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Post by AtomicWedgie on Oct 21, 2010 23:45:31 GMT -5
Not looking for rules, was just wondering what size slicks these cars are running for slicks? Also looking for rim backspacing used also.
Was thinking about running 29.5 x 10.5's. A little more tread and will lower my RPM's some. I have 28's are the car now. They have a 11.7 center section. With my 4.5 backspacing they are close to the inner fender. The 29.5's have a 13.1 center section. That is a 1.4" difference so do I just add 1 1/2'' to my backspacing. I have plenty of clearance to the frame rail so I am just concerned with the fender clearance.
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Post by Dave Schultz on Oct 22, 2010 0:18:57 GMT -5
Really depends on a lot of variables like tubbed, width of read end, model year, gears, engine grunt
I have a 9.25 65 coronet with 31X10.5W and my son has a 9.50 65 Coronet with 33x10.5W
My 63 Plymouth has 31s -- but a lot of the 63s are running 29.5
Need more infor on the car, engine, gearing
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Post by AtomicWedgie on Oct 22, 2010 23:52:07 GMT -5
I am running S/S springs moved in board, 3way comp eng. shocks, Dana w/4.56. 500cid(650hpish),727(4500 stall), Stock wheel wells.
Thinking about going with a 29.5 x 10.5 x 15 on 10" steelies w/6.5 backspacing on my 65 Coronet. Was just tryin to see if I am close to the right size for traction.
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Post by texoutsider on Oct 23, 2010 1:44:30 GMT -5
Many of the Mopars run a 29.5x10.5w or 31x10.5w on 10 inch wheels. With offset springs and a little frame rail massaging there is adequate room in the wheel well.
Mark
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Post by AtomicWedgie on Oct 23, 2010 5:50:15 GMT -5
Not sure if I want to mess with frame any so I guess I will stick with the plain 10.5 tire. What do u mean by message the frame?
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Post by Dave Schultz on Oct 23, 2010 7:36:04 GMT -5
You have a lot of gear for a short tire in a 1/4 mile. If it were me, I'd go with a 31" slick -- or down to a 4.10/4.34 gear with the shorter slick.
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Post by AtomicWedgie on Oct 23, 2010 14:05:51 GMT -5
I know that now. Should have went with a 4:30. If I go with a 29.5 shouldn't that lower it to an approx 4:30 or will it even make that big a difference.31" just seem big
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Post by texoutsider on Oct 23, 2010 14:50:26 GMT -5
There is a lip on the outer edge of the frame that can be cut off or hammered back to give another 1/2 inch or so of clearance. 29.5 x 10.5w will fit in there and if there is front to back clearance, the 31s will also. The 4.56s should be spinning yer tach to around 6600/6800 at the end........we run a 31 with a 5.00 gear and turn about 7600 or so.........
M.
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Post by poppaj on Oct 24, 2010 1:52:32 GMT -5
4.56 gear should be perfect for you car with the 29.5's. We ran as much as 5.13's with that size tire with a 451 motor. It takes a little more gear to make a big car go with a milder motor.
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Post by Dave Schultz on Oct 24, 2010 12:08:46 GMT -5
I was polling some of the faster cars at the last couple of races -- and was shocked at how many are running 4.10 and 4.34 gears and smaller slicks.
I was told (I've not verified) that I have 4.34 gears and I run 31" slicks on the Vitamin C car and I turn 7000 even as I cross the line. On the Big Red Ram car -- we changed the gears to 4.5X (Ford rear end and I don't recall the last number) and I cross the line at 7200 with 31" slicks.
I believe someone was telling me that their 29.5 slicks and 4.10 gears had them crossing at 6800.
Some of the numbers that people tell me they cross the line with their tire combinations don't agree with the tire/gear calculators (even adjusting for the real diameter vs the advertised) -- but the drivers swear its true and I believe them. I think the RPM when you cross the line can change based on how tight you wind up the motor in 1st and 2nd gear.
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Post by AtomicWedgie on Oct 24, 2010 13:35:14 GMT -5
I would like to cross around 6800. I know there will be a little rpm difference each way depending on shift points. Looks like I will have to change tires to 29.5's and test that and if still to high then swap to 4.30's. Still tuning car so I will have to figure out my shift points for consistency.
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Post by nssguy on Oct 24, 2010 20:29:03 GMT -5
I run 10.50 index with either a 30 x9 radial or 29.5 x 10.5 bias.
Differences = radial is about .1 faster but trap rpm is higher by 300+ rpm. 6800+ rpm with the bias and 7200 with the radials.
4.56 gears small motor, 451 ci., 3.75 x 4.375 no stroker.
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Post by torquer on Oct 25, 2010 17:53:39 GMT -5
Just ran a race in Bowling Green this past weekend (Buick Nationals) and was able to take the weight out of my B/NSS car. Was able to run 10.17 @ 130+ mph with a 31 x 10.5W and a 4.11 rear gear. Was crossing right at 6400, on the tach and the data recorder. I run 12" wide rims too.
Jim N.
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