Understeer

[gdr]

Got round to reading the CCC article on Stig's car and noted the power-on understeer comment from DW. Having recently had my first track day outing, although a novice, couldn't help noticing the same characteristics - front pushing wide when putting on the power coming out of corners. I guess this is better for the inexperienced than instant oversteer, and presumably what the factory wanted when they specced the recommended geometry. But is there a set up change that will make the handling a bit more neutral and less understeery without going over the top?

[pashby]

Do you have LSD fitted or not?

[james]

If you aren't sure what you're doing, you would do well to book a day with an experienced racer, to help you set the car up. Depending on who you use it'll probably cost you anything from £150 upwards to get somebody who knows what they're doing. They'll be able to drive your car and help you to set it up. In addition, they'll sit beside you all day and tell you what you're doing wrong, and how to do it right.

At the end of the day, you'll have a car that handles just how you like it, and a lot more knowledge about both driving, and setting up the car.

If you just try to adjust stuff yourself, without really knowing what you're doing, you can end up in a right old mess.

James

[davefiddes]

If you are looking for someone to provide tuition and car setup then it might be worth asking the question on www.scottishclubracing.co.uk/ . There are a lot of scottish race drivers on there who should be able to suggest someone/somewhere suitable.

Off the top of my head Ian Cowie is probably the man to speak to. He runs a lot of hire-drive-setup cars in the various scottish series (Caterhams, Mini Cooper Challenge, XR2s, etc) and really seems to know his stuff. Aly Hunter(Legends) and John Muir (MV Turbos) also do a lot of professional race car setup up here. Can get numbers/details if you are interested.

[gdr]

Good advice I think - at Knockhill trackdays there is usually an instructor available and these guys are generally involved in race car set up. May just be a case of me needing training to develop the confidence with the car to use it a bit more agressively.
Can't complain about the way the thing handled first time out though, even though track was slippery initially, apart from a couple of power induced twitches (which were easy to catch) car felt stable and safe.
Thanks.
ps I don't have limited slip diff either.

>> Edited by gdr on Monday 22 September 19:16

[ultiman]

What difference does the limited slip diff make?

[G Man]

a lsd will add to understeer on corner entry, you can configure race lsd for slippage and thus try to dial thus out

[gtrclive]

I may be wrong but a Plate diff ( original Porsche ZF ), may cause this a bit, but I think a Quaife gear type Torque baising diff does not effect it as much. But I surpose it's all about driving stile.

I have a original ZF diff and would not go back to a standard one if someone even payed me. They are more predictable than an open diff. (Plus alot more fun !!)

Just my penny's worth.
Have fun that's the main thing.

[ultimapaul]

ultiman said:

What difference does the limited slip diff make?

Because by it's nature an LSD will try and keep wheel speed even, it causes the car to 'push on' when entering a corner. Hence contributing to any understeer.

The main other factors are .....

Weight distribution
Toe in/out, front and rear
Aerodynamics
Tyres
Anti roll bars (if fitted)
Dampers
Front/Rear wheel drive
Power on/power off


So, many things can have an effect, thats why it is a bit of a black art to get the responce you desire. Understeer/neutral/oversteer.

Most manufacturers will dial in some understeer as a default setting because it is deemed to be the least dangerous when things go tits-up. I'm not saying this is what Ultima have done, you'd need to ask them!

Paul.