Complete K1 Tyre and suspension matchup

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Complete K1 Tyre and suspension matchup

Postby tsoob » Sun Aug 28, 2016 10:52 am

Hi all,

Please forgive the Renault talk.

I've just taken ownership of my Mk1 - My last (Well, car that is most compatible) to the MX5 was my old Clio Sport 172. Now the Clio handled very well, it was stock and in excellent condition, all I did was wrap the tyres in R888's and from then on it was very nimble, very stable and had loads of grip, it handled far better than the AWD WRX I owned after it (which had horrible coilovers from eBay which were set up wrong.)

My Mk1 has the same problem that the WRX did - It's on coilovers that are set for "low" rather than any sort of handling performance. I don't care about going low, I want a car that grips properly and like an MX5 should. Due to the old, shitty tyres on the wheels, the car pushes into corners and almost understeers, not nice, fat and neutral like I know Mk1's are capable of.

I need 4 new tyres, that's a given. That's a good thing, it means I can start from scratch. I'll research into what people like to run and make my own decision on that, but my question is the suspension.

Should I ditch the coilovers and go for more of an OEM setup? I'm not a race car driver, and the OEM set up obviously had a bunch of R&D put into it to make the car handle, but stock, are there any handling complaints?

Or do I go to a garage and have them set the coilovers (Which may be of dubious quality, I don't know what brand they are) with correct spring rates, or is it just not worth it?

Is there a well known/renowned suspension/tyre combination? With Clios, unless you spend lots and lots and lots of money and lots and lots of skills, the cars usually handle best with some swaybars, stock struts and springs, a cup chassis and good tyres, are MX5's the same?
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Re: Complete K1 Tyre and suspension matchup

Postby drumtochty » Sun Aug 28, 2016 12:52 pm

If you give us a clue to your location perhaps a member in your area can advise a garage than will have the expertise to set your car up and advise on your requirements or take you out in their car to give you a drive in a sorted car.

I could link you to the tyre expert on the national forum who specialises on selling the best tyre for each different Mk of the car and also what tyres are best on different size wheels on those cars.
99 Mk2 1.8 IS Silver
08 Mk3 2.0 RC Sport Copper Red
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Re: Complete K1 Tyre and suspension matchup

Postby 71NotOut » Mon Aug 29, 2016 10:44 am

I run Meister-r coilovers on my 1991 Eunos, with 14" alloys running 195/60/14 (so slightly larger than stock) Vredestein Sportrac 5 tyres.

My car also has an additional rear lower brace which might be standard on some imports.

I don't have it set to silly low, but on a run earlier this year it was complemented on the way it handled through the corners, flat as a pancake and very predictable.

I run my tyres at 26psi all round.

These wee cars are very susceptible to which wheels/tyres you run and the handling can suffer or improve depending on which way you go.
Previously in a 2003 Montana, now in a 1991 V-Special...
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Re: Complete K1 Tyre and suspension matchup

Postby mgrays » Fri Sep 02, 2016 8:21 am

A Mk1 MX5 is not a Clio 172 .. the Clio will always corner faster and feel more secure. The chassis designs are 10-15 years apart. The chassis/body flex on a pre Mk3 Mx5 is significant and affects how the suspension can work. The good thing is that the Mx5 is less stable and moves around more at lesser speeds so you are more involved in the driving experience at speeds that are less anti social. My data point is a 2005 Ibiza Cupra verus a turbo'd/tweaked Mk1 Mx5. The Mx5 is more fun but on a dark wet night when I am tired the Ibiza is a safe pair of hands, the Mx5 will require serious concentration but in the right hands could be quicker but with greater risk.

Measure your ride height from wheel centre to top of wheel arch. It should be at least 320-330mm at front, 340-350mm at rear. If you are less than this you will be cornering on the bump stops. See if you can adjust the coil overs to lift the ride height to these minimums. If you are creative you can add shims/spacers/grooves to lift the spring seats. The factory setup is more like 350mm front, 375mm rear and it is odd in terms of rolling and riding on the bump stops compared to standard car suspension (but I think the 172 does this a bit too at extremes). The suspension is realistically a bit short on travel so it will never ride like the WRX or 172. A reasonable aftermarket coilover will work fine if the springs are not too hard (car skipping over bumps too much) and shock absorbers are matched (no skipping over potholes yet no wallowing).. plus the springs have travel left (about 2" of air gap total at rest between the spring coils or it will go coil bound/run out of travel .. and then a mid corner bump will cause the wheel to stop "suspending" and start to skip/slide).

The important bit is that the suspension is fully adjustable from factory .. so you need to get that adjusted right. This will dial out understeer if you want that .. you can even set it up to drift into oversteer at 20 mph (as one of my cars was when I got it). Old school setting from Miq Millman are;

FRONT
Caster +4.7 to +5.5 (what ever the maximum attained is)
Camber -0.6 to -0.8 (this number varies with the caster)
Toe 1/16" per side, or 1/8" _total toe out_

REAR
Caster not applicable, there is no adjustment possible
Camber -1.1
Toe 1/16" per side, or 1/8" _total toe in_ or zero

The other old school way by a Jeff Thomson is/was;
1) Figure out what is the minimum rear camber you can achieve while maintaining the desired toe. Shoot for .16 deg positive toe (i.e., toe *in*) per side, maybe a bit less. Don't panic if you can't get less than -1.8 to -2.0 degrees (FWIW, I've got -2.1 deg in the rear). Whichever side has the higher camber, set the other side the same.

2) Take whatever figure you ended up with for rear camber, minus .5 degrees, and use that for the front camber. The greater the difference between front and rear camber, the greater the tendency for understeer. Decreasing the difference moves the handling towards oversteer. My first alignment after the suspension upgrade had my rear camber at about -1.9 and front camber at about -.7. The car understeered like a pig no matter what I did with the sways. I'm now running -1.6 front/-2.1 rear; much better. On my last alignment, I had the front toe set to 0; so far, I like the way it feels.

3) Set the front caster as positive as you can get it while maintaining the camber set previously.

So yes tyres are important but suspension settings are even more if messed with, most coilovers can be made to work if you take the time to understand them, alternatively get the latest fashion (coilovers seem to have fashion cycles!) .. but expect to be £50-150/corner in parts alone ... and you will be spending that on tyres already. I would caution about going too extreme on tyres if you live anywhere where you get ice (i.e. Scotland!) .. these cars needs sipes on the tyres for the winter/ice otherwise you must be prepared to walk some days! The track day specials are nice on a summers evening but will spit you backwards into a hedge/off a roundabout on a frosty morning or even just stop you driving up the high street (been there).. hence think about this. Next thing is what size of tyres are fitted.. 195/50/15" is a nice sweet spot, 16" work and give higher cornering forces but less fun!

.. and then there are anti-roll bars.. aftermarket ones can make a lot of difference to roll in corners but they have compromises again.. do some reading but be aware of fashion/trends!

Anyway welcome.. go look at Miata.net or search for NA Miata (NA is Mk1, NB is Mk2 etc)
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