Spring rates? Why not 3:2 ratio on HSD, yellowspeed etc?

[project.r.racing]

I've found a 16mm rear sway bar is way too much i've been trying to get an oem SE rear 14mm with no luck.

Personally i think the best sway bar combination is the RB 1.125" front and the oem MazdaSpeed 14mm rear with 949 endlinks all round. But as with anything sway bars come down to personal taste, get a front adjustable for sure (and rear if you can) as it really helps fine tuning of the car.

Funny, thats exactly what I am going to do.

Surely the damper settings on adjustables will modify the characteristics of the spring rates so that you can fine tune to your heart's content. I don't see the 3:2 ratio as being any more than a target to shoot for.

damper settings do not effect spring rates.

[Matty]

I agree with the 3:2 ratio "rule" and agree that most coilover suppliers seem to have their heads up their arses. "I know, we'll make the FWD MX-5 handles sweet as by making the rear really stiff so it won't understeer!"

This might have a small amount of merit at 6/10ths on the street, but is useless on the track at the limit.

On the other hand they may be working on another textbook theory which says that the rear bounce frequency should be higher than the front. There is again some merit in this, the idea being that as you go over a bump (front wheels first then rear), the rear up and down motion "catches up" to the front after about 1 bounce (after which it is damped out). The aim is to minimise pitching (back and forth rocking).

In theory, there's no difference between practice and theory. In practice, there is.

The trouble is you are sitting nearly over the rear axle in an MX so ride comfort goes out the window. The stiff rear springs introduce massive oversteer on their own. The F/R roll stiffness balance is then adjusted with the sway bars, by removing the rear bar or fitting a big front. Theory says you gain rear independence and therefore traction over bumps, but the stiff rear springs ruin this anyway, so you are basically back to square 1.

By having a 3:2 spring rate ratio, you maintain roughly equal passenger bounce comfort from both ends, and some degree of balance to the sway bar combo.

Shock adjsutments are only for tuning of turn in response and exit traction. You need good spring rates before you can do this, as the shocks will have no effect during steady state cornering.

[zephyrus17]

the HSD company DO recommend a 3:2 ratio of 9/6kg. But Otomoto here sells it as 10/8. I requested them to give me the original recommended 9/6kg. And they did so for free.

[botisto]

some good info above and yea i never got why otomoto changed the spring rates, i just contacted them and asked for the 8kg - 5kg rates I'm after and he said that was no problem as well. Looks like BC racing and yellowspeed allow you to specify your own rates also, good fact to know. Now i just have to choose which brand...