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First impression of Formula Atlantic slicks


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For a while now Tube80Z (Cary) has been suggesting that I try out some FA slicks for autocross use. With my bodywork (SubtleZ kit), the only ones that would fit are the 23.0 x 9.5 x 15 slick which are designed for use on a 15x10 wheel. So, I finally got some wheels (15x10 Spinwerkes series 82 with 5.25" backspace) and some used FA slicks off the internet (R25B compound).

 

The tires weigh 16 lbs each and are 22.9" tall. The Spinwerkes wheels weigh 15.8 lbs each. My old wheels and tires weighed 39.5 lbs and stood 24.7" tall.

 

Putting the new wheels and tires on the car lowered the car 0.9", and increased the track by 2". The new tires really fill up the SubtleZ body work.

 

I used the new tires at the autocross yesterday for the first time, and all I can say is that they rock. Absolute grip was slightly better than with the A6 tires, but the feel was completely different. With the A6, the maximum grip occurred at a lower slip angle. The A6 responded quickly to inputs but would loose traction if the driver pushed the tire past its ideal slip ratio. The FA slicks are different. They respond to inputs more slowly and require more slip to get maximum grip. If I needed to turn in deeper, I just had to turn the wheel. The front never seemed to wash out on me as it would have with the A6's under the same conditions.

 

The set the air pressure at 25 psi at all four corners and left the camber where I had it last year (-2.1 rear and -2.5 front). These tires heat up very quickly in 95* F conditions. I made seven runs and had the best performance when the tires were cool on the starting line.

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Excellent feedback. Can you easily gauge (vs. your competition) if you've picked up time over the Hoosier A6's? It sounds like the FA slicks are a little more forgiving, but less responsive, a fair assessment?

 

Photos of the new wheels and tires on the car are always welcome, not because it has any real relevance to the thread topic, but more because I'd like to see what a Z looks like on 22.9" tall tires.

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For a while now Tube80Z (Cary) has been suggesting that I try out some FA slicks for autocross use.

 

The set the air pressure at 25 psi at all four corners and left the camber where I had it last year (-2.1 rear and -2.5 front). These tires heat up very quickly in 95* F conditions. I made seven runs and had the best performance when the tires were cool on the starting line.

 

So how do you rate the performance versus the cost, that was the winner for me. For autox we usually set these around 22 PSI, higher for track work.

 

From back to back driving of a car with kumho radials to the atlantics I needed to change my driving style. What I found worked much better was to increase my steering input velocity, meaning I aggressively turned the wheel. If you used to watch Fernando Alonso a few years back on Michelens you'll get the idea. The other area where I found a large difference was braking, and you had to be a lot more careful you didn't lock a tire because the rotating weight is a lot less (I was using 13s).

 

At the temps you running we typically spray them down with water between runs. The 35s may be a better choice with the heat you have. Now we just need to convince you to put on the rears :-)

 

Cary

Edited by tube80z
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Richard,

Here are some pics of my old race sporting this combination. Sorry I don't have any input as I sold the car after converting to EFI and never did track the car.

I'm sure Cary (tube80z) will chime in with more pictures and info regarding this combination. CAry was it you that spearheaded the use of these tires on Z cars?? Any how, I am pretty sure Cary was instrumental in these tires being on my race car before I purchased the car. Flares are standard issue MSA ZG flares, rears were cut, spread, and re-glassed. Cary is now the owner of this shell along with the tires and wheels pictured below. Wheels are Diamond Racing, 13” diam, fronts are 10” wide, rears are 13” or 14" wide, I forget which. They just barely cleared the Z car front calipers, (I think the front calipers may have been lightly clearanced).

 

P3Medium.jpg

 

backMedium.jpg

 

P2Medium.jpg

 

P1Medium.jpg

 

fattyLarge.jpg

 

ZsMedium.jpg

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That's interesting. I'm running the same 23x9.5x15 and found the 35 compound are really too hard. Unfortunately with the radials now the big ticket I couldn't get the 25's last time I got some used ones. The R35's will last a season + easy but really suck in the cold. I find they get better each run as they heat up. Never had to even think about cooling them off. I also tried the radials but the squared off edge wears VERY, VERY, VERY quickly IME so I'm back to bias ply. You also dont need nearly that much rear camber. I kept going down and down in pressure and ended up between 16 and 18 PSI when I got my only FTD back in the day when I was faster ... before the V8.

 

Cameron

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That's interesting. I'm running the same 23x9.5x15 and found the 35 compound are really too hard.

 

That sounds more like a cantilever, not an FA tire. My experience with them was they require a different setup from the FA tires.

 

And for the edges wearing in the radials you need to control roll better or you will see that. That's one of the main reasons a bunch of us now run droop limited.

 

Cary

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I'll try to get some pictures of the car with the new wheels and tires and post them tomorrow.

 

Drax the answer to your question is yes. They are less responsive and more forgiving, and I believe the overall grip was better. We'll have to see how they wear.

 

Cary, by the end of the day I was driving as you stated, I had to "increase my steering input velocity." I really like the way they drove after I figured that out.

 

BRAAP, the tires you had on the back of that car were just obscene:mrgreen:.

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Another data point...

 

Extensive testing ($5K in tires, $1.5K in facility rental over two days, $350 in fuel, and $250 in food) on a customer's FP E36 BMW (about 2,100 lbs. and 250hp) showed that the 285/30-18 Hoosier A6 was faster and pulled higher steady state Gs then a 16" Hoosier 23.5 x 11.0R-16 in R25 or R35A compound. Later discussions with Jeff Speer at Hoosier indirectly confirmed this by saying Hoosier's upcoming R100 and R80 slicks are said to be a fast as their A6 tires for autocross.

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That sounds more like a cantilever, not an FA tire. My experience with them was they require a different setup from the FA tires.

 

And for the edges wearing in the radials you need to control roll better or you will see that. That's one of the main reasons a bunch of us now run droop limited.

 

Cary

 

They are the FA tires. I was running 225 lb front springs with the radials which I think was part of my problem with the severe tire wear. I also would push mid corner for I think the same reason. Since I drive on the street to the races I was shy going higher in spring. This year I switched to 300 lb front springs and have noticed NO negative effects to ride on the street at all but haven't raced enough to tell how they perform. Plus I have a set of bias to use up before trying the radials again. Thought this info may be useful to others contemplating using these. For the performance/$ you can't beat them - especially used - which is why I run them.

 

Cameron

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I am running the SubtleZ rear quarter panels, and the 23x9.5x15 tires fit well. The YZ rear quarter panels and the correct offset wheel will accommodate the larger 13.5 in wide rear FA slick (In hindsight, I sometimes wish that I had YZ rear Quarters).

 

I bought the 15x10 wheels so that I would have the option of running the FA slick or running the 275/35/15 Hoosier A6 tires. I am willing to bet that my car would be faster on the latter of the two. The deciding factor for me right now is cost. A set of the A6 tires would run me $1100.00 and last for one racing season whether I use them or not (time kills them slowly). This year, I am not able to race as often as I did last year because I am back in school working on my masters degree in Mechanical Engineering, so a set of expensive, time-sensitive tires would be a waste.

 

The used set of FA slicks cost me $108.00 shipped to my door. I figured if they work then great, and if they don't then I'm only out a few dollars. So far, I am quite happy with them.

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