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  1. #1
    Pax
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    My 7.5 FX need wider tires

    It was supposed to come with 32's from the factory but for some reason mine came with 28's. The amount of cobblestones and bad pavement I hit on the commute make me want something a bit softer.

    Does anyone know...what is the widest tire I could put on without changing out rims??

  2. #2
    Senior Member sh00k's Avatar
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    32s or 35s but, for the 35s, you may want to get a professional opinion. i know you can definitely do 32s.
    2009 Trek FX 7.2 (Blue) -- SOLD!
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  3. #3
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    look at your bike to see a label for what rims you have. for example, my 7.2 fx has matrix 750 rims. then google search your rim for its inner width. then look at sheldon's chart to determine a conservatively safe maximum width for the replacement tire. i bet you can go up to 37 without problem.

    http://www.sheldonbrown.com/tire-sizing.html#width

    or you use calipers and measure the inner width of the rim yourself (with tires removed).

    or you can call trek customer service 1-800-373-4594

  4. #4
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    I'm running a set of Conti Contacts 37s on my stock rims - '09 FX 7.5 - no worries and love the tires. I do believe that Contis tend towards the narrow side in terms of their sizing though.

  5. #5
    Pax
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    Quote Originally Posted by Holmes375 View Post
    I'm running a set of Conti Contacts 37s on my stock rims - '09 FX 7.5 - no worries and love the tires. I do believe that Contis tend towards the narrow side in terms of their sizing though.
    I just googled those, nice looking tire, thanks! Did you have to do any brake adjustments?

  6. #6
    The Improbable Bulk Little Darwin's Avatar
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    Brakes hit the rim, not the tires. If the tire fits the rim/frame/fork the brakes shouldn't need adjustment.
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  7. #7
    Pax
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    Quote Originally Posted by Little Darwin View Post
    Brakes hit the rim, not the tires. If the tire fits the rim/frame/fork the brakes shouldn't need adjustment.
    I was thinking more along the lines of would I be able to get the tire off (would it still fit between the pads) when I'm yanking the front wheel.

  8. #8
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    No, they won't fit through the pads if you're adjusted properly.

    Just pop the cables free from the V-arm at the noodle retainer and you're all set.

  9. #9
    Pax
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    Quote Originally Posted by Holmes375 View Post
    No, they won't fit through the pads if you're adjusted properly.

    Just pop the cables free from the V-arm at the noodle retainer and you're all set.
    Thanks.

    I emailed my LBS to see if they can order the Contis for me, here's hoping.

  10. #10
    aka Phil Jungels Wanderer's Avatar
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    I really, really like the Schwalbe Marathon Supremes. My 35's actually measure 35 on an 18mm wide (inside) rim.

    They aren't cheap, but their performance makes them frugal.

  11. #11
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    Quote Originally Posted by Pax View Post
    Thanks.

    I emailed my LBS to see if they can order the Contis for me, here's hoping.
    Most welcome.

    I've had the Contacts only a short time but I've run 'em pretty hard. My riding is probably 70/30 on/off-road and our streets here are pretty rough. Typical small Wyoming town! I've pushed them pretty hard on asphalt turns and they seem to corner pretty good for an all around tread. Hard pack dirt roads and gravel alleyways are no worries. Haven't been in sand or mud yet but I don't expect stellar performance in those areas

    Ride is decent, nice with reduced pressure and they're fast enough to be fun when pumped up. I'm using the reflective sidewalls as I ride quite a bit at night and this provides a better target for the motorists to lock in on

    Take care and pleasant trails to ya.

  12. #12
    Neil_B
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    34 cross tires are the widest I've been able to fit on my bike. I tried 36s and they rubbed against the frame in the rear.

  13. #13
    aka Phil Jungels Wanderer's Avatar
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    One more thing... My Crosstrail has 18mm wide rims, and 45mm wide tires as OEM. No problem with them whatsoever.

    Well, two more things...... I settled on 35 on the front, and a 40 on the rear, as the best mix for handling and ride. The 35 really makes the steering more precise, and the 40 really makes the ride more plush, without sacrificing handling.... I noticed no difference in ride when going from the 45s to the 40s, but a big difference in handling, with the 35 on the front, with no loss of ride quality.

    Best to measure around your installed tire - in all directions - to determine how much more space you have in there.

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    The "correct" tire size is related to the inner rim width, so recommending a tire size without specifying the inner rim width is sloppy at best.

    My Trek 7.5 FX has wheels with an inner rim width of 16 mm. According to Sheldon Brown, "A general guideline is that the tire width should be between 1.45/2.0 x the inner rim width." (http://www.sheldonbrown.com/tire-sizing.html).

    My calculator shows 1.45 x 16 = 23.2 mm and 2.0 x 16 = 32 mm.

    Your bike, your choice. An informed choice is better.

  15. #15
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    One must also consider the noticeable variation in actual tire size when compared to claimed industry size ratings. Having looked at numerous tires in the 32mm - 40mm sizes now I've discovered quite a variety of actual sizes when mounted on the same size rim.

    I've got a set of 37mm Contis that are shorter and narrower than a Kenda 35mm mounted on the same rim.

    Seems the industry standards, or at least the manufacturer's interpretation of the same, are somewhat flexible.

  16. #16
    Cyclologist Plutonix's Avatar
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    I have 38's on my 7.5. It was offered with something much narrower 28 or 32, 38 was the widest in stock. I've seen 40's sold here and there, but I didnt like the tread and that seems kind of rare.

  17. #17
    Papaya King waynesworld's Avatar
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    Quote Originally Posted by Holmes375 View Post
    One must also consider the noticeable variation in actual tire size when compared to claimed industry size ratings. Having looked at numerous tires in the 32mm - 40mm sizes now I've discovered quite a variety of actual sizes when mounted on the same size rim.

    I've got a set of 37mm Contis that are shorter and narrower than a Kenda 35mm mounted on the same rim.

    Seems the industry standards, or at least the manufacturer's interpretation of the same, are somewhat flexible.
    Isn't that the truth. I don't have them on the same rims, or even the same bike, since I sold the Kona, but I had 35mm Kendas on a Jake the Snake, and I swear my 37mm Contis on my Felt X city are the same size, or maybe even smaller. Nice tires so far though.
    Quote Originally Posted by rumrunn6 View Post
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