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Autox suspension/slicks discussion - FP


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Bryan and were able to fit the 23.5 x 9 x 15 slicks under the stock sheetmetal on his ITS 240Z and they worked very well on the track. So well we had to bump up the spring rates to keep the car from falling over on the outside tires under turn-in and acceleration.

 

Bryans_240.jpg

 

The above picture shows the car at the legal 5" ITS ride height. We dropped the car another 1.5" from this picture after the first test session. Unfortunately Zredbaron has to run 16" wheels to clear his brakes, otherwise these slicks in an R25 compund would be the answer.

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i hate myself.

 

Enough to sell me your nice car for $100 and solve your little self-esteem issue? :mrgreen:

 

Stop beating yourself up with hindsight. You built your car way back when to meet some goals, and now those goals have changed based on experience and knowledge you didn't have way back when. Get over it.

 

Sit down, write up your goals, and start working on a plan to get there.

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I'm not sure why anyone would want to run full on road race tire like a Hoosier slick for Auto-X, they will never come up to temperature to make them even slightly sticky in an Auto-X.

 

In my experience unless ambient temps are relatively low (< roughly 70 deg F) I've not had a problem getting heat in them for autox. Yes when it's cool/cold out they really suck and you would be better off with a sticky DOT tires ... but then again I'm running an R35 compound all year and if money were no object switching to a softer compound in the cold would help there.

 

Cameron

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haha, thanks john. i was kidding, of course. just frustrated, of course. i'm still in my 20s, so i've still got that youthful "but i want it NOW" bit of impatience.

 

i suppose that won't ever go away, either, right? haha.

 

the plan: get another chassis and start from scratch one day.

 

this car i think is better off staying the way it is. i can still have fun in SM2 on DOTs. lots of fun.

 

one last question still stands: are there any other geometry/linkage/mounts that I should consider in addition to camber plates and *slightly* stiffer springs [+25lbs] for SM2? i still like the idea of having freely moving linkage / low friction mounts. might as well maximize my finesse factor...

 

is this question too big / too general? i've gotten the response "if you want all out, go all out"...but no one has specifically addressed what i can still do to my SM2 car. the rules say i can have "subframe connectors." should i still look into those AZC control arms / TC rods and stuff?

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hmmm...after looking at the rear view of the yellow braap Z, seems that 1.5" flare isn't going to 'cut' it. gotta get this hybrid crap out of my mind. race car, mark. race car!

 

i'm thinking pick up a 'rolling shell' would be the way to go for me at some point. not anytime soon though, unfortunately.

 

 

 

Mark,

You've got mail....

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In my experience unless ambient temps are relatively low (< roughly 70 deg F) I've not had a problem getting heat in them for autox. Yes when it's cool/cold out they really suck and you would be better off with a sticky DOT tires ... but then again I'm running an R35 compound all year and if money were no object switching to a softer compound in the cold would help there.

 

Cameron

 

I guess it all depends on how you define hot. On a road course, the tires will get so much hotter than they ever will during a 60 sec autocross. I've run Hoosiers in an autocross, and they never really got as sticky as they do on a road course. Where shaven V700s or RA-1s got a lot stickier in less time. Maybe the Hoosiers were old, or the wrong compound, but they were no where near as sticky.

 

Just my limited autocross experience...

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it's supposed to be sun forget classing for now and work on the driver, stuff the biggest tires you can fit and keep learning, at nate last year the FP's outran the SM2 so I say SM2 isn't a bad place to be, getting on some decent rubber is gonna be a huge improvement no matter what size, but the larger tires are gonna help with turn in and corner speeds, the adjustable control arms will allow you to fine tune your alignment, which can be a measurable improvement, right now I say work on the driver and tires, anything else is will be marginal in comparison, pax is for slow cars, start looking at raw sort ;)

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one last question still stands: are there any other geometry/linkage/mounts that I should consider in addition to camber plates and *slightly* stiffer springs [+25lbs] for SM2? i still like the idea of having freely moving linkage / low friction mounts. might as well maximize my finesse factor...

 

Now that you have a plan to build a real FP car, my answer to this question is, No. Focus on the easily replaceable parts and save your money for the FP car.

 

Rear

 

Aluminum offset inner LCA bushings.

OEM rubber or poly outer LCA bushings.

280Z rear LCAs (if you want to strengthen things a bit).

ST rear anti-roll bar (19mm).

250 lb. in rear springs.

Camber plate.

 

Front

 

Aluminum offset inner LCA bushing.

Aluminum/delrin TC rod bushing or stock rubber.

Polyurethane steering rack bushings.

Solid steering shaft coupler.

Bumpsteer spacers (can't relocate the inner LCA mount up in SM2).

ST front anti-roll bar (25mm)

225 lb. in. front springs.

Camber plate.

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I have run the 15x9x23 Goodyear cantilever slicks for years now. They are the R250 compound. They fit the car without flares on 15x7 wheels with a -12 offset. The clearance is very tight and I could not go any lower than the AZC springs (which are too soft for the compound) that I run. I have a localy competitive FP z with a full interior that weighs 2300 lbs but I could never compete in a larger event than the local level. I have Paxed a few events though. I have also been on 2 wheel a couple of times and it scares the hell out of me. I am currently working on a dedicated racer but $ is tight so until then.... You could go into XP with the 3.1 motor the weight is calculated on the engine size but you would still need to cut the body and gut the car, ect.

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Hey Mark,

If you want to run Prepared with the 3.1... you can still run XP. You can turbo it, stroke it, V8 it, whatever! So long as it fits in front of the firewall, it's legal. (pretty much.) Don't spend too much time looking for sub 10" wide 16" slicks... they don't exist. There is no market for them, so no one makes them. That said the DOT-R's are not much of a step down. Especially if you are running on asphalt. For the slicks to REALLY show their strength you need some really grippy concrete or ultra grippy concrete (which is very rare). Many people in various prepared classes have begun to switch from the bias ply slicks to the radial DOT-Rs and I don't see that trend changing.

Another "plus" for XP is wheel widths and diameters are unrestricted, so if you decide you want to go up to 17" wheels, you do not incur any weight penalty.

If you ever do make it to true slicks, living in the south, I don't recommend going any softer than Hoosier's R35 compound (or equivalent), at least during the summer. They can overheat pretty quickly. Even the Kumhos prefer to be cooled off between runs when it's really hot.

Have fun with your car and if you can, try and make it over towards Tampa, and try and catch a ride with John Thomas in his 240. He will inspire you... to either go faster or quit... either way, you will be inspired! :)

 

Changing subjects a bit, earlier someone was saying I was running the 23.5x11.5x16... That was only for one season. I'm back on the 22x10x16. Both tires are speced to run on a 10" wheel, but the bigger tire is at it's lower limit. I don't think the wheel width was too big of deal as much i just didn't like the transient response of the taller tire. The 22x10 is just so responsive, that i was never happy with the bigger tire. The gains I may have made it ultimate lateral grip were more than offset by the slow response time. That said... I may try switching to the new 23x11x16 radial slick... we will see!

 

Tom

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  • 4 weeks later...

agreed...unsprung weight just sucks.

 

unfortunately, with my rim/fender limitations, i'm going with the kuhmo ecsta v710 DOTs for the time being.

 

any recommended tire pressures for me to start from on DOTs? my kuhmo ecsta mx street tires like to be around 37.5 for the front and 35.5-36.0 for the rear. same exact size... 225/50R16s.

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