Bumpsteer?

[Wuddie]

while driving, the front of the car seems to feel a bit light, and the car will follow grooves in the road and if the groove is big enough will actually start to turn the car. Any ideas what can cause this and what i should do to correct it...

I noticed it when i had my original suspension, but now i have S2 suspension it seems to be a bit worse.

[Fiona]

Do you still have standard tyres? I'm not in the least techie but both our Elise and A4 follow the slightest deviation in the road due to the size of tyres.

 

Not in the least bit helpful, btw!

 

Fiona

[Wuddie]

yeah im running 185 fronts and 205 rears.

[ipanter]

I believe it is call tramlining, and i think it is caused because of the width of the tyres. The tyres get caught in the channels in the road caused by lorries, and cause the car to follow them. I usually drive in another lane wherever possible.

[Mark H]

Yup tramlining, get it much worse on my Exige than I did on my Elise. Can find that as your tyres wear away it gets worse as the tread blocks wear down!

 

You also get it worse as your suspension wears out but that doesnt apply to you

[Wuddie]

Maybe then its just cause my new suspension is much stiffer so i notice it more??

[JohnnyM]

Wuddie, was thinking about it after we spoke this morning. when i used to have a racing puma it tramlined like hell and this was down to rock hard suspension and the wide & low profile tyres following the undulations in the road, it wasnt a problem as such. It can happen if the sidewalls on your tyres arent upto much as i found on the

 

It sounds weird that your steering goes light.... my elise only really did that at 120+ or before i got it geo'd and the camber was miles off !!

 

Johnny M

[JohnnyM]

....on the racing puma

 

 

 

must learn to finish my sentences !

[GCCK]

Presumably, when fitting the S2 bits, you ended up with a lower ride height?

 

One of the corrollaries of a lower ride height is an increase in bumpsteer. To compensate, you're meant to raise the rack by a similar amount by means of height plates on the rack mount (std Lotus part no.). The bolts which hold the rack on in the footwell are through elongated holes allowing up and down movement. The height plates are 1mm thick and you can get up to 10 onto the bolts safely. It involves some grovelling in the footwell to release the bolts and insert the plates.

 

Other effects of the lower ride height are Camber going more negative since you're changing the distance between the wishbones. There will also be changes to the bumpsteer curve which will affect toe in/out (most people call this "tracking") and you can insert shims to counter this also, but this is where I start to get lost.

 

If Mark A reads this, he'll be able to provide a lucid explanation, since he's one of the few people on here who really know what suspension actually does!

 

You there Mark?

 

Graeme

[tazbaz69]

i get the same effect also as i have 17'' wheels on front, i was hoping to get this sorted aswell, i,m fed up bouncing about on road all time,

[Wuddie]

I didnt really lower the car as such, as i had old s1 suspension so i was already running at 140/140 instead of the Newer 160/160, the front is now 130 and the rear 138 so not much of a difference.

 

as for the lightness..i'll see how that feels on the run on sunday, as the car doesn't really get a good thrashing during the week

[Scott_Mac]

I mentioned it to Mike, Wuddie...

 

He said if its a problem, pop back in and he'll try and dial some of it out for you.

[Wuddie]

HEH Nice one Scott...i'll see what its like after the run

[juicetin]

I'm very unimpressed with the steering on my car, after putting the S2 stuff on and having the geometry altered. Dont know what it is, could be the toyos ive put on, or maybe not enough toe out. I also have about 5-6mm of play developed in the upper UJs on the column which is a bugger. Does anyone know if these are adjustable, ive heard not (sealed unit) but would appreciate any knowledge.

[Wuddie]

you should be able to tighten the UJ's yourself although i wouldnt know where to start You sure its the Uj's and not your rack??