Using the “standard” escort rack results in a lot of bump steer. Does any one have a solution?

mount your rack as level a poss with track rod ends when engine ect is fitted and car is settled on susspension

I did mine with a mk2 rack and my theory was to get the track rods parallel to the bottom wishbones with everything built up. It seems to work o.k. and doesn't give any problems driving.

yours, Pete.

I'd suggest taking care with two points:

* track rod parallel with lower wishbone at ride height (works ok for cortina hubs, if your steering knuckle is higher, there are a bunch of alternate theories in Alan Staniforths 'race and rally car sourcebook' )

* End of the steering rack, at straight ahead, should be in line with the two wishbone mounts.

Damn, needs a picture, hang on ...

Very primitive piccy attached (I think), with stylised upright on the right (if you can't tell). I've drawn top and bottom wishbones, but no track rod. Steering rack to track rod join should fall in the grey area at straight ahead to minimise bump.

As above, track rod should be parallel with bottom wishbone.

Simplest choice if it don't fit nice is to shorten the rack.
Alternative is to move the wishbone mounting points. This could do heinous things to your suspension geometry affecting (primarily) camber and roll centers (i.e. proceed with care).



cheers,
Greg H
Rescued attachment rackendpos.jpg

Thanks for the replies. My rack is mounted as the book – as near as I can tell! Although you only notice the problem when driving over pot-holes in corners, it is a little disconcerting and needs to be corrected, if only for peace of mind!
The root of the problem seems to lie with the steering rack being longer than required. The distance between the track rod ends is about 22.5 inches. That’s about 2 - 4 inches longer than required! I've been told that MK Engineering use a shortened rack from a Sierra. Now that I’ve splashed out on a “quick” MK2 escort rack I’m reluctant the bin it.

the easiest way to check 4 bump steer is bounce the front of the car up n down, you will see the wheels move in n out if you have bump steer, paying attention to all the above will go a long way to cure it.

Bouncing the front up and down reveals huge bump steer. It seems the best way to cure this is shorten my rack! Is this as easy as it looks?

Easy Task? depends on skilled you are and if you have the right equiptment to do the job.
Take a look at
http://forum.locostbuilders.co.uk/xmb/viewthread.php?tid=5974

might help.

If the bump steer is occuring when you're steering, I'm not sure there's an aweful lot that you're going to be able to do since the pivot point will move depending on how hard you're steering. It's worth having a play about though, you might be able to lessen the effects, I suppose, but you're always going to have it there at some degree of steering.

Kingr

I had my escort rack shortened by a local engineering shop when I first started out. There is a lot from the aussie builders about it on TOL, as ADR are very strict when it comes to Bump Steer. If you look at the following thread, you'll get some usefull advice.

http://forum.locostbuilders.co.uk/xmb/viewthread.php?tid=6102

I spent ages on this, and now have no visible bump steer.

Regards, Ian.

Bump steer is very marked on a standard steering rack. You can make it slightly better by re-positioning but it needs shortening to bring ends between wishbone pivots. Trouble is that takes the
steering down tube closer in to centre of car and will interfere with engine unless modified.

it's even more marked with a quickrack and can be very unstable at high speed.
Sounds dangerous, but I take 'hands off' at speed and only make very very slight corrections keeping only a controlled light touch. Mostly it will resettle back without any input. Worst are slow undulating roads that produce a wandering effect.

It's one of my winter projects this year.

Dave,

You know what I mean

If it's an open road, I'm never slow, just think I am.

Bump steer on mine has been quite high since I built it, I just never got round to sorting it out.
I can actually see about 6mm of bump steer when car is set up on stands!

I've definitely got used to it and am constantly aware of it when driving on straight roads. Otherwise it doesn't cause a problem to me.

It's one of those things to be sorted this winter, along with change of clutch and gearbox.
Both knackered after foolishly doing multiple 0-60 run testing using a Performance Meter. It was just too hard on drivetrain. Still, same thing would have happened at the hillclimbs eventually with all the full power take offs.

Best time I got down too was 5.3secs 0-60 with wheelspin for first .5 sec that was useless energy according to run data. Most other runs were 5.5 ish.

G'Day PK, You can eliminate all of your bump steer by removing 103mm from the LH end of the rack. You need to rethread the rack bar and screw the tie rod / ball joint back in. I built 100mm wider and used a Mk11 rack. With carefull height positioning you can set it up perfect. Mine has no measureable toe change 50mm either side of ride height and 2mm toe in at full droop. Hope this helps.
Regards, Mike.
Adelaide. Australia.

why are you worrying about bump steer when you all use girls engines ?????

Here's a photo of the ideal rack width:
http://keith.miata.net/seven/flip.php?x=61

This is the rack out of an MX-5. I disassembled it and cut 5.5" from the center of the shaft. I didn't touch the threads on the end because they're rolled, not cut. The case was given the same treatment.

The shortened rack:
http://keith.miata.net/seven/flip.php?x=6

Keith