under steer

[p.mole1]

I seem to be suffering from quite a bit of under steer. It seemed particularly bad at Croft and the fronts were quite badly worn.  My Car is a 1995 Super Sport narrow track. It has a rear anti roll bar on its softest setting the front anti roll bar has orange bushes. 

I am running 14 inch Toyo 888 all round at 20 psi with Nitron shocks with 200lb front and 140lb springs. My car has an open diff and is  a 1,4. It could be down to bad driving as this is the first rear wheel drive car I have owned in over 30 years of driving. 

I would like to make the car a bit more neutral till I gain a bit more experience any ideas of what I should be adjusting

[Delbert]

Well you have moved on since we met at Cadwell 

First thought - has the car been flat floored with you in it ? Try getting a neutral set up as a datum

There are others who will know more about set up but I would look at front set up ( I think toe in gives greater turn in ) 

[Tazio]

Just to correct Delbert, conventional wisdom is that a little bit of toe out improves turn in, at the expense of nervousness on our deteriorating A and B road surfaces.

The best advice is that if you have adjustable platform on your shock absorbers take it to those that know how to and have the car flatfloored and set it up properly.

Money well spent.

[Jonathan Kay]

(Edited: Crossed with Tazio's.)

Extending Delbert's approach a bit I'd consider:

• Talking to a suspension expert about options for components, including the cost axis. There are a lot of recent reports of big improvements from this.
• Setting the geometry to some known starting position, such as the one in the Assembly Guide.
• Setting the corner weights.
• Getting it tested by an expert. But I don't know the best way of doing that and I don't fancy other drivers testing handling limits when I'm nearby on public roads. How do people do this in practice... track days, test days... ?

Jonathan

 

[Mark Durrant]

If your 'ooop north' contact Dave at Gemzoe Motorsport in Wakefield who can check and refine the set up on your car 

[p.mole1]

Hi Delbert, little did I know how much fun it could be and you can't fall off four wheels! I had no intention of track days when I bought the car, now I have little interest in driving it on the road.

Just to point out it's fine on the open road, It's only a problem on a track day. I have nothing to compare it too, probably a good idea to get someone else who is experienced with Caterhams to give it a drive on the next track day. 

Being Northern and tight with money, so far I have set the suspension with me in the car and my wife measuring the ride height, not ideal but Simon from Meteor recommends it and it should be in the ball park. I have altered the damping stiffening up the rear and softening the front this made a small improvement.Tracking is set to 0 toe out so I will try altering a spot of toe out. Probably a good idea having it looked at by an expert just to check all the wheels are pointing in the correct directions.

[RogerB]

I'm certainly no expert however I read recently on a Toyo website that simply adjusting tyre pressues to balance the car. Lower fronts and/or raise rears to reduce understeer.

I hope this isn't stating the bleadin obvious. 

[Simon.Rogers]

You have the Street Series Nitrons.  You have the correct springs and so long as you have the rake in the car that I suggested and there is no extreme tracking settings you have all the tools available to dial this out.

Tyre pressure is too high.  16 cold will be just fine.

Then whichever end of the car is sliding you need to soften the damping,  Do this by 4 clicks at a time.  Then 2 and then stick or adjust 1 click as you get closer and closer to the correct setting.

Track day driving can draw you into entering the corner with to much speed but the above will help.

 

[OliverSedlacek]

Caterhams can be tuned quite effectively using tyre pressures and also using rake. Raising the rear ride height should help as it raises the rear C of G relative to the roll center, promoting weight transfer at the rear.

[p.mole1]

Thanks everyone, could be my bad driving,hurtling into corners to fast! because I have so little power! To be honest I never even considered tyre pressures, I have just been using the recommended pressure in my 1995 manual.

[ScottR400D]

Wouldn't stiffening the rear roll bar help?

[A10ROX]

Is it all corners or just some?

certain carrying too much speed in can lead to under-steer ...

As stated above there are a number of ways to correct under-steer simplistically it requires more grip on the front or less grip on the rear, so try any / all of the following:-

get instruction from track specialist, Hawthorn will show up any handling issues, well set up Caterham is great from Tower through Jim Clark and Barcroft

check rake, most aim for 15mm

​adjust / reduce tyre pressure, is the 20 quoted cold or hot ( does the under-steer build with the number laps?)

adjust the rear anti roll bar (stiffener will create more over-steer to balance the under-steer)

adjust the dampers

trying doing one thing at once and feel the effects at one or two corners ... enjoy and keep it on the black stuff!

 

 

 

[p.mole1]

The worst is Tower,then I seem to start getting high speed under steer in the Jim Clark Esses.  Every where else is ok, so my bad driving is probably not helping. 20 psi is measured cold, I have 15mm rake. The rear anti roll bar is on its softest setting and so far it's been left it alone as so many people haven't got or seem to remove them, I will try that next. I have heard that the earlier cars front anti roll bar was too thick?

[The_ASH]

I'd try tyre pressures first (I've never run 20psi cold on a Seven) and then if it's still there try up one step on the rear arb. You have all the right kit and plenty of adjustability it's just a matter of getting the settings that suit your driving style (which is also adjustable). Be methodical about the changes, adjust one thing, if it's worse return to original and start again, perhaps keep written or vlog notes at the time.

[chrisbeddoe]

You mention that your rear suspension is on the softest setting. The softer the rear (i.e. the further down the bar it is) the more under steer you will get. Try moving the linkage up a notch or two. 

[A10ROX]

I don't have experience of your tyre - wheel combination as I run Avon on 13", however 20psi cold sound high ... I run 21psi hot which is 14-16psi cold

I suggest play with tyre pressure first as this is the easiest

if it improves - changes the handling daily to what you like and adjust rear anti-roll bar