Track Handling on an OEM suspension
 

Looking for some advice or experience on how to make the best handling package within limitations:

In the series we race in ANY non-OEM specification part from the original build of a base car from the factory is subject to a lap penalty. However, modifying the OEM parts is free. OEM specs for a 1994 are as follows:

154/97 lb/in springs
OEM Dampers with bump stops + top hats
19mm Front sway bar
11mm Rear sway bar

Current thought is to first replace the shocks with an "OEM repalcement" like KYB GR2 or more likely the Koni STR.T --- Any other OEM replacement shock we should consider? (Bilsteins are considered an aftermarket upgrade and incur a penalty as they are not on the base Miata unfortunately)

Second, we would be looking to remove a free coil or two on the springs in an effort to increase the spring rate and lower the car. We will also replace the OEM bumpstops with shortened ones.

Lastly, we are looking to drill a new hole up on the OEM front sway bar to shorten the torque arm length and essentially stiffen the system. Possibly removing the rear bar to bias towards slight understeer but preferably nuetral.

If you had to replace one part with aftermarket, what would it be (besides the shocks)? We are thinking the front sway bar

Thoughts or experience is welcomed, thanks in advance

You are going to be living on the bumpstops. That's what I'd do. The transition from soft OEM spring to hard rubber OEM bumpstop is nasty.

You can revalve stock shocks yourself using 10w40 or something. It's not a pretty process, but it's possible.

What's the AIV for the Miata?

I'm not looking forward to it, especially after going through several hours of testing/tuning with open rules to land on the suspension we ran at the end of this year at Road America, handled amazing!

With the new chump car rules his stock AIV is between $350-500 depending on what year miata he has. I believe everything he is wanting to do should not change the AIV.

$400 for the 1994, only thing we could possibly fit in the TCV is a front sway bar and it's a hefty $50 out of our cap at $500

A quick google has left me wanting, any leads I can follow to learn more?

I don't have any good resources on hand unfortunately for the shock revalving, but you basically just take a stock shock, drill it, drain it, fit a valve on it and fill it up with new oil, and then spend the better part of the day acting as a manual shock dyno pumping the shock by hand until it firms up.

I can't remember what the cost is for the sleeves and springs, but you might be able to get away with like $50 over (aka +2 laps) AIV by going with an eBay sleeve and springs and using your hand revalved stock shocks.

edit: Non-OE coil springs (including ‘coil-over’ kit): $20/corner
So technically you can get away having your car still come under $500 with this. You'll need to play with the spring rates to figure out what works with the stock sway bars or try to size up/down the rear to 11/12mm.

Convert to r-package?

Use honda civic bump stops?

If koni STRTs are legal just order a custom valved set.

Why do you shit up every thread about stuff that you have no idea about and nothing to contribute to? Whyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy yyyyyyyyyy

Intriguing, does changing the fluid viscosity affect the performance much? Trying to find any sort of dyno charts for something such as this...for most it's not worth the effort so they may not exist.

We had an eBay sleeve setup with Summit springs, but springs are now $80 and out of the question moving forward 2014-on

Every $10 over the $500 limit is a one lap penalty... rounded up. With the competition being as tight as it is, especially against the e30 and e36 crowd, we can't afford any laps.

Not allowed in chump car.

Might possibly be allowed, and or really cheap.

I have no clue is Koni STRT's would be legal or not, but I bet if you show up with konis and the techs notice them they will not be happy, even if they are "oem".

shuiend speaks the truth

An R-Package is "allowed" but will be assigned a starting value of "north of $600" for some un-holy reason. Conversions are not allowed however

Tirerack lists the STR.T Koni as an OEM replacement so I would assume they are allowed. Even so, are they the best option over the KYB GR2? Shaikh has posted in several threads that he prefers the performance of the GR2 over that of the Koni due to the Koni's weak damping curves and tendency to lose consistent performance via heat generation from their internal design. Anyone else have input?

I haven't had much time in front of the tech inspection, but the sleeves and coils are only $80, right? Or is it going to be $10/corner for a "non-OE suspension component"?

Correct, $80 on the springs/coils. Any other suspension component not already listed in the BCR is $10 each, like end links, top hats, etc. Wish it was $10 a pair...

What are team are you with? What region are you running in? We run the midwest area around Indiana

Not on any team (haven't driven since 2012) and Southeast. :v

I think it'd be worth the $20 hit to run the coilover setup because you will be able to change your spring rates to make your sway bars work. It's somewhat unfortunate that the Miata isn't competitive because it's so low in HP and so high in AIV.

Possibly, I'd like to explore every free option first. Most of the TCV budget will need to go towards power adders.

The Miata is very competitive in the SouthWest, particularly Texas. I agree though, it's doesn't seem that the new valuation is quite on par. We'll have to see how it pans out this season. We think we still have a very competitive package the way it's put together.

We may be at AMP this year, check out our website and let us know if you'd like to get back in the saddle!

I'm sorry I thought this was another one of those guys in that weird canadian racing leauge, where doring pretty much anything other than running stock was considered stock. I'm sure they got penalized for having less than half a tank of gas and taking a poop before racing if it wasnt in the factory manual.

I don't think that an extra 5-10hp is going to be worth the $100 of money you have to play with. I'd try to maximize on handling and just hope that the tracks don't have too many long straights.

Thanks for the offer.

Here are some dyno plots of the KYB and the Koni I found over at Miata.net. Is anyone versed in reading these plots and could advise on spring rates that would match well with them?

KYB GR2 (Excel-G)
http://forum.miata.net/vb/attachment...1&d=1324746415

Koni STR.T
http://forum.miata.net/vb/attachment...9&d=1284055703

Links not working.

Not sure, I can see them. Anyone else? Try Ctrl + F5 perhaps and see if they work

They work for me. The koni looks mega soft. The GR2 looks like it might be able to handle up to like 400 pound rates, maybe.

That was a crap plot of the Koni's, here's a better one of the rears that goes up to higher velocities (STR.T's have been referenced as being the same as Koni Sport's on Full soft). Still look low on matching spring rates?

http://forum.miata.net/vb/attachment...1&d=1329060613

On the volvo forums the ghetto way to get stiffer sways was to just run two of them. Under your rules would running two stock sways be considered modifying oem?

I wouldn't test my luck with going with a KYB or Koni. The first gen Integra I raced got popped for Tokicos and a stock front sway bar. 110 crank horsepower of fury on Tokicos got 2 penalty laps.

With Chump you need to get it good enough. It's not going to be a Xida or anything, but you can potentially do some real damage with a self re-valved shock and eBay sleeves and springs. You might need to burn a few weekends shaking down the car and finding the right balance so that you don't take laps for non-stock sway bars.

Are spring rubbers allowed? They work. Keep both sways and work on the spring rate balance between front and rear.

Slamming into the bump stops will upset the car. I would almost say to leave them long and shorten the springs so that the transition happens early. If it works correctly, the stops will have room to compress somewhat gradually. I thought I read once that the factory stops start at around 350 lbs/in under compression and go up from there as they get squeezed. Remember that the factory designed the car to contact them under hard cornering.

Haha that would be something to work out! I don't think that would fly as a no cost mod since it's not necessarily to OEM spec, that is unless the Miata got into some radioactive goo at the plant in Japan-land and sprouted some extra sways bar arms : )

We will definitely need a few weekends shaking down the car, luckily we have Putnam Park, Waterford Hills, Gingerman, and Gratten Raceway close by!

I think those would be a value add, at least $10 per rubber. Will read into them though as they may be a good way to increase spring rate while retaining ride height at a desired level. Have you driven with these first hand?

That's good thought on the stops, either shorten them and go soft or keep them lengthy and use them to effectively increase the spring rates. Regardless, an abrupt change in spring rate is never a nice feeling at threshold grip...

Well the miata was made in Hiroshima, there's got to still be some hot pockets from little boy.

Neat rule.

When you cut a spring, you raise the rate by the percentage of the cut. Which is not very much.

What if you did something more radical, like cut the spring in half to double it's rate, but then spacer it to put the ride height back up where you want it. Use modified bumpstops to set the up travel and limit straps to set the down travel. That would give you a racier ride height and higher rates.

For shock damping, I've drilled a drain hole at the top of a shock and drained the fluid. Replaced it with heavier fluid from motorcycle shops. Then put a rubber patch over the hole and secure it with a hose clamp. This was mentioned earlier...but I've actually done this. Worked fine.

For a stiffer front sway bar could you get away with using two stock swaybars, stacked like spoons? I've done that before attaching a lower bar with a whole bunch of hose clamps. You cut the last couple inches off to clear the links.

Kinda sounds like fun.

Instead of cutting the springs and adding a spacer, would placing solid materiel between the coils doing the same thing? Like an aluminium or hard wood? This would be less hassle and be non-permanent if you want to tune it a bit.

Yes, if you locked out half the coils. Spring rate is inversely proportional to the number of free coils.

But if they object to the spacers or blocks, you could also do it with half springs and just cut away the perch and weld it on higher. Pure mod, no extra parts.

Those guys did some great backyard engineering work, I've been referencing them a lot! Sure wish we had access to some of those shops or similar equipment, would make all this paper modifications sure go smoother.

Sounds like you have some good experience, have any pictures to share of your shock modifications or I would really enjoy seeing that double sway bar.

Raising the spring seat is a sweet and simple idea, no question it was a free mod

I'm reading and looking, it looks like you would have to go with a high durometer rubber to get any significant rate increase on your springs. Could certainly be an extremely handy tuning tool while testing at the track and maybe permanent use. Wonder why these aren't more common. Anyone used these on track or even around autocross or town?

Longacre Racing Online -- Tech Article "Spring Rubber Use"

Anyone ever used SACHS shocks? They're German if my research suits me but I don't see a lot of info on them. Parent company is ZF ZF Friedrichshafen AG | ZF Motorsports

APX Auto Parts Shock & Strut Pairs, Sets

put in 99 miata

Not knowing anything but the price of $125 for all 4...
"Great for the price of Good"
really?

Supposedly sensen are the budget winner of m.net. I think the tag line should be "Meh for the price of shit" if anything.

Its like 92 shipped if you buy them in pairs.

"Lifetime Warranty" I wonder if they would mind exchanging them once a month with a hole drilled in the tops of them

No way. This was stuff I did decades ago when I couldn't afford better and had to make all my own. Starving student stuff. I even made my own small steering wheel out of some curved aluminum pieces I duct taped together. It was all just junk, even then, but we had a lot of fun. A couple of us teamed up on a car and called ourselves Team Zebra. For zero bucks racing association. I haven't even thought about doing that stuff in years until I read this thread.

But trust me...it worked. That car was an old Datsun 1600 and we took a season win with it.

Sounds amazing, if we can get something like this through tech and make it robust enough to withstand a 24hr race we might be on to something here. Sure wish we had friends with a shock dyno, might have to make one...

A shock dyno? You're overthinking it. What you've described is a junkyard class and way not technical or serious enough to be worried about dynoing your shocks. Better to find some unmonitored asphalt and test your combinations. Being an autocross guy myself, I would highly recommend developing the car at autocrosses, especially practices, before putting the car on the track. Cheap, convenient and safe. Also fun.

I guess that would work if you wanted to be a mid pack car. To run at the front of lemons or chump you need to put just as much development into the car as you would for a "serious" class.

<- partial owner of a prepped lemons '72 dodge coronet, as of a couple days.

If you say so. I know nothing of that type of racing. But if you earn "bonus laps" I would think you don't need to run at the front. My only previous track racing was SCCA road racing and the cost after a few years drove me out of the sport. I would think this cheapo racing would be fun.

In ChumpCar (and probably Lemons) things have gotten quite competitive. While the racing is in a budget format, the preparation you need to be a front runner is significant. Coming with the success of the series and big sponsors, so have the "big" money teams arrived with big rigs and full setups.

Last year was our first year running this car and on a stock suspension with some bolted on parts we were top 1/3 mainly due to our reliability. By the end of the season, tuned aftermarket suspension and lots of test/tuning at our local autocross and track events later we placed 5th at Road America in the non-chumpionship class.

We are looking to be consistent top 10 finishers with obvious contention for the podium. It only takes 25% of the work to finish in the top 70%, but that last 30% takes 75% more work.

That's awesome, are you planning to continue running it with Lemons or appeal to both series? ChumpCar is running at Watkins Glen on May 23-25th for a 6+8+6hr set of races!

Want to run both series. Its a fire system away from legality. But its running lemons at CMP first without me and then VIR, hopefully it'l make its rounds up to me for the NHMS lemons race. I MAY be able to run down to SC and grab it for the chump race at limerock depending on if I can buy safety gear by then.

If I were you guys I would look more into bumpstops.

Does changing or adding bumpstops have a big affect on your "AIV" or whatever? One of the race teams I've worked for use to run in the "Firehawk" series way back in the day. That series required stock dampers and springs. The team stacked multiple bumpstops on each damper and basically used the bumpstops as "springs", the stock springs had such a low rate that they basically acted as helper springs. Bumpstops have spring rates, and if they are constantly engaged, there shouldn't be a harsh transition "on" and "off" of them.

Here's what I would do. Do the DIY revalve like WAM has suggested and try to get some sort of increase in damping. Then, cut the stock springs, I don't know how much but I would say at least two full coils maybe more. Find a bunch of bumpstops, old hard ones, soft spongy ones, etc. etc. etc. Use the bumpstops to get most of your spring rate and for setting the ride height. If you can homebrew some method of "approximating" spring rate with whatever combination of coil spring and bump stops, you can find out what combination of bump stops you need to get a good ride height and stiffness.

If adding bumpstops is going to change your AIV a bunch or add more than a couple dollars in cost, then maybe just forget what I said.

I'd go one step further and just run on bumpstops, period. No springs. Stack bumpstops on there until you get a combo you like. Then see if you can work out a deal to have AIV removed if you're "dumb" enough to run without springs at all.

If you are looking for a fire system I would recommend this one: 4.0 Liter Multi-Flo Steel Mechanical AFFF System

Safety gear isn't that bad, if it comes to it this company rents nice setups out for something like $125 a weekend, nice people too. RACE SUIT RENTAL | HOME

By running a long length bump stop setup or only bump stops that have an appreciable spring rate to them you would eliminate the transition but you would also limit suspension travel at full compression correct? That can't be a good thing and would be another factor to consider here.

Bump stops aren't TRULY infinite rate. There's softer and harder ones. By running just bump stops, you could end up dialing in ride height exactly where you want it, and maybe ending up with an effective "spring rate" in the 500s.

I believe the PacNW guys did this with "Lazarus" for a time, and were amazed at how well it actually worked. They used BMW bumps of some kind. They were running closer to SM times than you'd expect.

This is what I meant. He explained it better and added examples. It can work very well. As he said, keep the stock springs as helpers. Stacking another bumpstop is a good idea. It will reduce the overall rate as you add them to make it a more gentle ramp-up.

come to VIR, ill be there.