Whilst changing the shocks on my car, I realised that the bump steer was absolutely shocking, and quite easy to fix. The car has always been crazy
over bumps, but I convinced myself it was to be expected in a kit car. With no shocks on though, you could see it was crazy bad. Like, 20 degrees from
full bump to droop. Looking at the angle of the steering arm, you can see why.
Old angles bad
The rack couldn't be lowered because there's a chassis member right under the steering column, and the mounts are full welded anyway. So I
decided to change the track rod ends for 14mm rod ends, attached to the top of the arm on the upright. Ordered all the parts, which arrived today, and
it was actually ridiculously easy to do. Photos next post...
Drilled the taper out to 14mm...
Taper drilled out
New bolt. Not actually what I expected, I thought I'd got fully threaded high tensile, but this is marked at 4.8. Sure its fine though.
Steering bolt
Fully bolted up. It does need a small shim under the rod end, as it binds up a cm before full droop. Had it been a fully threaded bolt, I'd have
stuck a nut in, but I don't have any small washers to hand. The big washer is obviously too catch it if the rod end fails.
Complete
Final photo showing the angle now. The shim will improve it even more. As it is now though, there is no discernible bump steer from full bump to full
droop. Very happy. Sadly, can't test till new shocks arrive!
New angles good
Ps, no idea why the photos come out sideways and stretch res!
Nice one - should feel quite a bit more stable on the road.
I think I'd be looking for at least an 8.8 grade bolt and ideally a 10.9. I agree that 4.8 is probably fine but last thing you want is the rod
end becoming detached if you hit a pothole or something.
Try: https://www.namrick.co.uk
Let us know how you get on once back on the road.
Good job on the correction of the steer bump.
Although I second what Craig wrote about the bolt grade. I wouldn't go under 8.8 on a steering link.
Also, it is good the have bolt with an unthreaded part.
As we are talking about 2 bolts only, I would spend a few pennies more to get 12.9 grade bolts with an unthreaded part of a length as close a possible
to the thickness of the steering arm + the thickness of the rod end.
Hope that will help 
quote:
Originally posted by JoelP
New bolt. Not actually what I expected, I thought I'd got fully threaded high tensile, but this is marked at 4.8. Sure its fine though.
Steering bolt
I've always liked this video as an easy explanation on how to measure bump steer
https://youtu.be/LO07qmJ9zkk?si=UGcGfWRhpHGWNQ7t
I can confirm that handing on the motorway has been absolutely transformed. It's gone from a significant twitch from driving over a white line, to being fairly relaxed driving with one hand. Still wants to follow the dents from lorry tyres on a worn road though. Is that maybe not enough self centering, or would more castor etc make it follow ruts worse?
Oh yeah, having new front springs makes it quite noticeable that the rear shocks are not damped properly any more...
Practical suggestion, swap the bolts and nuts round 180 degrees. If the nut loosens the bolt will drop and you've no steering currently. If you drop the bolt in from the top and screw the nut up from below, then if the nut loosens and drops off you'll still have some wobbly steering.