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Discussion Starter #1
OK all you fat tire users out there. Here's a question for you. How much tire growth can I expect out of a set of 33.5-17/16 D1 Good Years?? The ones that I have now measure right at 109.5" circumference and they're about 2/3 worn out. Any ideas? I'm trying to figure what gear to run and I want to get a little more accurate idea of my trap speeds and RPMs. Thanks.
Rob
 

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Mickey Thompson told me that there 13-15" actual tread width tires could grow as much as 2-3". They say my 28x10.5's would grow as much as 1-2"@130mph depending on air pressure and rim width.
 

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Discussion Starter #3
I'm running a 16" wide rim and the tread section is 17" so I expect quite a bit of growth. Now is that 2"-3" in height or circumference?
Rob
 

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a 17" tire on a 16"wide rim your looking a about 3-4" growth on height , I run them on a 14" wide rim and we get close to 6" in growth at 190 mph but the contact patch starts getting narrow as if they don't spray the track right to the end as soon as we run off the VHT we go up in smoke
Frank
 

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Discussion Starter #5 (Edited)
Thank you VERY much Frank. Now that gives me, I think, a realistic number to work from. This width combo has been 6.75 @ 211 on this car "back in the day" so I'm confident that it has the potential to stick REASONABLY well on the top end. Thanks again ....Another quick question. Is it possible to inflate the tire (to a safe pressure) that will duplicate the growth factor???
Rob
 

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Discussion Starter #7
Thanks Frank, that's what I thought. Now, when I get a base line circumference measurement on the tires I need to have them at racing inflation, correct? And any suggestions on said inflation with a 1,750 LB car?
Rob
 

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First.... No data recorder to read driveline RPM your just fooling yourself!
Next you need the formula to convert rpm to tire growth.
As for M/T saying only 2 to 3 inch growth their FULL OF SHYT or you have one WEAK AS PIECE OF SHYT.
M/t tire 32 16 15s on 16 rim at 142 grows 3 to 4 inchs at 150 plus 5 to 6 inchs.
I had a set of goodyears on years ago 32 16 the tire size was 98 circ at 150 plus it grow almost 9 inchs.
As for the 28 10 mt that small of a tire should have 2 to 3 growth at 130 mph thats close.
As for controlled tire growth and not leaking air hoosier tires has it going on!!!
 

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Discussion Starter #11 (Edited)
I'm running double bead locks so leakage shouldn't be a problem. If it does then I'll just put tubes. Thanks for the heads up. 9"s huh? wow. All right, so do you all think that 4.57 gears are too low to turn in the low to mid 6K RPM's at say 160(ish)? The calculator that I'm using says 4.0 gears at 160 for a 6,200 trap RPM. This tire growth thing is the fly in the ointment. Where can I come up with some accurate growth figures?
Rob
 

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First off what are you running, class, motor, trans, and what rpm do you want to run? Its not the rims that leak it the tires beadlocks are good 16x16 lets spread tire out.
One thing if the tire is to big and the motor can't pull it your torque convertor slippage will go though the roof and you will never figure it out.
last thing what weather do you run in corrected air and base alt
 

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Discussion Starter #13 (Edited)
I'm running a hard tail, 220" Rear Engine Dragster that weighs in right at 1750 LBS. I'm pushing it with a 472" that's putting out about 650 horse and running a JW Glide, 1.76 low, brake, and a 4,500 stall 9" converter. At the present I'll be running brackets (dial in). The engine has a stock bottom end so I don't think that I want to turn it much past the mid 6K's, the top end will handle that easily. We have really good air up here, usually in the corrected of about sea level. Rear tires are 16"X16" Champion Double Bead Locks and the present tires are Good Year 33.5-17/16's, D1's. I'll be putting new rubber on it before it hits the track though, same size I'm sure.



Rob
 

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After running many differant cases 6200rpm ..33.5 and 109.5 cir 10% slipage it looks like 3.89 .
I think that your going need to put more air in the tires to get it move out of the hole or it will pull the motor down and it will not recover.
The low rpm is going to kill it plus the daul carbs and small stall speed.
Only going 160 that tire probable will not grow much 4 inchs would not be unreasonable
Your just bracket racing i would make the best of it.
 

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Discussion Starter #16
After running many differant cases 6200rpm ..33.5 and 109.5 cir 10% slipage it looks like 3.89 .
I think that your going need to put more air in the tires to get it move out of the hole or it will pull the motor down and it will not recover.
The low rpm is going to kill it plus the daul carbs and small stall speed.
Only going 160 that tire probable will not grow much 4 inchs would not be unreasonable
Your just bracket racing i would make the best of it.
Sorry for not responding in a while. I just looked up the thread again. THANK YOU Jeff, that's some really good info! I've found out more accurate info (different any way) since we posted this: The car will weigh-in at around 1,400 lbs, I've changed cams ( Comp 34-703-9) and should be peaking @ about 6,800 RPM. Still, according to the Wallace calculator a 3.89 gear should work well. I plan on using a 3 step so my launch RPM should be somewhat tunable. The car hasn't been run yet, I'm hopin for next season. Thanks to all you guys that chimed in.....
Rob
 
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