Steve Whitehorn

iTrader: (13)

Firstly - What a good idea for Scoobynet. Everybody bangs on about the cars and power, which is all good stuff. But by far the most important factor in safe rapid progress is the driver abilty/training/understanding. So despite having had a ton of fast road training and having driven for a living I am always eager to learn more - you never stop learning! I especialy don't understand that much about suspension/geometry and all that stuff, So I am quite keen to find out more. I obviously understand all about how weight is transfered about but not much about how a car can be set up to alter this. As I just drive the things


Lots of people on here swear by the Bumpstear mod, often undertaken at Powerstation.

How exactly does this change the driving charcteristics of a scoob.

My classic scoob always understeared very progressively near the limit. Which is what I like for a safe fast road car.

I look for a car that understeers on the limit of tyre grip as I feel that this takes less room and is easier to sort out on the road. Do people disagree?

I also look for a car that progressively lets go of its grip in a predictable manner.

Which is what my scoob used to do without the Bumpstear mod. Can you get it to understeer on the limit still with this mod but it just takes more to provoke it?

I feel that RWD (A tendancy to oversteer) is more fun, but something more for the track. For example an elise I drove on a track was great fun but not very progressive when it lost grip.

So to sumarise.
Do people agree or disagree with progressive understearing thing for the road.
And given that this is the kind of ROAD car I like. How can it be improved, with things such as Bumpstear. I would like to learn more about about the area of how cars can be set up.

Look forward to any coments/info
Best wishes
Steve

mutant_matt

I personally found my MY00, before the BSM, to be quite difficult to tell where the limit was, and found the response from the front end quite "woolly" (not to mention the bags of understeer). After the BSM, I found the car much more "talkative", went more where I pointed it and also, most of the understeer was gone (though some of this is due to the geometry setup Powerstation did at the same time as the BSM).

If I piled into a corner way too fast (not something I do as a habit), it still understeered, but crucially, it rarely understeered anymore during the middle to end of the corner. This was an issue I found with the car in standard form where you would have to wait a lot longer to get on the power and often couldn't put down nearly as much once you were on the power. I also found the car seemed to be more stable on the brakes and needed less correction to keep it going in a straight line when braking hard. I suspect that in extreme circumstances (whilst cornering), the tail might have let go a little earlier but to be honest, I never even came close to finding out on the road, and only ever drove up to the limits in this way on the track, after I had already had the BSM carried out.

Hope this helps,

Matt

Steve Whitehorn

iTrader: (13)

Thanks Matt that is a great help. Nice and simple for me in language I can understand
Ta
Steve

flat4

what exactly is done to the suspension with this mod? never actually heard it explained - how could i tell if my car has had it done?


kev

Faire D'Income

Steve,

rather than start a new thread I'll hijack yours slightly as it's closely related. I'm having my 02 Wagon's rear end sorted out this month with TSL's drop links fitted to the rear and another geometry set up.

What I can't get my head round is that by "stiffening" the rear end, this will reduce understeer. To my mind, this will "stiffen" up the rear end making it more inclined to oversteer rather than having any effect on the front end.

Any answers?

TopBanana

Bumpsteer is where the direction of a front wheel changes as that corner's suspension is compressed (e.g over a bump). The suspension is also compressed on one side and uncompressed on the other as the car rolls around a bend. This is how bumpsteer mainfests itself around corners.

You can measure bumpsteer by jacking one corner of the suspension and seeing how much the wheel turns. Demon Tweaks sell bumpsteer gauges to measure this.

Powerstation and others change the angle of the steering rack to minimise bumpsteer. Mine's being done tomorrow

TopBanana

faire d'income:

With the standard drop-links you effectively have a dual-rate anti-roll bar. The car rolls quite a bit before the anti-roll bar 'kicks in'. When you install solid drop-links, the bar is always working and the the steering will be much more responsive. This should give the back-end a welcome bit of outward momentum as you're starting to turn. That's how I understand it anyway

Gary C

As to how I like a car to handle, predictable is the answer. I do tend to prefer progressive oversteer, the MR2 roadster is great at this, was lovely to drive (until I flipped it end over end), The EVO 5 had the advantage with active yaw control as it allows more oversteer at lower speeds and controls it to a 4w drift at higher speeds which allows a chassis design with NO understeer at all, the newer 8 seemed not to be set up quite as aggressivly.

My STi is handling crap ATM. Tramlines badly and dives off course on bad roads. Had geo checked and it had positive camber !!!, been reset and is better, but want to try new tyres next as this seems to be a common complaint. On smooth roads it does oversteer slightly and is great to drive.

highlander

My Scoob used to 4 wheel powerslide quite happily on slow corners under max acceleration with a slight tendency to oversteer. On faster corners slight tendency to tail out and would only understeer on slow roundabouts!
Have now changed the suspension from the Japanese GAB setup that it used to have and am keen to know how to dial in this kind of handling again!

The car will have Whiteline front DropLinks, Powerflex Rear DropLinks and Complete powerflex bushing everywhere else. Standard Classic WRX Anti Roll bars, Adjustable KYB AGX dampers and Eibach Pro Kit springs.

Tyres were Falken ZE512 205/50/16 - they will now be 215/40/17 - probably Falkens again as I prefer them to anything else I have tried!!! Very predictable!!!

car will have approx 350bhp and 300lb/ft torque

Informed advice welcome!!

Steve Whitehorn

iTrader: (13)

Gary / Highlander

I have allways sworn by Goodyear F1s (GD 2s were a favourite of mine) As I have allways found them to be good in all conditions, have lots of grip and very predictable on/near the limit. So a good comprimise like all road tyres. Have you ever tried these Gary? I would recomend them.
Highlander I have never tried the Falkens, they sound good and are not a tyre that seems to mentioned so much unlike Toyos etc. Have you ever tried Goodyears? If so how do the Falkens compare? Are they a harder tyre than the Goodyears.

As an aside obviously what tyres and what pressures you run in them makes such a massive difference to how drivable a car is. And it all seems like a bit of a black art/gut feel thing to me, as differnet set ups seem to suit different people. It is almost like you have to try different pressures, different tyres on different road surfaces over the period of x months to get to point where the car feels just right for you and you have the best comrimise set up. You and the car are as one as it were.

Best wishes
Steve