Bump Steer Spacer size???

[Fostin510]

So, a while ago I installed bump steer spacers and the more I look at this set up it just doesn't look quite right. they're 1-1/2" thick. I also installed a more ridged spring and have not cut it down. This is a 280zx strut with the original 510 perches. The car is minus the drive train, so there's no weight on the front end. Thoughts??

[datzenmike]

1/  Come back to this when you are at the final weight. This is artificially high, your lack of rive train weight will let the springs push the body up.

 

Selecting a bump steer spacer is not guess work, there is a small measurement to take before selecting. You'll need the car on a flat level surface with wheels on the ground. For zero bump steer the tie rod must be level. As the body lowers the tie roe end on the right lowers with it and the outer end on the steering knuckle appears to rise on a slant. Using a spirit level measure this difference and install a bump spacer of equal size. This will effectively lower the left end of the rod and level the tie rod.  

 

 

I lowered my 710, above pictured. Measured left and right ends as best I could and the difference was 1/2". Being a cheap Datsun owner I made four 1/4" aluminum spacers out of 1/4 scrap.

 

 

Stacked two a side with 1/2" longer bolts. Checked the tie rod was now level. It's tilted down because I jacked the body up letting the wheel droop for the picture. I drove it with bump steer for weeks before I decided to do something. What a difference!!!!!!

 

 

2/  Here's a fact about coil springs. If you cut a coil spring, it gets stiffer. Never cut a coil spring to adjust the ride height or you will make the car stiffer, perhaps too stiff for your comfort. If you have stiffer springs for your zx they were probably designed to be about the same ride height as stock. So put them on first and see what it looks like. 

 

If they are firm enough but too high still you might want to look at trimming the old stock springs to get the lowering and the firmness you want. Again there are some measurements of the spring, a spring rate formula and some easy math to work out the spring rate and how much spring to cut to get the rate you want. This may result in a good firm ride but now too low and the cure is to add spacers above or below the spring to raise the body. Sounds complicated at first but it isn't and the results are fantastic. Let me know.

[Fostin510]

great info, thanks. I'll post the update when the car is almost done.