Pneall and bumpsteer on Classic Revival.

[Treeve]

You should be making efforts to reduce your bump steer as much as possible - +/-1mm is what I aim for.

The numbers in the rest of this thread, whilst 'accepted' for compliance and registration are pretty average and should be worked on.

[gjkrv8]

Originally Posted by Tenrocca

I don't think I spent any time in the dirt last year did I? Going too slow obviously......or getting too old to remember.

must have been me Gav was thinking about :-)

I had to get the high pressure hose out when I got hoe to get the mud out from under my rear guard when I went off the fish hook - was pretty muddy off the track. :-)

Andy - looks great - I think I need to have a look a re-POR15ing mine as it looks a bit average - maybe when I get my new front paintwork done :-)

[Tenrocca]

I reckon its something you only want to do once - hence I handed over to a guy to blast and coat the second time around. It was pretty reasonable cost wise ($250 including my quick jacks) and the finish is much better than por15 IMO.

[Tenrocca]

Some more tinkering and measurements today.

Definitely no go on turning the pivot bolt around Mike, so got some half lock nuts - thanks for the tip. Heaps more room there now.

Took out the single 25mm spacer on the rack and got a bunch of 3mm washers to muck around with spacing the rack. I also took a measurement with the rack not spaced and the rod end on the top of the steering arm - result was as bad as it looked to the naked eye. Im probably running a bit more castor than standard now so again it might not be the same result for everyone, but worth taking a measurement if you have done this.

My question is which of the 2 lines (with the rack spaced 12mm and 15mm respectively is better. The ride height is around 240-250 on the x-axis in the graph. With the 12mm spacer I get <=1mm toe from 20mm drop to full bump, but at full droop it toes out to 9mm - this to me looks a little better than the 15mm spacer which has a lower maximum toe, but is not as flat around the ride height.

I dont think I can get much better unless I shorten the rack which isnt going to happen (power steering)

[Aussie Mike]

Looks like I'll have to revisit my steering setup.

I've been looking at machining up some new radial mount calliper brackets for the jag uprights that also replace the steering arms. They would have the rod end mounted in double shear and allow it to be spaced up or down to tune out the bump steer.

[Morris]

As far as bump steer is concerned........015" thousandth per 1" inch of travel is what you want......anything less then that is even better....

That goes for the front and rear......

Morris

[Treeve]

Originally Posted by Tenrocca

Some more tinkering and measurements today.

Definitely no go on turning the pivot bolt around Mike, so got some half lock nuts - thanks for the tip. Heaps more room there now.

Took out the single 25mm spacer on the rack and got a bunch of 3mm washers to muck around with spacing the rack. I also took a measurement with the rack not spaced and the rod end on the top of the steering arm - result was as bad as it looked to the naked eye. Im probably running a bit more castor than standard now so again it might not be the same result for everyone, but worth taking a measurement if you have done this.

My question is which of the 2 lines (with the rack spaced 12mm and 15mm respectively is better. The ride height is around 240-250 on the x-axis in the graph. With the 12mm spacer I get <=1mm toe from 20mm drop to full bump, but at full droop it toes out to 9mm - this to me looks a little better than the 15mm spacer which has a lower maximum toe, but is not as flat around the ride height.

I dont think I can get much better unless I shorten the rack which isnt going to happen (power steering)

I'm used to seeing these charts with the axis the other way around, as it gives you a neater representation of the vehicle arm movement as you would normally look at the front edge of the tyre.

Also, normally you put the 'ride height' at 0, bump as positive and droop as negative from there. This helps evaluate how much of your suspension movement you're using - let's face it, you're rarely at full bump or droop, more likely within +/-50mm.

[Bender]

My 2 cents.
It is always better to have the least amount of toe change in bump.
Bump is when the tyre has the most load.
Compared to droop (less load than ride height).
Toe change in bump will cause darting when hitting one wheel bumps.
Also the front to squirm under brakes.

Bender

[Tenrocca]

All back together, did a quick fishing line wheel alignment (easier on a hoist) and took it for a spin today. Feels a lot better with the extra castor and urethane bushes, has a real go kart feel now and wheel centres much easier on the straight. Steering is maybe just a touch heavier - not sure how it would feel if you had a manual rack.

Final rack spacing I went for was the 12mm lower than stock, and a 10mm cone spacer with the rod end. I also machined the head of the bolt down to a chamfer to get enough misalignment clearance and meant I didn't need another spacer in there.

[Treeve]

you'll want to keep an eye on those rod ends for maintenance - they can get sloppy with only very small amounts of wear.

[Tenrocca]

No worries, I've got the rubber boots to go on them. I found the boots on the tie rod ends would split pretty easily for some reason, so was replacing them pretty regularly.

[Treeve]

Rubber boots need to be full of clean grease or they'll end up full of water and dirt. Best just to keep a regular eye on them.

[Bender]

The quality of the rod end is important too. Cheap rod ends have play in them when new. Industrial brass lining ones are a no go. NMB is a good brand. Available from local bearing shops. Silverline or Goldline are available from Eastern Raceparts. These are expensive but cost effective in the long run. All these three brands are used by the Supercar teams for ability to last.

[gjkrv8]

Originally Posted by Bender

The quality of the rod end is important too. Cheap rod ends have play in them when new. Industrial brass lining ones are a no go. NMB is a good brand. Available from local bearing shops. Silverline or Goldline are available from Eastern Raceparts. These are expensive but cost effective in the long run. All these three brands are used by the Supercar teams for ability to last.

I must have had cheap ones to start with on my CR top front upper A-arm.

After 11,000K's there was a lot of play.

Got some new QA1 Rod-ends with (I think) Kevlar impregnation etc and done a further 20,000K's and no play at all. Modena I think had play from day one in the cheap ones. Cheers Gregg

[Modena]

The cheapo QA1 rod ends had 0.5-1mm of slop in them, the kevlar ones are zero.

[Tenrocca]

I used the McGill Motorsport UK Ultra High performance XF series (Chromoly Kevlar lined). Great company to buy from - quick cheap shipping too.

Metric Female Ultra High Performance | Rod Ends, Motorsport parts UK | McGill Motorsport