With the explosion of Boost, Plus bikes, Mid Fat and other portly new rim and tire sizes for everything from road to cyclocross to gravel to mountain bikes, it’s a wonder there isn’t more confusion as to what will actually work together.

And by “work together”, we don’t just mean whether or not it’ll mount. We wanted to know what the compatibility limitations are for optimum performance and, more importantly, safety. If we’ve learned one thing from Mavic’s presentations over the years, it’s that tire and rim sizes really and truly are designed to work in tandem. Step outside the guidelines and you risk poor performance, component damage, or even a total blowout. And it’s not just Mavic. We spoke with WTB, Kenda, Schwalbe, Stan’s NoTubes and Industry Nine to see where everyone sits on the matter. Here’s what they had to say…



A very detailed ETRTO guidelines chart, courtesy of Mavic. Rim widths shown are internal measurements in millimeters. The “Straight Side” are hookless, and the “Crochet” type are the normal clincher with a bead hook.

First off, we should mention that it’s not only the brands listed here that are concerned about such things. Many more are part of the global conversation, most of which contribute to and follow design standards set by ISO for the ETRTO standards. According to Mavic, the ISO organization is currently updating standards to deal with the latest trends hitting the market, including:

  • Road Tubeless rims/tires dimensions
  • MTB tubeless with crochet/hooked rims
  • MTB hookless rims/tires dimensions
  • MTB tubeless hookless rims/tires dimensions
  • wider rims (up to 50 c) with bigger volume tires (up to 4 inches)

Looking at the chart above, it’s no wonder Mavic’s rim width growth has been moderate compared to the rest of the industry. They’d rather sell you a proper rim/tire system that’s designed to work flawlessly and safely then pump out a 40mm wide rim just because you think you want it. And maybe you do. And maybe that’s OK.


The official updates will be good, because WTB told us there are no current ETRTO tire size recommendations for internal rim widths greater than 29mm. That’s why you’ll find “N/A” next to some of their bigger tires on the charts above. They do have internal recommendations, though, so don’t be afraid to ask.

About those tire size designations – those are the ETRTO measurements, which are the global standard. The smaller number on the front refers to the tire’s width in millimeters. The larger number refers to the rim diameter they’re made for:

  • 622mm = 700c road and 29er MTB
  • 584mm = 650B/27.5″ mountain bike
  • 559mm = 26″ mountain bike

Side note: The 700, 650, 26″, 27.5″ & 29″ wheel size numbers that we so commonly use actually refer to an approximate average outside tire diameter, not the real size of the rim. Confused yet?


how to choose the right mountain bike tire width for your rim

While some brands follow strict charts, others provide a bit looser guidelines. Industry Nine have suggested tire width ranges for many of their rims and had this to say on how and why they come up with those figures:

“It is primarily based on experience, testing, and feedback from our customers as well as the professional athletes we work with.  The basics are that if you run a rim that is too wide for a particular tire you have a lot more issues with tire and rim damage, as the rim is much more likely to bottom out on lateral rock impacts causing tire or rim damage.

“Conversely, if the tire is too wide for a given rim, you get more tire roll due to the larger casing size and higher aspect ratio of the tire, which together create more leverage on the tire allowing the casing to collapse and roll over the rim during hard cornering. Our suggestions are based on what we feel is the best balancing act between all of these elements. However, some tires have more or less tread wrap which certainly affects this. A 2.25″ tire with a lot of tread wrap might function reasonably well on a 35mm (internal width) rim, but it is our opinion that the customer would still be better served on a narrower rim for the above reasons. In addition, wider rims are always going to weigh more – all things being equal. Customers who are generally considering narrower 2.1-2.25” tires are typically going to be more weight conscious, so they are going to be better served by a narrower/lighter rim in many cases.

All of this being said, there is certainly a large element of personal preference that comes into play as well, and the guidelines we offer are suggestions, not hard/fast rules. Of course, once you get to the extremes safety becomes a factor as well. You obviously wouldn’t want to run a 2.2″ tire on a fatbike rim or a plus tire on one of our Ultralite rims.”


Taking the graphical approach a step further, Stan’s NoTubes is readying new imagery for their website that list recommended tire width ranges for specific rims.


Their “Wide Right” concept helps us visualize what an appropriate tire shape should look like. Of course, this doesn’t do much good if you’ve already purchased the rims and tires only to find things are pear shaped, which is why the numbers are also handy. Something else to noodle on – Schwalbe says many tires are intentionally manufactured on the narrow side of the allowed tolerances because they’ll likely stretch a few millimeters during your first several rides.

kenda havok 27.5+ mountain bike tire

So far, we’ve talked a lot about fitting a wider tire on your existing rims. But what if you’re only upsizing your rim, hoping to gain a little extra width from your existing tire? Kenda has some guidelines on that, which they say work regardless of which wheel size (26, 27.5, 29, etc.) you ride:

“The general rule of thumb on the effect of rim width to tire width is for every 1mm, plus or minus, of difference from the design standard (i.e. ideal rim width for a given tire) the tire will change about 0.4mm in width in the same corresponding direction.

“For example, if a 2.20 tire (56mm) was designed to be used on a rim with an internal measurement of 24mm and you were to mount it on an extra wide rim with an internal measurement of 29mm, it would pull the overall width of the tire closer to 58mm, making the tire closer to a 2.30.

“There are upsides to making a tire wider this way, no added weight, no waiting for a tire manufacturer to make your favorite tire in a slightly larger size . . .  but this comes at the expense of changing how that tire contacts the ground. This could mean an increase in rolling resistance or it could change the relative location of the cornering knobs resulting in a tire breaking loose earlier in a corner.”

Simple translation: Put a wider rim on your bike and your tire will grow about 0.4mm wider for every 1mm of internal rim growth.



A more simple ETRTO guidelines chart, courtesy of Schwalbe.

For reference, a 62mm wide tire is 2.44″, which is where the current standards formally end. But, with some calculations of the ETRTO standards, we came up with a rough guideline suggesting your rim width should be between 32% to 70% of the tire width. For a 2.8″ tire, that means rims with an internal width of 23mm to 49mm. Based on all of these conversations behind this story, our hunch is that the “ideal standard” lies near the upper middle of that range, so something like a 35-40mm IW rim would be the best starting point for safety, optimized performance and a good tire profile. Disclaimer: That’s our math and opinion based on the charts and excludes the narrowest tire width fringes, so use at your own risk.



Using our formula, a 4.0″ (101mm) fat bike tire would need an internal rim width between 34mm and 71mm. That puts it at the starting point for many fat bike rims. The Hed Big Deal alloy comes in at 71mm inside, and the Sun-Ringle MuleFut measures 74.4 (for their largest 80 rim; they also offer a narrower 50). So then, how do you pair fat bike rims and tires? Are standards simply thrown out the window for these? Well, there are no guidelines, and it depends on how you want your tire profile.

We spoke with Tim Krueger, who’s one of the guys behind the new Terrene Tire brand and himself a fat bike enthusiast. He says there simply are no current standards. He also says that while the same concerns about tire roll with too-narrow rims or smashing rims with too-narrow tires apply to fat bikes, their massive tire volume somewhat mitigates those issues. It comes down to riding style and preference. Want a more squared off tire shape for floating on snow? Go with wider rims. Need a proper round profile for dry singletrack? Go a little narrower.

Industry Nine says their general rule of thumb puts a 90mm IW rim with 4.8 to 5.0 inch tires for snow. For more standard 3.8 to 4.0 inch tires, they’re pairing 75-80mm widths if you’re riding on snow. But go as narrow as a 50mm wide rim with higher pressures for summer riding. To them, that was the extreme, and probably not the best combo for most people, but they’ve seen it done.



Actual Measured Casing Width

Whether your riding road, gravel, cyclocross, trail or enduro, a good starting point is likely using a rim with an inside width of 50-65% of your tire width. Finding a good bike shop that’ll let you mount several rim and tire combos helps you know before you go, but don’t hesitate to contact the brands for their input, too.


  1. CL on

    Veloflex, Challenge tyres and other open tubulars (hand-glued clincher tyres) heavily rely on being mounted on the correct rim, following ERTRO standards. All those people complaining that their new tyres blew off the rim is mostly because they paired them on a rim that’s a couple millimetres too wide, or a sharp carbon bead. Challenge do show the recommended rim width for each tyre on their website.

  2. Other aaron on

    As an american with a fetish for the metric system, does anyone else love how the mountain bike industry just says “screw it” when it comes to unit consistency

  3. CL on

    “Side note: The 700, 650, 26″, 27.5″ & 29″ wheel size numbers that we so commonly use actually refer to an approximate average outside tire diameter, not the real size of the rim. Confused yet?”

    That’s why is much more convenient to use one metric size where it matters instead of relying in ambiguous and/or obsolete ways of calling things.

    • xxx on

      If only.. 🙂
      Its also funny how MTB sizes are M, L, XL… while road bikes are 56cm, 58cm, …
      same for tire sizes

      i wish the US would go all metric and call it a day.

      • JB on

        Seat tube length is meaningless for mtb fit (and somewhat meaningless for compact road bike fit). My new bike has a shorter seatpost but way longer reach than my old mtb. Should it be called a smaller size? Reach and stack are the two best indicators of any bike’s size, but even together they don’t describe a bike’s geometey adequately.

        • Simon David Burt on

          but the effective seat tube which a number of compact geo roadbikes get measured to these days (virtual length of seat tube to horizontal from top of heat tube) would leave the MTB still ball park the ‘same size’s’ as the old nomenclature, the longer toptube is all that really changes..

      • paochow on

        It’s all marketing. The bike industry sold you 29″ wheels to replace your puny 26″s and then sold you back to 27.5″ as the 29″ were too unwieldy.

        They are trying to do the same with Fatbikes, 27.5″ wheels to replace the wimpy 26″, even though many 26″ fat tires have a larger diameter than the 27.5″ fat tires. Nevermind the fact that both are larger in diameter than the 29″ MTB wheels that they told you were too big and unwieldy.

  4. Kris on

    50-65% width rule? So my standard 2.3 tire (57.5mm) needs about a 29-37mm internal width rim? What? That seems to be a bit extreme. guess I’m doing it all wrong with my tiny 27mm Arc rims….think of all the lost tenths of second I’m leaving on the table for my Strava time.

    • xxx on

      50-65% is a rule of thumb they’re coming up with.
      the 27mm inner with a 2.3″ tire might be quite fine, depending on the actual tire brand/type/name (note: 2.3inches is 58.42mm)

      Personally I feel like 45-55% is a better rule of thumb for the tires ive used so far with my 29er rims.

      To illustrate:
      Inner hookless rim width
      Tire 45% 55% 65%
      2.25″/57.15mm 25.7mm 31.4mm 37.1mm
      2.3″/58.42mm 26.2mm 32.1mm 37.9mm
      2.4″/60.96mm 27.4mm 33.5mm 39.6mm

      You’ll also notice that latest Mavic’s all around top of the line rims are 26mm inner width.. and that table shows why – because that works well/best with most common tire choices for racing.

      I suspects sellers of 30mm+rims just sell them because people buy them, but not for performance reasons. Heck some companies actually were late on that band wagon because it took them a while to figure out people weren’t buying what works best, but whatever they felt like was the new thing 😉

    • Eivind Tandberg on

      I kind of reacted like that too! Wtf ? Just bought a mavic xa elite front wheel w/tyre system, and the matchup is 25mm rim internal vs 2.4″ tyre. Runs like a dream. I would guess they know their stuff ?
      This article seems to give a lot of good reference information, and concludes by making a very general, but weird approximation that send people once again in the wrong direction… Truly weird.

    • John on

      Similar boat, been running 2.35 on OG Crests (23mm internal) for years and think it’s a great setup. No ‘lightbulb’ to my eye. The worst scenario to me is the bell shape (rim too wide). Effectively the block side knobs are engaged when you’re just rolling along in a straight line, seems that would be terrible.

  5. xxx on

    Thats a pretty good article which i enjoyed reading (as opposite to the advertisements where comments that criticise the product dont always get approved! 😉

    Ultimately the ETRTO standard is decently good but gives too large of a scale. That’s because tires vary.
    Thus.. ultimately indeed, tire manufacturers should give the acceptable range like WTB does, except WTB just echo’d ETRTO 😉

    The reason being that tire to tire of the same spec’d width I’ll have different results on different rim widths. The tire is not always the spec’d size, not always the same casing size, etc.

    I also like Stan’s graphics because it represent well enough why too wide is no good and too narrow is no good.

    I often see people running too wide of a rim with a narrowish tire, which does give them more traction as long as they’re not in turn. In a turn suddenly nothing grips because the tire is already stretched out and the tread is not touching the ground where intended.

    For example I run 24-26mm internal (dont ask why ive 2) on my 2.25 michelin wild r tires which works pretty well, but is pretty bad on the similar maxxis tires i have.
    In my use case i believe 26mm internal hookless is the best for 29″ all around tires though. Good mix of traction, rolling resistance, aerodynamic, weight, cornering and flat traction.

    My alternative would be 30mm internal hookless for 27.5+ tires, but I’m not too happy with the current tire selection.

    And don’t get me started on “gravel” bikes (ie 29″ with 32-40C tires that don’t have super pronounced treads – i feel like the rim choice is there thanks to MTBs but the tire choice that properly matches is pretty difficult (its slowly getting there)

    • Kristi Benedict on

      xxx – Thanks for the detailed comment. Regarding your first paragraph, we do not censor comments just because they disagree with any of our advertisers or our own opinions, but we do edit for language and overly negative comments that add nothing to the conversation. That helps foster open communication and good comments like the one you made here. Thanks!

      • Ricky Bobby on

        Really? I’ve found that most of my comments don’t make it through “moderation” and they are rarely negative and never use foul language, but are often critical of manufacturers’ marketing claims.

        I’ve got over 20 years of experience in the bike industry, but my opinion is often edited on Bikerumor specifically since you changed your moderator to Askimet.

  6. Mr. P on

    I have to wonder if recommended tire to rim size will be as accurate as recommended tire pressures printed on the sides of tires…

    Also, the BS in all of the graphics above is that they are showing the tire in space and not the weight loaded ground/tire contact patch! The only place it matters! The tire goes flat on the ground (depending on pressure) and widens, so “The Bell” shape never exists. Similar to this: http://www.texasmountainbiketrails.com/wp-content/uploads/2013/11/wider-rim-better-contact-patch.jpg

    I’ll even go further and point out road/cross recent rim/tire width ratios are much lower than MTB. Cross example: 32c tire on 21mm internal rim. And no one is complaining, all I hear are good reports. Road: 25c on 21mm or 19mm.

    I think I’ll set the industry info on ignore… Like we have done when riders pushed tubeless convertible into commonplace with industry resistance/conservatism.


  7. James. on

    …So Trek and Hed, Easton, Specialized, Pacenti, and whoever else I can’t think off the top of my head are wrong to use 19-21mm internal width rims for 25mm tires? I’m going to go with Mavic still being behind in development and trying to rationalize all the 13mm internal width rims they still make, or are sitting on in warehouses.

    • John on


      Mavic were literally the last of the wheel manufacturers to move away from skinny width rims. (And the tipping point seems to have been when they bought out ENVE, not any internally driven insights.) So I’m not sure how they have any credibility on the subject of wider rims.

  8. ChrisC on

    So I shouldn’t be using 25mm tires with my Bontrager Aeolus D3 rims?

    Sorry, couldn’t hear your answer over the sound of how AWESOME that combo rides!!!

    • Joe on

      My Aeolus 7 clinchers are amazing with the Vittoria corsa speed 23. The tire/rim interface is perfect for good aero quality. Likewise my kinlin xr-31t runs with 19mm internal run very well with 23 and 25 mm tires.

      I think this may be a good chart for MTB but for road is straight stupid.

  9. Ryan on

    From what I see there are so many caveats in this article that you could just distill it down to, “well, it depends…” Which is basically the same answer you’ll get if you ask about rim width vs tire width anywhere else.

  10. sad on

    in 2 years from now going slightly narrower rims will be the new trend until we settle back on the “actually right size rim for the tire size” (which is bigger than 5 years ago and not as big as people buy today lol)

    Mainly because people today are convinced 35-40mm+ are good for their 2.3″ tires.

  11. bearCol on

    Funny that only now is the industry really talking about pairing the right rim width with the right tire width. When the wider trend started the industry was happy to sell too wide rims for the tires on the market. For those of us that ran 30mm internal rims in 2002 know well 2.3 tires are too narrow for rims that wide. At least now the industry is offering tires designed around wider rims.

  12. Jo on

    What is this article telling us except repeating an outdated norm? What we really need is ETRTO updating their norm, and a whole bunch of people riding tire/rim width combination that were never testes or approved by manufacturers, so they can push all liability to the rider.

  13. Tom on

    Nice article. My simple takeaway is that the vast majority of mtb riders would be well suited with a 26 to 30 mm inner width rim.

    • Mark Csendes on

      And 2-2.3 tires would be more than enough for most disciplines with addequate suspension set up… the again we’d be in 2007 w/o tons of fat bike shit! And plus size non sense! /ofc peps who really needed it due to terrain got a fat tire even back then/

  14. Frank on

    It’s fascinating to learn that I spent my first decade of mountain biking on rims that aren’t even wide enough for my road tires.

    • Eduardo on

      Me too, however I remember that I was not using tubeless and running much higher pressures than I use nowadays. When I try to run my mtb from the 90’s with the pressure I use nowadays I feel like dancing over my bike.

  15. Vova on

    Mavic does radial lacing on drive side of their wheels. Why should we rely on that firm? They say only that they want to sell.

    I use 23-25 mm Conti 4000SII on my Velocity Ailerons, that have about 20 mm of internal width. It fits absolutely perfect. No snake bits at all and perfect handling/cornering of my bike.

    Just stop listening to that marketing firm and ride bike.

  16. Charles Dye on

    Hoping to get a bit more clearance between my chain in the granny gear and my 27.5+ tire (Schwalbe 70-584), I just switched from an i35, to an i29 rim… and it sucks! The i35 was, in hindsight, just right for that tire. This i29 makes the tire too round. Grrrr.

  17. Bryan Boldt on

    Parting math quiz:

    End of article says “Whether your riding road, gravel, cyclocross, trail or enduro, a good starting point is likely using a rim with an inside width of 50-65% of your tire width.”.

    So for a 2.35″ (60mm) tire you are saying to start with a rim inner of 30-39mm wide. Really? That seems to fly in the face of all the previous info which indicates that rim size would be too wide.

  18. Steven Michael Preston on

    I have wtb speed disc rims and cst cabellero tyres 26×2.00 on my cannodale,Pls can someone tell me what type to get to replace them as when they’re inflated they have a lip that Pops on the rim and I’m not sure wether they are a certain type if that makes sense..

    • Peter on

      well im running a 2.4 dhr II rear/ 2.5 dhf front on stock giant 2017 23mm rims for a couple days now with no issues, knock on wood. Thinking of getting Stans Flow MK3/neo hubs, Im sure this will be night and day compared to stock.

    • Nestor Michalopoulos on

      I’m running 2.4 onza ibex (61-584) on 21mm rims width and with 28 psi rear and 23 psi front tyre pressure. Everything works fine.

  19. Rich on

    I think that we been duped long enough by the bike industry to actually believe this BS on rim width vs. tire width. Look at all the stuff they have thrown at us that we were all excited about then later on they change it up. Why? They suddenly got smarter? I don’t think so.
    I have run 2.6 tires on my my 50 mm external rims as well as 3.25 tires. Both work well on them with no issues.
    They used to say road rims were the way to go for mountain bikes back in the 26er day. I used to run Ritchey Zmax 2.35 tires on Velocity aerohead rims which were like 15 mm internal rims. Surprisingly I lived to tell about it!
    How about super narrow bars and bars well below the level of the seat and 72 degree head angles? Now it’s bars as wide as a ball room, well above the seat level and super slack head angles. What gives? Did physics change over the years?
    Check back in a year or two and all these assumptions will change.
    Be very careful for falling for all these new standards.
    How about rider weight, sidewall stiffness and tread profile? Why aren’t these taken into account when suggesting rim width? I weigh a buck thirty and my friend weighs two bucks forty. Lots of variable here to pigeon hole things into one neat tidy package.
    Now everyone is in love with long top tubes, tons of travel and low bottom brackets even though people are getting launched regularly from pedal strikes. But damn they can sure rail those turns!

  20. Dodo on

    The tech-talk at Bike Rumor is an embarrassment: 50-65% of tire width? It means that with a 2.25 tire should use a minimum of 28 mm inner width? With optimal width at around 57.5% which gives an even crazier 33 mm?

    If they only read the wide-right Stan’s page https://www.notubes.com/technology/wide-right, instead of claiming that they “spoke with them” and posting an outdated image from it, they would find the correct answer.

  21. Jonathan Pizzato on

    I have been running 29 x 2.6 Schwalbe Nobby Nic’s on a Hope Enduro 23mm rim with no issues what so ever.

  22. Philip S on

    Last year I emailed Mavic as to why their 2017 Ksyrium Elite UST Disc rims (19mm ID) shipped with 25mm tires which is outside the recommended (28-62mm) tire in their chart above and their reply was that “The table … does not take into consideration Road Tubeless configurations. With Road Tubeless wheels (as the new Ksyrium Elite UST Disc), the conditions are changing. Indeed, the rim profile has the ability to lock the tyre bead more firmly than a conventional tube-type rim design.” So basically, the chart is not for tubeless.

  23. bobby dunn on

    I think this has been beaten to death and way overthought. I am running 29×3.0 on Blunt 35’s, have done so for a year and its all been fine with 3 different tire brands.

  24. MrRibs on

    I’ve got 18mm A23 rims with 40mm tires and no issues. Thinking of going for wider tires, but how bad would it be if I tried 50mm tires on those rims?

  25. Ricky Bobby on

    Here’s the truth…

    We collectively ran 1.9-2.3″ tires on 17mm internal rims for roughly two decades, because that was the only option.

    I got 23mm internal rims about 10 years ago and was super happy to have some extra vpluvo, because I had tubeless and bigger tires and more rim width so I had more compliance, PTL!

    Now I have 21mm internal rims on my road bike with 28mm tires and 30mm internal rims on my MTB with 2.4 tires. I’m still super happy with the way everything works together.

    Ride your bike, if you’re happy with the way it rides, then don’t mess with anything.

  26. DugZ on

    Using the right tyre/rim width combo is the correct way to go, but! What the rider feels comfortable with needs to be taken int account with out going to far outside the extremes of compatibility, On average if the tyre is 1.4 – 2.2 x the rim width, it will work without compromising the tyre or rim in any way, up to 3x the width will work but can and does start to have problems like making the sidewall more vulnerable to rock strikes etc. However, all that is all well and good, as is most of what all the others have said, but! It was only touched on in the article, which really didn’t tell us anything we didn’t already know, and that is ‘actual’ tyre size! The quote from Schwalbe mentioned that some manufacturers don’t make their tyres strictly to the recommendations on sizing by ISO/ERTO or WTB for that matter! I think one of the comments touched on it too, and I’m amazed it has not been picked up on more.
    How many of you have actually measured the width of your tyres? So we’re talking about what tyre/rim size combination works best, but shouldn’t you know how wide your tyre is before you choose a rim to fit it to? Or switch that around and know how wide the tyre actually is you want to fit to your rim!
    I recently experienced a discrepancy that has had me calling manufacturers and asking suppliers for the ‘actual’ tyre width, NOT what it says on the sidewall, and I was amazed! A project for an 11yr old kids hardtail mtb needed nice ‘fat’ tyres to make it look good, it’s what they wanted! The rims were straight sided basic Kinlin’s, 25mm wide inside, clearance allowed for 2.35’s and would fill the forks/frame well. Budget wouldn’t run to that size but I found a pair of 2.125 by Finicci in a semi-slick tread, £15 the pair was ideal. Except when they arrived they looked ‘narrow’, I thought it was optical and would be ok once fitted, but no! Fitted they still looked narrow, so I measured them, 46mm wide!!! The sidewall says 26 x 2.125 (57-559)! How can a ‘supposedly’ 57mm wide tyre be only 46mm wide! Tyres were refunded, and the supplier couldn’t explain or understand, saying it must be a bad batch! Asked a few other suppliers, some would measure and relay what they found, the same! Others said they would but never got back to me, either they were shocked or just couldn’t be bothered! Started ringing manufacturers, couldn’t find a contact for Finicci, not really surprised but shouldn’t be the case, seems they are imported in small batches, and as yet the main supplier has not replied. So far Schwalbe is the only one to want to talk about it, they were happy to say that their tyres are within 2-3mm of the ISO/ERTO ‘standard’. So far no other manufacture has been able to say the same, but rather ‘dodge’ around the issue! I looked at other tyres I have and all bar the Schwalbe’s are undersize on the stated size, but at least 5mm on all! My Maxis Ardents is another matter, they state (54/56-559), are they just trying to cover all the bases! I even have two fairly aggressive mtb tyres by different manufactures, both the ‘same’ size as in 26 x 2.25 but the ISO/ERTO size has one at 51-559 and the other as 54-559! Odd how the cheap titan tyres on my hack are 1.95’s and measure as 51mm fitted at max pressure, I’d say that was OK!
    Now if anyone out there is saying, so? Well! If you want to get the right size tyres for the rims you have, then you need to know how wide the tyre is to start with. It is no good looking at the sidewall and ‘believing’ that what is on there is correct! As I have found, the tyre could be at least 10mm different to the size stated!
    In this day and age. with all the technology available, one would think a tyre made as a 57-559 is actually a 57-559, not a 46-559 (26 x 1.75) in disguise! So think about it when you buy your tyres, are the 2.35’s (60’s) or what ever but mostly mtb types, going to be the optimum fit on your rims, given that they could be smaller (more narrow) than you are led to believe!! Lets face it you could actually end up with a tyre that is too narrow for the rim and have the problems of over stressed sidewalls or added vulnerability!
    The problem doesn’t stop there though! How many of you struggle to buy shoes or clothes that fit properly if bought to a particular size. IE, A size L is not always a size L, likewise a pair of 10’s by Shimano are not the same size as a pair of 10’s by Specialized! The list goes on and on and on!
    It will take a miracle to get all the manufacturers to get on board considering it’s not just tyres that are not sized to a standard, which considering there are ‘standards’ in place is ridiculous, one would think the ‘standards’ authorities would do something to keep them in line, but then as they are run by the governments it’s no wonder the situation is as it is!!

    • Darien Mann on

      Wow I really enjoyed reading of your experience with undersized tires. Late with my reply, but I’ve encountered the same difficulty recently. The only compensating factor is tires stretch a couple millimeters. A Continental Trail King Apex 2.4 came in at 58mm, but a week later is 60mm. A NOS Panaracer Swoop 2.4 from 2015 came in at 60mm, and is now 62mm. Yay! But everything else, as you’ve described, is 5 or 10mm smaller than advertised. A frustrating and expensive exercise.

  27. Bryin on

    Had new tires blow off Stan’s Alpha rims (have heard many instances of this)… HAS NOT ONE THING TO DO WITH TIRE OR RIM SIZE…. it has to with tire pressure… was running 115psi (well under max tire pressure for the tire)… it was because Stans rims are NOT MEANT TO RUN HIGHER PRESSURE (MY GUESS IS 90 PSI MAX) Stans rims are not really meant for clincher tires, they are meant to be run tubeless and at lower pressures. But Stans does to tell people this… so if you run over 90psi on Stans rims you are taking a big risk.

  28. People Power on

    If I were a tire maker, I would publish a small graphic for each tire in my line showing the allowable range of rim widths and what the tire profile looks like at both ends of the width range. Customers need only know the rim width to shop for tires without surprises.

  29. Sam on

    Look, they all say what ever they NEED to not get sued over. That is all. It doesn’t matter what they tell you. They don’t want to get sued. Plus, they want to ensure you keep buying without suing. The advice is good and the guidelines are appreciated. But who is the problem? We are. It’s that simple. Experience speaks volumes as is shown by all the comments from those with such a concept. That’s where the best and most useful guidelines are. Happy riding all.

  30. Inigo on


    I just bought “entry level” Fulcrum Racing 6 wheels to use on a Colnago E1 road bike with 23mm tires but my surprise was the ETRTO is 622x17C and according to the FULCRUM manual the recommended tires are from 25mm to 50mm but unfortunately the frame design of this bike makes the 25mm tyre clearance is near 1mm which does not give me any confidence.

    Could I mount 23mm tires (avoiding security problems) or is it preferable I return the rims?

    Under Schwalbe’s criteria it’s possible to mount tires under 25mm.

    Thanks for your time.


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