Suspenstion guidance wanted

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Suspenstion guidance wanted

Postby bsalisbury » Fri Jul 30, 2010 3:19 pm

Hi Brian - I have a 2004 Mazdaspeed Miata with JIC coilovers. They have 9/8 kg spring rates which are great on twisties, but the car is prone to significant oversteer when autocrossing. To help address this, I ordered a Racing Beat 1.25 inch front sway bar from you, but as you know RB had some fabrication problems and the product has not shipped. In the interim, I obtained some used 12 kg front springs from JIC. I am looking for some guidance in terms of installation priority. My questions are:

1. Should I start with the sway bar and hope that this will help address the fact that front and back springs are too similar?

2. Or should I install the 12 kg springs first, and possibly the sway bar as well? I have read that some autocrossers have similar setups.

The car only sees about 2500 kms every summer and I have been doing a fair bit of autocrossing. I don't find the ride objectionable with the 9 kg front rates so don't mind a firm ride.

Someone also suggested that I should disconnect the rear bar. All of this said, I am not highly technically versed in suspension issues - all I know is that I want a much stickier ride:)

The car has the original Racing Harts and 215/40/17 inch Dunlop Direzza Star Specs. I have run the rear shocks at close to full soft and this has helped a bit to reduce the oversteer. A local racing company has done the alignment so I don't believe this is an issue. Any thoughts would be appreciated.
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Re: Suspenstion guidance wanted

Postby Brian » Fri Jul 30, 2010 3:39 pm

I would put the 12kg springs in.....the resulting combo of 12/8 is real close to what we usually ship to the autocrossers anyway as you can see in our online store. You will still want the front bar on top of that (my silver miata runs 13/8 and NC LIGHT runs 13/7 currently...with big tubular sway bars). So, my suggestion is add the 12kg springs while you wait on the sway bar upgrade.

Many of my autocross friends run with no rear bar. Personally, I prefer having a rear sway bar.....but there is a lot of personal preference involved in that choice (no 'right' answer).
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Re: Suspenstion guidance wanted

Postby bsalisbury » Fri Jul 30, 2010 5:00 pm

Great - I am on it. The real issue, of course, is that I need to become a better driver, but this will help my times I am sure!! Thanks for your advice.
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Re: Suspenstion guidance wanted

Postby bsalisbury » Fri Aug 27, 2010 1:15 pm

I am just posting an update on the results of changing out the 9kg front springs on my JIC coilovers to 12 kgs and adding the big Racing Beat 1.25 inch tubular front sway bar. I was able to track the car yesterday and the ride was simply transformed. Firm, of course, but the car was amazingly balanced. One of the instructors, and a top autocross driver here in British Columbia, rode with me twice and commented on how neutral the car felt. With his encouragement I was able to be quite aggressive accelerating out of turns and never felt the car really wanting to over-steer [okay, clearly I was not going fast enough :lol:]. In any event, the 12/8 kg spring set up and big front bar are just the ticket [so to speak]. I am going to be a lot more confident at autocross events going forward. Thanks for your help on this Brian.
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Re: Suspenstion guidance wanted - final thoughts

Postby bsalisbury » Mon Sep 27, 2010 4:51 pm

Hi everyone - I have now completed my suspsension set up. My latest decision was to unhook the rear sway bar. I now find the car quite a bit more firmly planted. If anything it is prone to a little bit of understeer but I much prefer this over the other option :lol: In any event, I plan to leave the big Racing Beat tubular sway bar at the softer setting. Yes, the ride is firm on our local roads, but it is not too severe. Knowing that I can now be very aggressive on an autocross track is a confidence builder, even in the rain, which we often get here in British Columbia in the fall.
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Re: Suspenstion guidance wanted

Postby Brian » Mon Sep 27, 2010 7:46 pm

Congrats. Sounds like you are having lots of fun and making progress making this Miata fit your desires.
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Re: Suspension guidance wanted - one more update!

Postby bsalisbury » Mon Oct 18, 2010 5:52 pm

My reclamation project continues - I give two thumbs up to the rebuilt 5 speed I put in to my 2004 Mazdaspeed Miata last week. Who knew you could go so far, so fast in first and second gear on an autocross track. It makes me wonder what Mazda was thinking when they decided to put a 6 speed gearbox in the car. I must say that this change really helped the car's performance.

Brian - I do have two questions - next year I will put 15 inch 6UL rims on the car - so, my questions are, what is the maximum size tire [Hoosiers] I can put on and should it be the 8 or 9 inch width rim - thanks for any guidance.
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Re: Suspenstion guidance wanted

Postby Brian » Mon Oct 18, 2010 7:50 pm

I have gone down the same road and I too have come back to the five speed several times as my first choice....particularly for autocross.

With coilovers you can do the 15x9 and that would better support 225/45/15 all four corners. I do have a few MSM customers with BIG extra power using 225/50/15 in the rear to get even a little taller effectively gearing but now that you have the 5 speed I would start with the 225/45/15 all around on the 15x9.
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Re: Suspenstion guidance wanted

Postby bsalisbury » Mon Oct 18, 2010 8:14 pm

Thanks a lot Brian - I really appreciate the advice.

A more pressing issue is the fact that my 16 year old daughter was less than a 1/10th of a second slower than my best time yesterday. I guess I could always make her drive her stock 1990 Miata instead of my MSM :lol:
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