kntr

I know mine did 60 at 2000rpms with 4.10 and stock tires.
According to your chart it should have been 1782 rpms.

adaycj

A tach based on the crank signal on OBDII and newer (CAN) vehicles should be dead on. I have worked on hundreds, if not thousands, of vehicles with high res crank sensors with a scan tool hooked up and I have not found one tach to be wrong. Nefarious practices of motorcycles manufactures aside, we should be able to count on our tachs.

I agree however that the data gets screwed up by guesses, bad memories, and inaccurate speedos. It is the same reason that a performance modification that increases engine efficiency by less than a percent can net 2 MPG according to many users.

+5 on the overgeared part. Not only is rotating mass increased, but most of the modified rigs with big tires have lifts and accessories. Adding more wind resistance and weight to the equation.

Regearing past the stock point will also add one more interesting twist to the equation. Many people are used to slow speedos and short odos with bigger tires. When you overgear you get a fast speedo and a long odo. At least it makes the MPG look better before corrections.

boots

I tought I was confused before.

With all the numbers, and plus and minuses of weight and air drag, not to mention the gravitational pull of the extra weight because I had a Big Mac for lunch. I don't know what gear to go with. 4:88's or 5:13's

When all is said and done, I guess it's up to each individual to pick what gears they will run with what tire combination. I for one am still confused.

But heck, I still have another week to decide.

UCLA JK Rida'

B:

I hope you enjoy whatever ratio you decide to go with. Incidentally, this thread has been mad helpful to me. I'm still awhile from upgrading to lift, gears, wheels, and tires...but it has given me great assistance in deciding what to roll with. 5.13s and 35s seems to be a safe bet with 2 door, automatic, and aftermarket bumpers and winch (which I already have).


Russ D.

Sv650

You could just buy what makes you happy!

SV

boots

Yes, you are right. The best thing is I have it narrowed down to just two gear sets. 4:88's and 5:13's

Sv650

The numbers I quoted do not allow for any slippage that might occur in the A/T.

Also, if the tires are actually 31.5, your speedo is 5% out, and you misread your tach by 50 rpm due to parallax error or equipment error, the numbers are pretty close!

Also is the diff actually 4.10, or 4.11 or..... , is the transmission 0.69 or 0.685 or.....? Small differences are multiplied (pun intended) throughout the equations I used. There may also be rounding errors in the calculations the author used in creating the calculator.

There's too many variables in the equipment available to us in this instance to quibble over about 200 rpm. However, the circumference of the tire translates accurately back to the crankshaft, if you have accurate numbers for each of the steps.

Also, remember, 4.10's with either 35s or 37s are already better than the stock 3.21s with 32s!

SV

Sv650

Based on what I learned from digging around to create the above list, I'd consider 5.13 for an auto on 37s, and 4.88s for a 6 speed!

SV

kntr

Exactly!!!!!

Ben Hedrick

AZ Bulldog,
Sidebar: How do you like your Fox Shocks? I am think about changing my shock to an adjustible style or a resivor style. What do you think?

Thanks, Ben