Understeer

[DC]

Having just completed my second car build (1800 SS 6 speed standard suspension) and after running in for 700 miles, I am just beginning to open it up. The one thing that I have immediately noticed that is different from my previous car (1996 1600 SS) is the new one has understeer, particularly noticeable in roundabouts and tight corners, where the nose keeps wanting to push out.

 

I have had the post build check, and CC say that they have checked the alignment, and the tyre pressures are correct for my 16" wheels (Avon ZZ1s now, Pilots previous). Has anybody any advise on the setup to provide a more neutral handling car.

 

Dave C

[stevefoster]

Try a little more toe out.

Up to 0.5 Degrees as a max. Any tyre place should have a run over or even laser guage that you can check with.

Most Road 7'ers favour 0 but if you have this then try a little toe out. Too much toe out and the car will be darting and nervous at speed.

 

You need a 19mm spanner to undo the nut and 11mm to turn the trackrod end. Turn both sides to keep your steering wheel central.

 

 

[StewartG]

I would suggest that you go very carefully with the toe out as too much can dramatically increase wear on the inside corner of the tyres. I'm not sure that toe out increases front end grip and therefore reduces understeer I suspect it just makes the front end more responsive to steering input at the expense of straight line stability. I also assume that having had the geometry checked at the factory it's ok anyway. In my experience the best way to balance the under/oversteer compromise is adjustable spring platforms, whichever end you lower gets more grip. Another easy tweak is the rear anti roll bar. It might be worth stiffening the rear arb to give a little less rear grip to balance the understeer. You could also adjust the tyre pressures a little less air in the front tyres might make them grip a bit more. There's a few other things like camber but they should all be correct from the factory check.

[anally retentive]

Stewart,

 

Why do your tyres have corners. I know you like to be controversial, but do you really have square tyres???

 

How do you fit them to round wheels - is there a special convertor???

 

Or I suppose you could have square wheels. Where did you get them from and how much were they?

 

Do you have any pictures of them fitted to your car?

 

Finally if they are aluminium can you tell me if they are aerospace material and exactly what specification material.

 

Thankyou in advance

 

AR

[StewartG]

Just trying to be helpful and not political for once. What would you call them Edges? Shoulders? Inner-portion-of-the-treaded-area-of-the-tyre?

 

Edited by - stewartg on 22 Apr 2001 12:40:06

[DC]

Thanks for the advice so far. I do remember that my previous car, which handled like a dream did suffer from wear on the inside edge, so maybe a little toe out will be the answer, but I don't like the idea of the nevourness on the straight line stability. The tyres still lasted on the front for 10,000 miles. I think that I will go to my local garage and have the geometry checked first, and have a little play with the tyre pressures.

 

Dave C

[Dartmoor7]

>>Avon ZZ1s now, Pilots previous

 

There's your answer.

[Peter Carmichael]

I reckon Stewart is spot on regarding ride heights and ARBs.

 

I would try and find the *correct* tyre pressure and not muck around with it.

 

Toe out? Naah.

[Eugene]

Dave,

I performed a little research a few years back and you can see the results at http://freespace.virgin.net/shaw.clan/roadholding.htm

Not sure if it will help but...

 

Small Boy - with Big Toy!

[DC]

Well I went down to my local garage at lunchtime, and Caterham Cars had got it spot on 0. So I adjusted it to 0.5 degrees tow out and hey presto, a completely transformed car (well it suits my idea of handling). I've just come back from a thrash through the beautiful sunny Dorset countryside, and all traces of understeer have now gone. The front just goes where it is pointed to, and there seems to be no effect on straight line stability (only just over the limit). Thanks for everybody's advice. I'm now going to enjoy.

 

On the question of tyres, has anybody any experience of a tyre like a Yokohama for a 16" wheel?

 

Dave C

 

 

[Dartmoor7]

You can get 032s but in 205/50x16

[Warren S Smith]

I believe that Yokohama offer an AO539 which will fit the 16" wheel (205 45). I am interested in this tyre but does anyone have an opinion?

[Mike Bees]

It's nothing special, just an update of the A510/A520. Better than a stock Michelin or Avon I suspect, but not anywhere near the same league as A021R/A032R/ACB10.

 

Mike

[DC]

I've just checked on the web, and the Yokohama A032-R has a diameter of 610mm whilst the Avon ZZ1 is 590mm. That means the speedo is going to be out, and the ride height will be increased. Has anybody fitted the Yoko's?

 

Dave C

[Mike Bees]

You'll be travelling approx 3% faster than before for the same speedo reading. I'd be surprised if your speedo was that accurate anyway. If you're on a limited mileage insurance policy then you'll get 3% more miles...

 

Ride height will go up by 10mm as you say.

 

I would imagine that A032R in that size is horribly expensive, best to get some 13in wheels wink.gif

 

Mike