whats my speed bigger tires

[marcuspur]

ive got an 88 ranger 2.9 5 speed and want to know how off my speedo is i belive its slower but not sure i have 3.73 gear ratio and 31" tires thanks

 

[marcuspur]

ive got an 88 ranger 2.9 5 speed and want to know how off my speedo is i belive its slower but not sure i have 3.73 gear ratio and 31" tires thanks

sorry didnt mean to post this in the 4wd section

 

[strvger]

http://www.therangerstation.com/tech_library/Speedometer_Change_From_Tires.html

 

[Lrpalo]

This is a really good one
http://1010tires.com/TireSizeCalculator.asp

 

[feellnfroggy]

At 55 mph with 235's and 327,s I ran approx 53 mph based on police scanner, when I added 31's I was deadon accurate. Adding the 3.55's will drop me back to approx 53 mph again. With your gears and 31, you 'should run approx 1-2 mph slower than me, assuming your gauge is also 2 mph slower than factory settings prior to any mods.

Old speed new speed old speed new tires
--------- / ------------ = -------- * --------- =
Old tires new tires old tires new speed

55mph x(variable) 55mph 31's
---------- / ------------ = -------- * --------- =
29's ? 31's 29's ? x(variable)

1705
----- = x = 58.7931
29x

At 55mph according to your speedo you are moving 58.7931
Assuming your Ford speedo is 2mph slower than actual like mine, you are doing approx 56.80 mph when showing 55mph,


Hope all this makes sense. Ill post the results of one of those links to see how far off I am.


Edit::This stupid thing wont put my spaces in properly so the algebra looks all skewed(it may be geomtry) but you ge the idea, I did post the solution after all.

 

[feellnfroggy]

55/58.7931=0.93548 (55mph is 93.58% of 58.7931mph)

This show basically 6.5%difference. which is roughly what the chart above shows too.

In the end you prolly already figured all this out. But I;m really proud of myself and my math skills right now, so don't blow it.

 

[rangershea]

get a gps!