Sporty Street Spring Rates Recommendations

plohl · Postby **plohl** » Tue Apr 01, 2014 10:24 am

I think the 9 & 6 with the mca's will be fine with stock sway bars on the street... depending on the roads... I am tempted to buy a few sets of springs in different rates to start playing around with them. Manga_blue inspired me haha. I want to put 9 and 6 on my ohlins so we can compare them to the mca's.

I have run 8 and 6kg/mm springs for a while now with a number of different anti-roll bar settings.

1. 24mm front, 12mm back (stock na6)
2. 24mm front, 16mm back
3. 19mm front, 12mm back (stock na6 all round)

1 tends to understeer... lots. Not bad for steet driving, but rubbish at the track.
2 was very pointy and relatively easy to get it to oversteer. I only ran this once at the track and it worked well.
3 pretty neutral, tends towards oversteer. Only used on dirt track. Took me about 4 rounds to get used to it, but it proved effective.

I am currently running around on 7.2 and 4.5kg/mm AVO coilovers with 24mm whiteline front ARB and 11mm (stock NA8). It loves understeer.

kazama · Postby **kazama** » Tue Apr 01, 2014 10:41 am

what were you alignment figures plohl?

mx5s need more static neg camber on the front than on the rear. with a "proper" alignment your #1 would be the most neutral out of the three #2 & 3 would be oversteer biased and would require a bandaid alignment

plohl · Postby **plohl** » Tue Apr 01, 2014 11:15 am

The last wheel alignment was...

Front, ~2* camber, ~5.5* caster, 0 toe
Rear, ~2.5* camber, 0 toe

This was with set up 1 and 2. I changed rear ride height a little when I did 3, but never got it re-aligned.I doubt it would have changed the rear camber too much. Need to get the new car aligned at some point as I just put a new steering rack in it and I need a baseline. I was going to aim for more front camber this time as per the 949 guide just to try it out.

What's the reasoning behind the more neg camber at the front relative to the rear?

kazama · Postby **kazama** » Tue Apr 01, 2014 11:23 am

dynamically we gain more camber on the rear than on the front. since im no suspension guru and arent that good at paraphrasing either :lol:

heres a FCM link

http://forum.miata.net/vb/showthread.php?t=340198

plohl · Postby **plohl** » Tue Apr 01, 2014 11:27 am

Haha - cheers man! I'll look into it.

roket52 · Postby **roket52** » Tue Apr 01, 2014 5:08 pm

Mangna Blue, thats interesting you say that the shock length doesnt affect the alignment and that only the ride height does. My new lowered shocks have added a lot of negative camber as the vehicle is now lower. I have since raised it up to around the 330mm mark.

Question for you though magna as Im not sure myself - Will altering the ride height (which in turn alters the camber) have any effect at all on the toe of the vehicle? or caster for that matter?

manga_blue · Postby **manga_blue** » Tue Apr 01, 2014 5:26 pm

It may change caster and toe a little bit but, from my experience, not significantly either in terms of feel or wear patterns. I raise my car about 50mm again for daily duties after each event and it's never been an issue.

One of FatCat's mates published a java app for camber change with height. http://www.virkki.com/jyri/miata/camber/

Back to your original question, roket52, I don't think there'd really be much noticeable difference between 9/6 and 10/7 spring rates on a street car, except probably ride comfort. I prefer the sound of plohl's 7.2/4.5 for a street-only car, but only if he put a 14mm rear bar on it.

roket52 · Postby **roket52** » Tue Apr 01, 2014 5:44 pm

thanks for that reply magna interesting to hear .

As for the softer rates well Ive tried 9/6 and the 6 especially was too soft for my application (street/track) so moving up to 10/7 + the increased damper valving. Iam in a slightly heavier NB though than most people who are posting spring rates.