Front Spring Rate

[KenEvans]

I want to increase the front spring rate on my 2000 model standard track car. What's the standard Caterham spring rate out of the box please? Is 250lb/in the next step up?

 

It's a road-going car doing about 5000 miles and 12 hillclimbs/sprints a year so I'm looking for that happy compromise between comfort (ho ho ho) and competitiveness.

 

The car has already been dropped down a bit with the with the front being about 10mm lower than the back and I'll be adjusting the rear arb to its max setting after the harder springs go on. Tyres are list 1A Potenza SO2.

 

Any comments please?

Ta

Ken

[Alex Wong1697456877]

What engine?

[KenEvans]

The best Alex............... .......a K Series 1600......180BHP..........(about)

 

Ken

[Alex Wong1697456877]

My setup is Front - SLR race dampers , 250lb springs ,1/2" arb , 2+2+2 washers for castor , 2.5deg static camber , paralell toe .

Rear - SLR race dampers , 130lb springs , 1/2" arb on minimal setting 1 , ACB ears .

Heights - 65mm under leading edge of sump , rear 14 mm higher .

---

 

Dave Jacksons setup 200BHP+ 1600K and VERY fast.

 

Copied from the Curborough results thread

 

Edited by - Alex Wong on 30 Aug 2002 11:12:49

[Graham Perry]

Is Dave Jacksons widetrack or Standard, as that would be another variable, as that would influence the spring rate ?

[Mike Bees]

150lb is the current 'stock' Caterham front spring. Springs are generally available in 10lb increments. 250lb is a good choice. I wouldn't run the rear ARB on max stiffness - in the name of traction I tend to run with mine disconnected altogether for tight/twisty venues.

 

See you at Loton!

 

Mike

[Peter Carmichael]

My setup from Curborough:

 

Front: 250lb/in springs. 18mm ARB. Nitron dampers. ~1.5 degrees camber. ~1mm toe out. three washers in front, one behind. Ride height approx parallel lower rear wishbone arm.

Rear: 120lb/in springs. 1/2 in ARB on 3rd setting (one off stiffest). 0.25 degree de dion ears. watts linkage. Ride height random and determined by springs that were too short. Nitron dampers.

 

 

[KenEvans]

Lots of good info there - thank you. Most of it will be winter projects but I might try to sort the 250lb/in springs before Loton next weekend.

 

Mike - why should more rear roll give greater traction? Is it simply weight transfer to the outside wheel under cornering? (Yes see you at Loton - I'm better there than at MIRA (and Curbourough come to that!))

 

Ken

[Mike Bees]

Increasing roll stiffness increases weight transfer to the outside wheel, hence the inside wheel is more likely to spin.

 

Peter's setup is quite similar to what I found worked well at Goodwood the other week - 250/130 springs, Juno front ARB on full stiff and Caterham rear ARB on 3rd setting. My 'oddity' is that to cope with 15in wheels I'm running the rear radius arms in the upper position (too much roll-induced understeer on such tall wheels on the lower setting), which hitherto has made the car *very* keen to spin like a top on high-speed lift-off. The stiffer setting on the rear ARB seems to have tamed that trait, which is logical. IMHO it's too stiff for the hills & Curborough, but then corners at these venues are relatively slow.

 

I'm a lot worse at Loton than I am at MIRA - I've only been to Loton once and there's a lot more to learn. 'Tis a wonderful hill.

 

Mike

[KenEvans]

Ah!! Now that's interesting Mike! My Achilles heel seems to be a tendency to spin while trail braking after a high speed approach. I did it at Curborough and it's happened several times at Loton! I thought it was me being a crap driver (maybe it still is)

 

I too have 15 inch wheels but the radius arm is parallel to the road with the arb only in the number 2 position (1 off softest). I don't want to make too make more than one change at a time so I think I'll try stiffening the arb just one hole and see what happens.

 

Ken

[Peter Carmichael]

Ken,

 

You might just need to lower the rear ride height a smidgen - two turns on the platforms will be plenty. Watch out for excessive understeer though. Mike's solution is to stiffen up the car so that the rollsteer never occurs rather than to use the geometry to neutralise the roll steer. Worth trying both.

 

Edited by - Peter Carmichael on 30 Aug 2002 14:20:24

[KenEvans]

Thank you Peter - I had the car lowered by Clive Kenrick because these sort of jobs to Clive and Robert are like shelling peas - while I go for a nice walk around Llangollen.

 

With the standard springs the rear is apparently at its lowest setting possible. I take it that 130 springs are not too far removed from standard, are they a little shorter too? I don't want it too firm on the back because they don't seem to be able to make smooth roads in Shropshire.

 

Ken

 

 

 

Edited by - KenEvans on 30 Aug 2002 15:13:15

[KenEvans]

Appt. made with Clive to get the 250lb springs fitted

[Peter Carmichael]

Not sure whether 250lb/in springs need to be fitted with helper springs on standard track. Clive will advise.

[KenEvans]

Yes..................................so what exactly are helper springs Peter??

[scooby dooby doo]

stiff springs will not get much longer when you remove the weight of the car from them so its possible that at full droop the spring isn't touching the damper at the top. a helper spring is a very weak spring designed to fill this gap and stop things rattling around and getting out of place.

 

HOOPY CYCLE WINGS CUCUMBER