Suspension for Hill climbing - & good in wet

[George K]

I am 90% certain that I will change my Clio Trophy for a DC5. I run the Clio in the Production Class in hill climbs; it handles very well and is ultra competitive in the wet, but is lacking on the power front, and even if I were to spend a lot on the engine, would still not have the same power to weight ratio as the DC5.

My concern is hill climb cars tend to be set up a lot softer than circuit cars (whether single seater Goulds, Dallaras or saloons) and most of the suspension kits for the DC5 would seem to have a track bias; this would seem far too stiff for the hills, particularly in the wet. To give you an idea the Clio, which is not that much lighter than the DC5, has front springs in the 200 lbs/inch (3.6 kg/mm) range, whereas the softest Tien kit is 330 lb/inch (6 kg/mm).

I am reluctant to sacrifice being competitive in the wet, and so am looking for recommendations which may be suitable. Any ideas gratefully received – even if only to whom I should talk.

 

[celox performance]

I've got the D2 coilovers which probably have the softest spring rates of any of the coilovers available for the DC5. They can be picked up from Ebay for around £475 for the complete kit

They are of very good quality and are Cusco copies. I would also advise a Spoon plated LSD which will give you a load more traction in the wet . From experience I wouldn't recommend a plated diff if you'd also be using your car daily as they can be a pig to drive on the roads, but they're great for getting the power down.

 

[George K]

Hill climbing

Celox, thanks very much for this info - pardon my ignorance, but who or what are D2?

Do you know where the AST kit fits into the scale of things?

I take your point about the diff - working in the transmission world I am aware that gear types don't work once one wheel is off the ground, and also about the drawbacks of plate type diffs. Best answer for road use would be a combined VC and plate, but they need quite a big housing.


Regards

 

[C&S Evo7]

look at HKS hypermax III as they will be available for the UK market with Full backup from HKS, they will be able to revalve and tune damping to suit.

I was using hypermax pros for track use and found them very reliable but much too hard for road.

speak to Tom at TGM he will be the best to advise you

 

[Turtle]

Be a little cautious trying to compare spring rate alone as an indication of how compliant a suspension setup is. The damping has a large impact as well - you can have the same spring rate with very different feel due to different damping.

Also you can't compare spring rates between cars (or ends of the same car even...) without knowing the motion ratio - the leverage acting on the spring. For example, the motion ratio on the rear of the DC5 is very different from the front, so a 10kg/mm rate on both front/rear axles gives very different effective rates. The Clio will be different again.

My initial suggestion would be to try find a few people with setups that you think might work and ask for a passenger ride. You'll get a rough idea at least of the performance/compliance of the different setups then and you'll have a basis for comparison. For example you could come back and say "I went out in X's car with Y dampers on it - I liked X about it, but didn't like Y - can anyone recommend something else to try?".

-Brian.

 

[George K]

Turtle, Both the Clio and DC5 have struts at the front, so the installation ratio is the same, whereas qite obviously the set-ups at the rear are very different. Also I have programmes from my motor racing days to calculate springs rates and allow for different installation ratios and spring/damper angles.

Agree that damping will change the rate of change of attitude of the car - but the spring rate is a fundamental base - also need ot factor in arbs, but must get springs rates right first. I do find the Bilstein method of rating most helpful as it gives like for like comparison of low speed damping as well as the relationship between bump and rebound.

 

[Turtle]

Turtle, Both the Clio and DC5 have struts at the front, so the installation ratio is the same

No, they're not the same. Similar, but struts still have a different motion ratio depending on the geometry.

-Brian.

 

[George K]

Brian, Can you explain, afaik the only difference will be Cosine of the angle of inclination, which is the KPI - these are unlikely to differ by more than a couple of degrees and so surely the effect should be minimal?

 

[Turtle]

Yes, the inclination change is not a large effect. However there is still the basic leverage. I am nit picking somewhat as it's not a huge difference (unlike the rear!). There's some other geometric effects at play - while it's common to assume near 1:1 with a strut setup, 1:1.1 would be a more useful ballpark for the DC5 - while that's not the exact figure it's close enough for what you need.

-Brian.

 

[George K]

Brian, thanks for your reply and I assure you that I am not nit picking or point scoring either - but surely as the wheel /hub is rigidly attached to the strut and if anything there will be a negative scrub radius, I still don't really understand your leverage point. Always willing to learn - every now and again the scales drop from my eyes and I shudder to think how wrong I used to be!

Regards

 

[Turtle]

Fixed yes (ignoring angular changes), but where the load goes through from the contact patch of the tyre compared to where the spring load is fed through the hub to the lower arm isn't 1:1 (which is the usual assumption). It's a bit tricky to measure - you have to look at the lever connections from the bottom ball joint rather than just the theoretical view from the scrub radius/kpi etc. You have to look at what loads go through the spring from a multibody dynamics point of view, not just the traditional geometric view.

-Brian.

 

[George K]

A bit multi-dimensional, but i think that I follow.

BTW do you know that installation ratio at the rear - have not yet got a car to measure!

Thanks and regards

 

[Turtle]

Sent in a pm. For anyone wondering why I've not just posted the figure, every so often I think it's nice to encourage people to go and measure things themselves. :lol:

-Brian.