Rear wheel offset 74 cuda

[Carlwalski]

As a matter of interest, what speedo gear drive do you use with the 275/60/15 rears, as I`m about to fit some?

What are you wanting to achieve Neil? Highway cruising, stop light action, both?
I run 3:91's but also have a GV overdrive. 3:55's are the preferred for most daily drivers.


 

[ShelbyDogg]

AXLE RATIO 24" 26" 28" 30"
2.76 2538930 2538928 2538926 2538924
2.94 2538932 2538930 2538928 2538926
3.21 2538935 2538933 2838931 2838929
3.55 2538939 2538936 2538933 2538931
3.91 2538943 2538940 2538937 2538935
4.10 2538945 2538942 2538939 2538936
4.30  2538944 2538941 2538938
4.56  2538945 2538943 2538940

Please note: these numbers are for the standard style pinion gear
also last two numbers are the number of teeth, 2538945 = 45 teeth

Here is the chart above.  For my 28" tire, the chart advises a 33 tooth pinion, so that is what I use.
When I drive long distances and match up with mile markers, for every 10 miles I'm about 2 tenths fast. If I calculate for a 34 tooth gear, the speedo would be too slow.  I have a computer in my ashtray for my fuel injection unit showing true RPM, so I use that to calculate true speed.
Rob

[ukneil]

thanks for that. So if I read that correctly, with my grandma gears of 2.76 and 28" tyres, I`ll need a 26 tooth red speedo gear? I hope so, cos that`s what I bought
 

[Carlwalski]

thanks for that. So if I read that correctly, with my grandma gears of 2.76 and 28" tyres, I`ll need a 26 tooth red speedo gear? I hope so, cos that`s what I bought
 

Yes, you got the correct part (number). 

[Bullitt-]

Saw this somewhere & kept a copy JUST FER U. Hope it helps. 
Speedometer Gear Selection Guide
Overall Tire Diameter

Axle Ratio
24" 26" 28" 30"
2.76 2538930(Yellow) 2538928(White) 2538926(Red) 2538924(White)
2.94 2538932(Black) 2538930(Yellow) 2538928(White) 2538926(Red)
3.21 2538935(Orange) 2538933(Yellow) 2838931(Green) 2838929(Black)
3.55 2538939(Green) 2538936(Red) 2538933(Yellow) 2538931(Green)
3.91 2538943(Blue) 2538940(Orange) 2538937(White) 2538935(Orange)
4.10 2538945(Yellow) 2538942(White) 2538939(Green) 2538936(Red)
4.30 2538944(Black) 2538941(Red) 2538938(Blue)
4.56 2538945(Yellow) 2538943(Blue) 2538940(Orange)


Please Note: These part numbers are for the standard style pinion gear. The last two numbers of the part number is the number of teeth for the gear (Example 2538943 = 43 teeth).

Here is an example on how to calculate the wheel diameter to select a speedometer gear to use with the desired ring/pinion gear.

Tire Size: 245/60/15

245mm/25.4mm = 9.64 Inches Section Width

9.64 in. X 60% = 5.79 in. Side Wall Thickness

5.79 in. X 2 = 11.57 in. Total Side wall height

11.57 in. + 15 in. (Rim Size) = 26.6 in. Diameter

So with this Tire Size and 3.91 Gears, I would use a 40 Tooth Speedometer gear.

[ukneil]

useful

[Swedish]

Hello 360cuda!

What backspace do you have on your 15x10 centerlines ?

[Swedish]

Hello 360cuda!

What backspace do you have on your 15x10 centerlines ?

sorry! i missed it!     

[360 'CUDA]