Suppose you were going to build a light weight (somewhere between 2500 and 3000 lbs as a goal) 2wd diesel drag racing car or truck somewhere in the 600 to 650 hp range. How would you go about choosing the right size tire?
How to select the right size slick?
- Thread starter JoshH
- Start date
How do you come up with that? Is there a general rule of thumb for selecting the size, or are you just going off experience? What about width?
No particular goal, but with the weight/power estimation, I would think it should run mid 9s at around 140 MPH maybe.
Depends on trans ratio, rear end gearing and rpm range You don't want to go too tall with not enough motor but if you have the power then the taller the better.
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I am here: http://maps.google.com/maps?ll=32.519842,-92.180931
Suppose the transmission gearing is that of a 4L80E (2.48, 1.48, 1.00, 0.75) launching off a trans brake.
Assuming the engine would be falling of the power pretty significantly past 4000 RPM, I would say you want to be through the traps before you get there. If you have 3 different gearing and tire size combinations possible for close to the same RPM at the same trap speed which would you say is better?
31" tire with a 3.40 gear that runs 145 @ 4000 RPM
33" tire with a 3.50 gear that runs 150 @ 4000 RPM
33" tire with a 3.60 gear that runs 145 @ 4000 RPM
when its all said and done i think you will end up running 3.08stake into consideration the massive amount of torq the diesel puts out!! u dont need alot of gear for low reving torg engine
I can't find anything higher (or lower depending on how you look at it) than a 3.40 in the gear sets I'm researching.
A 3.50 gear with 33" tires would be almost identical to the 3.08 with 29" tires though. Is there any reason you recommend the shorter tire over the taller?
Slicks (bias ply, 15psi) grow ~5% in the 120-130mph range on the big end with a 3400lb raceweight.
Going past peak HP RPM through the traps doesn't hurt as much as not getting to max HP in top gear. If you are spraying or running a GT4202+ single, you should do the math for 4500rpm, since you will peak at 4000rpm, then ride slowly back down the curve.
Lots of tire is mo' better than not enough. Not enough means you are at the mercy of the track prep that day, and all the rice who drive through the water.
Going past peak HP RPM through the traps doesn't hurt as much as not getting to max HP in top gear. If you are spraying or running a GT4202+ single, you should do the math for 4500rpm, since you will peak at 4000rpm, then ride slowly back down the curve.
Lots of tire is mo' better than not enough. Not enough means you are at the mercy of the track prep that day, and all the rice who drive through the water.
i was assuming u were building a car, (you know what they say when u assume):roflmao:.. thats why i suggested a 29 or 30 in tall tire, if ur building a truck u have plenty of room to run a taller tire, there for u can run a taller tire to get closer to ur desired gear ratio...
This isn't a for sure project, and there is nothing set in stone. I'm just kind of doing some preliminary research, but if I do anything, I'm leaning towards a small truck.
I run a 3.22 gear with 32-13.5x15 m/t slick. I have an Allison and in 5th gear going through the traps at 3450rpm at 126mph. The higher the gear the better off you are. If you can fit a 33 or 34" tire I think you will be fine with the 3.40 gear.
I run 3.42 gears and 33x16.5x16 slicks and go through traps 2900rpms in 5th gear @116-117mph. I need more hp but love the tire combo and wish I had 3.08's so I could go through in 4th.
Gears
I have a big pinion 3.20 9" pro gear for sale if anyone is interested. You want a big tire but not so big that your pulling more tire (wieght) than you need. You also need to watch with the low gear at the starting line. The more low gear you have the harder it is to stage and spool. Use the TQ the motor has and you will go faster. Jeff
I have a big pinion 3.20 9" pro gear for sale if anyone is interested. You want a big tire but not so big that your pulling more tire (wieght) than you need. You also need to watch with the low gear at the starting line. The more low gear you have the harder it is to stage and spool. Use the TQ the motor has and you will go faster. Jeff
I dont have any tech for this post only an observation,last time at the track there was a truck there with a very mild tune in it,i was told he found a set of very low profile street strip drag radials.The truck looked radiculous but as i was laughing at him and watched the run.I do not remember the terminal mile per hour but i was amazed to see the time 12.78 12.75 consistantly.While getting my truck tuned by Bo-Bo he was telling he did the tune in truck and that the guy got the tires for next to nothing and tryed them out.I for 1 will be going back to 265s the next time i go to the track on pyos.Just my 2 cents