[zenflow]

How do you change your tire size settings with the Xcal2? I am planning on getting some 17" GT takeoffs. The only option I noticed was something about revolutions. I don't remember exactly what the option said. What should the option say where you change the tire size? Will it list different sizes in the standard format "235/55/17" or whatever? Thanks.

[fishingjts]

Originally Posted by zenflow

How do you change your tire size settings with the Xcal2? I am planning on getting some 17" GT takeoffs. The only option I noticed was something about revolutions. I don't remember exactly what the option said. What should the option say where you change the tire size? Will it list different sizes in the standard format "235/55/17" or whatever? Thanks.

It's the "revs per mile" option... so you need to calculate the number and plug it in... for instance the 235/55/17 works out to 742 revs per mile (using this little tool: http://www.miata.net/garage/tirecalc.html )

When you go to plug in the revs it will only do it in increments of 5... so you'll need to plug in either 740 ro 745 revs per mile...

[stlwagon]

Originally Posted by zenflow

How do you change your tire size settings with the Xcal2? I am planning on getting some 17" GT takeoffs. The only option I noticed was something about revolutions. I don't remember exactly what the option said. What should the option say where you change the tire size? Will it list different sizes in the standard format "235/55/17" or whatever? Thanks.

What brand of tire?? Same size tires from different manufacturers will vary somewhat in revs/mile.

[zenflow]

It will be the Perellis that come with the GTs. I'm going to get the takeoff set of wheels and tires all together.

[fishingjts]

Originally Posted by stlwagon

What brand of tire?? Same size tires from different manufacturers will vary somewhat in revs/mile.

yeah... was going to mention that.. or actually rolling out the tire when it is properly inflated.. but since the X-Cal2 only does increments of 5... LOL!

I will say that my speedometer's needle is off a couple of MPH compared to the what computer is reading...

[zenflow]

thanks for that link! The info is as follows.

V6 with stock wheels and tires: 215/65-16 = 747 revs per mile

GT Takeoffs with Pirelli Pzero Nero: 235/55-17 = 742 revs per mile

So, not a very big difference. I think it came out to like a 0.6% change. When I get them I guess I'll just use the 740 setting.

One more question though: Will the GT tires be just as wide (amount of rubber on the ground) as the stock V6 ones? I guess the measurement nomenclature is kinda confusing me. I'm guessing they would be at least as wide, certainly would not want to go more skinny. Thanks again.

[zenflow]

This raises an interesting question....if the Xcal2 only goes in increments of 5, and therefor you can't get it precise, then won't that mean that the tach will be off as well, reflecting more or less miles on the engine according to if you put the setting slightly under or over the precise revs per mile?

[stlwagon]

Originally Posted by zenflow

This raises an interesting question....if the Xcal2 only goes in increments of 5, and therefor you can't get it precise, then won't that mean that the tach will be off as well, reflecting more or less miles on the engine according to if you put the setting slightly under or over the precise revs per mile?

That is true... I always set mine over.

[zenflow]

Sounds like a plan. Now what about that tire width? Would the GTs be just as wide or wider than the V6 (amount of rubber on the road)?

[stlwagon]

Originally Posted by zenflow

thanks for that link! The info is as follows.

V6 with stock wheels and tires: 215/65-16 = 747 revs per mile

GT Takeoffs with Pirelli Pzero Nero: 235/55-17 = 742 revs per mile

So, not a very big difference. I think it came out to like a 0.6% change. When I get them I guess I'll just use the 740 setting.

One more question though: Will the GT tires be just as wide (amount of rubber on the ground) as the stock V6 ones? I guess the measurement nomenclature is kinda confusing me. I'm guessing they would be at least as wide, certainly would not want to go more skinny. Thanks again.

Tire revs per mile for the all-season Pirelli P Zero Nero, 235/55 ZR17, is 768.

[stlwagon]

Originally Posted by zenflow

Sounds like a plan. Now what about that tire width? Would the GTs be just as wide or wider than the V6 (amount of rubber on the road)?

20mm wider (235-215).

[zenflow]

That calculator on that site must be off then...that's weird.

[zenflow]

Ok, went to tirerack.com and it says:

V6 w/ stock = 776 revs/mile

GT w/ stock =768 revs/mile

So looks like you were right. Looks like the setting will be 770 then. Thanks for all the info. Learned something new today.

[Benz-vettes]

I have an 06 with the 235/55/17 pony pack wheels. is my comp already set up for that size wheel so I dont have to change the Rev/mile using my tuner?

[zenflow]

Good question. You could always just go reflash your tune and make sure the revs/mile are correct in the user adjustable settings. Seems like that would be easy to make sure of.