I installed a new set of trailing links and toe arms over the weekend. The installation instructions basically say to match the length of the existing factory arm with the new arm before tightening up the jam-nut and installing. Okay, easy enough, but I'm thinking that even if you eyeball it as best as you can, there's going to be a little variation in length from the factory piece. How does the length of the trailing arm affect the suspension geometry? I plan on getting the car aligned anyway just to ensure the toe links are properly setup but I am unsure if an alignment would catch or fix any issues with the trailing arm being a few millimeters too long/short.

 

Sounds like you’re talking about Toe links, not trailing arms,

A digital alignment can show @ toe in hundredths of a degree… if the alignment guy is good he’ll be able to set it up for your driving style, rather than just in the green (the acceptable range based on mfg’s specs)

 

I'm talking about the trailing arms. I set both the trailing arms and toe links to the length of the original parts as best as i could. I'm aware the alignment shop will adjust the toe links during an alignment. What I'm worried about is that the trailing arm may be slightly off in adjustment and that they won't touch it because it's not a normal thing to have to mess with since the factory one isn't adjustable. I also want to know what detrimental effects having a misadjusted trailing arm will have on the suspension geometry.

 

I think if you get the length within 1/16" you should be fine.

It will affect the caster angle. I don't think this is as critical in the back, but in any case an alignment will measure the caster and no alignment shop worth touching an FD will flip out at the idea of adjusting it.

Most alignment techs I've talked to are happy to have more adjustability.

 

I have also installed adjustable trailing arms and toelinks and just matched them to the same size as the originals, took it for a lazer alignment and got it almost spot on, the guy said he only adjusted them to make it worth my money otherwise it would have been withinin tolerances, a very reputable shop as well.

 

The trick I used to match length of trailing arms to was stand both the stock one and the aftermarket one side by side standing on the flat concrete garage floor and run the bolt through the stock one until it went through the aftermarket one. This works better than an eyeball test since you are matching the length more exactly to the mounting point where the bolt goes through.