Rim Width - How Wide is Too Wide?- Mtbr.com
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  1. #1
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    Rim Width - How Wide is Too Wide?

    I am looking at building up a new set of wheels for my trail/AM bike and have been considering some rims that are around 40mm wide on the outer width. Does anyone know if there are any downsides to the wider rims (other than weight)? I ride in Colorado on a lot of fast rocky trails and worry about rim durability. At what point does a rim get too wide and cause increased impacts with rocks due to less rubber protecting the rim? All thoughts, opinions or better yet real life experiences are appreciated.

  2. #2
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    As the rim's interior width increases, you'll see different performance and appearances in your tires.
    Basically, the same tire will sit and perform differently on a narrower rim vs an even slightly wider rim.
    So, if you have a favorite tire/tire size on your current rims, they'll ride different as you go wider.
    My favorite do everything trail tire is a 2.4 Continental Trail King.
    On a 21mm inner width rim it sits high volume with a rounded profile. I can run it in all conditions with a tube. I rarely ever ding the rim and rarely ever get pinch flats at 35-38 psi with a tube. When run tubeless at that rim width I can easily burp the rear under hard cornering and hard hits. It's sketchy run tubeless on a 21mm inner width rim.
    On a 25mm inner width rim, the tire sits noticeable squarer and hooks up better in corners in all conditions. I can run it tubeless at 32psi in the front and 36 in the rear and not worry about burping or dinging the rim.
    If I run just a few psi lower in a tubeless set up on the 25inner width rim, I'll ding and flat spot the rims.
    So, you'll need to factor in PSI, tire size, and rim width in to the equation.
    Depending on tire choice and preferred PSI, I think you can go too wide in rim width.
    In my experience,25-23mm inner width seems to be a good spot for many trail tires in the 2.4-2.3 range.
    Just a few mm increase in inner rim width can produce positive performance results.

  3. #3
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    I guess I should have stated that I currently run 23mm inner width rims with 2.35" tires, so I understand the advantages of wider rims. I am really wondering if there is a limit to those advantages as the rims get very wide (40 mm outer width, 33mm inner width). I am thinking about picking up a set of carbon rims that are 40mm wide but I am concerned that the incremental width might cause the same tire to be even more square and therefore have almost vertical sidewalls. Which would cause the rims to have more exposure to rocks.

  4. #4
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    I think there is an optimal rim width based on tire preference.
    Some tires perform better when run wider and squared off, some perform better in a more rounded profile.
    23-33mm is a big jump for a 2.35 tire.
    33mm could be the sweet spot for another tire.
    Go for it, but be open to switching to a different tire to optimize performance if you don't like the ride.

  5. #5
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    If we are talking about 29ers....the biggest problem I have had was a heavy wheel. Going 35plus mm is going to add way too much weight. I currently ride some 30mm OD carbon rims and they are 380 grams, that is what makes the 29er wake up and ride playfully. Very fast when accelerating as well. 35mm is going to be great for traction but depending on the tire chosen, may corner like crap because it is too squared off. Ask yourself this question...Mavic had a 35mm DH rim years ago and after it came out all the riders went back to the smaller width. I understand it was because the wide rims squared out the tire too much and made it corner like crap.

    Most of us ride with a group of friends and are usually competitive with each other. A light wheel makes a big difference.
    Last edited by Atomik Carbon; 10-14-2013 at 04:56 PM. Reason: Add

  6. #6
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    Quote Originally Posted by YaMon View Post
    Ask yourself this question...Mavic had a 35mm DH rim years ago and after it came out all the riders went back to the smaller width. I understand it was because the wide rims squared out the tire too much and made it corner like crap.
    ^this. I'm waiting to hear some solid reasoning why a wider rim is better. Currently we have "wide" rims being offered by people who don't have professional testers or engineers or alliances with tire companies. For the type of riding I do, I prefer knowing that the top riders have done the r&d and I trust what they trust.

  7. #7
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    There was a video of a booth at Interbike showing their wheels and they said they did a lot of testing and found diminishing returns going any wider than 32mm rims as I recall but I can't remember who the company was (Sun maybe?). Hopefully someone else will chime in. I really hope Derby does well with his new 40mm rims but I have to question the advantage, especially if you like square edge tires like me (DHF's) where 23mm inner widths work great.

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  8. #8
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    Quote Originally Posted by Gman086 View Post
    There was a video of a booth at Interbike showing their wheels and they said they did a lot of testing and found diminishing returns going any wider than 32mm rims as I recall but I can't remember who the company was (Sun maybe?).
    This is my question, was the 32mm width they referenced an inner or outer width?

  9. #9
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    I read something about optimal width from the owner of American Classic
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  10. #10
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    I think it is important to list what the most important requirement when it comes to YOUR wheels. Personally, for me they are:

    1. Weight
    2. Stiffness
    3. Grip

    There are too many compatibility issues with going very wide. Right now it is the in thing and a fad..... What about the clearance issues, is a 40mm really stiffer that a 32mm and can you actually feel the difference ? 29ers already have great grip....don't want to lose sight of the other important things..

  11. #11
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    this thread came up #1 in my google search on the topic. I wanted to resurrect the discussion after another year of real world testing.

    I ride 2.35" tires, tubeless, for about 90% of my riding and swap out for a 2.5" 2-ply or UST tire for a few enduro races throughout the year. I'm sensing the happy medium in strength, weight and performance using a 2.35" and 2.5" tire is a 25mm ID rim. anyone say or experience otherwise?

  12. #12
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    Quote Originally Posted by RTM View Post
    this thread came up #1 in my google search on the topic. I wanted to resurrect the discussion after another year of real world testing.

    I ride 2.35" tires, tubeless, for about 90% of my riding and swap out for a 2.5" 2-ply or UST tire for a few enduro races throughout the year. I'm sensing the happy medium in strength, weight and performance using a 2.35" and 2.5" tire is a 25mm ID rim. anyone say or experience otherwise?
    I personally prefer a 25-27mm internal width rim for AM/Trail riding using 2.2-2.5" wide tires. There are some advocates of wider rims who claim that the wider rim will impart more lateral stiffness to the tire, allowing you to run lower pressures before the tire rolls laterally on the rim while cornering. But if I were to run any lower pressure than I currently am, I'd be pinch-flatting.

    Now if I were going with a carbon rim, I might try something in the 27-30mm range (like the Nox Composites or Derby rim).
    Tire Design & Development Engineer. The opinions expressed in this forum are solely my own.

  13. #13
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    Interesting research from Syntace. This is their MX40 wheel which to me is probably a bit too wide. I do plan on building up a pair of MX35's.

    Rim Width - How Wide is Too Wide?-image.jpg

    Don't want to be be danging up that rim hook.

  14. #14
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    Quote Originally Posted by Swissam View Post
    Interesting research from Syntace. This is their MX40 wheel which to me is probably a bit too wide. I do plan on building up a pair of MX35's.

    Click image for larger version. 

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    Don't want to be be danging up that rim hook.
    Well that's a bit unnerving. I just ordered up a set of Nox AM rims. And the tires that just shipped to put on them: Minion DHF and DHR2 2.3. Hmmmm...
    If jackasses could fly this place would be an airport.

  15. #15
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    Quote Originally Posted by Swissam View Post
    Interesting research from Syntace. This is their MX40 wheel which to me is probably a bit too wide. I do plan on building up a pair of MX35's.

    Click image for larger version. 

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ID:	930142


    Don't want to be be danging up that rim hook.

    That's barely coherent
    Tire Design & Development Engineer. The opinions expressed in this forum are solely my own.

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