Helps - revs per mile
07-10-2009, 06:43 AM
#11
MF Administrator
Join Date: May 2005
Location: South Carolina
Posts: 8,191
That method does NOT correctly calculate the tire revs per mile. The load and speed factors will throw off the calculations because of the tire's flattened contact patch.
IMO, stick with Nitto's number for that size tire. If need be, run down the highway with a friend in another car and compare speeds (a cell phone will help, but you could go "old school" and just yell out the windows like we did in the old days!).
07-10-2009, 09:17 AM
#13
6th Gear Member
I suppose you could try resetting your trip meter when your car's nose reaches a mile marker and compare it to subsequent mile markers as you drive down the road. Since our trip meters read in tenths, the farther you go the better in determining how accurate (or inaccurate) your speedometer is.
07-10-2009, 09:37 AM
#14
6th Gear Member
Thread Starter
Join Date: Nov 2007
Location: Montaner
Posts: 6,193
In the end I just settled on the 730 revs per mile.
Incidentally I pulled up another spreadsheet which shows engine rpms at various speeds in various gears. And after putting in my tires and my gearset the car seems to be correct according to that document. At 75mph I am right around 2500rpm which is exactly what the document states after filling out the fields.
Someday I will verify it with a GPS if I get the chance but right now it appears to be within a couple percent of accuracy.
Incidentally I pulled up another spreadsheet which shows engine rpms at various speeds in various gears. And after putting in my tires and my gearset the car seems to be correct according to that document. At 75mph I am right around 2500rpm which is exactly what the document states after filling out the fields.
Someday I will verify it with a GPS if I get the chance but right now it appears to be within a couple percent of accuracy.
07-10-2009, 11:23 AM
#15
Cut & Paste Expert
Join Date: May 2007
Location: NW Arkansas
Posts: 13,322
Mark out 63360 inches on a flat stretch of road.
Drive down it at the average speed you normally drive.
Take all the speeds you drive at and average them.
Have someone count the revs the tire turns during
the 1 mile (63360") trek. Thats your revs per mile at
that particular tire pressure. If you really want to know
what your set-up produces rev/mile wise for those tires.
Otherwise, just guess or get a GPS. Or dont worry about it.
Drive down it at the average speed you normally drive.
Take all the speeds you drive at and average them.
Have someone count the revs the tire turns during
the 1 mile (63360") trek. Thats your revs per mile at
that particular tire pressure. If you really want to know
what your set-up produces rev/mile wise for those tires.
Otherwise, just guess or get a GPS. Or dont worry about it.
07-10-2009, 11:31 AM
#16
6th Gear Member
07-10-2009, 11:46 AM
#18
6th Gear Member
The spreadsheet I have takes into account gears, tire size, tranny type... it even shows changes between tire/wheel/offset combinations in addition to various graphs. Unfortunately, it's on my main computer which isn't hooked-up (recent move). I DID forward it to a few forum members so perhaps someone can forward it to you.
07-10-2009, 12:58 PM
#20
5th Gear Member
Join Date: Mar 2007
Location: Orlando, FL
Posts: 2,031
original tire diameter / new tire diameter , then multiply by rear gear ratio = new gear ratio
Dont worry about the revs per mile. As long as you are passing all the cars around you, you know you are driving fast enough.
Dont worry about the revs per mile. As long as you are passing all the cars around you, you know you are driving fast enough.