Wow! Powerstation, Cheltenham - everything (good) I've heard about their bumpsteer removal modification is true. It's transformed my car (MY98) completely - it veritably leaps into corners with the agility of some kind of crazed Gazelle...

Admittedly, a lot of the difference would have been made by the geometry settings they make before doing the mod - the geometry was so far out it was surprised them I managed to drive it there... "Didn't do right-handers very well, did it?" they said, looking at the report...

So, the bumpsteer used to be about 48 minutes - now it's 2. Not bad by any measure.

The overall effect, though is massive - not only is it grippier, with better turn-in, and more positive feedback, it seems to run smoother and quieter on a straight road, too.

All in all; confidence-inspiring stuff - I thought my car used to handle well anyway - now it's fantastic.

So, the moral of the story - if you've not had it done, do it - it'll revolutionise your enjoyment of your car...

 

More info on what this is please. Bump Steer???

 

I'm sure a search on here would give a better description, but it's basically when the front wheels change direction when the suspension is compressed (e.g over a bump, or during braking).

The standard suspension causes the wheels to toe-out more, as the suspension compresses - i.e the left turns fractionally left, and the right, fractionally to the right. The net effect is less front-end grip, with the tyres working against each other, and therefore more understeer.

The bumpsteer mod is effectively a few twists of a spanner on the suspension bits under the car, but it aims to reduce the amount of toe-out under load. Mine went from a mammoth 48 minutes (48/60th of a degree) to a max of 2 minutes, which is nothing...

Hope that makes sense!

 

how much did it cost?

 

£120 + VAT - £60 for the geometry setup, £60 for the bumpsteer.

Not bad, since I've seen some places that charge £90 just for the geometry.

And it took about 1.5 hrs all in.

[Edited by Dodge - 5/19/2003 11:52:13 AM]

 

I've heard that its heavy on the insides of the front tyres?

 

Is there any way I can tell if my car's had this done (it was bought 2nd hand from the original owner)?

 

Re: the tyres - they can do as much as you want, we went after loads of problems we had with the geometry (6mm thread on the outside, down to the metal on the inside - I won't mention who set it up before...) and said we wanted the tyres to wear evenly but as good as we could get for the road - now - it's excellent! Tyres (so far) wearing fine, and as it's an MY98 it handles as discribed above...superb and well recommended

 

Running loads of -ve camber will wear the inside of tyres as well. Someone told me a way to check for "excessive" -ve camber was to feel the temperature of both edges of the tyre after a run. If the inside edge was vastly hotter than the outside it indicates there is more camber than perhaps there needs to be for your driving style and the types of road you drive on.

I did this check and reduced the -ve camber on my car a little bit from maximum (with my trusty spirit level, tape measure, tri-square and flat bit of ground...) (I don't know the angle - just that I backed it off by a couple of mm measured from the top of the wheel.) and it made the car feel better, but I still get round the corners at the same speed.

I need to do an accurate alignment check, as my way is very approximate, but better than nothing! (I'm not seeing strange tyre wear now, but there was evidence of this when I bought the car.)

I'm not sure how the bumpsteer mod affects this, but I'm prepared to try most things once... Hoepfully I can run with a more consistant setup that doesn't change as much from the static settings.

[Edited by dnb - 5/19/2003 12:41:14 PM]

 

Burr

The effect of removing the bumpsteer is opposite completely. The bumpsteer as well as promoting understeer will also cause excessive wear to the inside edges of the front tyres because of the toe out induced when the suspension compresses. Dodge's had 48 minutes worth and mine had 42 minutes. It may not sound much but the effect is significant. Everything Dodge and Jen say is correct as far as the dramatic improvement in handling goes. My car is just the same. My front tyres were wearing seriously on the inside edges like Jen,s but now after 9000 miles the tyres wear absolutely evenly. I believe Subaru built the bumpsteer in to make the car feel more stable for inexperienced drivers. This is done on quite a few makes of car. The rear end does not want to slide any more than it did before the mod. In fact with the Whiteline solid anti roll bar links the car now feels totally balanced during fast cornering.

The way to tell, Scoobysnacks, is to look at where the steering rack is bolted to the car with U clamps. If you can see some shimming between the rack and the top mount that it fits into, then the mod has been done.

That method you state dnb for setting the camber does work very well, I had 10J and 14J wheels on my old racer and I used to do a fast corner and stop and check tyre temps across the tread on the outside wheels. A bit of careful adjustment got the temperatures equal across the treads and the handling improved out of sight! I just had to set the cambers the same on both sides later.


Les

[Edited by Leslie - 5/19/2003 12:45:57 PM]

 

The car is put on one of those great big car-lifts, and the way they measured the bumpsteer angle was to hang 2 big blokes from the (tow?) hooks on the front of the car, thus compressing the suspension.

If the toe doesn't change significantly with 2 blokes hanging off the car, then the mod has been done, or doesn't need it doing.