Tire speed

[kirby21]

How much speed would you gain going to a 14.9x38 from a 15.5x38.

 

[BushogPapa]

Depending on the Tire Maker, it will vary by a large amount..
Generally, a 14.9x38 IS taller than a 15.5x38..
I have 15.5x38 Titans on one and Good Year 15.5x38 on the other..the Titans a probably close to 4" Taller than the GoodYear tires..
I am sure you will find Circumference lists for each tire but you will need to know the circumference for Each Brand also..

Ron..

 

[BushogPapa]

I have no measurement, but I CAN tell you that the top speed traveling on the ROAD is significantly faster..fast enough that the Steering gets really Touchy at full throttle..
I don't run it that fast..but I would guess it picked up over a (One) full MPH on the road..
BEAST-wise..it will step right along in 3rd gear with 4x16"...

Ron..

 

[north puller]

Papa is right about brands being different. Also the amount of tread wear makes a difference.

For a F&R, for example, a 15.5 has a rolling circumference of 184" and the 14.9 is 190". This makes the 14.9 1.033 times taller, or 3.3%

With a 2.5 mph gear, you would go up to 2.58mph. 3.5 would become 3.62mph etc.

 

[chuck machinist]

Try this and see if this helps http://www.4lo.com/4LoCalc.htm good luck