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Re: 68 GTX Autocross Build for CAM Class
[Re: MuuMuu101]
#2269799
03/15/17 03:06 AM
03/15/17 03:06 AM
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Joined: Nov 2016
Posts: 200
Colorado
Bob J
OP
enthusiast
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OP
enthusiast
Joined: Nov 2016
Posts: 200
Colorado
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How short is the 285/30/18 in your opinion? I've seen a guy fit it in the front of an A-body, but that's more than an inch shorter than my 255/40/18. I guess that I think that the tire is to short. With a 3.55 gear at 80 MPH the engine turns at 2,848 rpm and 3,500 with 3.23. Remember that highway speeds are 75 out here in the west so the flow of traffic is like 85. So I would like a taller tire. With soft springs the shorter tire may be better since it has firmer sidewalls. Or you have 2.92 or 3.23 gears it may keep you from changing gears.
07 Porsche C2 997.1 6spd DD and SCCA Solo II SS
68 Plymouth GTX Convert. 493cu Hotkiss Wilwood Classic air, Building for Solo II Cam
65 Chrysler 300 Convert. project
57 Desoto 2dr. Firesweep 392 Hemi,Wilwood Project with son
2003 Dodge Dakota R/T "DEAD"
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Re: 68 GTX Autocross Build for CAM Class
[Re: Bob J]
#2269803
03/15/17 03:12 AM
03/15/17 03:12 AM
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Joined: Dec 2010
Posts: 12,375
SoCal
MuuMuu101
I got lucky at Woodward!
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I got lucky at Woodward!
Joined: Dec 2010
Posts: 12,375
SoCal
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How short is the 285/30/18 in your opinion? I've seen a guy fit it in the front of an A-body, but that's more than an inch shorter than my 255/40/18. I guess that I think that the tire is to short. With a 3.55 gear at 80 MPH the engine turns at 2,848 rpm and 3,500 with 3.23. Remember that highway speeds are 75 out here in the west so the flow of traffic is like 85. So I would like a taller tire. With soft springs the shorter tire may be better since it has firmer sidewalls. Or you have 2.92 or 3.23 gears it may keep you from changing gears. It's only that fast out here if there's no traffic. Lol. I think I'm turning about 2300-2500 rpm @ 85 mph with 3.55 gears, 0.5:1 ratio, and a 26" tall tire. Unfortunately, exhaust drone kicks in at about 1800-2200 rpm which is anywhere between 65-80 mph in 6th.
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Re: 68 GTX Autocross Build for CAM Class
[Re: Bob J]
#2317888
06/07/17 11:56 PM
06/07/17 11:56 PM
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Joined: Nov 2016
Posts: 200
Colorado
Bob J
OP
enthusiast
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OP
enthusiast
Joined: Nov 2016
Posts: 200
Colorado
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I just picked up a set of Rival S 315x30x18 with 11x18 wheels for the 911 and I wanted to see how they fit on my GTX. Well they fit with no leaf springs in the car. They are pretty tight makes me wish that I went with coil overs. So it looks like 285x30x18 square for me. Now maybe I car get back to building the car in about 3 weeks as we will have about 3 weeks off from racing.
I don't think they will fit in the car when the leaf springs are installed.
Last edited by Bob J; 06/07/17 11:57 PM.
07 Porsche C2 997.1 6spd DD and SCCA Solo II SS
68 Plymouth GTX Convert. 493cu Hotkiss Wilwood Classic air, Building for Solo II Cam
65 Chrysler 300 Convert. project
57 Desoto 2dr. Firesweep 392 Hemi,Wilwood Project with son
2003 Dodge Dakota R/T "DEAD"
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