We often get questions on bicycles.stackexchange about fitting wider tires or narrower tires (for search - bigger tires, smaller tires) to bicycles. We have a large number of these with answers suiting the specific bike or style of bicycle in question, but I have been unable to find one that provides a generic answer covering off all things that need to be considered. For most bicycles, the answer is the same regardless of the specific style and sizes of tires in question.

This is intended as a canonical question that we can point closed questions to.

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    I suggest adding minimum tire width as well. Commented Mar 14, 2018 at 21:02
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    And rim compatibility also needs to be discussed. The old 24 and 26-inch fractional (not decimal) width tires had varying rim diameters (and 16s were all over the place). See Sheldon. Commented Mar 14, 2018 at 21:42
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    To Future Readers - note this can be a bit of a moving target. The current accepted answer quotes specs from 2015, but in 2020 this is being reviewed and we will likely see a revised set of standards soon. So do read and compare all the answers below.
    – Criggie
    Commented Dec 16, 2020 at 2:57

6 Answers 6


Maximum tire width is dependent on two main factors, clearance at the frame/fork, and the width of the rim.

As for the frame clearance this can usually be visually inspected and easily distinguished if a larger tire than the present tire will cause issues. Brakes such as V-brakes or cantilevers may also cause clearance problems with some tires so attention should be paid to them as well.

Mud or other debris should also be considered for mountain bikes and applications with fenders/mudguards. You should not run clearances so tight that one little pebble caught in the tread will hit the frame, fenders or other parts.

Think of the difference between both sizes you are considering and then split that number in half, that is the distance you will need to be able to clear on either side of the tire at the chainstay essentially. So if there is a 4 mm difference in road tires, the new size will roughly add an additional 2mm onto either side of the existing tire is one way to think about it, but the top of the tire needs to also be checked as the new tire may also be taller in addition to the increased width.

Knobs on MTB tires can also vary greatly and play a part in your decisions and fitment as well. One 2.25" tire may come out to be shorter than another more aggressive 2.25" tire due to the shape and size of the knobs.

As for rim to tire interface there are multiple guidance charts available online that give a rough estimate if a tire is compatible with a certain rim width, such as this one from J&B Importer's, a bicycle parts distributor's catalog.

As an example you can see that a rim width of 19mm (top row) should be compatible with tire width of 28mm/1.10" through 62mm or about 2.5". But seeing as 28mm is the lower end of that column it might be reasonable to go a little larger and avoid the extreme values.

Tire/Wheel Compatibility table

However just because it will fit on the rim does not mean it will not rub on the frame so that is what is most important.

For small changes such as from 26 x 1.95 to 26 x 2.125, or 700C x 23 to 700C x 25 you are almost certainly safe from a rim standpoint if the bicycle was factory equipped with 1.95"/700x23 tires.

To be certain, the model of rim should be referenced and the width noted.

Please also note that the same applies to going to a smaller tire size, too small of a tire on the same rim could not seal well and potentially cause flats or blowouts when the tire bead cannot seal against the rim well enough.

Edit: July 2020 - Suggest reading the the answer posted by @Weiwen Ng which contains updated information.

  • Feel free to edit/add on/ correct me if I'm wrong
    – Nate W
    Commented Mar 14, 2018 at 21:38
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    +1 - a nice answer. At the end of the third para I'd change to "frame, fenders, or other parts" after my own experience. You might mention different knobblies coming up different heights (or even widths if you look at the shoulders). And a typo in the last para "aslo"
    – Chris H
    Commented Mar 14, 2018 at 21:57
  • Maybe mention the word "mudguards" as well as "fenders" (assuming that's what is meant by "fender") for people outside the US?
    – psmears
    Commented Mar 14, 2018 at 22:23
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    @ChrisH it was my understanding that it was generally considered bad practice to combine knobby tires and fenders. The knobs are more likely to pick up debris that can the jam in the fender leading to a crash.
    – Rider_X
    Commented Mar 14, 2018 at 22:39
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    @WeiwenNg You may add it in addition if you would like to. I find that one harder to read especially for beginners that aren't as familiar with tire sizing personally.
    – Nate W
    Commented Jul 9, 2020 at 23:00

Tire to Rim Fits

I was investigating the source of the document on rim vs tire width in Nate W's answer. This focuses on the rims first. I discovered enough new information to warrant writing a new answer. Basically, the maximum tire size that you can fit on your rims is very likely larger than what's specified on the chart. The chart is based on an older specification by the International Organization for Standardization (ISO) that is in the process of revision. (Note that a new set of specifications may have been finalized in 2021.)

While answering a different question, I referred back to this question and answer. The information there caused me to realize that the ISO standard may be a bit dated in 2020. For example, many performance road bikes made within the last 5 years come stock with 25mm tires (note: that's nominal width, i.e. the width printed on the sidewall, rather than width as measured). 25mm tires were technically out of compliance with that questioner's rims.

On further research, the tire size guide Nate cited stems from the International Standards Organization (ISO), standard 5775. That document was published in 2014/2015, and it appears to be under review at the time of writing in 2020; ISO reviews its standards every few years. The documentation of the standard is gated. However, in 2016 Bikerumor appears to have published a table based on the ISO standard, reproduced below. Note that it's similar but not identical to the documentation that Nate gave. (NB: you almost certainly have "crotchet type" rims, which have bead hooks; some modern drop bar wheels are hookless, and these would be "straight side type" in the chart.)

enter image description here

In the Bikerumor chart, it appears that the ISO only approved 25mm tires on rims with 13mm to 17mm internal width. However, many clincher rims in 2020 have 18 to 20mm internal width. A number of new carbon wheels from the likes of Zipp, Enve, and Roval have internal widths of at least 21mm. I have had 25mm Continental Grand Prix 4000 S-IIs mounted to rims with a 19.4mm internal diameter for at least a year, and I've never experienced a blowout (NB: these tires measure 27.6mm or so when inflated; they were notably wider than the nominal size). Worse, Zipp's 303 Firecrest wheel has an internal width of 25mm. Since it's a hookless design, it appears that the smallest tire that ISO approves would be at least 45mm in width. And yet, Zipp recommends a minimum size of 28mm.

If the ISO specs are correct, a lot of people on current generation wheels should be experiencing some sort of tire failure, and yet there doesn't appear to be a spate of such failures. So, the ISO specs are wrong. But where does that leave current riders whose tires and rims don't fall into the officially approved list?

  • First, check if your wheel or rim manufacturer lists specific tire incompatibilities. Some examples: Enve lists specific tires as incompatible and requires tubeless; Zipp merely requires tubeless on its 303 Firecrest and 303S, it doesn't test specific tires, and it listed a minimum width of 28mm for the Firecrest, and I believe 25mm for the 303S.
  • Continental's new GP 5000 S TR tire is a version of the GP 5000 S, adding compatibility with hookless rims. This Cycling Weekly article reproduced a picture from Continental. The company is recommending that the 25mm versions of this tire be used with a maximum internal rim width of 21mm, and a maximum internal rim width of 25mm for its 28, 30, and 32mm tires. Many new tubeless road rims are converging on this internal width in 2021, although it is very wide compared to older rims. It's unclear if Continental is making this a recommendation or a hard requirement.

enter image description here

  • If there are no compatibility specs, then for newer performance road wheels, the practical minimum tire width is likely smaller than the ISO specifications. For example, the Hed Belgium Plus and associated rims have internal widths of 21mm. For both the disc and rim versions, Hed specified a minimum tire width of 23mm and a maximum of 58mm. 23mm tires should be OK to mount on rims with internal widths of 17-20mm, even though this appears to conflict with the ISO chart. 25mm tires, similarly, should be fine on road rims of 18mm to 20mm, despite the chart.

  • I'm not certain about compatibility on modern rims for tires smaller than 23mm. But such tires are rare, anyway. An interesting side note: when Hed released the Jet aero wheels with a 21mm internal width rim, they appear to have recommended tires of at least 22mm, and they seem to have tested tires of 22 and 23mm in the wind tunnel. The Continental Attack tire may have been available in 22mm at the time of release, but it may have been re-specified as a 23mm tire. I'm not actually aware of any current road tires narrower than 23mm, although I don't specifically look for these tires.

  • For wheels with internal widths over 21mm, I would avoid nominal 23mm clincher tires out of caution. Lennard Zinn recommended this.

  • For 700c wheels with road tires, if you have reasonably current wheels, the maximum tire width may not be a concern. Many rims, especially hooked rims are likely to be OK with any tire that you might want to put into your frame.

  • For 700c wheels with gravel tires, based on the ISO chart, the theoretical maximum width probably exceeds your frame clearance anyway. Consider that if you somehow have 700c rims with a only 17mm internal diameter on a gravel bike, ISO thinks that you can mount a maximum 52mm tire, which is a bit over 2 inches. In 2020, the largest gravel frame tire clearance for 700c tires that I'm aware of is around 50mm. Rest assured that gravel rims are trending much wider than 17mm. Ergo, gravel cyclists don't need to worry about the maximum safe tire width on their rims.

  • If you have 650B rims on a gravel bike, then I would expect most of these to be well over 17mm internal diameter anyway.

I'd expect the standard to be updated soon. Hookless rims are ubiquitous in cars and current mountain bikes, but they may only just be starting to make their way to drop bar bikes, and then mostly for carbon rims. Removing the bead hook does simplify the manufacturing process for carbon, which potentially reduces cost. It also may smooth the tire/rim interface, improving aerodynamics slightly. The new ISO standard might revised to account for the tire width issues mentioned above and the advent of hookless rims on performance road bikes.

Further note: Tire to Bicycle Fit

Most of us, except Criggie, had focused on the question about tires fitting to rims. I'm adding some information for newer cyclists on fitting wider tires to their bicycles.

As already stated, you need some clearance between the tire and the closest parts of the frame, and sometimes between the tire and the bottom of your brake caliper (applies to rim brakes). I believe that the ISO requirement is a minimum distance of at least 4 or 5mm.

Many bikes can fit slightly wider tires than they came stock with. If you can find the manufacturer's specifications for your bike, many bikes may list a maximum tire width - however, cheaper bikes are less likely to have those specs published, and older bikes may have had that documentation lost to the sands of time. For many owners, buying a tire whose nominal width (i.e. the width printed on the package) is 1-2mm wider than the tires that originally came with the bike is probably OK. If you have an older performance road bike, you may not have room to play with the width much.

To check your current clearance, you can use hex wrenches as feeler gauges, i.e. fit a wrench in between the frame and the tire, or you could use measuring calipers. Once you've measured or estimated how much clearance you have right now, you can then guesstimate how much you will have with the new tire. However, be aware that a tire's nominal width will vary depending on what rim it's mounted to (this is why I refer specifically to the nominal width). It's best to err on the side of caution when buying a new tire.

A further note on tire to rim fit

Note that the approved tire widths in the Bikeradar chart and the J&B Importer chart differ slightly, although many are similar. Bikeradar's chart lists 23mm tires as compatible with 13 to 16mm internal width rims. J&B's lists 13 to 17mm. For 25mm tires, Bikeradar's chart says 13 to 17mm rims, whereas J&B says 13 to 19mm. It's possible the charts are both based on different revisions of ISO 5775.

Finally, note that Jan Heine of Rene Herse Cycles might disagree with many of my statements above. He states that if the rims are too wide, the tire pressure won't push the bead against the bead hooks strongly enough to retain it. This could lead to tire blow out. He does admit that the ETRTO chart is conservative in this respect. He has a rule of thumb that the internal rim width should be at least 20% narrower than the tire. For a 25mm tire, this would suggest a maximum internal rim width of 20mm. Even so, this puts my main set of wheels in compliance with my usual 25mm (nominal width) tires. However, this suggests that Hed's tire width recommendations for its Jet rims, and the similar Belgium rims, are too narrow (at 21mm internal width, they should have at least 26.25mm nominal tire width by the Heine rule).


The minimum is dictated by the width of the rim. Sheldon Brown has tables, here: https://www.sheldonbrown.com/tyre-sizing.html

The maximum size depends on the space between the stays at the rear and the width of the brakes and the space under the mudguards where the tyre has to fit. This has to allow for the dynamic shape changes the tyres undergo while you're riding and for mud or debris sticking to the tyre itself, if you don't want to be thrown off the pony by a locking wheel.

These are no laws of Nature. If the size works it's OK.

  • I'd caution the difference between a static fit and a dynamic fit. A 28mm tyre might fit nicely in the workstand, but under rider power there may be rub. Best to check after a couple of rides for movement or witness marks.
    – Criggie
    Commented Jul 29, 2018 at 9:57

Another gotcha is the fit of other parts around the tyre.

Rim brake arms and calipers can change their profile throughout their stroke, and their stroke can change as the pads wear down.

V brake arms are pulled in toward the side of a tyre as you brake. So a close fit here can mean interference once they close up. This would be exacerbated by worn down brake pads.

I personally have a 28mm tyre with a shimano 105 rear rim brake where the underside of the caliper's arms touch the tyre if my inner brake cable is slackened-off. Mind you I can'f refit that rim if it has an inflated tyre, so tolerances are quite tight.

Mudguards/Fenders can have a problem with larger tyres too - though these are generally quite adjustable.

Toe Strike Slightly unusual, but if you're going to aggressively knobbly tyres then its possible for your toe to clip the knobs while turning. If you had smoother tyres, then catching the knobs with your shoe can catch where the original tyres might just rub.

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    Those of us who ride small size frames will know that the toe strike is far from unusual. I think it may even be unavoidable with S size and 700c. And once one gets used to it it is just usual. Commented May 17, 2020 at 9:17

In practical terms, people usually seem to ask this question because they need to replace a tyre on their bike but can't find tyres in exactly the same width as the one they already have. Unless the existing tyre was close to the limit of what will fit, using a slightly different width (e.g., and eighth or tenth of an inch, or a couple of millimetres) is going to be fine.


I have never utilized a formula, or some all-purpose rule for determining tire width. often I rely on frame manufacturer specifications. there are too many variables, such that it's easier just to eyeball it (for me, anyways). tires can measure wider or narrower than their specified widths, and that width also changes depending on what rim it's mounted to. got a flexy frame or wheel? expect the tire to wobble on a sprint or climb, requiring buffer space on either side so it doesn't rub the frame. some brakes can have higher or lower arches, again affected by rim width or just where they mounted the bridge. is it an older tire? might be wider than it used to be.

if you want a more empirical method, use spare wheels and just measure the gap between rim and frame. tire width is roughly gonna be the height of the tire too (not accounting for tread). it's a pretty rough measurement but it'll give an approximation at least, and when mounting tires it should never come down to the millimeter anyways. just don't forget to check down by the bottom bracket as that's as often a limiting factor as the brake bridge. also factor in whether you'll be using fenders. when in doubt, size down.

one other way i used to think about it was in terms of what age and type of bike it is. i could pretty much guarantee that a hybrid bike would be able to fit up to 38c. whereas i wouldn't push it any larger than 25c on an aero or road bike (unless i specifically knew it was designed with larger tires in mind). high-end cross bikes would get 33mm because that's the biggest you're allowed to use. 26" mountain bikes could almost always take up to 2" knobby tires... there were exceptions, sure, but this worked more than it didn't.

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