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Discussion Starter · #1 ·
I need to replace my rear tire and was looking at going with the BT023. I noticed that it's available in both sizes listed above. I generally like somewhat higher ride height and more aggressive geometry, so I was wondering if there is a good reason to avoid the taller tire.
 

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Many seem to find their speedometers more accurate with the 70 series tire installed, so that is the way I'd go. Slightly taller= more protection for the wheel hitting potholes and the like too. Probably will be slightly heavier, but I can't imagine you'd notice on the street. With equal width, the taller tire should have a more 'pointy' profile...so if you like quicker steering this would be the way to go.
 

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Woody's Lackey
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Many seem to find their speedometers more accurate with the 70 series tire installed, so that is the way I'd go. Slightly taller= more protection for the wheel hitting potholes and the like too. Probably will be slightly heavier, but I can't imagine you'd notice on the street. With equal width, the taller tire should have a more 'pointy' profile...so if you like quicker steering this would be the way to go.
most of whats in this post is correct, i dont know what effect it would have on the accuracy of the speedometer though.
so with that said, lets have some fun with math, shall we? to find out the difference in the tires height we would do this.

ex. Tire size 160-60-17z

160= the tire's section width in millimeters.. to convert to inches just divide by 25.4 to get inches. 160mm = 6.29 inches wide

60= this is called the aspect ratio or the amount or height of the sidewall. It does not mean that the sidewall is 60mm tall. It means that the sidewall of tire is 60% tall as it is wide...

17= rim size

Z= speed rating

so you take the width of the tire 160 and multiply by .60 and that gives you 96mm tall. now that is the sidewall height from the top of the rim to the top of the tire. so add 96 for the top sidewall, plus 96 for the bottom sidewall=192mm and divide by 25.4to convert to inches and that gives you 7.56 inches now add in the 17 inches of the rim and this gives you 24.56 inches tall.

now lets try with 160 70 17 to see what we get.
160mm = 6.29 inches wide
160 x .70 = 112mm
112 + 112 = 224mm divide by 25.4 = 8.81 + 17 = 25.81

so with a 160/60 17 tire you would be 24.56 height
and with a 160/70 17 tire you would be 25.81 height
so that would be more then an inch of height, which would throw off gearing, speedometer, rear suspension, front suspension, bike geometry, and handling, all of which would make a big difference on the race track, but you will prob never notice unless your pushing your bike at over 80%.
 

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Discussion Starter · #5 ·
Many seem to find their speedometers more accurate with the 70 series tire installed, so that is the way I'd go. Slightly taller= more protection for the wheel hitting potholes and the like too. Probably will be slightly heavier, but I can't imagine you'd notice on the street. With equal width, the taller tire should have a more 'pointy' profile...so if you like quicker steering this would be the way to go.
Not going to make any difference in speedometer because it's the rear. Effectively taller gearing, though.

Many people go with a taller front tire, I'm talking about a taller rear tire.
 

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I was wondering when others would notice that you were talking about a rear tire, not a front. You can't exactly go by absolute numbers from a formula to determine tire hgt. It depends upon the tire brand. A taller rear tire should increase corner turn in speed since you are increasing rear ride hgt. How much of an affect depends upon the difference in hgt for that particular tire model and brand. I would think that a more triangular front tire profile would have a greater affect than raising the rear.
 

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Woody's Lackey
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I was wondering when others would notice that you were talking about a rear tire, not a front. You can't exactly go by absolute numbers from a formula to determine tire hgt. It depends upon the tire brand. A taller rear tire should increase corner turn in speed since you are increasing rear ride hgt. How much of an affect depends upon the difference in hgt for that particular tire model and brand. I would think that a more triangular front tire profile would have a greater affect than raising the rear.
i hope everyone thought i was talking about the rear tire, i know my post was confusing to some, but yes, sometimes numbers cant be counted on due to some tire companies vary it a SMALL amount, but it will be about the same either way.
 

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Not going to make any difference in speedometer because it's the rear. Effectively taller gearing, though.

Many people go with a taller front tire, I'm talking about a taller rear tire.
Ooops! Sorry. Speed reading again. I'd never seen a 160/70 until I looked at the BT023's. That would quicken the steering a little, and raise the gearing (taller) a bit also. Might cause interference with a hugger.
 

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most of whats in this post is correct, i dont know what effect it would have on the accuracy of the speedometer though.
so with that said, lets have some fun with math, shall we? to find out the difference in the tires height we would do this.

ex. Tire size 160-60-17z

160= the tire's section width in millimeters.. to convert to inches just divide by 25.4 to get inches. 160mm = 6.29 inches wide

60= this is called the aspect ratio or the amount or height of the sidewall. It does not mean that the sidewall is 60mm tall. It means that the sidewall of tire is 60% tall as it is wide...

17= rim size

Z= speed rating

so you take the width of the tire 160 and multiply by .60 and that gives you 96mm tall. now that is the sidewall height from the top of the rim to the top of the tire. so add 96 for the top sidewall, plus 96 for the bottom sidewall=192mm and divide by 25.4to convert to inches and that gives you 7.56 inches now add in the 17 inches of the rim and this gives you 24.56 inches tall.

now lets try with 160 70 17 to see what we get.
160mm = 6.29 inches wide
160 x .70 = 112mm
112 + 112 = 224mm divide by 25.4 = 8.81 + 17 = 25.81

so with a 160/60 17 tire you would be 24.56 height
and with a 160/70 17 tire you would be 25.81 height
so that would be more then an inch of height, which would throw off gearing, speedometer, rear suspension, front suspension, bike geometry, and handling, all of which would make a big difference on the race track, but you will prob never notice unless your pushing your bike at over 80%.
Motorcycle tires have rounded profiles and different carcass shapes which adds complexity. You can NOT use this math to get accurate measurements for motorcycles tires. You need to physically measure them as every manufacturer designs their carcasses differently. I think if you went out and actually measured various tires in various sizes tires you would get very different numbers than the ones posted above.

One example, a 200 Pirelli Diablo Supercorsa is only a few mm wider than a 190, not 10mm as one might expect.
 
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