Downsides to a 35mm inner width for a 2.4-2.5" tyre?- Mtbr.com
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  1. #1
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    Downsides to a 35mm inner width for a 2.4-2.5" tyre?

    I'm looking at the Ibis S28 or S35 rims. For my rear wheel I plan on using a 2.4 - 2.5" tyre most of the time. Is there any downside to using a 35mm inner rim width on that small a tyre?

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    I've been on the Ibis 741 rims for more than 4 years now, and have mounted Schwalbe 2.35s, but mostly Maxxis DHRII 2.4s on both front and rear. The recommendation for tires to use with wider rims is typically to choose one with a rounded profile. I've not encountered any downside to these setups, but it should probably be said that you need to lean into turns to make full use of those side knobs.

    I also liked very much the E13 TRS tires (first version) on the Ibis rims, but with the new version, they got squared off so I didn't go back to them.

    Never used a plus tire, and don't intend to.

  3. #3
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    Quote Originally Posted by j0dan View Post
    I'm looking at the Ibis S28 or S35 rims. For my rear wheel I plan on using a 2.4 - 2.5" tyre most of the time. Is there any downside to using a 35mm inner rim width on that small a tyre?
    Aren't those the external dimensions of the rims?
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  4. #4
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    "To simplify things, Ibis now uses the internal rim width to differentiate between just two models. The S28 has a 28mm (technically 28.6mm) internal rim width, while the S35 has a 35mm internal rim width. ... The Logo wheels utilize a hub Ibis designed in house.May 21, 2019" --off Google.

    Rim width is a tuning option to match with the tire you need for your terrain and speed.
    If you're riding sharp rocky terrain at enduro speeds you'll need a heavier sidewall tire at higher pressure with generally bigger knobs.
    In contrast if your trails are hardpack with some loose and with rounded rocks/roots and shorter ups/downs(more medium speeds)you can try for more footprint. A tire with a flexible lighter sidewall and smaller lower knobs at lower pressures can give you usable corner traction. The 35 is no problem for a higher volume more rounded profile tire on those trails. This is my situation and Bontrager XR2 and 3 work.

  5. #5
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    Quote Originally Posted by eb1888 View Post
    The 35 is no problem for a higher volume more rounded profile tire on those trails. This is my situation and Bontrager XR2 and 3 work.
    Thanks. What width XR2/3 are you using?


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  6. #6
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    I'd suggest the XR3 29x2.4. It has larger edge knobs and smaller center knobs like the XR2. You can lower the front tire pressure until you get rim hits in the rocky parts of your trails. You can add CushCore to the rear to protect your rim and still use lower pressure. Rear is usually 4 psi more than the front for me. 35mm rim.
    The other Bonty alternative is a 29x2.6 XR2 Team on a 40mm rim. Trek Tech Support has no problem with that width for that tire. #553991 in gray and black color only on the web site. https://www.trekbikes.com/us/en_US/e...olorCode=black

    Wheels are unfortunately more expensive than tires to play around with. For my terrain wider is better.

  7. #7
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    Quote Originally Posted by j0dan View Post
    I'm looking at the Ibis S28 or S35 rims. For my rear wheel I plan on using a 2.4 - 2.5" tyre most of the time. Is there any downside to using a 35mm inner rim width on that small a tyre?

    YES. Once you start going below a tire to rim ratio of 2.0 (really about 1.8), the tire casing may start getting wider than the side knobs. That means if you scrape something hard, your sidewall can get cut, possibly to the point of a blowout. Also, because the sides of the tire are getting stretched out laterally, and there is only so much surface area for the side casing AND the top tread, it tends to point the knobs up, including the side knobs. That may increase straight-line grip but it's not going to help turning. I don't think it's a huge deal on the back but I would not do it on the front. 25-30mm is plenty for a 2.4 or 2.5 tire, the side knobs will stick out from the casing like they are supposed to, even for a WT tire. My rear is a Rekon WT 2.4 on a 22mm internal rim, side knobs measure 2.30, casing 2.20, does just fine, sometimes squirelly but that may be just the tire itself. You don't want the side knobs to measure 2.20 and the casing 2.30...
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  8. #8
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    Quote Originally Posted by richj8990 View Post
    YES. Once you start going below a tire to rim ratio of 2.0 (really about 1.8), the tire casing may start getting wider than the side knobs.
    It looks like Ibis is doing a 2.6 on a 35 by default which is 1.88 ratio. Is that right?


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    You're seeing an example of the other tuning I listed. You have to match your terrain.

    I'm luckily not at all bothered by this sidewall width ratio 'problem'. Zero interest in it for my terrain.
    I luckily have rounded rocks not sharp shale. . . .so when I run through a garden the tire slides off one rock into another with plenty of sidewall contact. . . .And with low enough pressure the front sidewall is wrinkled to give a big footprint as I change direction when cornering. That big footprint traction is getting me slow slideouts with plenty of time to make a line change and recover. So no crash. . . .And I've not had any sidewall slices.
    But Bontys are very rounded tread profile and high volume to work like this on wide rims without the tread getting squared off.
    Again, I want all the traction I can get and have zero worries about sidewall slice for my rocky/rooty terrain. Plenty of sidewall scuffs with no harm.

  10. #10
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    One of my older bikes, a full suspension 29er, came with really narrow rims. I didn't like the bike at all out of the box. I built a set of 30mm rims for it and moved from whatever the original tires were, 2.2 or 2.1 to 2.2 on the rear and 2.35 on the front. A short time later I converted to tubeless.
    After a few months on the 30mm rims, I decided to try some 35mm rims. I built em up and used the same tires. I ended up running 2 psi less with the wider rims. Bike became a blast to ride.
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  11. #11
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    Another consideration for terrain with sharp rocks. Reducing the rim width isn't going to save you from slices.
    You need sidewalls thick and heavy enough to resist. Shale is still going to contact your sidewalls without regard to rim width.
    When you go with thick less flexible tires at higher pressure you don't see as much benefit from wide rims.
    Why not? You can't get as big a footprint from low pressure.
    You still can get some benefit from a higher volume rounded profile tire.

  12. #12
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    I have 30mm rims and they work well with Maxxis 2.4 and 2.5 tires. Too wide and you're also putting the rim out to get hit by rocks more. I would not run anything smaller than 2.6 on a 35mm.

  13. #13
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    Ibis seems to have no problem with that combo if these are the rims you are talking about. That said I have 2.4's on 32mm internal and my tire profile is still round but the sidewall is out there.
    Attached Thumbnails Attached Thumbnails Downsides to a 35mm inner width for a 2.4-2.5" tyre?-ibis.jpg  


  14. #14
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    Quote Originally Posted by eb1888 View Post
    "To simplify things, Ibis now uses the internal rim width to differentiate between just two models. The S28 has a 28mm (technically 28.6mm) internal rim width, while the S35 has a 35mm internal rim width.
    Ok. I have their earlier carbon 928's, ~24 internal. DT 350 hub rr but unlabeled fr. Any idea what their house brands are/were? Looking to get boost adapters to run wheels on new v4 build.
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  15. #15
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    A little more to think about as you decide. Mikesee from LaceMine29 builds custom wheels in Western Colorado. Best on this site.
    https://forums.mtbr.com/wheels-tires...l#post14467041
    In this discussion at post 80 he mentions that 90%+ of his riding is on 40mm rims.

  16. #16
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    Quote Originally Posted by eb1888 View Post
    A little more to think about as you decide. Mikesee from LaceMine29 builds custom wheels in Western Colorado. Best on this site.
    https://forums.mtbr.com/wheels-tires...l#post14467041
    In this discussion at post 80 he mentions that 90%+ of his riding is on 40mm rims.
    On what size tires I wonder?

  17. #17
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    You want to avoid squaring the tire off too much. It will increase the lean angle at which you come off of the cornering edge of the side knobs. This means it will be easier to lean the bike too far causing washouts. This won't be an issue for people who don't aggressively lean the bike though.

    I haven't owned 35i rims but some of the 2.3-2.35" tires I've ran on 30i rims were pretty square. That's not an issue on the rear so much though.

  18. #18
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    If you think a high bb makes your bike handle bad, try riding with squared off tires - even worse!

  19. #19
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    I had dual 35mm ID wheels and found them stiff and unable to lean very well, even on WT Maxxis tires F & R they just didn't work very well.

    I have since moved first to a 29mm ID F & R, and am now on 28mm Rear ID & 33mm Front ID. Running a 2.3" rear tire and a 2.5" front tire this combo is easily the best yet.

  20. #20
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    Quote Originally Posted by Cerberus75 View Post
    I have 30mm rims and they work well with Maxxis 2.4 and 2.5 tires. Too wide and you're also putting the rim out to get hit by rocks more. I would not run anything smaller than 2.6 on a 35mm.
    Maxxis tires with the WT (Wide Trail, I think) designation are supposedly "optimized" for use on 30-35mm rims. Seems like anything 2.4" and wider are only available with the WT designation when I looked at their offerings a month ago.

  21. #21
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    Quote Originally Posted by GiddyHitch View Post
    Maxxis tires with the WT (Wide Trail, I think) designation are supposedly "optimized" for use on 30-35mm rims. Seems like anything 2.4" and wider are only available with the WT designation when I looked at their offerings a month ago.
    Yeah, I've read that as well. The 2.4 DHR2 looks to be at the max on 30mm and could go narrower. The 2.5 Assegai is perfect on the 30mm the DHF seams a little wider in the casing and might be ok a tad wider.

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