Understeer help

[Guest]

Hi All,

I'm starting to get used to my 7 a bit now and having fun with it but have a question regarding understeer.

The car feels nice when cornering at moderate speeds but if I up the pace, understeer creeps in which I would like to reduce. The car is a 1.8 VVC K series S3 with widetrack suspension. I know the front ARB was changed but can't remember what colour it was changed to. I have read that changing the front ARB can reduce understeer but don't know any more detail than that.

What would be a good way or reducing understeer without making it too tail happy please?

Thanks,

Lee

 

Edited by - Leebert on 13 Mar 2014 14:13:13

[Jonathan Kay]

Wheels, tyres and pressures?

 

Jonathan

[Guest]

The wheel are 14" KN Minators shod with R888 (medium) at 16 PSI.

[shn7]

Rake (no not the lawn kind)

[PL15 Lowflyer]

Lee,

What diameter is your front ARB?

R.

[A10ROX]

Stiffen (edited) rear anti roll bar ...

Add a touch more rake, lower front raise rear

 

Then start with front suspension geometry

 

Also try increasing rear tyre pressure

 

 

Edited by - A10ROX on 13 Mar 2014 20:24:14

[Guest]

It's about 14mm. So that makes it Blue I think.

 

The suspension is standard wide track - can I raise the rear with that?

[The Pikey]

Are the front wishbones parallel to the floor and is the rear 15mm higher than the front measured between the the chassis and floor under the rear of the lower front wishbone and between the chassis and floor where the rear wheel arch meets the body?

 

I'd set to the above and if no good raise the rear about 5mm and see how it go's.

 

J

[garybee]

Quoting A10ROX: 

Soften rear anti roll bar ...

 

Do you mean the front?

[Gavin H]

Is the damper travel very short - I had a 7 that would turn in nicely, then end up on the bump stops and get major understeer... I took th earb off on track days, got nice turn in and then used the throttle to moderate the rear end - not efficient but a lot of fun 😬

[PL15 Lowflyer]

Lee,

Only way to easily alter the rake is to fit adjustable platform shocks (unless otherwise corrected).

R.

[Guest]

I just had a quick measure in the garage. The front wishbones are near as makes no odds parallel with the floor.

 

The front height is about 165mm - measured here

 

The rear height is about 155mm - measured here

 

So, is my Seven running nose high?

[The Pikey]

you need to measure at the rear of the wishbone. The rear wants be be 15mm higher going by the book. I found when using a LSD it needed another 5mm.

 

 

Jason

 

 

 

Edited by - Jason Fletcher on 13 Mar 2014 21:04:31

[Guest]

D'oh! My bad

Measured at the correct position, it's a shade over 140mm (after settling the suspension a few times). Given that my garage floor probably isn't flat, it's most likely set to book figures.

 

From what I have seen of other Sevens, the dampers look normal (standard Bilsteins).

 

One thing of note though is that it was upgraded to an LSD back in 2008 which is probably making the understeer worse.

 

I'm guessing that the only thing I can do without buying more goodies such as adjustable platforms is to stiffen the rear ARB?

[The Pikey]

I think adjustable platforms are the way to go. Or a nice set of Nitrons 🥰 🥰 ... Sorry..

[myothercarsa2cv]

The sleeves and collars do crop up from time to time, keep an eye out. If not, buy a second hand set of billies off someone, swap the collars over and sell on for £20 less

[LesG]

Also have a close look at your damper bodies; you may have grooves machined into them which will allow you to raise or lower your ride height, by moving the circling up or down, which your damper platform rests on.

If you haven't got any 'spare' grooves, you could look into having some others machined in for yourself. You just need to measure your current ride height, and then work out where you need it to be.

[7 wonders of the world]

Remember all geometry and ride height checks and adjustments should be carried out on a level floor with ballast to reflect driver and or passenger weights, otherwise you will just be chasing your tail.

 

 

 

[elie boone]

if you have progressive springs the rake should be 35mm, you need to know how much rake you have before you start to change things. check your suspension and compare it to the std settings, a std setting is always a good starting point.

[myothercarsa2cv]

35mm Elie? That seems a lot more than the recommended 15mm... Any reason?

[elie boone]

John, linear springs are 15mm, progressive springs are 35 because the first inch or so of the spring is really soft. If you have a mount under the tube it's very likely you will have progressive springs

[myothercarsa2cv]

I do have the progressives. Interesting! Time to jack up the rear 😬 Any excuse to fiddle instead of drive

[Nick Woods]

I'd just like to reiterate what 7wotw said - all measurements should be done with the driver or an equivalent ballast on board.

 

To me, 35mm rake seems way too high unless that's with the car unladen; in which case the car will settle down according to the weight of the driver who gets in it. My car has a noticeably wonky attitude until 95Kg ( ) gets added to the drivers side when I get in.

 

IMHO a proper corner-weight and ride-height session is always a good place to start before you start fiddling with anything else, assuming your shocks have adjustable platforms or the grooves already mentioned.

[elie boone]

All Caterham data about rake is without driver.

[SLR No.77]

Nobody has mentioned driving style .......

 

Stu.