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Discussion Starter #1
Hi guys, I'm new to slicks and was wondering if someone could help me. I was running 119 MPH in my Cobra at the end of the quarter with drag radials but now have about another 50 HP. I'm now at 469 rwhp so I guessing 122 - 125 is possible. Should I go with a 27" slick or a 28" slick? I have 3.55 gears. Not sure which will fit a fox body (lowered 2"). I calculated a 27" tire at 5500 RPM with 3.55 gears puts me at 125 MPH, so I'm guessing 27" tire is the way to go? Will 27" tire fit under a fox with a 2" drop? I plan to use pony 5 stars (since I have some laying around) so that unfortunately brings the tire in a bit due to the Cobra offset.
 

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Its been a long time since I've messed with slicks, but I remember that you can't go by the number on the side of the slick. I found getting the rollout (circumference) was a better way to calculate. Some 28's can get close to rubbing on the fender lip (front edge) depending on what control arms you have and how they are set. Keep in mind the slicks will grow a little at higher speeds.
 

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Discussion Starter #4

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28x10.5 and 28x11.5 ETstreets here on mine, but I narrowed it to fox width to get a more available wheel to fit. Moving the car to 5 lug now and going another .5" narrower w/9" ends for Alumastar's 6" vs 6.5" offset. Its tight, but a tall tire always wins out. But you don't have enough gear for that (3.73-4.10).
 

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Discussion Starter #8
That helps a lot, thank you guys!
 

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You will have some difficulty fitting the 28" slick if you are still using the cobra rear end. A 28x9 will fit but it is tight. Anything wider will not fit. I eventually went with a custom wheel with more backspacing to tuck the wheel in more due to the additional width of the cobra rearend.
 

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I have an 87 notch tt cobra swap. I had 26/10/15 mt et drag slicks with 3.90 gears and was about your exact power on the baby tune. I switched to 28.2" 275/60/15 mt pro radials and 3.27 gears with much more power. The slicks did sway quite a bit on the big end. Around 120/125+ on the street. The radials don't sway and I shut her down now on the street in 4th around 155mph. The slicks felt like I was towing a trailer on a windy day on the street. I think I ran 16lbs in them, no tubes. I would use a stiff sidewall slick if you go that route. I had bias 26/4.5/17 fronts also. The radials with bias fronts don't sway at all. Let me know any questions you have. For what it's worth I'm doing mini tubs shortly and more tire. I can blow them off at 140 easy now.
 

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I would go with a 26" or 27" tire on that car. I run a 27x10.5 QTP - it has ~9" tread. My wheel wells cover the top of the tire, limiting what I can run. This is the biggest I can comfortably drive on the street. I've gone as quick as 1.41 60' - traction is never an issue.

Running the numbers, I'd lean towards a 26" tire - 124 mph is only 5,700 rpm. I'm assuming you're still a 5 speed.
 
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