Choosing the right gear and tire size
03-30-2005, 03:32 PM
#1
Need help choosing the right gear and tire size So there are many important factors in drag racing such as suspension, weight, power, etc. But to get the most out of your set up you need to choose a gear and tire size that will get you through the traps at the end of your power band. I'm just surprised we don't have a sticky for a gear/tire size calculator. We need one that also considers converter slip%.
Right now I'm trying to pick a gear and tire size that will get me through the traps at 6800 rpm and 125 mph. I went here: http://www.tciauto.com/tech_info/calculators.htm#4 and scrolled down to Optimum Rearend Ratio Calculator. I want the biggest possible tire I can fit without rolling the fenders. What is the biggest tire that can fit on a 2002 Camaro Z28 without cutting the fenders or banging the wheel wells? I have 15x8.5 Convo Pros w/ 5" back spacing. I also want either 4.30 or 4.56 gears. However, in order to calculate the Optimum Rearend Ratio, the converter slip% is needed. How do I calculate this? I am going with an 8" ATI converter with a 5000~5500 stall speed.
Any help would be appreciated.
Right now I'm trying to pick a gear and tire size that will get me through the traps at 6800 rpm and 125 mph. I went here: http://www.tciauto.com/tech_info/calculators.htm#4 and scrolled down to Optimum Rearend Ratio Calculator. I want the biggest possible tire I can fit without rolling the fenders. What is the biggest tire that can fit on a 2002 Camaro Z28 without cutting the fenders or banging the wheel wells? I have 15x8.5 Convo Pros w/ 5" back spacing. I also want either 4.30 or 4.56 gears. However, in order to calculate the Optimum Rearend Ratio, the converter slip% is needed. How do I calculate this? I am going with an 8" ATI converter with a 5000~5500 stall speed.
Any help would be appreciated.
Last edited by PewterZ28; 03-30-2005 at 04:27 PM.
03-30-2005, 07:14 PM
#2
I'm getting a 28 inch tire with a very high growth efficency working out to ~ 125 MPH @ 6800 RPMS in 3rd gear with a TH350 and a 4.30 gear.
FWIW I ran a 28X9 Hoosier Tire last year and it didn't run at all, I'm going to a 28X11.5 tire this year and I'll let you know if it rubs when I try to test fit it.
FWIW I ran a 28X9 Hoosier Tire last year and it didn't run at all, I'm going to a 28X11.5 tire this year and I'll let you know if it rubs when I try to test fit it.
03-30-2005, 08:28 PM
#3
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I ran a 28x11.5x15 MT ET Drag and had to modify the fender wells. I think 28x9.0x15 would fit better. I would also say for your application, 4.56 gears would be the most. I run a 29.5x9.0x15 tire with 4.33 gears and cross the traps at 6700 rpms with my TH400.
03-31-2005, 09:06 AM
#4
Can someone tell me what slip percentage I should allow for the torque converter? A site I found calculated 2% but searching on this site I have seen numbers as high as 5%~6%.
P.S. Floyd, am I ever going to see you at the drag strip or are you going to be working on that car forever?
P.S. Floyd, am I ever going to see you at the drag strip or are you going to be working on that car forever?
Last edited by PewterZ28; 03-31-2005 at 09:30 AM.
03-31-2005, 09:26 AM
#6
I tried that one and the weird thing is I get different values if I make a slight change in the variables. I guess tire height and gear ratio effect the slip percentage of the converter. The highest value I get is 5.5% so I better use that one just to be safe. Right now it's looking like a 28.0" height tire (Hoosier QTP 28x11.5x15) with 4.30 gears is the way to go. Only problem with that tire is I think I will have to cut the fenders and take a BFH to the wheel wells. 
For now I am going to be cam only and plan on trapping around 124 so I could probably get away with a 27.0" tire. But when I get ported heads I plan on trapping around 128 so at that time I'll need the 28.0" tire.
I guess I can go with a 27x11.5x15 tire for now. I don't think I will have to roll the fenders with that tire. Does anyone know for sure?
For now I am going to be cam only and plan on trapping around 124 so I could probably get away with a 27.0" tire. But when I get ported heads I plan on trapping around 128 so at that time I'll need the 28.0" tire.
I guess I can go with a 27x11.5x15 tire for now. I don't think I will have to roll the fenders with that tire. Does anyone know for sure?
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04-01-2005, 03:13 PM
#10
Does that formula take into account converter slippage?
4.10 gears and 26" tire
(125x4.10x336)/26 = 6377
(130x4.10x336)/26 = 6633
4.30 gears and 27" tire
(125x4.30x336)/27 = 6688
(130x4.30x336)/27 = 6956
4.56 gears and 29" tire
(125x4.56x336)/29 = 6604
(130x4.56x336)/29 = 6868
If that formula considers converter slippage, then any three of the above combinations would work. I'm sure the 29" tire won't fit without modifcations to the fenders and bumper but I'm not sure about the 27" tire.
Has anyone stuffed a 27x11.5x15 tire onto their LS1 Camaro without modifications?
4.10 gears and 26" tire
(125x4.10x336)/26 = 6377
(130x4.10x336)/26 = 6633
4.30 gears and 27" tire
(125x4.30x336)/27 = 6688
(130x4.30x336)/27 = 6956
4.56 gears and 29" tire
(125x4.56x336)/29 = 6604
(130x4.56x336)/29 = 6868
If that formula considers converter slippage, then any three of the above combinations would work. I'm sure the 29" tire won't fit without modifcations to the fenders and bumper but I'm not sure about the 27" tire.
Has anyone stuffed a 27x11.5x15 tire onto their LS1 Camaro without modifications?
04-01-2005, 03:25 PM
#11
I don't think that formula considers converter slippage.
If you go here: http://www.tciauto.com/tech_info/calculators.htm#4 and scroll down to 1/4 Mile RPM Calculator, then enter 26" tire, 125 mph, 4.10 gears, 1.0 trans ratio and 5% converter slippage, the RPM it gives you is 6957. Your formula gives 6377 RPM.
I'm not ragging on your formula, it is probably accurate but just doesn't consider converter slippage.
At this point I'm going to go by the tci formula since it gives a higher RPM and I'd rather be on the conservative side. Now I'm just trying to find out the biggest tire you can fit on a LS1 Camaro without modifications. Surely someone knows?
If you go here: http://www.tciauto.com/tech_info/calculators.htm#4 and scroll down to 1/4 Mile RPM Calculator, then enter 26" tire, 125 mph, 4.10 gears, 1.0 trans ratio and 5% converter slippage, the RPM it gives you is 6957. Your formula gives 6377 RPM.
I'm not ragging on your formula, it is probably accurate but just doesn't consider converter slippage.
At this point I'm going to go by the tci formula since it gives a higher RPM and I'd rather be on the conservative side. Now I'm just trying to find out the biggest tire you can fit on a LS1 Camaro without modifications. Surely someone knows?
04-01-2005, 03:46 PM
#12
I wouldn't go with a 27x11.5 tire, that might need cutting of the fenders (wide tire). I would think the 27x9.0 would tuck up a lot better, the 27x10.5 would be close but I don't have experience with either setups. I do know that if my 29.5x9.0 was shorter (28" possibly, 27" definately), it would have tucked up in the fender wells nicely.
04-01-2005, 03:57 PM
#13
Hoosier QTP's only come in 27x10.5 and 27x11.5. The 10.5 has a 9" tread width and the 11.5 has a 10" tread width.
The other tire I thought about was the MT ET Street Radials. Unfortunately they do not come in 27" size. The QTP's have worked great for me so I think I'm going to stay with them. Just need to figure out if their 27" tires will fit. Of course I could end all of this and just roll the fenders and cut the bumper. 
The other tire I thought about was the MT ET Street Radials. Unfortunately they do not come in 27" size. The QTP's have worked great for me so I think I'm going to stay with them. Just need to figure out if their 27" tires will fit. Of course I could end all of this and just roll the fenders and cut the bumper.
04-01-2005, 04:42 PM
#15
My formula assumes its about 6% slippage.....
It works on my car 124 MPH x 4.10 Gear X 336 Divided by 26.3 = 6495 and my car traps right at 6500 threw the lights.
My tire is 26.0 but grows about .3 above 120MPH...
Looks like my Yank verter is very very good
It works on my car 124 MPH x 4.10 Gear X 336 Divided by 26.3 = 6495 and my car traps right at 6500 threw the lights.
My tire is 26.0 but grows about .3 above 120MPH...
Looks like my Yank verter is very very good
04-01-2005, 04:53 PM
#16
Then that formula on TCI's website must be crap. Enter those same numbers in their formula and see what it comes up with. Very different.
That is odd though that you are trapping 124 mph with a 26" slick and 4.10 gears! I also have 26" slicks and 4.10 gears and my car traps 119 mph at 6500 RPM with the converter LOCKED! 
That is odd though that you are trapping 124 mph with a 26" slick and 4.10 gears!
I also have 26" slicks and 4.10 gears and my car traps 119 mph at 6500 RPM with the converter LOCKED!
04-01-2005, 07:41 PM
#18
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I'll post on sunday what I cross the traps with my 8" 5500 and 28" tire.
btw.. when you get the 8" verter you're going to think its a joke cause its so damn small!!
btw.. when you get the 8" verter you're going to think its a joke cause its so damn small!!
04-04-2005, 11:39 AM
#19
Magnus, you have 4.10's right? What speed and rpm did you cross the traps at yesterday?
JS, I also have a Yank TP (4400 though). I can't for the lift of me figure out why there is such a big difference between where you cross the traps unlocked versus where I cross the traps locked.
JS, I also have a Yank TP (4400 though). I can't for the lift of me figure out why there is such a big difference between where you cross the traps unlocked versus where I cross the traps locked.