Turn-in & Understeer

[Robin C]

I'm running a 1.8K supersport with 16" wheels and (the original) Michelin Pilot tyres. Whenever the surface is slightly slippy my car will not turn in and suffers dreadful understeer. I've never had it "flat floored" and would call most of the settings "factory". Can anyone suggest some simple steps I can take to improve this handling aspect.

 

PS I do have adjustable spring seats.

[Graham Sewell]

Jumps in head first with:

 

Dump the wheels for 13" running Yoko's... (either 21's or 32's depending on your preference)...

[The Stig]

Er... mine never suffered from understeer even on 16" wheels. I have the VX in the front too. I changed for 13" wheels as my prev 7's have had and much prefered the performance but more to do with tramlining and acceleration than grip or balance.

How old are the tyres?

Is it only in the wet you have the problem? Very old tyres dry out and won't grip well but will be more noticeable in the wet.

 

What toe are you running? Are the dampers in good working order?

 

 

[Blackbirdman]

Robin

 

You may find te understear is just more noticable in the wet, or do you find it does not undertears on track in the dry?

 

As you have adjustable spring seats try dropping the front or raising the rear. This will reduce understear and add overstear. Best to try this on a track or airfield if you can. Too much and it will be very tail happy.

 

Check the current ride height against the build manual as small canges have a big impact.

 

If you have an adjustable rear ARB this can be used to trim the handling once you get it about right.

 

Good luck.

 

Matt

 

Is it a bike? Is it a car? No it's Blackbirdman cool.gif

[Peter Carmichael]

Raise the rear ride height. Forget about the front as it has much less effect. Just two turns has a significant effect. If the car feels nervous, you have gone too far so back down a touch. A bit more toe out can help, but if it is as severe as you say the fix should begin with the ride height.

 

Tyre pressures and the age of the tyres are other possibilities, as already mentioned. Others who have run the 16 inch wheels will know what tyre pressures are appropriate, but from where you are it sounds like less rather than more is the direction to be heading.

[John]

Do you have an LSD diff fitted? You may be getting push on due to the pre load on the diff being too great for your car.

 

Also, what tracking settings are you using? Good turn in can be promoted by slight toe out. Also try decreasng the front tyre pressures by 2 psi.

 

Also check your king pin inclination for your front wheels. A line through the centre of the top and bottom outer ball joints on the front suspension and projected down to the road will the giveaway here. The contact point with the road should be within the tyre contact patch. Lesser offset wheels will help here if its miles out. Beleive it or not, larger wheels mask this problem due to the effective ride height increasing the contact points outward projection. Smaller wheels are more desireable for manual sensitivity through the steering.

 

John

 

 

[kjp]

Same sort of subject, I bought a 1400K race car last year which had been run Hyperion. I did a couple of 750MC races and limited testing and always thought the car handled well (I am sure that I am not that sensitive, however). I never touched the suspension set-up other than remove the roll bars for a wet Snetterton meeting. I have now just measurd the set-up before rebuilding and found the car toe's out by nearly 1 degree. This seems odd. I now can't decide if I should go back to this set-up or start be toeing in? I will also go from narrow to wide track, any thoughts?

 

Thanks

 

KenP

[murph7355]

I've never had 16" wheels but I'd bin the Pilots first up in favour of something like Bridgestone S03's..

 

Pilots are horrid in 14" form on a 7. Can't believe they're much better on 16"s!

 

That said, 16" tyres won't be cheap so you could twiddle with the suspension as PC says as a free test (if you have adjustables...