90/100-21 front tire - Kawasaki KLR 650 Forum
2008+ KLR650 Wrenching & Mod Questions For repair, maintaining or modifying discussions related to the newly updated 2008 and beyond, Generation 2 KLR650 Motorcycle.

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post #1 of 12 Old 02-15-2019, 06:57 PM Thread Starter
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90/100-21 front tire

So stock is 90/90-21.

I want to try out the Motoz front and rear.
The front I want is available in 90/100-21, not 90/90-21.

What effects might the taller profile have on handling/ride ability both on street and dirt, good or bad?

I know this is a rather general question, just looking for others that have gone taller front and what they noticed. I’m not concerned with speedo.

2016 KLR 650
2017 BMW S1000RR (traded in for
2018 Ducati V4S
1983 GL1100 Goldwing
2017 Yamaha R1
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post #2 of 12 Old 02-15-2019, 07:31 PM
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I'll suggest that most of us would never notice the handling difference between a tire with 81 mm tall sidewall vs 90 mm tall sidewall.

If you discover that you think can feel the difference just slide the fork tubes up 10 mm and ride it again or add a notch of preload to the rear spring or both.

The numbers are only approximates anyways. You will have to measure both old & new when fitted on the bike to find the true difference.

Changing from a street tire to an off-road tire even with the same numbers probably makes more total difference.
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post #3 of 12 Old 02-15-2019, 10:54 PM Thread Starter
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Thanks Paul, your insights are much appreciated.

2016 KLR 650
2017 BMW S1000RR (traded in for
2018 Ducati V4S
1983 GL1100 Goldwing
2017 Yamaha R1
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post #4 of 12 Old 02-16-2019, 10:07 AM Thread Starter
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Surprising the difference you mention.
I measured the 90/90 labeled street tire on the bike now, width is real close to 90 mm wide, but height is barely 50 mm. A long way from 81 mm.

2016 KLR 650
2017 BMW S1000RR (traded in for
2018 Ducati V4S
1983 GL1100 Goldwing
2017 Yamaha R1
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post #5 of 12 Old 02-16-2019, 12:05 PM
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The 90mm width tire supposedly is suppose to have a 90% tall aspect ratio. So supposedly 81mm. And supposedly these are supposed to be Carcass measurements, not tread width to carcass measurement.
And when one looks in the books, the street tires differ from dirt tires when converted to simple Inches!

So like I said, 'approximates' or maybe better yet just a WAG!

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post #6 of 12 Old 02-17-2019, 08:16 PM
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Quote:
Originally Posted by dan filipi View Post
Surprising the difference you mention.
I measured the 90/90 labeled street tire on the bike now, width is real close to 90 mm wide, but height is barely 50 mm. A long way from 81 mm.
How did you measure the height? Is the tread on the tire new?
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post #7 of 12 Old 02-17-2019, 08:50 PM Thread Starter
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Quote:
Originally Posted by Voyager View Post
How did you measure the height? Is the tread on the tire new?
Itís a street tire, less than 1/2 worn.
I measured from the rim edge at the rubber, to the tread face.

2016 KLR 650
2017 BMW S1000RR (traded in for
2018 Ducati V4S
1983 GL1100 Goldwing
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post #8 of 12 Old 02-18-2019, 12:11 AM
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I just measured a 50/50 knobby with 90/90 marked on the sidewall mounted air aired. From the outside edge of the rim to the outside of the carcass measured 2.75 inches or about 69 mm. Adding in about 1/2 inch for the part of the tire inside the rim gets really close to 81mm.
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post #9 of 12 Old 02-18-2019, 06:41 AM
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Quote:
Originally Posted by dan filipi View Post
Itís a street tire, less than 1/2 worn.
I measured from the rim edge at the rubber, to the tread face.
That was my suspicion. You measured incorrectly on a worn tire. The aspect ratio is only accurate with a new tire and the height is measured from the inner radius of the bead to the outer radius of the brand new tread. Add the bead height and half the tread height to your number and I bet you will be much closer to the published aspect ratio.
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post #10 of 12 Old 02-18-2019, 08:27 AM Thread Starter
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Quote:
Originally Posted by Voyager View Post
That was my suspicion. You measured incorrectly on a worn tire. The aspect ratio is only accurate with a new tire and the height is measured from the inner radius of the bead to the outer radius of the brand new tread. Add the bead height and half the tread height to your number and I bet you will be much closer to the published aspect ratio.
I doubt that would make up over 30 mm, or even close to it. This tire always looked low profile to me. I never thought to measure it when new and mounted.
With such a large difference with this tire, 10 mm larger than stock is no longer a concern to me.

2016 KLR 650
2017 BMW S1000RR (traded in for
2018 Ducati V4S
1983 GL1100 Goldwing
2017 Yamaha R1

Last edited by dan filipi; 02-18-2019 at 09:15 AM.
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