Inliners International Forums General Discussion Drive Train Borg Warner T5 Transmission and Engine RPM VS. SPEED RATIOS, 3.08~3.43~3.73~4.11:1 RE

Borg Warner T5 Transmission and Engine RPM VS. SPEED RATIOS, 3.08~3.43~3.73~4.11:1 REAR END RATIOS.

Speed vs. RPM For Tire and Gear Ratio
A real accurate way to determine your tire diameter is to draw a line on the bottom of your tire, then draw a line on the ground which lines up with the line you just drew on your tire. Then move the car until the car makes one full rotation of the tire and mark the ground where the line on the tire is at the bottom again. Now measure the length between the two lines and divide by pie (3.14) and you'll have your tire diameter to use on the calculator (don't forget to use inches). This is the preffered method to use in determining your actual tire diameter. Tire sized 28.5'' to a typical modern radial Chevy standard size rim. If yours is taller then add MPH.

The columns are a bit off but they really do line up properly. My spreedsheet did not line up as I thought. This is purely for your information. Accurate to +/- 4%.
Enjoy

CHEVROLET T-5 Borg Warner Transmission Ratios:
1st: 2.95 2nd: 1.94 3rd: 1.34 4th: 1 5th: 0.74
Tire Diameter: 28.5 inches
Rear Gear Ratio: 3.08:1
READ MPH ACROSS ROW /READ RPM DOWN the FIRST COLUMN, then LINE UP THE SPEED IN EA. CORRESPONDING CROSS COLUMN.
RPM 1st 2nd 3rd 4th 5th 6th
1000 9 14 20 26 36 0
1500 13 20 30 40 54 0
2000 18 27 39 53 71 0
2500 22 34 49 66 89 0
3000 27 41 59 79 107 0
3500 31 48 69 92 125 0
4000 36 54 79 106 143 0
4500 40 61 89 119 161 0
5000 45 68 99 132 179 0
5500 49 75 108 145 196 0
6000 54 82 118 159 214 0
6500 58 89 128 172 232 0
7000 63 95 138 185 250 0
7500 67 102 148 198 268 0
8000 72 109 158 211 286 0


Tire Diameter: 28.5 inches
Rear Gear Ratio: 3.43:1
READ MPH ACROSS ROW /READ RPM DOWN the FIRST COLUMN, then LINE UP THE SPEED IN EA. CORRESPONDING CROSS COLUMN.
RPM 1st 2nd 3rd 4th 5th 6th
1000 8 12 18 24 32 0
1500 12 18 27 36 48 0
2000 16 24 35 47 64 0
2500 20 31 44 59 80 0
3000 24 37 53 71 96 0
3500 28 43 62 83 112 0
4000 32 49 71 95 128 0
4500 36 55 80 107 144 0
5000 40 61 89 119 160 0
5500 44 67 97 131 176 0
6000 48 73 106 142 192 0
6500 52 80 115 154 208 0
7000 56 86 124 166 224 0
7500 60 92 133 178 241 0
8000 64 98 142 190 257 0


CHEVROLET T-5 Borg Warner Transmission Ratios:
1st: 2.95 2nd: 1.94 3rd: 1.34 4th: 1 5th: 0.74
Tire Diameter: 28.5 inches
Rear Gear Ratio: 3.73:1
READ MPH ACROSS ROW /READ RPM DOWN the FIRST COLUMN, then LINE UP THE SPEED IN EA. CORRESPONDING CROSS COLUMN.
RPM 1st 2nd 3rd 4th 5th 6th
1000 7 11 16 22 29 0
1500 11 17 24 33 44 0
2000 15 22 33 44 59 0
2500 18 28 41 55 74 0
3000 22 34 49 65 88 0
3500 26 39 57 76 103 0
4000 30 45 65 87 118 0
4500 33 51 73 98 133 0
5000 37 56 81 109 147 0
5500 41 62 90 120 162 0
6000 44 67 98 131 177 0
6500 48 73 106 142 192 0
7000 52 79 114 153 206 0
7500 55 84 122 164 221 0
8000 59 90 130 175 236 0


Tire Diameter: 28.5 inches
Rear Gear Ratio: 4.11:1
READ MPH ACROSS ROW /READ RPM DOWN the FIRST COLUMN, then LINE UP THE SPEED IN EA. CORRESPONDING CROSS COLUMN.
RPM 1st 2nd 3rd 4th 5th 6th
1000 7 10 15 20 27 0
1500 10 15 22 30 40 0
2000 13 20 30 40 54 0
2500 17 26 37 50 67 0
3000 20 31 44 59 80 0
3500 23 36 52 69 94 0
4000 27 41 59 79 107 0
4500 30 46 67 89 120 0
5000 34 51 74 99 134 0
5500 37 56 81 109 147 0
6000 40 61 89 119 161 0
6500 44 66 96 129 174 0
7000 47 71 103 139 187 0
7500 50 77 111 149 201 0
8000 54 82 118 158 214 0

Thanks for posting the info.

The way I have always determined actual diameter of the "weighted" tire on the vehicle is to place a 24" level on the top center of the tire, level the bubble and then measure straight down to the floor to get the diameter. Of course you want the tire correctly inflated and loaded as you would be driving it.(full tank of gas, etc).

That would be the actual diameter the rear ring/pinion turns on the road. The number on the sidewall would be inaccurate if plugged into tire formulas.

The 35" tall(sidewall number)Goodyear tires I run on my 4x4 are 33.5" tall when mounted and installed. Thats what my axle really turns.

Shouldn't the tire diameter increase at speed due to centrifugal force, or is that too esoteric?

Hey Eagle . . .

Centrifugal force only kicks in at extreme RPMs - like what you see in a 'wrinkle wall' tire on a dragster during burnout . . . but CF doesn't help the tire to carry weight or to put horse power on the ground . . . which is why the effect at burnout is very different from what you see as the same tire 'piles up' behind the contact patch when a dragster comes out of the hole on a real launch.

For regular street driving the technique that El Ply has pointed out is an excellent approach to accurately measuring effective diameter. It also points out the real problem of under-inflation. When a tire is under inflated the sidewall gets crushed down several inches at the bottom of every rotation - and expands as it leaves the loaded portion of the wheel - if RPMs are high enough it will stretch under centrifugal force (as you have surmized) as it goes over the top - this 'kneading' creates heat in the rubber and an when exteme can cause a sidewall to soften to the point of blow out.

Thanks for the table data Carolines Truck!

regards,
stock49