Tire Sizes, bad?
- Thread starter Canada
- Start date
GarnetTy1473
Donating Member
Re: Tire Sizes, bad?
Those are about 1/2" different in height, so yes it will be a problem. I would just go 245 all the way around.
Those are about 1/2" different in height, so yes it will be a problem. I would just go 245 all the way around.
Richard Le
New member
Re: Tire Sizes, bad?
Here is a great calculator: http://www.1010tires.com/tiresizecalculator.asp
FYI, stock size is 245/50-16.
Of course it will. Where are you getting mixed results?
Here is a great calculator: http://www.1010tires.com/tiresizecalculator.asp
FYI, stock size is 245/50-16.
dcracer
New member
Re: Tire Sizes, bad?
I'm confused, I'm running 275/40/17 front and 315/35/17 rear this should be ok?
I keep seeing post about width, why? http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=46
I'm confused, I'm running 275/40/17 front and 315/35/17 rear this should be ok?
I keep seeing post about width, why? http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=46
sytyguy
Moderated User
Re: Tire Sizes, bad?
For those who want to do math and observe rev-per-mile differences: http://www.discounttire.com/dtcs/infoTireMath.dos
Your's are very close (a difference of 0.02" in diameter & 0.06" in circumference). You can get a 0.02" change in diameter with tire pressure.
For those who want to do math and observe rev-per-mile differences: http://www.discounttire.com/dtcs/infoTireMath.dos
V
Donating Member
Re: Tire Sizes, bad?
Be careful when using an online calculator to compare revs/mile. 1010tires.com uses a mysterious "industry" formula which is supposed to factor in traction variables. Discount tire uses simple math.
Below are their revs/mile numbers for a 275/40/17 tire:
1010tires...............810.60
Discount tire..........785.93
Compare that with the stated revs/mile of some random tires (275/40/17):
Goodyear F1-D3...................811
Michelin Pilot Sport PS2......814
BFG G-Force Sport...............800
IMO, circumference or diameter are better numbers to compare tires.
Be careful when using an online calculator to compare revs/mile. 1010tires.com uses a mysterious "industry" formula which is supposed to factor in traction variables. Discount tire uses simple math.
Below are their revs/mile numbers for a 275/40/17 tire:
1010tires...............810.60
Discount tire..........785.93
Compare that with the stated revs/mile of some random tires (275/40/17):
Goodyear F1-D3...................811
Michelin Pilot Sport PS2......814
BFG G-Force Sport...............800
IMO, circumference or diameter are better numbers to compare tires.
sytyguy
Moderated User
Re: Tire Sizes, bad?
width in mm/25.4 (to convert to inches)
width in in * (aspect ratio * .01) = sidewall diameter
sidewall diameter * 2 to get overall tire diameter
overall tire diameter + wheel diameter = tire height (d)
c=πd to get circumference (in inches)
63,360/c = revs per mile
Example (stock wheel/tire):
245 / 25.4 = 9.65"
50 * 0.01 = .5
9.65 * .5 = 4.825" (#)
4.825 * 2 = 9.65"
9.65 + 16 = 25.65" (overall tire height)
25.65 * 3.1415 (pi rounded to ten-thousandths) = 80.57" (circumference)
63360 / 80.57 = 786.40 rpms (+- 0.01 for rounding)
# redundant math FTW but it's necessary for anything other than 50 aspect ratio
The math isn't rocket science (c=πd), and Tirerack's math is right. But it's easy enough to do it yourself.
width in mm/25.4 (to convert to inches)
width in in * (aspect ratio * .01) = sidewall diameter
sidewall diameter * 2 to get overall tire diameter
overall tire diameter + wheel diameter = tire height (d)
c=πd to get circumference (in inches)
63,360/c = revs per mile
Example (stock wheel/tire):
245 / 25.4 = 9.65"
50 * 0.01 = .5
9.65 * .5 = 4.825" (#)
4.825 * 2 = 9.65"
9.65 + 16 = 25.65" (overall tire height)
25.65 * 3.1415 (pi rounded to ten-thousandths) = 80.57" (circumference)
63360 / 80.57 = 786.40 rpms (+- 0.01 for rounding)
# redundant math FTW but it's necessary for anything other than 50 aspect ratio
Black Knight
I Glow Therefore I am
Re: Tire Sizes, bad?
Two problems with this though.
1) Tread height isn't taken into consideration a range of anywhere between 2/32" (legal limit) and new 14/32" (rough guess), multiply by two for both sides of the tire. That factor needs to be taken into consideration.
2) Tires just simply don't match up that well. Eviltwin and I tried to put a pair of his 275/40R-17 D/R on my Sy which has stock wheels and tires and his tires were about an 1" taller. When in theory they should be almost identical.
Two problems with this though.
1) Tread height isn't taken into consideration a range of anywhere between 2/32" (legal limit) and new 14/32" (rough guess), multiply by two for both sides of the tire. That factor needs to be taken into consideration.
2) Tires just simply don't match up that well. Eviltwin and I tried to put a pair of his 275/40R-17 D/R on my Sy which has stock wheels and tires and his tires were about an 1" taller. When in theory they should be almost identical.
sytyguy
Moderated User
Re: Tire Sizes, bad?
It's a comparison. You're leaving it out for both tires. Now if it was added in for one and not the other then there would be a problem. Assume both tires have 8/32 tread depth (1/4"), that makes the tire 0.5" taller overall. Now let's play with some .5 differences in the math:
25.5" OD * pi = 80.108
26.0" OD * pi = 81.679
> a difference of 1.57" circ
32.0" OD * pi = 100.528
32.5" OD * pi = 102.098
> a difference of 1.57" circ
41.0" OD * pi = 128.801
41.5" OD * pi = 130.372
> a difference of 1.57" circ
All equal a uniform circ difference. It's a moot point when used as a comparison. But if we're nitpicking, then we have to account for tread wear and tire pressure (at a specific temp), so the only way to be sure is to measure the SOB with a tape measure. And then what if you have the fronts at 36 psi and the rears at 32 psi to help the xfer case. What does the road speed temp increase do to that overall diameter?
The point I'm making is that it's a bench math estimation to help get the rpms close.
It's a comparison. You're leaving it out for both tires. Now if it was added in for one and not the other then there would be a problem. Assume both tires have 8/32 tread depth (1/4"), that makes the tire 0.5" taller overall. Now let's play with some .5 differences in the math:
25.5" OD * pi = 80.108
26.0" OD * pi = 81.679
> a difference of 1.57" circ
32.0" OD * pi = 100.528
32.5" OD * pi = 102.098
> a difference of 1.57" circ
41.0" OD * pi = 128.801
41.5" OD * pi = 130.372
> a difference of 1.57" circ
All equal a uniform circ difference. It's a moot point when used as a comparison. But if we're nitpicking, then we have to account for tread wear and tire pressure (at a specific temp), so the only way to be sure is to measure the SOB with a tape measure. And then what if you have the fronts at 36 psi and the rears at 32 psi to help the xfer case. What does the road speed temp increase do to that overall diameter?
The point I'm making is that it's a bench math estimation to help get the rpms close.
V
Donating Member
Re: Tire Sizes, bad?
The intent of my post is that revs/mile is not apples-to-apples. The "industry" formula that 1010tires informed me of accounts for real world variables (including the wear factor that Roy stated). But sometimes, you will find the "simple math" formula that Michael posted. Both are correct, but adds confusion.
The intent of my post is that revs/mile is not apples-to-apples. The "industry" formula that 1010tires informed me of accounts for real world variables (including the wear factor that Roy stated). But sometimes, you will find the "simple math" formula that Michael posted. Both are correct, but adds confusion.
Last edited:
sytyguy
Moderated User
Re: Tire Sizes, bad?
Assuming proper tire rotation and no abnormal tire wear sessions (burnouts, extremely poor autocrossing, etc...) our tires should wear evenly. Regardless of the amount of wear (assuming it's even amongst all 4), the circ difference would remain equal.
For instance, let's look at a set of 2001 ZO6 Wheels:
Front: P275/40ZR-17
Rear: P295/35ZR-18
The fronts have a overall diameter of 25.66" resulting in a circumference of 80.62". The rears have a overall diameter of 26.13" resulting in a circumference of 82.09". Now lets subtract a 1/2 inch of wear (1/4" depth x 2).
Fronts: 25.16" = 79.04" circumference (80.62 - 79.04 = 1.58)
Rears: 25.63" = 80.51" circumference (82.09 - 80.51 = 1.58)
So, despite being completely different tire sizes, equal wear results in an equal drop in circumference. The bonus is that as the tire wears (diameter gets smaller) the rpm differ (F to R) gets smaller. So for us, if you get a tire combo that has (let's say) an rpm difference (F to R) of 0.6 rpms and the tires wear 1/4 on the tread depth, then the rpm difference drops by 0.01 (to 0.59).
The overall moral though is that the closer you get the F to R rpms, the happier the transfer case will be. Get too wide an rpm difference and don't be surprised if you hurt a transfer case.
Assuming proper tire rotation and no abnormal tire wear sessions (burnouts, extremely poor autocrossing, etc...) our tires should wear evenly. Regardless of the amount of wear (assuming it's even amongst all 4), the circ difference would remain equal.
For instance, let's look at a set of 2001 ZO6 Wheels:
Front: P275/40ZR-17
Rear: P295/35ZR-18
The fronts have a overall diameter of 25.66" resulting in a circumference of 80.62". The rears have a overall diameter of 26.13" resulting in a circumference of 82.09". Now lets subtract a 1/2 inch of wear (1/4" depth x 2).
Fronts: 25.16" = 79.04" circumference (80.62 - 79.04 = 1.58)
Rears: 25.63" = 80.51" circumference (82.09 - 80.51 = 1.58)
So, despite being completely different tire sizes, equal wear results in an equal drop in circumference. The bonus is that as the tire wears (diameter gets smaller) the rpm differ (F to R) gets smaller. So for us, if you get a tire combo that has (let's say) an rpm difference (F to R) of 0.6 rpms and the tires wear 1/4 on the tread depth, then the rpm difference drops by 0.01 (to 0.59).
The overall moral though is that the closer you get the F to R rpms, the happier the transfer case will be. Get too wide an rpm difference and don't be surprised if you hurt a transfer case.
sly dvl
Ya, it's got a Turbo
Re: Tire Sizes, bad?
Because the "series" or "aspect ratio" (35 series, 40 series etc...) is a percentage of the width.
Because the "series" or "aspect ratio" (35 series, 40 series etc...) is a percentage of the width.
teamvortec
New member
Re: Tire Sizes, bad?
Searched for other things and found my answer.
Searched for other things and found my answer.
Last edited:
teamvortec
New member
Re: Tire Sizes, bad?
I mounted my 275/40/17 Maxxis tires on the 17x9.5 front wheel and mounted 315/35/17 Sumitomos on the rear 17x9.5 wheels. According to what I have read these tires should match up fine. When I stood them up beside each other and placed a straight edge across them the rear tires were actually taller by 10mm. Is this going to be too much difference in height? Can I just lower the tire pressure in the rear by a few lbs to make them the same height from the wheel to the ground when mounted on the Ty and be fine. I was really hoping I could run these until they sold and I could get some Chrome C5 Z06 wheels but I don't want to tear the transfer case up.
I mounted my 275/40/17 Maxxis tires on the 17x9.5 front wheel and mounted 315/35/17 Sumitomos on the rear 17x9.5 wheels. According to what I have read these tires should match up fine. When I stood them up beside each other and placed a straight edge across them the rear tires were actually taller by 10mm. Is this going to be too much difference in height? Can I just lower the tire pressure in the rear by a few lbs to make them the same height from the wheel to the ground when mounted on the Ty and be fine. I was really hoping I could run these until they sold and I could get some Chrome C5 Z06 wheels but I don't want to tear the transfer case up.
sytyguy
Moderated User
Re: Tire Sizes, bad?
Place the pressurized front tire (32 psi or so) on a flat surface (verify with a level to be flat and true). Place the level on the top of the tire and measure with a tape measure to the bottom of the level. Repeat for the rear tire. Compare the two ODs. In theory, they should be about 0.02" in difference (about 1/2mm.....not 10mm). If you come up close to that, they're safe enough to run (about 0.6 rpm difference). If they are indeed 10mm, then I would be leery as that results in a 11-12 rpm difference. That's a lot to ask of the transfer case.
teamvortec
New member
Re: Tire Sizes, bad?
I guess I am going to just sell the ZR1s with the tires and find some ZO6 wheels and then worry about tires.
I guess I am going to just sell the ZR1s with the tires and find some ZO6 wheels and then worry about tires.