Spring Rating

Donovan · Post by **Donovan** » Tue Aug 14, 2012 9:19 am

Is there any way to tell what rating a spring is if the part numbers have all worn off them.

I have a set of 12kg rated springs from Keith that I am going to try on the front, and was intending on putting the existing front ones to the back (until I get myself a set of 8kg ones for the rears) as I thought in theory they would be beefier, but looking at the two sets, they look pretty much the same.

WideOpenThrottle · Post by **WideOpenThrottle** » Tue Aug 14, 2012 10:34 am

Try this link if you can do the math!

http://www.therangerstation.com/tech_li ... ngrate.htm

Growler · Post by **Growler** » Tue Aug 14, 2012 2:18 pm

Most suspension companies should be able to test them for you...

kuroneko · Post by **kuroneko** » Tue Aug 14, 2012 5:19 pm

Slightly off topic, but..

from what I understand, the shocks in the coilover are matched to specific spring rates. A lot of coilovers have a specified tolerance to how stiff/soft a spring rate you can run. Usually +/- 2kgmm from whatever it comes with.

Too stiff or too soft may lead to premature wear on the shock's seals.

Someone correct me if I'm wrong. Only felt the need to pull this up because most street coilovers for MX5 I think are rated at 8f/6r. Running 12kgmm springs might be ok in the short run.

Angreal · Post by **Angreal** » Tue Aug 14, 2012 6:05 pm

I think the mass of the V8 engine in the front of Donovan's car might do more wear and tear than upsized spring rates if I was to take a stab in the dark... That and general abuse on the track

Donovan · Post by **Donovan** » Tue Aug 14, 2012 9:04 pm

Er, yeah, I have figured out that my shocks aren't most likely going to be a lifelong part of the car, so just trying to get the best out of them in the mean time.

Just hoping that they hold out long enough for me to save up for these.

http://www.good-win-racing.com/Mazda-Pe ... 5Race.html

Donovan · Post by **Donovan** » Tue Aug 14, 2012 10:12 pm

So I sat down and worked out the spring rate, based around that online calculator, and provided my measurements aren't too dodgy (which the most likely are) and my maths is correct (which it most likely isn't) I have the old front springs rated at 7.32kg/mm and the rears at 4.977kg/mm, which I suppose sounds about right. But looking at them, I can't tell the difference.

I suppose the acid test will be taking the measurements from the new springs and seeing if they work out to be about 12kg/mm

Donovan · Post by **Donovan** » Mon Aug 20, 2012 4:30 pm

Hmm, maybe my calculations are a bit off, go 10kg/mm for the 12kg springs that I have borrowed from Keith.

Might have to take them to a testing place after all.

Donovan · Post by **Donovan** » Tue Aug 21, 2012 2:34 pm

Got the springs rated, seems my calculations and measuring were a bit off. So the old front ones that I am moving to the back are rated at 5.7kg/mm, the old rear ones are at 4.5kg/mm and Keith's ones that I am going to try out are 11.6kg/mm (sorry Keith, not the full 12kg, and they "twinked" one of your springs writing the values on them)

had a chat to them about rebuilding/revalving the Tein's that I have, and it is $95 a shock to do.

kuroneko · Post by **kuroneko** » Tue Aug 21, 2012 3:38 pm

Just out of curiousity, where did you take your springs to be tested, and what did they charge?

Donovan · Post by **Donovan** » Tue Aug 21, 2012 4:17 pm

Took them out to Autolign out at unit 5, 99 Carbine Road, said it was going to be $10 a spring to rate, ended up doing it for nothing.

kuroneko · Post by **kuroneko** » Tue Aug 21, 2012 11:49 pm

What GC's. I've heard many good things from them, dealt with them once too, seem like a good bunch.

When are the springs going in? It'd be good to see your impression of the new setup

Donovan · Post by **Donovan** » Wed Aug 22, 2012 8:23 am

Who are GC?

Everything is ready to go back into the car as far as the suspension is concerned at the moment, won't do the rebuild of them till later down the track, but I am waiting on a raft of other things before I can put them back in.

I have to do a bumpsteer test as part of the compliance, and that is with the shocks in, but no springs in them, so I have got the car setup for that, which is supposed to be happening tomorrow, still waiting on my stuff that I need to repair the front 6pot calipers from the US along with another set of pads, and that stuff still hasn't shipped yet, so I am guessing another couple of weeks before it gets put on the ground again. Not really sure how it is going to go with 12kg/mm on the front, and 6kg/mm at the rear, whether is going to go from an oversteer monster to the nose wanting to go straigh ahead all the time.

Mr. Shine · Post by **Mr. Shine** » Wed Aug 22, 2012 10:26 am

Donovan wrote:Who are GC?

Err, a GC is a good... uh, a good chap...

Not really sure how it is going to go with 12kg/mm on the front, and 6kg/mm at the rear, whether is going to go from an oversteer monster to the nose wanting to go straigh ahead all the time.

Would have thought that relative mismatch of springs would possibly make it quite understeer-happy?

Donovan · Post by **Donovan** » Wed Aug 22, 2012 10:39 am

Oh, ok, change chap for something else I take it.

Well, it was pretty oversteer happy before, so be interesting just how much it throws it the understeer way. I was hoping that the old front ones where about 7kg as it would be closer to what might be a happy medium between the two, but I guess that is not to be.

Just going to be a bit of playing around to try and get the right balance with the right sets of springs to how I like the car to handle on the track.

kuroneko · Post by **kuroneko** » Wed Aug 22, 2012 12:12 pm

Have you had the car corner weighted since doing the conversion? It'd be interesting to see how much the weight differs and in which areas.

Donovan · Post by **Donovan** » Wed Aug 22, 2012 3:27 pm

Yes, it has been corner weighted, have a look at the following post, about 5th or 6th post from the bottom of that page.

http://www.mx5forum.co.nz/viewtopic.php ... &start=100

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