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Thread: Why 90/90-21 front tire on 300XCW TPI?

  1. #11
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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    Are they the same brand and model front tires? Or same with the w having the wider of the two. Different forks might be part of the equation.
    Victor

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  3. #12
    KTMTalk Member pumpkinator's Avatar
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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    My understanding, and I could be wrong, is that the 80/100 being more narrow helps the bike turn in faster and bite into the terrain whereas the wider 90/90 or 90/100 slow down steering and cause the front tire to float more. Depending on the terrain, the wider tire could cause the front to push and slide. More experienced riders can correct me but it seems the XC with the 80/100 would be more aggressive and faster handling whereas the XC-W new front would dumb down handling. I've tried the wider tire on big four strokes and didn't like it. But maybe wider is better for some types of terrain?
    '19 XC-250, '17 6 Days 300XC-W, '14 500XC-W

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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    Basic physics says a larger front tire has a larger diameter and/or more rotating mass therefore will be slower to turn. A long time ago I put an old heavy 3.25 metzler (which was awesome on an old maico) on the front of a CR500. It was absolutely terrible and steered like a bus. I just ordered a 80/100 for the front of my xc to replace the 90/90. I am hoping for more precise steering. Cam

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    Lifetime Team KTMTalk DonS's Avatar
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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    Thanks pump and KX...that's exactly the info I'm looking for.
    You are what you do when it counts ― John Steakley, Armor

    Plank owner, Wyatt's Torch Maintenance Department.

    Accept failure as inevitable and it will be.

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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    A more narrow tire will fall in quicker, and thats either front or rear.

    Choice to me is more about attitude of the bike. where ever you are riding it.

    just like raising the forks in the clamps(drops the front end )and quickens front steering, so will a skinnier and or smaller diameter tire.

    now if the focus is more on high speed stability, all that reverses.

  7. #16
    KTMTalk Member pumpkinator's Avatar
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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    Quote Originally Posted by KXcam22 View Post
    Basic physics says a larger front tire has a larger diameter and/or more rotating mass therefore will be slower to turn. A long time ago I put an old heavy 3.25 metzler (which was awesome on an old maico) on the front of a CR500. It was absolutely terrible and steered like a bus. I just ordered a 80/100 for the front of my xc to replace the 90/90. I am hoping for more precise steering. Cam
    Yes something I've been learning lately is that bigger/wider doesn't always help for both the front/rear tires. Having a rear tire that hooks up too much can cause the front to push because you can't get the rear tire to break loose and slide around a corner. I put a new IRC M5B 130/80-18 on my 250 XC and installed heavy duty tubes and the bike handles bad. Especially on the small pipey 2 stroke, you need to ride differently than a 4 stroke, get on the pipe hard on corner exit. Whereas the 4 stroke riders can flat track/roll around corners. This also explains why the big IRC can work on a 300, because it can be ridden like a lazy 4 stroke.
    Last edited by pumpkinator; 10-18-2020 at 12:00 PM.
    '19 XC-250, '17 6 Days 300XC-W, '14 500XC-W

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    Lifetime Team KTMTalk DonS's Avatar
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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    Thanks spud.
    You are what you do when it counts ― John Steakley, Armor

    Plank owner, Wyatt's Torch Maintenance Department.

    Accept failure as inevitable and it will be.

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    KTMTalk Member Cactus73's Avatar
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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    Quote Originally Posted by griffbones View Post
    My bikes have always had 80/100-21 front tires. I see the spec for the 2021 300XCW TPI is 90/90-21, yet the XC still specs the 80/100-21. What is the reason for this tire size? Sorry if this is a dumb question.
    Where are you seeing this spec? I can't find anything relating to tire sizes for the 2021's.
    2020 TE300i

  10. #19
    KTMTalk Member Suva's Avatar
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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    I'm pretty sure this is a classic case of KTM publishing the wrong specs. From what I understand KTM specs 90/90 (euro size, so not much different than 80/100 US ) FIM tires in markets other than the US.
    '18 300XCW,
    '18 TX300,
    '04 200SX
    '99 380EXC,
    '93 CR250

  11. #20
    KTMTalk Member griffbones's Avatar
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    Default Re: Why 90/90-21 front tire on 300XCW TPI?

    Quote Originally Posted by Cactus73 View Post
    Where are you seeing this spec? I can't find anything relating to tire sizes for the 2021's.
    I first saw it on Motosport and Rocky Mountain web sites when I put in the model information and the sites list what stock sizes are for tires, gearing, stock plug etc.
    Since then I downloaded the owners manual from KTM and it shows the Special Models as having a 90/90 but the XCW as having an 80/100.
    See attachments:
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    So it appears that some aftermarket web sites are not correct.

    And what's up with the final drive ratio? I assume it is 13-50 not 14-50?
    Click image for larger version. 

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    Last edited by griffbones; 10-19-2020 at 03:37 PM.
    2007 250XC-W
    2006 KDX 200
    1997 DR350 w/407cc big bore
    1983 CR60R restored bike show item

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