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Bicycle tyre sizing and dimension standards

What do size marks on bicycle tyre package mean, how to “read” them, which bicycle tyre size can fit a given rim? This post answers all those questions, providing an easy, uniform, standardized way to tell a tyre (tube and rim) size using ISO (ETRTO) standards. For detailed tube sizing gude, see: Bicycle tubes – types, valves and sizing explained. Effect of tyre size on speed and comfort is explained here: Are narrower tyres “faster” – rolling resistance.

Table Of Contents (T.O.C.):

  1. Expressing (noting) bicycle tyre dimensions
    Table 1: standard bicycle tyre sizes
  2. Tyre widths
    Table 2: which tyre width fits which rim width
    Table 3: which fat-bike tyre width fits which rim
    Table 3b: Schwalbe’s complete size chart
  3. Frame fit room (maximum width)
    Table 4: real tyre height relative to its pressure and nominal size
    Table 5: real tyre width relative to its pressure and nominal size
  4. Tyre size and fitting video


1. Expressing (noting) bicycle tyre dimensions

At first, tyre dimensions were expressed through mounted (and inflated) tyre outer diameter. That is why today we still often note tyre sizes like 26″ (now less often), 27.5″ or 29″ for MTB, and 28″ for road bicycles. A 26″ tyre fits on a rim with a 559 mm diameter. When a 2″ wide tyre is mounted on such rim, the outer diameter of such wheel with an inflated tyre is around 660 mm (26″). To further complicate things, different standards were made in different countries. This led to situations that same sized tyres were differently noted, or that the same dimension note was used for tyres that differ in size. Does this sound complicated and confusing already? 🙂 Here’s a picture that takes 26″ “size” as an example:

Bigger wheel with a narrower tyre has the same outer diameter as a smaller wheel with a wider tyre.
Bigger wheel with a narrower tyre has the same outer diameter as a smaller wheel with a wider tyre.


That is why ISO standard notation was introduced and is in use today. Standard was introduced by ETRTO (The European Tyre and Rim Technical Organisation). Diameter of wheel tyre bead seat in millimetres preceded by tyre width in millimetres. Tyre width is also a bit non-exact measurement. It is width of an inflated tyre mounted on a rim of standard width for that tyre size. However, the most important information: wheel bead diameter is noted exactly in millimetres, so there can be no confusion. 559 wheel and tyre are always compatible (at least in terms of diameter, see about tyre and rim width compatibility below).

When bead seat diameter (BSD) is known, a tyre of appropriate dimensions in mm is required. It is as simple as that.

Bead seat diameter and inner rim width - all that matters.
Bead seat diameter and inner rim width – all that matters.


For example, the 26″ wheel diameter is 559 mm and it can take practically any tyre of that BSD, whether wider, or narrower, such as 47-559 (26×1.75″ by old nomination), 60-559 (2.35×26″ by old nomination) and so on. All the manufacturers today mark tyres with ISO dimension standards, sometimes adding old nominations as well, but ISO is always noted and can be used as a safe(st) reference.

Standard road bicycle wheel size today is 622 mm and it usually takes tyres of 23-622, or wider 25-622. Today when off road bicycles with wheels larger than standard MTB wheels started to be popular, it’s wheels are marketed as 29″, but in fact are 622 wheels with wider tyres (so that outer diameter is close to 29″). Tyres for those bicycles are always marked with ISO standard (sometimes along with the “old” standard 29″) saying something like: 57-622, 60-622 and similar, depending on tyre width.

Tyre with dimensions noted in ISO, English and French standard.
Tyre dimensions noted in ISO, English, and French standard


In case a tyre has no ISO (ETRTO) marks, here is a cross-reference:

ISO (ETRTO)
Bead Seat
Diameter
Traditional Designations
787 mm36 inch
686 mm32 inch
635 mm28 x 1 1/2, 700 B
630 mm27 x anything except “27 five”
622 mm700 C, 28 x (two fractions), 29 inch, 28 x 1 1/2 F.13 Canada   Road 28″ wheels and MTB 29″.
599 mm26 x 1.25, x 1.375
597 mm26 x 1 1/4, 26 x 1 3/8 (S-6)
590 mm26 x 1 3/8 (E.A.3), 650 A
587 mm700 D
584 mm650B, 26 x 1 1/2, 27.5″  MTB 27,5″ wheels
571 mm26 x 1, 26 x 1 3/4, 650 C
559 mm26 x 1.00- x 2.125, also fatbike tyres up to 5 inches wide MTB 26″ wheels.
547 mm24 x 1 1/4, 24 x 1 3/8 (S-5)
540 mm24 x 1 1/8, 24 x 1 3/8 (E.5), 600 A
520 mm24 x 1, 24 x 1 1/8
507 mm24 x 1.5- x 2.125 – Big kids bikes with 24″ wheels.
490 mm550 A
457 mm22 x 1.75; x 2.125
451 mm20 x 1 1/8; x 1 1/4; x 1 3/8
440 mm500 A
419 mm20 x 1 3/4
406 mm20 x 1.5- x 2.125  – Kids small 20″ wheels, BMX.
390 mm450 A
369 mm17 x 1 1/4
355 mm18 x 1.5- x 2.125
349 mm16 x 1 3/8
340 mm400 A
337 mm16 x 1 3/8
317 mm16 x 1 3/4
305 mm16 x 1.75- x 2.125  – Kids 16″ wheels.
254 mm14 x 2.00
203 mm12 1/2 X anything. Small kids 12″ wheels.
152 mm10 x 2
137 mm8 x 1 1/4
Standard bicycle tyre dimensions (ISO, and obsolete standard notation cross-reference)
Table 1

– T.O.C. –


2. Tyre widths

After explaining tyre dimensions, a few words on tyre widths. Generally, narrower tyres are good for fast road riding on pavement, while wider tyres are better suited to rough terrain, or heavily loaded bicycles (heavy rider, carrying children or heavy baggage on a bicycle etc.). Depending on rim width, a range of tyre widths can be used. The important measure here is inner rim width. Outer rim width is irrelevant (for this purpose), just the inner rim diameter.

Rim cross section, with inner and outer diameter. This one has 19 mm inner rim diameter.
Rim cross-section, with inner and outer width. This one has a 19 mm inner rim width.


The following table tells the range of acceptable tyre widths depending on inner rim width, expressed in mm, according to ISO (ETRTO) standard:

Tyre width
(mm) /
Rim width
18
20
23
25 28 32 35
37
40 44 47 50 54
57
60 62
13xxxx
            
15  
x
xx
x
          
17   xxxxxx
x
x
x    
19    xxxxxxxxxx  
21      xxxxxxxxxx
23       xxxxxxxxx
25         xxxxxx
x
27          x
xx xx
x
29            xxxx
Which tyre width can fit which rim widths (in millimetres)
Table 2


Fat-bicycle tyre sizing chart:

Tyre width
(mm) /
Rim width
65
2.60″
70
2.80″
80
3.10″
100
4.0″
110
4.40″
115
4.50″
120
4.80″
30
xxx
   
31xxx
 
32
xx
33
xxx 
34
xxx   
35
 xx    
40
  x   
45
   x  
50
   x
70xxx
100xx
Which fat-bike tyre width can fit which fat-bike rim widths (in millimetres)
Table 3


Below is a chart which includes many modern (more recent) tyre and rim widths. It was made by the Schwalbe company and in my experience it is a safe guide (I’ve even exceeded the there-recommended ranges without problems). Both the dark-blue Schwalbe range, and the light-blue ETRTO range are fine – as long as you stay within either of those, you’ll be fine:

Tyre-rim width compatibility chart by Schwalbe
Tyre-rim width compatibility chart by Schwalbe
Source: www.schwalbe.com
Table 3b


If a tyre that is too narrow is mounted on a wide rim, the rim can easily be damaged on a bump. If too wide a tyre is mounted, there is a risk of the tyre coming off a rim (with a loud explosion of the tube).


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– T.O.C. –


3. Frame fit room (maximum width)

If there’s limited space for fitting tyres in a frame, note that rim width also influences tyre width and height when mounted:

Difference of outer dimensions when mounted on various width rims.
Difference of outer dimensions when mounted on various width rims.


It should be also noted that one nominal tyre size (e.g. 622-28), in various models and manufacturers, is not of the same actual width when mounted and inflated. Some models are known to be of a smaller “real” size, some are known to be larger. If, for example, the old tyre has a nominal width of 23 mm, and one considers replacing it with a wider one of 25 mm (nominal) width, and there is only about two mm extra room, it should be confirmed what the actual tyre widths when mounted are. If the old 23 mm tyre is among the “narrower 23s”, and the considered 25 mm one is among the “wider 25s”, it is very likely that the wheel will not fit into the frame with the new tyre.

Pictures below are taken on a frame with lots of extra room for wider tyres (and mudguards). They are just a demonstration of where the “tight” spots usually are, and where attention should be paid (and measuring taken) before going for wider tyres. Depending on frame geometry and brake type, some other spots may be the tight ones. It should always be checked and measured at the tightest spot, with the least tyre clearance – and that is usually in (one of) these places:


Table overview of how tyre inflation pressure affects its real height, depending on its nominal size (dimension) – inner rim width used or measuring was 19 mm:

Tyre model and
nominal dimension
Real
height
at
3 bars
pressure
Real
height
at
4.5 bars
pressure
Real
height
at
6 bars
pressure
Continental
Grand Prix 4-Season
ETRTO 622-28
27 mm27.5 mm28 mm
Continental
Terra Trail
ETRTO 622-35
32 mm32.5 mm32.75 mm
Schwalbe
Lugano 2
ETRTO 622-25
22 mm22.5 mm22.75 mm
Real tyre height relative to its inflation pressure and nominal size
Table 4


Table overview of how tyre inflation pressure affects its real width, depending on its nominal size (dimension) – inner rim width used or measuring was 19 mm:

Tyre model and
nominal dimension
Real
width
at
3 bars
pressure
Real
width
at
4.5 bars
pressure
Real
width
at
6 bars
pressure
Continental
Grand Prix 4-Season
ETRTO 622-28
29.5 mm29.7 mm30.1 mm
Continental
Terra Trail
ETRTO 622-35
34.7 mm34.8 mm35.15 mm
Schwalbe
Lugano 2
ETRTO 622-25
24.6 mm24.8 mm25.3 mm
Real tyre width relative to its inflation pressure and nominal size
Table 4

– T.O.C. –


4. Tyre size and fitting video

Can I put a wider/narrower tyre on my bicycle/rim?
Will a wider tyre fit a rim?


Related post – To what pressure should I inflate my bicycle tyres:

To what pressure should I inflate my bicycle tyres?
To what pressure should I inflate my bicycle tyres?

– T.O.C. –

54 thoughts on “Bicycle tyre sizing and dimension standards”

  1. Hi Everyone, thanks for providing all of the information in this article. I’ve learnt a bunch. However I’m still quite unsure in regards to what I need before investing too much money for nothing.

    I’ve got my old MTB hitched onto a home trainer/ stand and want to change the tyre to a slick (otherwise noisy). The current tyre is a 26×2.1 (hb-575). I seem to only find 26×2.0 Slicks anywhere near this size and was wondering if that will work…. Can you confirm? Could you also let me know if there is a “range” I could work within to broaden my search and get a good price tyre e.g between 1.75 – 2.1 (just picking nimbers). Obviously doesnt have to have the perfect fit for an special performance but needs to fit on the rim and work.

    Thanks so much in advance to you and the community for your help.

    Scott

    Reply
    • Hi Scott,

      Two things to consider here:
      1) Tyre fitting properly on a rim.
      2) Ride quality, performance etc.

      1)
      Regarding tyre width, table 2 in this article provides info on the range of tyre widths that fit a given rim width (the picture above the table shows what I mean by rim width in this context).

      Goes without saying that the tyre diameter should match the rim – chapter 1 and table 1 explain that.

      For the intended use, indoor trainer, any slick tyre that fits the rim should do the job.

      2)
      Writing this in case anyone looking for a street/pavement tyre in 26″ size reads it. It’s not really important for a trainer – any slick tyre will do for that, the cheaper, the better, generally speaking.

      For 559 mm (26″) wheels, I don’t like using tyres below 1.75″ (47 mm), because those make for smaller total wheel diameter, require relatively high pressures and don’t make for a very smooth, nor very fast ride.

      For paved road riding (not mud or snow), 1.75 seems to be the sweet spot. The tyre is not needlessly wide and heavy, but without the downsides mentioned above.

      Having said that, with high-quality slick tyres, even 2″ width is not a problem. Sidewall quality (and overall tyre quality) is more important than the size.

      So, with all that in mind, my priorities are like this:
      – 1.75″ (47 mm) or wider
      – High quality – with at least 60 TPI per layer, preferably 100 if available/possible (tyre quality explained)
      – Slick profile (for pavement – minimal thread, none at all if possible/available)

      I wouldn’t rule out a high-quality tyre even if it’s wider than 2″, but I’d first try to find one that is between 1.75 and 2″ wide (preferably 1.75 🙂 ).

  2. Thanks very much for the article and video which are really helpful. I’ve been having a terrible time trying to fit Schwalbe Marathon Greenguard tyres on my Kona Honky Tonk road bike. It came with Continental Sports that had 28-622 (700 x 28C) on the side. The wheels, however, are Racine Elite and on the rim the information given states the ETRTO (it uses that term) rim size as 622 x 13C, 18mm – 25mm Tire section width, and Inner rim width 13C. This would seem to fit with your table, which is the only one I’ve found to mention a 13mm inner rim size. Does the 25mm equate to a 622 x 25C tyre?

    When I try to fit the Schwalbe Marathon 700 x 28Cs it seemed like the tyres were too big. I had trouble seating them in the rim. I don’t mean trying to get them over the rim, it was too easy. They just wouldn’t stay in. I had to tie them on with toe straps. Then, several times now the rear tube has just exploded when I try to inflate it up to pressure. The technician in my local bike shop suggested I’d be better with 700 x 25C. Is he right, or is 700 (which is the same as 622 as I understand from your article?) just too big in Schwalbe’s Marathon tyre sizing? If so, what should I go for?

    I can eventually get the current tyres to fit after about an hour of wrangling, but it would be tricky trying to repair a puncture out on the road as I wouldn’t be able to get the tyre back on easily. I’m also worried about how safe they are if they are not right for the rims. I would really appreciate your advice. Many thanks.

    Reply
    • Hi Martin,

      As far as I know, 700 C is the synonym for the 622mm ETRTO size (only, the former standard was apparently written by a drunk lobster, not an engineer – it’s that unintuitive and confusing 🙁 ).

      The table 2 on this page states that 13 mm wide rims take 18 to 25 mm wide tyres.

      The tyre you are trying to mount is 28-622 ETRTO, i.e. 28 mm wide. The “C” marks (“700 x 28C”) are good for garbage (if you’ll pardon me for being so blunt), due to their inconsistency, at least in my opinion and experience.
      I tried hard to stress that in this article – I’ll add a note right before the charts to make it less confusing, the tables refer to ETRTO sizing standard only.

      Having said that, I’ve used 622-28mm tyres with 13-622mm rims with no problems. Also, it’s worth noting that not all the tyres and rims are built to highly precise tollerances. Combine a rim that is “a bit on the large side” (for its nominal ETRTO size) with a tyre that is “on the small side” (for its nominal ETRTO size), and you get a “thumb squashing” combo that is very difficult to mount. Vice-versa could be the situation in your case – and one must make sure to inflate slowly, re-aligning the tyre in the process if needed, to make sure it’s properly seated (without any part of the tyre trying to squirm out of the rim) before pumping to the optimal pressure.

      So, if the technician you talked about is a good mechanic, it may be worth asking them to give it a look and try to mount the tyre, before swapping for a narrower tyre (a 25-622 ETRTO).

      Again, the tables on this page are quite conservative (a safe bet), and I’ve often exceeded those recommendation both on the wider, and on the narrower side. But it’s quite possible that some tyre and rim combos are not as “flexible,” and that might be the case here, so a 25 mm wide tyre might in fact be required.

      Hope this helps.

  3. HI Rely,

    Thanks for your reply which was very helpful. I think on this basis I’ll go ahead and try the 25Cs. I need tyres that it would be possible to change if I have a puncture. The Schwalbe 28Cs just don’t want to stay in when trying to fit them.

    Thanks a lot.

    best regards,

    Martin

    Reply
    • the 622X13 rims you describe are mainly used with the narrow 700×22 tires as they are racing rims,i have the same width rims and i run 622×22 or 622×25 tires,the 25 width tires are good allrounders if your looking just for comfort,try continental grand prix tires for a nice ride,in the west they use 622 or 700c when describing tires,they mean the same thing,i would not like to ride your bike with 28 mm wide tires on those skinny rims

  4. Hi Again Relja (and sorry for getting you name wrong in my last post, I blame autocorrect),

    I meant to ask, would 25Cs be best or should I go for 23Cs which I’ve just seen are available? I’m looking for comfort/safety, not speed. My route has a few gravelly tracks so I’m not sure narrower is desirable.

    Thanks.

    Best wishes,

    Martin

    Reply
    • Hi Martin,

      The ISO (ETRTO) tyre width ranges listed in table 2 are very “conservative” so to speak.

      So, If you stay within the there-noted acceptable width range for a given rim width, you should not expect to have any problems.
      In other words: any problems will be only due to a defective rim, defective tyre, improper mounting technique, or improper tube size (one not excluding the others). But not because of the tyre being too wide or too narrow for the rim.

      P.S.
      To note again, for anyone looking for answers in the website comments:
      Tyres noted as 25C (or 23C) may not always be 25 mm (or 23 mm) wide. The “C” and other obsolete marks are too arbitrary (and not enough unequivocal) in my opinion & experience.

  5. Hi this is a good webpage and the comments section rocks,
    Here is a long story made short:
    I bought a Cannondale Trail 8 because I wanted to ride a 29er with the WTB Ranger (29×2.25) tyres.
    It was nice until I ran up against a curb and the rear wheel because wobbly.
    The same shop that sold me the bike could get a new wheel but it would cost nearly half the price of a new bike. This sent me on a months long journey to junk shops looking for a cheaper wheel.
    Finally, I came across a set of Bontrager Affinity TRL that go to a Trek bike; the size is 21×622.
    According to your rim-compatibility graph a rim of 21 can accommodate 35 – 62 tyres. The Rangers are 55-622 so I think it would work. Just double checking here.
    Big Thanks,
    JuDAWG

    Reply
    • Hi, 🙂

      Yes, the table chart is quite “conservative,” so combinations shown to work there are pretty certain to work with practically every rim and tyre model combo.

      Just make sure to measure the rim’s inner width, as explained and depicted in the article (19 mm in the picture just above the table 2.

  6. hi
    I m working in a old bike fit with 35-590 tires, do you think I can fit on the same rim 45-599 tires/
    thanks

    Reply
    • Hi Luca,

      The answer is no.

      Rim and tyre diameter must match in order for tyres to fit.
      Even when the difference is very small, like 622 rims with 630 tyres, it doesn’t fit.

  7. Hello, wonderful explanation!!!

    I have a rim that is 26” 559 x 14, any ideas on the tires to fit?

    Reply
    • Hi Ekene,

      Table 2 shows which tyre width fits which rim. It’s conservative, i.e. I’ve exceeded the limits shown there by a size or two on occassions without any problems, but staying within the given limits gives good results for any tyre and rim combination I’ve seen.

      Now, if your question is about a tyre model, not tyre size, I’d have to know the budget, intended use (off road, mud, paved roads etc.), do you (intend to) use full coverage mudguards, and ideally, the country (and/or which brands are available at your location) – as it makes no sense to recommend Schwalbe if you are in Serbia, for example.

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