11 replies to this topic

[Tedski]

just fininshed changing our steering rack replacement, i need 3 days off work now to recover!!!, I note that the rack is mounted with 4 bolts thru the bulkhead (slotted holes). I have got alignment positioning plates fitted on our vx and I aligned it up with the small hole at the bottom of these plate. Not driven the car yet obviously tracking needs to be checked out, my question is how bad is the bump steer if you get it, the car is fitted with gaz gold suspension so i guess it may be slightly lowered.

As an Engineer i am surprised that the rack itself is not located on dowels to ensure it parallel to the tub suspension mounting points, just leaving it to these alignment plates appears to be a bit hit and miss, in view of the fact that the tolerance for alignment in tracking is so critical and to tight tolerances.

 

The bottom UJ was a major bit of hard work in removal, on taking the track rod ends off one was screwed to the end of the thread and the other was hardly on the thread, got it now equal equals, so some previous history there.

 

With regard to the track rod ends can you fit either S1 or S2 track ends, S1s are shorter in length apparantly.

 

Tedski

 

 

[Kieran McC]

If you feel unsure about the bump steer add the rackriser plates , They helped with mine. Only cost a few bob from eliese parts etc

Edited by kieranmcc, 26 October 2014 - 06:36 PM.

[Bumblebee]

I have no problem with bump steer

[fezzasus]

I have no problem with bump steer

 

Turbos already have the bump steer plates fitted from factory.

[Bumblebee]

I have no problem with bump steer

  Turbos already have the bump steer plates fitted from factory.

That's interesting, learn something new everyday

[Nev]

If your think your are suffering from bump steer there is a somewhat expensive kit you can buy from Elise Parts. In essence it supplies a modified pair of steering arm ends that allow approx. 2 cm of more lowered suspension adjustment, along with spacers and longer ball joints to allow some flexibility in adjustment. When the car is sitting on the ground, the steering rod ends should be pointing upwards marginally for OEM ride height and OEM bump steer (not sure exactly what angle). You can measure the current height from the ground to the front most part of the the car's chassis rails to see how low you current ride height is at the moment, OEM is 140 mm BTW. Good luck.

Edited by Nev, 27 October 2014 - 07:00 AM.

[alexb]

The alignment plates only ensure that the larger holes are at a certain position in the slots. Using the raiser plates that means that the steering rack is as high up as possible. You don't really need the plates for that. To minimize bumpsteer, the rack should be as high up as possible. To minimize further, the balljoints on the steering arm should be lowered a little (mm's). That's impossible (ok, not impossible, a lot of work) with the OEM arm. The Elise Parts kit allows you to do that by lowering the steering arm mounting point for the balljoint and by using rod ends that sit lower. It allows you to shim, so that you can adjust bumpsteer to almost nothing.

 

BTW, why worry about bumpsteer if all you did is to change the rack? Shouldn't change. You'll have to set toe again and the car is very sensitive to that. Very slight changes in front toe you will notice. Even with the rack up as high as possible, using the OEM steering arms, there is a lot of bumpsteer. Whether that's a good thing or not is open to discussion. Would have been very easy for the suspension engineers to decrease it. Lowering the car will bring you in a different range in the bumpsteer curve, but given that people normally combine lowering with increased spring rates, the nett effect might as well be that you have less bumpsteer, as the wishbones travel to a smaller range.

[siztenboots]

make sure the preload is set on the new rack before fitting

 

http://wiki.seloc.or...e_steering_rack

[Tedski]

Many thanks for your response, not actually driven the car at the moment awaiting delivery of 2 new track rod ends.

We have an elise in the family an early S1 and i have never experienced bump steer at all in this car, interestingly the elise manual shows the raiser plates fitted as standard and secured in position by pop rivets at the lower small hole so that secures and this aligns/locates the mounting bolts to true position during steering rack fitting. Agree the rack needs to be as high as possible you can get it.

 

Our vx appears to have had a raiserplates/pop rivets fitted but has corroded away (pop rivets) by the dreaded bi-metallic corrosion which is all over these cars, if you look on Lakeside Lotus site you will see front suspension towers rotted away on an elise. I cleaned our towers and yes there was a deposit forming but only surface fortunately.

 

 

Going to get the car tracked up etc, not a big fan of the Geo laser prefer the conventional laser setup, adjusting to 0.2mm or 0.008in is fine when the car is brand new/rebuilt suspension, but slight play in bushes/ softing effects; allowing flexing in motion and wheel bearings (slight play, but still MOT pass) will give a different result everytime, yes i have tried it and gone back 4 times and got different results and the suspension appears firm by inspection. The geo tech laser like any system is purely static checking, ideally you want dynamic/vehicle moving check and this would show up any suspension issues/set up changes required, obviously would cost to much.

 

Bumpsteer

To ensure each front wheel moves in equal amounts (steering rotation) to the other during all suspension movements the rack has to be parallel to the suspension points and also the tie rods need to be the same length also ie centre of ball joint to centre of inner tie rod, in other words parallel geometry. If this is not the case of one the 2 wheels will toe out/in more than the other in front end bump/dive conditions  and hence pull the vehicle in that direction left or right as you drive over bumps. The geometry has to be equal other wise trouble. Basically the standard steering rack geometry appears to be roughly inline with the track rod ends, the eliseparts kit lowers the track rod end position (angled up to the rack/rack higher) and would give a toe out effect during going over a bump.

 

Sorry to go, on thinking aloud!! must go out and try the car, may be worrying about nothing!!

 

Tedski

 

 

 

[siztenboots]

the elise s1 has 15" fronts so you get the much lower ride height, but without changing the wishbone angle

 

[Pidgeon]

You do worry about nothing!  I and many others set up the geo with two lengths of string.  You know where it is, can adjust easily and most importantly, know how adjustments equate to movement at the wheel.

[alexb]

I geo with strings too and can set front toe to 0.5 mm consistently. Car is 12 years old and didn't have a suspension refresh yet. And you're talking about the difference in bumpsteer between left and right. Usually we assume it's about the same left to right. It's not only the rack and the toe links, it's all the suspension mounting points. It'll be mm's difference here and there. The beauty of it is that statistically they average out.

 

I worry too much too. When I started to do my own geo, I was convinced that I had to find the middle of the car. To set the strings parallel to that. Well, good luck finding the middle of the car. Sounds easy, until you try it. Use track, ah, but that depends on camber and is that the same left-right? And are the mounting points the same? wishbone length etc. Too much to worry about. Just take two stings with the same distance between them and make sure they're as parallel as you get by equal distances from the wheel hubs left-right.