel to full stop, reach around the tire and attach a zip tie on the strut shaft tightly, snip excess, push the zip tie down to the strut body, lift the front of the vehicle, remove tire, measure distance between strut body and zip tie (droop), measure length of strut shaft (stroke).
Back rear up on ramps, from under the vehicle attach zip tie to strut shaft, slowly drive off ramp, then lift and repeat front procedure to find existing droop. Alternate method: lift rear, remove wheel, attach zip tie, mount wheel, lower vehicle, drive around block, reach around tire and push zip tie down, lift vehicle, remove wheel and measure zip tie gap.
Back of envelope math with known strut stroke example: spring rate of 450 in/lbs compressed by (sprung weight example) 600 lbs = 1.33 inch/33.87mm, 1/3thrd of (stroke example) 115mm = 38.33mm, add 4.46mm of unbound helper spring to reach minimum droop. The adjustment can be accomplished with the struts on the vehicle, and the math can be done on the kitchen table if strut stroke is known (ask manufacturer if spec not published).
There is greater variability in measuring a distance of 13+ inches/330mm between two arcs than between two flat surfaces (ground/pinch weld) on a vertical plane with a span of around 140mm. Then there is wheel ratio disparity between front and rear suspension to account for in the fender measurement method. The pinch weld is a good representation of underbody rake (positive, negative, or neutral) and is almost in line with the struts.
Keep in mind the usable stroke for the selected spring during this study.
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Old 04-03-2023, 06:17 AM   #4328
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I'm considering getting rear lower arms with ball jointed inner joints, partly because my current -2.5 is a little more negative than I want but also because I feel that ball jointed inners won't lose some camber due to bush deflection while cornering, so the ideal static rear negative camber will be less with ball joints rather than rubber bushes.

My question is does replacing the lower arms with ball jointed ones but leaving the stock toe arms cause undesirable toe change while cornering? The STI link set including both lower arms and toe arms got me thinking about potentially undesirable toe change while cornering if the toe arm has bush deflection but the lower arm doesn't.
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Old 04-03-2023, 06:52 PM   #4329
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My question is does replacing the lower arms with ball jointed ones but leaving the stock toe arms cause undesirable toe change while cornering?
The opposite question has occurred to me. I have Cusco upper control arms and SPL toe links, but the LCAs are still stock. I haven't spent time staring at the rear suspension to get an idea of how bushings would react to cornering forces.

-Mike
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Old 04-06-2023, 05:18 AM   #4330
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My question is about toe and roll center adjustment

At what amount of ride height change should one consider getting RCA kit up front ?

Same question for adjustable toe links in the back... Target rear toe would be 0

last question is there anything on the market to adjust rear roll centers ?

Thanks
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Old 04-07-2023, 09:56 AM   #4331
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My question is about toe and roll center adjustment

At what amount of ride height change should one consider getting RCA kit up front ?

Same question for adjustable toe links in the back... Target rear toe would be 0

last question is there anything on the market to adjust rear roll centers ?

Thanks
Past 30mm of lowering (arc fender to hub center, stock is 375mm), which is around 140mm pinch weld height on stock wheels.

To adjust rear roll center I suggest you to play with upper control arm offset bushing and get the camber back to spec using the lower arm. Otherwise you have to shim the entire subframe, SPL makes a kit for this purpose. .

As for the 0 toe you should not have any problem till 40mm of lowering.
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Old 04-07-2023, 10:20 AM   #4332
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Past 30mm of lowering (arc fender to hub center, stock is 375mm), which is around 140mm pinch weld height on stock wheels.

To adjust rear roll center I suggest you to play with upper control arm offset bushing and get the camber back to spec using the lower arm. Otherwise you have to shim the entire subframe, SPL makes a kit for this purpose. .

As for the 0 toe you should not have any problem till 40mm of lowering.
Thanks for the info. I will definitely get adjustable rear LCA just wasn't sure if I needed the toe links as well. Honestly based off the amount of surface rust on everything I might just replace everything I can HAHA.

I will be going with the RCE SS2 which I think recommend a minimum drop of at least 25mm but I might be wrong. I want to keep my ride height as high as possible without effecting performance
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Old 04-07-2023, 10:34 AM   #4333
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Thanks for the info. I will definitely get adjustable rear LCA just wasn't sure if I needed the toe links as well. Honestly based off the amount of surface rust on everything I might just replace everything I can HAHA.

I will be going with the RCE SS2 which I think recommend a minimum drop of at least 25mm but I might be wrong. I want to keep my ride height as high as possible without effecting performance
In addition to what marco said...replacement toe arms are not needed at that amount of lowering BUT I like the change from the factory rubber bushing to a pillowball. It's noticeable in my opinion. Also, a lockout of the factory adjuster can be helpful. Mine has only slipped in a rallycross...but still...

All that said, they are optional.

- Andrew
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Old 04-07-2023, 01:01 PM   #4334
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Originally Posted by marco_mc22 View Post
Past 30mm of lowering (arc fender to hub center, stock is 375mm), which is around 140mm pinch weld height on stock wheels.

To adjust rear roll center I suggest you to play with upper control arm offset bushing and get the camber back to spec using the lower arm. Otherwise you have to shim the entire subframe, SPL makes a kit for this purpose. .

As for the 0 toe you should not have any problem till 40mm of lowering.
I have the SPL kit and I didn't like the way the car felt with the subframe raised. It felt a bit looser with trying to put power down on corner exit.
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Old 04-07-2023, 01:36 PM   #4335
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I have the SPL kit and I didn't like the way the car felt with the subframe raised. It felt a bit looser with trying to put power down on corner exit.
That is cause when you raise the rear roll center you also add anti squat geometry, combine them and that’s why your rear end feels looser.
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Old 04-07-2023, 03:16 PM   #4336
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That is cause when you raise the rear roll center you also add anti squat geometry, combine them and that’s why your rear end feels looser.
I wasn't sure but I thought that may be the case. I really didn't find much benifit in the rear RC correction though my thoughts may be tainted by the issue with adding anti squat. I do like the RC correction in the front.
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Old 04-07-2023, 05:11 PM   #4337
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I have the SPL kit and I didn't like the way the car felt with the subframe raised. It felt a bit looser with trying to put power down on corner exit.
I probably should just google the SPL kit but…. How’s does it work in conjunction with the subframe bushing inserts?
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Old 04-07-2023, 05:57 PM   #4338
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I probably should just google the SPL kit but…. How’s does it work in conjunction with the subframe bushing inserts?
It doesn’t work with the inserts. The SPL kit replaces the subframe bushings with solid aluminum inserts. In your subframe thread you can see them in the picture I posted. It comes with spacers to move the subframe up/down in relation to the chassis.
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Old 04-07-2023, 06:40 PM   #4339
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It doesn’t work with the inserts. The SPL kit replaces the subframe bushings with solid aluminum inserts. In your subframe thread you can see them in the picture I posted. It comes with spacers to move the subframe up/down in relation to the chassis.
Thanks for that. I had a look at the kit and it makes more sense now. Is there much height adjustment being done when using the bushing inserts ? I honestly never even though about this aspect till now ha
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Old 04-07-2023, 06:46 PM   #4340
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I wasn't sure but I thought that may be the case. I really didn't find much benifit in the rear RC correction though my thoughts may be tainted by the issue with adding anti squat. I do like the RC correction in the front.
IMO keeping the rear RC slighlty lower combined with the reduction of anti squat (within a reasonable ride height of course) is benefical for the twins, we all know where our rear subframe came from…and we all know it’s not ideal.

As you said, keeping the front RC in a correct spot is much more of a concern for a decent handling.
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