Spring Rates And Sway Bar For 240 Track Car?

[GregTas]

Hi,

 

I'm starting to get my suspension sorted for my car (240). It will be a track car, but will possibly get some limited road use. I've done quite a bit of searching on the web and on the forum on what people are doing for the suspension, but some things like spring rates seem to vary quite a bit e.g. in the front from 200lb up to 500-600lb (seems very stiff).

 

I know there's a lot of variables and so things setups can vary, but was after some thoughts or info from those that are running track cars and have tried a few things.

 

Some years back I ran a 240 with konis, coil overs, 330lb in front, 280lb in the rear, stock front bar and no rear bar. It handled ok, but that was the only setup that I tried.

 

My new car has:

  -welded in cage

 - seam welded

 - 15x8 wheels (not yet bought and so could got 16x8". Not sure which is best option here)

  - will have treaded track tyres I'm thinking 225x50x15, but could be 16x8 with 225x45x16.

 

Suspension set up:

 - Koni gold (decided). Sectioned struts.

- 65mm coil overs (decided)

 

What I was thinking for the springs and sway bars was;

325lb front, 300mm long

275lb rear, 300mm long

22mmm front bar

Rear bar - no idea?

 

Does someone with some track experience have some thought on where I'm thinking of starting for my spring rates and sway bars?

I know it'll just be a starting point, but was hoping to start somewhere fairly close.

 

Thanks for the thoughts, Greg

 

[RLY240]

Hi Greg, FWIW I'm running front 275lb and rear 300lb with whiteline front and rear bars and that gives me a pretty good balance.

Koni yellows and 205 x 50 R16 semis.

[260DET]

My aim with a S30/S130/Z31 is for the front to carry as much of the cornering load as possible. That involves power steering, a big front ARB and none at the back, heavier springs than the back, 8* caster and so on. The whole idea is to improve rear grip in the corners to avoid that characteristic sudden loss of the back end but it does require three way adjustable MCA type dampers for fine tuning purposes for best results, mainly to control understeer which is always lurking with this sort of setup. A video I posted illustrated this theory in action, my big heavy 280ZX compared with a couple of S30's. Unfortunately it seems that most thought this video was posted for other reasons and so the lesson was missed or ignored. So take it or leave it.

[dat2kman]

Greg, those spring rates are good.

Maybe go up in front bar to 24mm

Run a standard size stock rear bar, and balance the over/understeer, by backing off the nylock nuts on the rear bar droplinks.

In the wet, remove rear bar droplinks.

Rim diam/tire o-all diam, and diff ratio will depend on what track you can attain max rpm in top gear at, before you brake for that circuits fastest corner

Use/download a free software program called "Gearcalc" by a Peter Ogden, you enter car specs, it displays speed info and rpm drops between gearchanges. Play around with tire diam and diff ratio.

 

If you havent sourced 15x8 rims, i have 2-3 sets, fitted with proper semi's that are ex my Z and another Datsun, can palletise and freight.

Tassie is a bugger due to the crossing, for some reason on frieght charges. If you knew someone in Melb, can send there, to await your next trip ver?

[GregTas]

Thanks for the thoughts guys.

 

Richard that video is quiet interesting. The S30s seemed about the same as you until the tighter pit corner, where things are obviously a bit different. It would be interesting to who how your setup compared with theirs. Interesting that you suggest no rear bar. I didn't have one on my old car and it handled ok, but never tried with one so don't know if it would have been better or worse. I'll have to see if I can understand that set up a bit more.

 

Dat2kman sounds like I'll go with those springs. If I go with the thicker bar then I'm assuming I'd have to also have something on the rear to balance it out. I'll do some searching and see what options are out there. My local track is Baskerville which is quite tight and has a couple corners which drop away on the inside so I wonder if I need to be a little careful about the stiffness.

 

On the old car I had 15" 60s tyres and with 3.9 diff which was ok. 3, 4 and 5th gear used. Was turbo L series and so only 6500 or so in the revs. I'll download the program and have a fiddle.

 

For the wheels I was planning on going with 15x8 Rota Rs in a +4 offset, but haven't bought them yet. I'd be interested to know what the wheels are that  you'd sell. Perhaps send me a PM with pics.My sister lives in Melbourne and has wanted me to drop over for a while, but I don't think she'd be too happy if some wheels turned up at her placed and I just dropped over to collect them. I think Id be in trouble

Edited July 25, 2017 by GregTas