Roadsport Track Day Suspension Setup

[Benjam]

Hi

Purchased an ex-Academy Roadsport car a few years ago and have had a great time skidding about on track days with my dad.

He loves the car but its way too soft for my liking and bottoms out in places when I'm driving, taking the drivers seat backwards in the process (which is frightening when your flat in 5th going through the compression at the bottom of the Foxhole @ Nurburgring)!

Not running a silly ride height and plenty of rake so its pretty obvious the car is too soft and whilst no stranger to car setup, I have not yet touched the Caterham beyond fitting a rear ARB and CR500's. Fair to say there is a difference in driving ability between us (MSA International license holder with Elise Trophy wins, VLN and 24-hour experience vs a 65 year old track day nut) but the emphasis needs to remain on track day fun.

Don't really want to switch to a full Nitron setup as not chasing lap times so was planning to simply up the spring rates 30-50% but not sure how the standard Bilstein damper valving will cope or whether there is a better way to achieve a the same outcome.

All advise welcome please.

Cheers
Ben

[PeterY27]

I'd suggest fitting the tracksport/supersports Spring and damper setup, it works well on the cars and is well tested. It is also still usable for the road.
You could just replace the springs but replacing both will give a more consistent setup.

[sfaulds]

As Peter says above, but you also need to look at your floor and seat runners as a matter of priority - it shouldn't move when it bottoms out!

[Benjam]

Thanks guys. Is the tracksport/supersport setup also know as Caterham's wide track upgrade? If so, I though that retained the same spring/damper combo (albeit perhaps with increased rates) or am I thinking of something else?

Cheers
Ben

[SimonRogers]

Matching the damper and spring is critical. Simply upping the spring rate is pointless.
Personally what I have seen on the Dyno I would not use anything harder than the standard road set up springs with the standard dampers.

The newer tracksport M5 damper and spring combination is over sprung.

[David Rowe]

The supersport springs/dampers are a good solution and they can be purchased separately to the wide track wishbone kit they are not mutually exclusive to them.

If the car is bottoming out the car is either too low at the rear (say when you are 2 up, which is most likely) or the springing too soft. In which case your only option is to either increase the spring rate or increase the static ride height.

It sounds like if you are taking the car around the Nurburgring for fun then having the damper ratios perfectly optimised isn't really going to be a priority especially if there's a slower driver who's not at the limit. It sounds like you need a low cost, simple solution. My opinion would be to retain the narrow track, and front springs/dampers then assuming the rear ride height is not actually too low fit the uprated progressive springs sold by Caterham which increases the spring rate by 30% apparently. This will reduce bottoming and also keep the progressive benefit of the system. I wouldn't change the rear dampers yet, I think the damper although softer than the M5 damper will be ok to run.

Next to reduce roll fit the largest anti-roll bars sold by Caterham (in fact you can special order a thicker version from redline), this setup will keep good ride complaince for bumpy tracks like Nurburgring but then the bars will help the roll control which you are experiencing as excessive.

Doing it this way just requires 2 springs and a new front roll bar. Making sure the car is drivable is probably a good thing at that kind of circuit!

Hope this helps.

Also the seat issue sounds sketchy, as Stuart says I would get that sorted, not sure how bottoming out will make the runners move.

[Benjam]

Thanks David, your assessment of our requirements is spot on. Whilst I appreciate the need to match damper valving and spring rates from race experience, the driver combination and use of the car does not warrant any significant investment.

The car is running loads of ride height so I dont think thats an issue, to me the car is simply under sprung so hitting the deck when 2-up. Its the drivers seat mounting bolts that hit first hence the seat movement!

Already have a red front ARB and full hard rear ARB so will try going stiffer with springs before Supersports. Given the cars use I very much doubt it warrants any damper investment... given the strong residuals it would be better to sell the car and buy an R300 to be honest!

Are the items in question:

Rear Spring - 30% Uprated - Progressive
SKU: 74076 http://www.caterhamparts.co.uk/product.php?id_prod...

and...

Front Spring - de Dion - 170lbs/in
SKU: 75517 http://www.caterhamparts.co.uk/product.php?id_prod...

Thanks
Ben

[Benjam]

Would it also be worth fitting an 18mm ARB as well?

Front Anti Roll Bar - 18mm - XF / Vx
SKU: 72094 http://www.caterhamparts.co.uk/product.php?id_prod...

Cheers
Ben

[gareth h]

There are many with more knowledge than me, but could the problem be with the dampers? Surely more compression damping would control the spring and prevent the car bottoming out?
I've had a couple of suspension sets from simon (quantum and nitron) and they are night and day compared to the caterham bilsteins (and I am definitely not chasing lap times!)

[k20erham]

Dave flat floored my car and made it fantastic from what it was, I then went onto 3 way Penskes from Simon and it was unbelievable so so compliant and to be able to soften it off in the wetis great, again I don't race it but just made finding my limits easier. I need tuition now!!!

[anonymous-user]

Benjam said:

Thanks David, your assessment of our requirements is spot on. Whilst I appreciate the need to match damper valving and spring rates from race experience, the driver combination and use of the car does not warrant any significant investment.

The car is running loads of ride height so I dont think thats an issue, to me the car is simply under sprung so hitting the deck when 2-up. Its the drivers seat mounting bolts that hit first hence the seat movement!

Already have a red front ARB and full hard rear ARB so will try going stiffer with springs before Supersports. Given the cars use I very much doubt it warrants any damper investment... given the strong residuals it would be better to sell the car and buy an R300 to be honest!

Are the items in question:

Rear Spring - 30% Uprated - Progressive
SKU: 74076 http://www.caterhamparts.co.uk/product.php?id_prod...

and...

Front Spring - de Dion - 170lbs/in
SKU: 75517 http://www.caterhamparts.co.uk/product.php?id_prod...

Thanks
Ben

The car's actually hitting the ground under the seat?! Are you sure? Surely the springs will bottom out long before that happens?

[SimonRogers]

Just for info the majority of the dampers we sell are for road use but each set is a bespoke set up for that particular customer. Everything from car spec and use is taken into the equation.

[David Rowe]

Benjam said:

Thanks David, your assessment of our requirements is spot on. Whilst I appreciate the need to match damper valving and spring rates from race experience, the driver combination and use of the car does not warrant any significant investment.

The car is running loads of ride height so I dont think thats an issue, to me the car is simply under sprung so hitting the deck when 2-up. Its the drivers seat mounting bolts that hit first hence the seat movement!

Already have a red front ARB and full hard rear ARB so will try going stiffer with springs before Supersports. Given the cars use I very much doubt it warrants any damper investment... given the strong residuals it would be better to sell the car and buy an R300 to be honest!

Are the items in question:

Rear Spring - 30% Uprated - Progressive
SKU: 74076 http://www.caterhamparts.co.uk/product.php?id_prod...

and...

Front Spring - de Dion - 170lbs/in
SKU: 75517 http://www.caterhamparts.co.uk/product.php?id_prod...

Thanks
Ben

Yep you got it nailed there ben, you already have the front 170lbs Spring fitted so leave that, but order the uprated progressives you have linked up above. It'll probably be a special order via Caterham now as they don't show stock. For the front roll bar the 18mm is a good start but you may wish to go to 3/4" bar where the bush colours are yellow. This is a special order from redline, give them a call. The roll bar stiffness works at the 4th power of the diameter so you get a large stiffness gain from only a small step up in diameter.

http://www.redlinecomponents.co.uk/

Redline may be able to supply the prog. Uprated Spring also but not 100% sure.

This will be the simplest solution by far, no getting away from decent correctly calibrated
dampers bieng an ultimate benefit all round but doesn't sound like you need to go down this road yet. The Caterham dampers tend not to have enough low speed rebound or with the M5 have too much bump so there's a simple improvement to have from a revalved set without getting too technical.

[Canuck7]

Just remember that the rear of a DeDion caterham can use two different shock body lengths, depending on year and modifications. They used to use centre of tube mounts, then bottom of tube mounts, then de dion tubes with both options. Not sure of academy cars used dedion or not, but it is something you have to check for sure. (and that all hooks into which dedion tubes are prone to failing.)

Another thing; if front/rear spring rate ratios get out of synch, you can actually end up feeling sea-sick at certain speeds when cruising on an highway. Unlikely these minor shifts in spring rates will be enough to do that - but it does demonstrate how suspension is really a single carefully balanced entity, that can have odd repercussions.. :-)

A fat front rollbar may simulate stiffer front springs, but it will most likely create more understeer than a stiffer spring set would.

I put a set of nitron one way shocks with eibach road rate springs on my caterham. They were cheaper than the forks for my mountain bike. :-D One of the best shock - ooops - damper systems I've tried. I've only been on KYB, ohlin (basic), Koni, and K&W systems usually on subarus, so not much to compare to, but the KW's are two way with remote reservoirs and quite nice, and the basic nitrons match up to them quite well. I'd say getting 2 way nitron's with the recommended spring rates, would be well worth it, even for the most benign of track days. Mine certainly improve the road feel tremendously. The extra safety on the 'ring would be worth it, in my mind. The suspension is so easy to swap on a caterham, you could take them off and sell them separately, to get some extra cash back, if you decide to sell the car.

[Benjam]

Just checked the car and have 75511 front springs which are 150lb I believe so would going 170lb front with the 30% stiffer rears ensure the same front/rear change without touching the front ARB? Thanks, B

[HustleRussell]

Some of these suggestions seem pretty bodgy

This is a Caterham we're talking about, and for track use to boot.

We know nothing about the existing setup apart from the springs / dampers / roll bars.

How many miles on the existing suspension? is it healthy? what is the ride height front and rear from chassis rail to road?

When it bottoms out, what part of the car is hitting what part of the circuit? Is it just the rear tow eye or exhaust on curbs only or is it bottoming out on it's arse in the middle of the circuit?

How do you find the handling generally, is it OK apart from the bottoming out?

If everything is healthy on the existing suspension then a change of springs and dampers is in order

Also can somebody please explain how a gigantic front anti-roll bar is going to influence the rear ride height over straight bumps and crests?

P.S. as already mentioned, please secure your seat OP. Have a look at the construction of the floor. There isn't much keeping you in and Aluminium doesn't do well in fatigue.

Edited by HustleRussell on Monday 4th January 16:37

[HustleRussell]

Benjam said:

Just checked the car and have 75511 front springs which are 150lb I believe so would going 170lb front with the 30% stiffer rears ensure the same front/rear change without touching the front ARB? Thanks, B

This sounds sensible, although those springs may give your shocks a bit of a hard time especially if they're well used. Before you tear the thing apart, Measure the front and rear ride height. With CR500s (175/55r13?) you may find it too low even with the new springs. The solution to this would be to fit adjustable platforms, a cheaper alternative would be to move the spring seat up into a higher groove, having a higher circlip groove machined into the damper body if necessary.

Alternatively change to 185/60r13 tyres.

Fitting a fatter front roll bar will just increase the understeer. The best setup I have experienced had no ARBs whatsoever.

[SimonRogers]

As I said you have to look at the entire set up.

It's what Meteor does.

[David Rowe]

Hi Guys,

Without getting into a long debate and to add some clarity for confidence, what I suggested was an "option" for a simple, cost effective solution which has been thought about from an experienced, engineering perspective to suit his needs. As the owner and engineer at DPR Motorsport I have extensive on-track experience (around 9 years with Caterhams alone) with the exact model of the car in question. I also specialised in vehicle dynamics when studying Automotive Engineering at University.

What I have suggested I have track tested myself on the *exact* model of car he is talking about. From experience, you have to make some drastic changes to the fundamental configuration of this car to produce a handling trait that is completely in the wrong place or at worse dangerous. Spec dampers will cope with some variance in ride/roll rate without there being a huge problem in an 'under-damped' car or 'over-damped' car.

I give one example to prove this, on a Caterham platform ideally there needs to be damping control of ride movement and roll movement. Springs deal with ride and roll and ARB's deal with roll only. Therefore the effective wheel rate in roll is higher than in pure ride. Ideally there needs to be one damper for ride and one for roll movement unlinked (not to mention specific damping for single wheel bump and pitch). So with only one damper for roll damping and ride damping you are already compromised! There is no perfect solution in this case. With progressive or dual-rate springs again the damping should be variable depending on the spring preloaded/loaded position, but it cannot be.

I have assumed the car is in a serviceable condition.

As for roll bars creating too much understeer over springs, why? Weight transfer distribution changes the cars handling balance and its a combination of roll bars and springs which then produce a specific wheel rate in roll. If you have a soft spring, stiff bar the wheel rate could still be the same for a stiff spring/soft or no bar. There are however other important dynamic situations going on with the two which do make some differences but I'm not going to go into that now, but this is partly why I suggested stiff anti-roll bars and keep the springs std. This is not a generic positive solution for all cars, as Simon has said you need to look at the whole package.

If anyone wants to talk further about this, particularly Ben for some further advice I would be happy to receive an email, [e-mail].

Edited by David Rowe on Saturday 9th January 14:05