TR6 Suspension

Here we are in August of 2004 and this project has been underway for three years and on the road for the last year. Now that I’ve owned the car for about fifteen years it’s time to treat it to a real four wheel alignment. This car has had a frame off restoration including rear swing arm bushing replacement as well as the corresponding frame section replacement. In the front the upper control arm bushings have been upgraded to polyurethane and the sway bar links have been replaced. A set of competition spring from Richard Good have been installed, front and rear. And in the not too distant past the upper ball joints were replaced. The trunnions felt tight. Front tire wear was mostly on the inside so rather than break out the string why not go for a laser alignment.

The Alignment

The alignment went horribly wrong. Not that the shop messed things up but that there were things that they couldn’t correct. Rear camber was improved by swapping around swing arm mounts. Not perfect but pretty close since they had no TR6 specs. I had planned to have the chart prepared by Nelson Riedel with me for the alignment. I’m sure thay could have done better had I remembered the chart and the assortment of swing arm mounting brackets! The front was the real problem, especially the right hand side where the wheel was visibly tipped in at the top (negative camber). Prior to my purchase of the car it had been in a very minor fender bender involving the right front. The forward lower swing arm mount was pulled outward affecting not only camber but caster.

It seemed strange that I had driven this car all these years and not noticed the right front camber problem, then it dawned on my that new front springs had lowered the car over an inch. As the height goes down the angle of the upper control arm increases, pulling the top of the wheel inward. This wheel was now so far inward that even without any alignment shims (-2.1 degrees) the camber could not be corrected. The alignment shop said the top of the wheel needed to move outward nearly half an inch! First thought was to build a set of adjustable upper arms using hiem joints to connect to the upper fulcrum. The left side also had negative camber without any shims but not nearly as bad.

Looking things over very carefully showed that the right front’s forward lower control arm frame mounting bracket was bent outward. This caused the bottom of the wheel to be pushed outward and back. The “back” is important because this same wheel had very little caster.

A Special alignment tool, actually a 2 foot section of bronze propeller shafting and a large sledge hammer, were used to persuade the forward mount back to where it should be. Measurements from the far side frame rail showed it had moved back nearly 5/16″.

Back down on it’s wheels without any shims it still had negative camber -not nearly as much but clearly not right either. The good news was that the right front looked every bit as good as the left

 

Next up was to raise the front about 7/8″, correcting camber not to mention lessening “bump steer”. I’ve seen several advertisements for front spring spacers that stated a 1/2″ thick spacer would raise the front about one inch. A spacer measuring .519″ raised the front an inch and a quarter. I think the difference in advertised height to final result was that the springs were stiffer and designed to lower the car about an inch. Cutting the spacers down to 375″ did the trick. Still lower than stock but stiffer for better handling. New tie rod ends along with all the bushings and the right side trunnion were replaced. Now to get it back for the final alignment.