Tire Circumference Help!

Rudi Eidam · #1 11-06-2009, 04:33 PM

Just got some new cooper stt's and need help adjusting the tire size for my Gryphon. They are 33x12.5x20. I cant seem to find my manual with the formula to convert to mm. Thank you!

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**Bluejay** · #2 11-06-2009, 04:37 PM

Edge lists 2632mm for 33s, but I would reduce that by 3% for squish. So I would enter 2553.

Rudi Eidam · #3 11-06-2009, 04:46 PM

Thanks Bluejay! Any idea if i should be changing my gear ratio? Or where i might look to see what i have?

**Bluejay** · #4 11-06-2009, 04:51 PM

Quote:

Originally Posted by Rudi Eidam

Thanks Bluejay! Any idea if i should be changing my gear ratio? Or where i might look to see what i have?

Assuming your gears have never been changed, check the tag on your drivers door, for the Axle Code.

Compare to this list:
F-150:
19 – 3.55 Non-LS
18 – 3.08 Non-LS
H9 – 3.55 LS
B6 – 3.73 LS
Then, when you go to custom settings, see what the default is in the unit. If not what your axle code says, then change it.

NCSU_05_FX4 · #5 11-06-2009, 04:54 PM

No, unless it's wrong to begin with you don't want to change your gear ratio unless you've actually swapped out your gears.

- NCSU

**Bluejay** · #6 11-06-2009, 05:09 PM

Quote:

Originally Posted by NCSU_05_FX4

No, unless it's wrong to begin with you don't want to change your gear ratio unless you've actually swapped out your gears.

- NCSU

My Edge always defaults to the wrong ratio, so it's good to make sure.

NCSU_05_FX4 · #7 11-06-2009, 05:18 PM

Does that happen even if you have one of the tunes loaded up?

- NCSU

**Bluejay** · #8 11-06-2009, 05:23 PM

Quote:

Originally Posted by NCSU_05_FX4

Does that happen even if you have one of the tunes loaded up?

- NCSU

Not sure what you are asking. Been a long time ago, but I am pretty sure if I was in Level 2 and did not save the settings, if I switched to Level 3, I had to change my tires and my gears, along with the shift pressures, etc. When I got the custom tunes, I asked Bill to set them on 3.55s and he forgot to do it in one of them, so it still defaults to 3.73 and I have to change it. It may have to do with my Edge being an early model and I never downloaded any upgrades to it.

NCSU_05_FX4 · #9 11-06-2009, 05:30 PM

Gotcha, I'm using the Xcal2 and with the custom tunes everything is already set up for my truck. Wasn't sure how the canned tunes work in that regard.

- NCSU