Sporty Street Spring Rates Recommendations

roket52 · Postby **roket52** » Wed Feb 12, 2014 5:59 pm

Hi All,

Currently in the position to upgrade the stock suspension on my stock 01 NB. Im looking for decent quality coilovers at a reasonable price and narrowed it down to MCA blues. Possible other options could be HSD or BC's.

More importantly is the spring rates to choose.

My application will be mainly hitting the adelaide hills which can be a little bumpy and tight and also the occasional track day. The car is not daily dríven, more of a weekend toy so looking to set it up nice and sporty but to also be compliant over the bumps. Would prefer a neutral setup over a setup biased towards understeer

Suggested rates which have been recommended so far are 9kg front and 6kg rear or 8f and 5r. Personally that sounds kinda on the hard side but without trying it I'd only be guessing. so im after recommendations from other owners who have tried and tested their sporty street setups and are happy with it.

Current wheel setup is stock 16's but car will eventually have the lightweight 15x7's

Any help here would be appreciated!

sailaholic · Postby **sailaholic** » Wed Feb 12, 2014 6:25 pm

Worth talking to mca about what they recommend for your application. I'm sure they have a road oriented set up the would recommend.

Quality of the valving can make a big difference to the perceived stiffness of a set up. The ohlins I think run 8/6 but are very comfortable.

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roket52 · Postby **roket52** » Wed Feb 12, 2014 6:30 pm

I have spoken to Josh but he mentioned that he has only set one up for track at this point and used 9 and 6 which worked well. We are talking about setups at the moment but Im just trying to get a guage on what other people have found to be acceptable spring rates on the street also.

Totally agree with you on the valving comment

emily_mx5 · Postby **emily_mx5** » Wed Feb 12, 2014 8:22 pm

Look up the fat cat Motorsport excel table, you can put in different figures and it calculates important aspects like front roll couple etc.
And plan for a front swaybar.

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sailaholic · Postby **sailaholic** » Wed Feb 12, 2014 8:50 pm

Shouldn't need a front sway bar with the correct spring rates based on my reading? I've got one anyway...but that's what you get for doing things in stages.

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roket52 · Postby **roket52** » Wed Feb 12, 2014 8:56 pm

thanx yeah a sway bar may come into the build at some stage but what I really want advise on is tried and tested spring rates for my application if anyone has some input here?

Magpie · Postby **Magpie** » Wed Feb 12, 2014 9:14 pm

Springs rates will depend on the frequency that you are looking for possibly 1.5 Hz for road and 2 to 3 Hz for track.

MX5's are very susceptible to changes in unsprung weight. What sort of tyres/rims are you running compared to stock. You will get more value from the FCM calculations if you input accurate information, do you know the weight of your car, wheel weights etc? If you don't, find out. I assume that you have not done any modifications that would change the motion ratio.

Sway bars can be used to refine the suspension set up.

MattR · Postby **MattR** » Thu Feb 13, 2014 10:42 am

If you are going the MCA's I would just run with what Josh suggests, they don't have the reputation they do in the race and rally world for being numpties.....

emily_mx5 · Postby **emily_mx5** » Thu Feb 13, 2014 11:45 am

here is the table for NB

here is a conversion table for kg/mm to lb/in

the generic 8/6 is perfect on an NA with a larger 22mm front sway. The NB table is slightly different so might not be the same.

roket52 · Postby **roket52** » Mon Mar 31, 2014 9:21 pm

Just some feedback for anyone interested. Fitted the mca 9/6 blues and found the front rate to be quite good for street and the 6kg rear was a bit too soft for me personally. I'm moving up to 10kg fronts and 7k rear on my nb8b and paying for a slight increase in damping ability also . This will be a streetable setup which will perform well out on the track also. Once I get them back from mca I'll be able to give some more feedback of the higher spring rate

manga_blue · Postby **manga_blue** » Mon Mar 31, 2014 10:07 pm

I've run 10/7 springs on Tein shocks for a few years now with either stock sway bars, no sway bars or Whiteline 24/16 adjustable sway bars.

OEM sways are slightly better on the track than no sways, purely for braking stability. No sway bars were slightly better on the highways, just a bit better planted on the bumpy bits. The heavier Whiteline sway bars over those springs were pretty horrible everywhere, basically far too skittish and gripless.

10/7 with sways is a good balanced track setup: very precise handling with a touch of oversteer. It's quite a livable setup on the highways. I do a periodic 300km run up the coast on B roads to Sydney in a Sparco seat and it's really quite comfortable. In the city it's a pig - you jar over every pothole and rut on the road at low speed.

The only thing I'd really fault about 10/7 is that it's still a touch soft under brakes. Periodically I think about stepping up to 12/9 or 14/10 to firm that up - but then it'd no longer be doable as a daily.

sailaholic · Postby **sailaholic** » Tue Apr 01, 2014 6:22 am

I've just put the 9/6 reds in with a 24/16 sway bars. MCA recommended going back to standard sway bars but I wanted to make one change at a time.

Only did about 10 minute test in the wet. Car was very flat, too much so I suspect. Under steered fairly readily through runabouts with no throttle and would switch to oversteer easily with throttle. Both happened at lower speeds then I was suspecting and given there was no body roll with out a lot of warning that grip limits were close.

My plan is to leave everything how it is until I can give them a decent test and then return to standard bars.

Manga, you might be interested to know MCA weren't real keen on poly bushes and recommended rubber replacements if required.

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roket52 · Postby **roket52** » Tue Apr 01, 2014 8:44 am

interesting feedback sailaholick . Has ur car been aligned yet? the length of the shock with throw ur alignment out a fair bit which will certainly compromise grip levels and predicability. It being wet too certainly wouldnt have assisted with grip obviously. Would be interesting to hear how you go in the dry once aligned?

For me I plan to keep the stock sways for the moment.

Are you in a NB or NA??

manga_blue · Postby **manga_blue** » Tue Apr 01, 2014 9:47 am

Shock length has nothing to do with alignment on MX5s. NAs and NBs have unequal length non-parallel control arms top and bottom, front and rear. Unlike a strut suspension car, the control arms are the sole determinants of suspension geometry - the springs and shocks just keep the car off the ground. Camber does change with deflection however. For example, lowering the car will increase static negative camber.

I understand what they mean about poly bushes, Sailaholic. Mine are a mixed blessing. They're very stable and precise but they're prone to binding and they need serious work to get them re-lubricated every year or two. Next time I'll go with hard OEM style rubber bushes.

sailaholic · Postby **sailaholic** » Tue Apr 01, 2014 10:08 am

No, not aligned yet, but I'd guess my ride height has changed since last alignment (my old springs have sagged since the last alignment).

The RSRs are also 3 years old now so getting hard.

Manga blue, I do remember you having issues with that. Pretty much what MCA said. I've copied below

"The main issues is that if the arm has to twist as well as pivot then poly will probably restrict it a lot, and some times the bush is too wide and gets preloaded when tightened up, which will restrict it's ability to even pivot. I've been able to do chin-ups on a suspension arm on an mx5 once because the poly bushes were too tight. So you can imagine that's not ideal. They can be ok, it's just something that's a bit risky when it's not a highly experienced and knowledgeable person installing them. And unless the bush is huge and there's a lot of rubber, there's not much wrong with standard ones."

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