Caster query

[Seppi72]

Folks may remember that I crashed my '72 last fall and bent the left front frame rail (see photos). Over the winter, we replaced that frame rail with a new one from Zedd Findings. There was a bunch of other work done too: new paint, exhaust upgrade, refurbish the entire suspension (with camber bushings in the front), etc. The car was on the road for the first time this year yesterday and that was to head to the alignment bay at NTB.

Fortunately, the technician who did the work is a local SCCA autocrosser (Honda Civic Si) so we hit it off quite well, he took his time and involved me in making decisions. Once he did the best he could, we ran across a problem in the caster values. The right side unloaded value is 2.9 degrees (factory spec is 2.92 ± 0.50) but the left was only 1.3 degrees. I had noticed a pull to the left when driving to the shop, but because the toe and camber were just guesstimates from when I reassembled the front end, I couldn’t be sure of the cause. We went for a short hop on I-71 and still felt the leftward pull, which the technician called "caster steer". Obviously, even though we measured a number of times, we didn't get the T/C bracket installed exactly equivalent to the right side location.:stupid:

So, how do I rectify the left side caster value and get it close to 3 degrees? In reading old threads, I saw where Kevin Mack had a similar problem and thought about using washers to push the T/C rod forward. I figure that I could do the same thing and want to get the opinion of members who are far more knowledgeable on the subject. Also, how would I go about roughly measuring caster in my garage - :bulb:an inclinometer pressed against the trailing edge of the spring coil stack maybe?

For the record, the T/C rods currently have the aluminum/delrin ball and socket kit in front of the frame bracket and a urethane rod bushing and large washer behind it. (What should I have on the back side?) I could convert to urethane bushings front and back if needed. I am also running Eibach progressive springs with 225/50-15 tires (if that helps anyone) and my control arm geometry is darn near parallel to the ground (as near as I could eyeball it on the alignment lift).

Is any other info needed?

Edited June 17, 2009 by Seppi72

[Arne]

Wasn't someone making an adjustable TC rod? that would be an easy answer.

[70 Cam Guy]

Wasn't someone making an adjustable TC rod? that would be an easy answer.

They sure are

http://www.technotoytuning.com/productdetail.php?p=668

I believe there are even some available at MSA. T3 does make some good parts, I have seen a lot of the AE86 bits.

Some other interesting products on their news page

http://www.technotoytuning.com/racing/

[jmortensen]

The G Machine bushings leave very little room for shimming the rod back and forth. The adjustable rods suggested above are a better answer. You can even up the caster settings and call it a day, but I'd try for 4 degrees on both sides if you're going with something adjustable. The more caster the harder it will be to steer and the better the front end will turn (generally speaking).

Do be conscious of the turnbuckle length. If you have to screw one side way out to get the setting you want, you might consider getting a little longer turnbuckle on that side. More threads showing on the rod end and TC rod is weaker.

[Seppi72]

Thanks guys. I'm going to go with the T3 adjustable rods. At "only" $200, they're a pretty good deal. I was planning to seriously consider a number of adjustable suspension parts for my original owner '72 now in rebuild and this will give me an opportunity to assess T3's fabrication competence - which looks pretty good on the computer screen.

And, JonM, thanks for that advice on the caster setting and the caveat about the threads showing. I'll discuss that with T3 when they call me back.