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tbuck
11-08-2003, 18:19
Dillema,
I currently have 235/85/16 tires on my truck.
I am planning a trip into icy weather and have a set of 265/75/16 studded tires.
Will that change my gear ratio very much?
I have 4.10 gears and I will be towing a trailer full of camping/hunting/etc. gear.

Any opinions?
jlog
11-08-2003, 19:20
according to scotts tire size calculator the change you are planning will give you 1/4 % thats .25% smaller tire size. Should be no noticible difference in performance.

john
markz
11-08-2003, 19:20
I think 4-10 gears are to low to begin with, so I run 285 tires and haul a gross weight of 15,000 lb. with no problems.

Mark
markz
11-08-2003, 19:22
oops, I didn't read your post correctly, I though you where going bigger not smaller.

Mark
G B Sisson
11-08-2003, 19:31
A 265 tire is smaller in dia. than your 235 as it's a different ratio.(It's wider) The 235 85 16 is31.73 dia and the 265 75 16 is31.65...To answer your question,you are gearing a tiny bit lower,so pack on a few extra pounds of gear...Have a good trip! Gary
tbuck
11-09-2003, 12:31
Well I'm getting confused.
I thought the 235 tire would be smaller than the 265?
Is there a website that shows the diameter of tires?
JohnC
11-09-2003, 18:15
The 235 has a slightly narrower tread width, but it has a higher aspect ratio (85 vs. 75 for the 265), so it ends up having a greater (slightly) diameter. The RPM program available on the DP has a tyre diameter calculator, or you can use the formula (((treadwidth/25.4)x (aspectratio/100)) x 2)+ rimsize. For the 235/85-16 that's (((235/25.4)x.85)x2)+16

Bottom line is you won't notice any difference between the 2.
matt-max
11-10-2003, 06:10
to be certain, find the manufacturers' spec's for the tires on their website or published data and compare the overall height.

more accuractely, try measuring on the truck or wheel with a string or cloth measuring tape.

a worn tire may lose substantial height or circumference as the tread goes away.

matt
C.K. Piquup
11-16-2003, 13:30
You`re not going to notice any difference(nor will your truck)between the 2 tire sizes.They virtually the same in rolling resistance,even though their dimensions criss-cross fractions apart.
RCF
11-16-2003, 14:51
Go here for all you need to know on diameters and gear ratios...........

http://www.dirtroad.com/gears.htm
Kidd
11-16-2003, 19:22
If you want a website giving diameter of tires etc. go to the website of your tire maker. I did this before buying mine, very informative.