setting up ride height on new nitron 46's

[Dipper]

posted this on selec but thought id see if there were any gurus here.

my suspension knowledge is limited to mountain bikes where the terminology and goals are a bit different so bear with me.

before replacing my old ntr 40's i took measurements of the current ride height. for ease i took the measurements from ground vertically to underside of wheel arch(im trying to replicate the previous ride height and geo as it worked well)

fitted new suspension and the front sat 20mm too low and the rear 15mm too high.

5 turns of preload on the front brought it up 7 mm. backed off 5 turns on the rear brought it down 5mm

with 10mm still to go on the front im concerned im putting too much preload on the front end. the helpers will be pretty much fully compressed.

on the rear the helpers will be totally uncompressed to get it down 10mm

if this was a mountain bike id be changing the rear springs for lighter ones and the fronts for heavier ones to get the desired ride height

any advice?

[robin]

It is absolutely typical of these to have the front preload so hard that the "tensioner" springs are in fact just spacers and the rears so loose that they rattle on full droop. I don't understand why Nitron cannot either fix this issue or at least tell you that you'll need new brackets to make it work "optimally" - i.e. with the tensioners still under some tension on full droop, but not coil bound.

IMHO you need new brackets. Luckily elise parts sell brackets for various ride hide changes but they're not specifically designed for this challenge and it's mind bending to get your head around which of the brackets they do sell will give you the offset you need in order to take advantage of your shiny-but-useless helper springs.

Ask Nitron, or whoever supplied them, how they're supposed to work on your car and see what they say?

Cheers,
Robin

[woody]

Few questions first:

Is the car on completely level ground?

You sound as though you're not measuring at the recommended place; at the front and rear of the main sill to the floor?

What height if any did you spec?

What was the car at previously? 10mm lower at the front than the rear is desirable.

Is the car ballasted (75kg in each seat plus half a tank usually, but I've just ballasted the drivers seat with a full tank in the past)?

Car is an S2 K series converted to NA Honda?

ETA, the point I was getting to is the same as Robin's. Sounds like a change of brackets is required, just working out which.

[Dipper]

the 46's came with their own top mounts but theyre just wider than stock. i realise the helpers will be fully compressed once the cars on its wheels but it seems daft for them to be coilbound while unweighted. rears are already loose and still 10mm higher than it was before! i agree that new brackets would be the answer.

car is on level ground. i didnt spec any heights and theres no ballast. none of that should matter anyway as all i was after was a reference point from before. there was @ 10mm difference front to rear. if i can get it to the same as it was with the 40's ill be in roughly the right place. then i can check underneath for sizes.

i bought them from dave at seriously lotus so ill try him first.

cheers

[Dipper]

did a bit of tweaking and took it for a short run to settle the suspension(damn me id forgotten how good it is!)

ive taken the measurements from the jacking points between the front wheels and on the clam just in front of the rear wheels

FL 120mm FR 123mm
RL 128mm RR 128mm

no preload at all on the rear and helpers almost squished flat on the front! still, it felt good. a bit less bouncy than the old 40's that came off.

[Dipper]

Spoke to Dave at seriously lotus. He reckons the front sounds fine but the rears are on their limit. He's recommended 3" helpers at the rear. That should sort it.

Not much wrong with the ride heights as they are but if I want to drop the rear at some point I can't unless I swap the helpers.

Thumbs up to Dave for taking time to call me on a Sunday as well

[Dipper]

edit to the above.

dave's just been on the phone. it turns out there are 2 different length dampers. one is for standard road heights and theres a slightly shorter sport version for running lower than 130mm rear. I could run longer helpers but the droop to bump ratio wont be right. he's sending me the new dampers and i'll get them swapped when i get back from offshore. result!

[C7Steve]

Have you got your suspension set up as you had hoped now?

Steve.

[Dipper]

yep. dave sent me new rear dampers. might still raise the front a fraction as its pretty low. its better on the road than the old 40's. not tried them on track yet