What can I expect from this change?

[Guest]

OK, so did my first track day on my newly aquired car, a Duratec with about 260BHP, in France. No set up done prior to leaving, so I drove it as I bought it. First thing I noticed was that compared to all the other 7's, I was really struggling to hold on over fast bumpy roads on the journey down.

 

Did the trackday without incident but didnt feel overly confident in the corners and it was difficult to get power down without spinning the wheels.

 

Anyway, another bumpy journey back home and whilst parked up, I compared my back end to the other 7's and pushing down on the back of my car showed a very stiff setup, with hardly any movement. All other 7's were very soft in comparison. I could see any adjusters, so assumed any changes to get the back softer would have to be done via the spring rates.

 

Back home and yesterday Ichecked out the shocks (Avo's) and indeed there is an adjuster but via a small "key" which I found on the key ring. I wondered what it was for!! The shocks were turned up to their maximum hard setting!

 

So, softened them off but didnt get time to drive. Question is, what can I realistically expect the difference in handling on track with a softer setting? Will the car turn in easier and allow me to get power down?

 

They were so hard, my neck hurt on some bumpy french roads that we were baltting down!

[Budjuggler]

I compared my back end to the others

No change there then. And yes your bum did look big in that

[charlie_pank]

Hmmm, it's a lot more complicated than that!

 

I would guess that 'as stiff as they go' is not going to be right, but the previous owner must have done it for a reason... Perhaps you ought to have a think about the suspension in general - how's the rake? (Height of front axle vs. height of rear axle)

[Grim Reaper]

Could also be being affected by bump steer, look into the steering rack height (type and orientation of rack supports) as they are not always right.

I fitted some 9mm blocks under my rack mounts and it made a dramatic difference to how the car behaved on bumpy roads.

[charlie_pank]

Quoting Grim Reaper: 

Could also be being affected by bump steer, look into the steering rack height (type and orientation of rack supports) as they are not always right.

I fitted some 9mm blocks under my rack mounts and it made a dramatic difference to how the car behaved on bumpy roads.

 

 

With absolutely no intention to ruffle your cloak: just because that worked for you, doesn't mean that's what's wrong for him, or that your 9mm adjustment would be right for him.

[Guest]

front end seems fine, no bump steer problems. I simply want to know what to expect going from full hard to soft, in terms of changes to handling characteristics.

 

I'll experiment on the next track day and get it set properly but I'm hoping a softer than massively hard setting will improve traction, grip and turn in.

[charlie_pank]

Very generally, by softening the rear, you will make it squat down more when you accelerate and you will also make it quicker to react to undulations in the road. This will make the rear grip more.

 

Normally this means that you will get more understeer because the rear has more grip relative to the front. You probably need to think about the whole setup, rather than just one part in isolation...

[Mark Durrant]

Mike

 

I recommend that you have the set up of the car checked, corner weights, tracking, camber and caster so the car is optimised for you. You can then adjust the damper settings and see what difference it makes. I have just had my car set up by Andy Jupp of Partridge Green Motorsport and can highly recomend him

[Pendennis]

Yep could be lots of reasons, could be ramp angles in diff, rear could be too stiff, rear could also be too soft dependent upon front, front could be too soft. Personally, I would look at camber, toe on front and rear, rear wheel alignment and rake, but try and establish spring rate.

 

[Guest]

I now have the info I need, thanks CP. I wasn't necessarily looking for advice to set the car up, or to correct a handling issue, just wanted to know what to expect in terms of change from hard rear to soft.

 

As suggested, I'll get the car set up properly, corner waited, camber and toe in checked.

[Pendennis]

Understood and to be fair to Charlie his comments are generally a good rule of thumb.

 

However, to throw some fuel into the fire my car has gone from Kumhos to ZZR tyres, it now has oversteer.

After viewing videos and photo's of my last race I am going stiffer

 

Point I am trying to make, simply going softer on the rear may not allow you to turn in easier or get the power down, could have the opposite effect and cause the car to push on whilst getting power down. If your drag racing, well that's a different matter 😬

 

A poor setup Caterham is chalk and cheese from a good set up one

[Grim Reaper]

With absolutely no intention to ruffle your cloak: just because that worked for you, doesn't mean that's what's wrong for him, or that your 9mm adjustment would be right for him.

 

Which is why I said "could be", "look into" and "not always right".

I gave the details of what I did to my car as an example.

I won't bother replying with any suggestions in the future if all people can do is flame them at the first opportunity. 😔

 

[Tony Whitley]

Quoting Culminator: 

First thing I noticed was that compared to all the other 7's, I was really struggling to hold on over fast bumpy roads on the journey down.

 

They were so hard, my neck hurt on some bumpy french roads that we were baltting down!

I'm not surprised, the lunchtime run (on race damper settings) to fill up was enough for me. The rear wheels were leaving the tarmac frequently at speeds over 50 I think I told you that the first time I drove mine I had to slow down because I felt sick from the jolting. It was on 20 clicks out of 24 as I remember, I now have it on 6 all round for commuting.

[charlie_pank]

Sorry you feel that way. Your comment didn't seem relevant. I don't know how I could have got my point across more gently.

[Simon.Rogers1]

TBH you should always count from full hard backwards to full soft.

 

So FH the -1, -2 -3 etc. This will give you the best base line -ie the needle and jet will be closed at full hard - dont force it past its natural hard point - it won't always go to the next click!

 

Full hard is when the shims will have an effect at full soft or probably within half a dozen clicks of full soft the bleed through the jet and piston will be taking the majority of the oil and so there won;t be much difference to a click at this softer end of the scale.

 

However from experience the dampers are not likely to be the same on the same click settings any way and the only way to tell if they are is to have them dyno tested.

 

[Guest]

Simon, understood and I'm going to have a play. Tony, just out of interest, what settings for the rear were you on for Saturday? As our cars are identical, it would be interesting to see where you had yours set as a guide starting point for future track days.

[Grim Reaper]

Quoting charlie_pank: 

Your comment didn't seem relevant

 

While I read

Quoting Culminator: 

First thing I noticed was that compared to all the other 7's, I was really struggling to hold on over fast bumpy roads on the journey down.

as he was having trouble with bumpy roads, which is what uncorrected bump steer will give.

I give up.

 

[Simon Owen]

Do you know what spring rates they are ?

 

 

 

[Simon.Rogers1]

My guess from the description of the handling is that the spring rates are to hard not the the damping in the units themselves - mind you I guess there will be to much rebound and not enough compression also.

 

I have been there and driven cars with rear springs in particularly that are to hard. Bounce you all over the place.

[charlie_pank]

Quoting Grim Reaper: 

Quoting charlie_pank: 

Your comment didn't seem relevant

 

While I read

Quoting Culminator: 

First thing I noticed was that compared to all the other 7's, I was really struggling to hold on over fast bumpy roads on the journey down.

as he was having trouble with bumpy roads, which is what uncorrected bump steer will give.

I give up.

 

 

 

Quoting Culminator: 

Question is, what can I realistically expect the difference in handling on track with a softer setting? Will the car turn in easier and allow me to get power down?

 

Quoting Culminator: 

I wasn't necessarily looking for advice to set the car up, or to correct a handling issue, just wanted to know what to expect in terms of change from hard rear to soft.

 

 

Yawn

 

[Tony Whitley]

Quoting Culminator: 

Tony, just out of interest, what settings for the rear were you on for Saturday? As our cars are identical, it would be interesting to see where you had yours set as a guide starting point for future track days.

I was on -4 all round. I think I've tried -0 on track before and found that it slid around a lot (I presume because the suspension has too little compliance to stay in contact with the track) - but I prefer hooning around to spending a lot of time on set up.

 

@Simon.Rogers: when adjusting the dampers mine goes from bouncing like a kangaroo with several inches of suspension travel to barely moving if you jump up and down on the back. I demonstrated this to Mike in Calais car park

[Guest]

Thanks Tony!