Anyone have the data on how much "lowering effect" you can get from pre-loading the upper A-arm bushings?

I'm guessing 1/4"-3/8"


I searched and couldn't find any data.

 

No one? I know some one running stock class knows the answer to this.

 

The last I heard of someone doing this for stock class was from Wynveen (windscreen) on his AP1 back in '07. Most AP1s and early AP2s lower when dropping the pressure from the shocks. My '05 AP2 lowered about 1/2" when I put the "autox" valved Koni Yellows on. My CR didnt settle much. This was most likely due to the higher spring rates. This worked out better since tire rubbing is an issue with the S2000 in stock class.

-Marc

 

Technically in BS and RTR we can't run shorter shocks or anything. The shock pressure thing could work but it would make the car softer then it already is. I remember reading about C-kit or someone like that talking about loosing the upper a-arm bolts and jacking the wheel up past ride height and re torquing the bolts. This preloads the bushing and causes the shock to jack down ever so slightly and lowers the ride height. The first time I put my stock shocks back on I didn't "preload" the arm to stock ride height before torquing the bushing. The car looked alittle higher then normal so I measured everything then went back and jacked up the arm and torqued the bushings. It lowered the front of the car about 3/8" or so.


I was thinking about this eariler when I was thinking about Tims CR. It would be free to do and could get the car a hair lower. I was just looking for any info on this because when I searched I couldn't find it.


Basicly heres what I would do..

picture of our suspension, clearly everyone know what the upper arms look like....


- Measure the ride height of the car from fender to hub center with it on the ground
- Put the car on 4 jack stands
- take off wheels
- disconnect sway bars
- start on one corner and lossen the two bolts in the upper A-arm (17mm)
- jack the lower arm up with a jack until the hub center to fender is 2" (or what ever used the same all around fr even preloading) lower then your starting measurment
- retorque bolts to 65 FT/LB (I think thats the spec off the top of my head)
- lower jack
- repleat on the other 3 wheels
- put on wheels
- put car on ground
- remeasure the fender to hub gap to see how much it lowered the car. I'd actually measure twice at the begaining, once hub/fender to know how high to jack the car up and the second one at the pinch welds so you have a precised measurement on how much you lowered the car.


jack the lower arm up like this then re-torque the bushings.




Some may think of this as a "cheating" way to lower a car in stock class but at the end of the day it's racing and people are going to push the limit within the rules. Kind of like the FRS guys already talking about sanding down the crash bolts/holes to the service limit to gain more camber. The only "bad" thing I can think of is the slight binding of the bushing causing pre-muture wear on the bushings (??) and it may also cause a slight increase in rebound force at the wheel due to the bushing binding as it goes back to resting ride height. Although thats not really a issue.


I've read about other people doing it but can't seem to find that info. Which is why I asked. Is this a good idea to get that extra little edge of maybe 3/8" lower ride height or is it a bad idea? If so why? Plus it's free and we could alway re-torque them to stock position if it we don't see any gains. I want to talk Tim into letting me do it and see what kind of gains we can get. I swear I like tinkering just as much as I do driving.






Thanks Guy!

 

In my experience it's a bad idea. I did this inadvertently on an old CRX and it destroyed the bushings in short order, as it was under a considerable amount of strain at rest.

 

Thanks for your input!

 

That was my post. I didn't measure, but it was clearly obvious to anyone seeing it beside another car that hadn't had it done. Wild guess: ~1/2" lower. They key is to do ALL bushings. In hindsight, doing the shock bushings probably put a bad sideload on the seals, so I wouldn't do those again. I had debated trying to corner-weight the car this way, but the car was pretty good as it was so I didn't want to spend the huge amount of time to do this.

Is it legal? You're using the stock adjusting mechanisms within their adjustment range with no modifications. That's explicitly spelled out as being legal!

All that said; I'd recommend just spending the same amount of time thinking about driving better. It would likely tear the bushings up over time.

 

Thanks. Guess its a bad idea lol

 

I don't really understand whats going on here, how do you get it past ride height? Wouldn't you have to take out the spring and shop assembly to do that?

Aren't you supposed to preload the suspension to ride height before tightening everything back down?
In the below DIY, its the step with the red jack, where after you install the coil overs you jack the car up by the control arm to get it to ride height.
https://www.s2ki.com/s2000/topic/441...coilovers-diy/

 

Right but if you jack the arms say 2" past normal ride height compressing the shock and then tighten everything down when the suspension decompresses it won't go back down as far due to the resistance of the bushings being twisted.

As said above a generous estimate is you can lower the car up to 1/2" this way. The down fall is premature wearing of the bushings according to a few people.