mark_st

Can anyone offer any advice here.

I have a MY1999 Turbo that has not been modified with regards to suspension or wheels. On track I find that it understeers big-time, which is a bit annoying and boring.

Are there any alterations that can be made to the standard suspension and setup to reduce, or ideally, remove this?

Any help or information would be greatly appreciated.

IWatkins

Mark,

You may consider a trip up to Powerstation in Cheltenham for the "Bump Steer Modification".

Click <B>

RON

Mark
I noticed that you are in Hampshire, well if you want to get it 'sort of' sorted get yourself up to Micheldever Tyre services and get the geometry changed to 'Prodrive' settings, a lot of people have had it done , and it reduces the understeer to a minimum.
I had it done on mine, and I now only get understeer when drivin like a complete loon! Mind you I haven't been on a track (yet).
The cost was about £50 a year ago, and it's easy.
Enjoy
Ron.

SteveB

iTrader: (1)

Driving technique.....


Steve.

mark_st

I guess I need to book my car into Powerstation then..........

mark_st

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by SteveB:
<B>Driving technique.....


Steve.[/quote]

Thanks Steve. Cheeky bugger!!!!

A chap by the name of Willie Green (quite nifty round the 'ring) took my car out with me as a passenger and was having the same problem. The only difference was that he was able to really **** off the bloke ahead of us in a 964 RS who couldn't get that Impreza behind him to get any smaller in the mirrors.

Darren Thompson

Also get the Prodrive tarmac settings on the car this sorted mine out nicely.

Darren.

mutant_matt

Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation Powerstation

Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod Bump Steer Mod

Seriously, you <B>need</B> to get this done - it's the dog dangly bits and costs next to nothing - you won't regret it!!!!

Matt

Hoppy

Mark, there seems to be a lot of evidence that factory geometry settings have generous tolerences. Some people can get around corners, while others appear to get massive understeer.

First, on track try pumping up the front pressures. Maybe 40 psi?

Second, Prodrive geometry is a vast improvement. Any dealer should be able to do it. But negative camber wears the front rubber if you do a lot of motorway etc.

Third, the ultimate fix is to get PowerStation (Cheltenham) to a) set the geometry exactly right, then b) dial out the built-in bump-steer. Better than Prodrive and no tyre wear probs.

Good luck.

Richard

Mungo

Two questions:

1. Do the Prodrive settings involve lowering the car at all?

2. If not, is it worth declaring the mod to your insurance company? I'm only asking, because you probably wouldn't tell them if you kerbed the wheels and shagged the alignment (making it more likely to lose control due to dodgy handling), so what difference does it make and how would they know any better?

Regarding telling the insurance co, do you neeed to declare if you have upgrade the tyres,brake pads or brake fluid? We all know that these will improve performance, but as they are "consumables" do they need to be declared? I guess that's a similar question to "do I need to tell them if I run on SUL instead of UL?"

Sorry, more than two questions, but I just got thinking. (dangerous pastime I know...)

SteveB

iTrader: (1)

Mark st,

Sorry, i've seen/heard a lot of people moan about understeer that just can't drive(fast in slow out!). A bit like some that are obsessed with horsepower (300 ++)that get left behind by a std uk scoob!!

I have heard that some cars come in with the geometry way out. It may be worth just getting this checked out before changing the settings as this is designed to scrub the tryes to create the extra grip.

Steve

mark_st

Steve,

I understand where you're coming from. To quote a couple of people who have given me some guidance on track "the most significant upgrade you can make to your car is to the driver". I went on the Don Palmer wet handling course and would recommend it to anyone. It makes you think about what the car is doing and what you need to do in order to keep it going in the direction you want. Trying to drive around the concentric circles at MIRA sideways has to be one of the biggest grin-inducing things I've done. Basically, you get to be a hooligan on a great big roundabout with nothing to hit (unless your very stupid, unlucky, or both) on a surface that mimics packed snow. The best bit is that it gives you more confidence about how to react if it all starts going a bit Pete Tong.

From looking at the information on the Bump Steer Modification on the Powerstation site it would appear that the problem being corrected is the front wheels splaying out under load. If the responses from people who have had this modification carried out are anything to go by then it would appear that this is a good thing. As my car is going in for a service this week I will also ask my dealer about the current geometry setting.

I guess the main areas I hope that this will improve things are accelerating out of tight corners and the amount of speed you can carry through sweeping corners. In both cases I find that I have to back off the throttle to tighten up whereas others do not need to so much. I'm only talking about playing on track here.

........or maybe it's my lead boots and ham-fisted steering?!!!!!!!

Anyway, thanks to everyone so far for the tips. Hopefully it won't be too long before my humble UK Turbo is snapping at the heels of its P1 and STI big brothers, maybe even some of those funny German cars with their engines in the wrong place.


Mark

Adam M

Just out of interest, i was sure that increasing the tire pressure at the front would reduce the size of the footprint and hence the grip. Less grip at the front would mean more understeer.

Someone please correct me if I am wrong.

NOZZER

Steve,
Understeer with Leda!!?? Never!
Mark,
The bumpsteer and geometry is well worth doing.
Mungo,
No it does not involve lowering the car.
Ian

Hoppy

Adam, increasing tyre pressures will reduce the contact patch a bit, but it's not the size of the contact area that determines grip - load (weight/downforce) is key most of the time.

The benefit of increased tyre pressure (within reason) is better rigidity. If your tyres are soft, they will distort and you'll be riding on the sidewalls, squirming all over the place. Low grip, overheating due to sidewall flex, high wear rate. Hopeless.

Tyre pressure is fanstically complex and sometimes the reverse applies. But in the relatively controlled conditions of track driving, generally speaking higher pressure equals more grip. The downside is that your tyres will 'go off' more quickly (overheat) because of the improved grip (more friction = more heat). Delicate balance.

In racing conditons, 2 psi is the difference between winning and finishing in the top ten.

Richard

DavidRB

Only up to a point though Hoppy. Too much pressure and the tyre distorts the other way, so you are riding around on the centre part of the tread, while the edges are practically off the road.

It's not just about contact patches, a tyre is also a spring connecting the wheel to the road. Increasing the pressure is like stiffening the spring, so it may make the car react quicker, but have less grip on the limit.

Personally (and I have no scientific data to back this up! ) I have often wondered if the current trend of running the fronts 4-6 psi higher than the front is one of the reasons why people complain of understeer.

My UK MY00 has 17" wheels and I run them at 32psi all round.

For some reason, unlike other cars (such as the Sierra Cosworth for instance) the Impreza is very sensitive to geometry and tyre changes, so it is worth spending the time to make sure that the standard tyres & suspension are setup "just right" before you start spending money on replacing them.

superstring

What I'm wondering is: With this topic coming up so often, why has no one suggested reducing the neg. camber of the rear wheels? I know, it's "none adjustable". However, with a grinder it's possible to elongate the bottom slots on the strut, making some adjustment possible.

My car (MY 98 Impreza 2.5RS) came with 1 degree negative camber on the rear (even though the manual specifies 0.16 degrees negative!). Took it to the alignment shop, they ground the slots and, presto, adjustable rear camber. I run the car with 0.8 degrees negative (equal) on the front and 0.2 degrees neg. on the rear. Toe: parallel front and 1mm in rear. Result: more turn-in bite and minimal understeer. I appreciate the settings would vary somewhat for the Turbo, but the principle remains the same.

Anyone have any thoughts about this approach?

paul corrigan

any places in the north west that will do this bump steer mod?

stick

Hi there.

I've just been through this issue with my car. It's a '95 STi and it handled like a boat under power. To fix this (with advice from MRT Rally in Australia -