8 replies to this topic

[Redescape]

Hi there, I have currently two MX5's, One a 1989 NA that runs in classic trials (just cage & mild tune) and one that is being built right now , to compete in our "run what u brung" class. EG, so long as it passes tech, you're good to go. So this car is minimum weight - normally aspirated NA model, with Spax coil overs, pillarless with a low cage. running 15" wheels with Toyo R888's -has a Lsd etc...

My question is - If you could run any sway bar combination (not restricted to your Sepc Miata rules etc) what would it be? we are running on closed circuit race tracks by the way.

ive tried both stock & racing beat bars, but figure these all are a compromise for street use r to comply with rules I dont need to worry about.

Any advice greatly appreciated

[forestdweller37]

Shaihk (sp?) over at Fatcat Motorsports has a spreadsheet on his web site for calculating front roll couple distribution based on spring rates and sway bar dimensions. We use it quite extensively when setting up our STS autocross Miatas. Try using it to look at the FRC % of your current setup and adjust accordingly based on how you'd like to see the balance change. For reference, autocross Miatas tend to run higher FRC % than track cars.

I've seen a CSP Miata with a very adjustable "NASCAR" style front swaybar. I think the owner sourced the components for it from Speedway Motors. The downside to it was that it was considerably heavier than the Racing Beat sway bars. And that weight is located a long distance from the CG.

-Chris

[wheel]

The best handling advice is to get rid of the 888s and get a set of Hoosiers. The 888s are just about the worst tire I have ever raced.

[Redescape]

Thanks for pointing me at the spreadsheet- awesome. Yes, bars are(very) limited in availability here, & that makes me need to get a set made & was planning on fully ajustable links to tune the effective torsion. Its the diameters and rate that causes me concern going away from stock. Oh, also Unfortunately Hoosiers aren't readily available here for anything except dirt track speedway...but I get your point. Thanks guys . I really appreciate your assistance. cheers.

[FTodaro]

I do not know what the rate is on the spec rear sway for the miata but I think its too stiff and run at the soft setting. My two cents.

[Caveman-kwebb99]

Thanks for pointing me at the spreadsheet- awesome. Yes, bars are(very) limited in availability here, & that makes me need to get a set made & was planning on fully ajustable links to tune the effective torsion. Its the diameters and rate that causes me concern going away from stock. Oh, also Unfortunately Hoosiers aren't readily available here for anything except dirt track speedway...but I get your point. Thanks guys . I really appreciate your assistance. cheers.

If you want to know everything NON SPEC MIATA this is the man. Several time NAT. SCCA Champ in a MIATA (NON SPEC THAT IS) Jesse Prather http://jesseprathermotorsports.com/ He can build, source or setup anything you want for your miata. Not to mention he is a very nice guy!

[wheel]

+1 on Jesse Prather.

[Redescape]

Thanks everyone, Ive managed to get the spring rates sorted for the coil overs, sway bar sizes etc all sorted. Swaybars been made & the car is off for cage & paint too - very excited! Huge thanks to Fatcat motorsports for their spreadsheet data too- invaluable.

[Redescape]

A quick update - car finished & running hard now, I did decide on a 26mm solid front bar ( ugh- heavy!) - a 15 mm rear, -all custom made -matched to a set of spax rsx with 32/20 n/mm springs.- great thanks to one of the spax engineers in the uk. FYI for the scientists- by the numbers I think that makes the frc 64% and roll stiffness 1600.

A bit of alignment work was needed to get rid of dreaded "mr spin" . Careful setup of shocks was critical too - they're really really sensitive - (guess that's why the street guys sometimes grizzle - v easy to make them rock solid, but for racing- nice ajustability) so in summary -body roll? Nope! Neck strengthening exercises needed - yep! Corner speed and lat G's is amazing...catches quite a few who try to out brake me. Now, for more hp...