Vonzack

Hi,

Saw on www.litimports.co.uk that they can remove 'Bump Steer' from MY03 WRX's.

Haven't seen this offered anywhere else, can anybody tell me what it is and how it affects the car?

Cheers.

greasemonkey

In an ideal world, the wheels should maintain their steering angle throughout the suspension travel. In other words, if they're pointing dead ahead, they should stay pointing straight ahead if the suspension is fully compressed, fully extended, or at any point in between.

Bump steer is the term that's applied when this doesn't happen - it literally means that a steering input is caused when the car rides over a bump, or indeed when the car rolls onto its outside wheels in a corner. This can manifest itself as a lack of directional stability if you're trying to drive in a straight line on bumpy roads, or indeed a lack of front end grip when the car has settled into its line round a corner.

To eliminate bump steer completely, the geometry of the suspension arms, steering column and track control arms must be absolutely perfect, and that's difficult to achieve when the steering system has to be packaged round the engine and other bits.

The classic shape Impreza was known to suffer from an amount of bump steer, which is why a fix was developed by a couple of tuning firms (the fix involves repositioning the steering rack on a couple of shims).

However, this is supposed to be greatly improved, if not fixed on the newer shape cars, so Litchfields are offering a fix for the MY03's, they've presumably found that it's still possible to improve on the standard setup.







[Edited by greasemonkey - 1/21/2004 5:30:43 PM]

Vonzack

Thanks for the explanation GreaseMonkey

LitchfieldImports

I'm afraid the option info on the website is a little dated as there is very little bumpsteer on the MY01+ cars. It'll get amended soon in the meantime speak to Powerstation www.powerstation.org.uk who do all of my setup work

Regards

Iain
www.litchfieldimports.co.uk

mark*b

I'm in two minds about the bump steer mod. I'd love my scoob to be an oversteer demon however there are some advantages to bump steer.

Correct me if I'm wrong but I thought it was a very intentional trait on the manufacturers behalf to improve the stability of a car over a bumpy road. When the front wheels hit a bump the suspension will move up and the wheels will toe out slightly which helps to keep the car in a stable position. Correcting this from happening could possibly cause the car to deviate from its trajectory, which would make it a little skittish on a bumpy road.

Would love to hear from anyone with back to back experience on this.

Mark

coulty

I have just had the bumpsteer mod and full alignment done on my sti2 and WOW what a difference! Where it used to understeer and wander offline through a corner it just stays planted and goes even in the wet. It was tramlining too and that has been cured.
I was VERY sceptical before getting it done and took ages to decide if i should. Now i wonder what the hell stopped me????? It is an amazing transformation into what the car should have been like anyway.

Just my opinion
Stuart
BTW i did get my anti-roll bar bushes changed at the smae time so that could have helped too.

mutant_matt

That is one description, yes. Another would be that car manufacturers often cater to the lowest common denominator, i.e. they want to make the car safe for a low skilled, average driver as they don't want the car to get a reputation for being "difficult" or unsafe to drive.

Unfortunately, this ruins the drive for a lot of the type of people this kind of car attracts so if you know what you are doing, and can drive, the Bump Steer is an annoyance. On the old shape Impreza, the removal of Bump Steer improved the car no end and certainly doesn't make it unstable or skittish. It just makes it like a normal, proper car should be.

I have also had this done/coupled with a proper Geometry setup on my MY02 STi at Powerstaion as well and this improved the car quite noticable also, due to the large tollerances all Subaru's come out of the factory with

Matt

warrenm2

Recently had the bumpsteer mod, 4 wheel geometry and ALK (anti lift kit) done at Powerstation, and BOY! does it make a difference. They said it would be like a different car and they werent wrong! It feels like a huge weight is now sticking down the front end, whereas before the front felt quite floaty and vague (and thats before the understeer!). Now it just goes where you want it to with no drama. It feels "tight" is probably the best way to describe it, and in high speed corners, the car just takes "a set" immediately i.e. it just leans to whatever degree and thats it, no wandering or minor adjustments needed, it just smoothly tracks the corner like a scapel.

Downside is the front is a bit more harsh (noise and vibration are increased a bit), but within accepatable levels.

I know this sounds a bit over the top, but performance per pound, its great value! (£335 + a camber bolt I needed at the back -£360 all in). I would say these mods are better value than springs/dampers although no doubt someone will disagree! Understeer is greatly reduced - off on a track day soon to see what its like under real pressure!

To summarise - do it!

andy hs

I have Eibach springs fitted and am thinking of replacing the front & rear drop links for MRT ones and putting on an adjustable rear Anti Roll bar and Anti Lift kit is this worth doing then having a geometry alignment.

Andy

greasemonkey

No, it's laziness. There are a few cars employing roll-induced rear wheel steering to either sharpen cornering response or improve stability, but these often have undesirable effects on bumpy roads. At the front bump steer is almost always undesirable and unwanted.

That doesn't work in practice. Far from increasing stability, bumpsteer usually has the opposite effect on uneven surfaces.

Sure, if both wheels are loaded and compress equally, the car will continue to track straight. However, if one side or the other is carrying more weight (if the car's cornering for example), or if the bump is on one side of the road rather than all the way across it, the induced steering input will push the car off line.

If the steering angle is maintained during compression, on the other hand, the car will continue to track straight no matter whether both struts are compressed, or just one.

Unwanted steering input will make the car deviate from its trajectory. The lack of bump-steer will also allow optimal tracking to be maintained on both inside and outside wheels when the car rolls into a corner, resulting in a net improvement in front end grip.

tmo

How much is it for the bump steer mod at powerstation.

Also how long does it take