Tyre/wheel sizes

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Darkman
Posts: 144
Joined: 30 Aug 2019, 8:46pm

Tyre/wheel sizes

Postby Darkman » 4 Nov 2019, 10:35am

Another day, another thing I don't understand!

My bike has 29" wheels. Simple, buy 29" tyres for it, right?

But there's 700/700c, 28, 29er (which some places say is the same as 700, while other places say it's 28", not 29").

I'm just looking to replace the knobbly off-road Ground Control/Fasttraks with something geared more toward road use.

Also, will a 1.75" tyre fit on a rim that currently has a 2.0/2.1?

Finally, does it make any difference whether I use wire/folding bead? I'm not tubeless.

I have never swapped a whole tyre in my life, except on a wheelbarrow once but I don't think that counts. :|

[edit] Apparently the rims I have are 20mm internal width.

hamster
Posts: 3715
Joined: 2 Feb 2007, 12:42pm

Re: Tyre/wheel sizes

Postby hamster » 4 Nov 2019, 11:46am

Forget all about the imperial tyre sizes. As you say they are confusing and look at the end wheel diameter.

The key thng is the rim size, which is given by the ETRTO number. Its the diameter of the tyre bead, put simply.
26" MTB: 559mm
27.5 MTB: 584mm (also known as 650b road)
700c road: 622mm
29er MTB: 622mm
27" road: 630mm (obsolete size)

Buy the tyre with the right number and job done.

Brucey
Posts: 42167
Joined: 4 Jan 2012, 6:25pm

Re: Tyre/wheel sizes

Postby Brucey » 4 Nov 2019, 1:01pm

hamster wrote:Forget all about the imperial tyre sizes. As you say they are confusing and look at the end wheel diameter.

The key thng is the rim size, which is given by the ETRTO number. Its the diameter of the tyre bead, put simply.
26" MTB: 559mm
27.5 MTB: 584mm (also known as 650b road)
700c road: 622mm
29er MTB: 622mm
27" road: 630mm (obsolete size)

Buy the tyre with the right number and job done.


well, yes, but '650b' should be '650B' and '700c' should be '700C'. And the current tyre markings are often ISO and take the form of

XX-YYY

where XX is the nominal tyre width in mm and YYY is the bead seat diameter in mm.

Also you shouldn't just 'forget about imperial tyre sizes', because tyres are very often listed and have primary markings using these sizes. What you can do is to look for tyres in the imperial sizes and then use the ISO markings to confirm that they are correct.

The primary source of confusion is between tyres marked say

26 x 1-3/8"
vs
1.4 x 26"

(which are different tyres)

or

26 x 1-1/2"
vs
1.5 x 27.5"

(which are the same size tyres)

or similar in other sizes. The 26 x 1-3/8" designation has been around for over 100 years and hundreds of millions of tyres have been sold with only these markings on. Ditto 26 x 1-1/2" markings. These tyres are often known as 35-590 and 38-584 respectively, in ISO. French people call 38-584 '650B' and recently wider tyres that fit on rims of the same diameter have been called ** x 27.5" tyres where ** is a decimal value in inches.

If you see a tyre marked ** x 29" the chances are its ISO designation is XX-622.
If you see a tyre marked ** x 26" the chances are its ISO designation is XX-559.

If you see a tyre marked 'ZZ x WWW' where ZZ is an inch value and WWW is a width in inches expressed as a fraction not a decimal then it is marked using the original Dumlop markings and you should check the ISO size to ensure compatibility (there are about fifteen different common rims sizes in this scheme, plus a load more obsolete ones) . Some 700C (ISO XX-622) tyres are marked as 28" x WWW markings.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Darkman
Posts: 144
Joined: 30 Aug 2019, 8:46pm

Re: Tyre/wheel sizes

Postby Darkman » 4 Nov 2019, 1:02pm

Crikey have I opened a can o' worms here.... :shock:

User avatar
Chris Jeggo
Posts: 196
Joined: 3 Jul 2010, 9:44am
Location: Woking

Re: Tyre/wheel sizes

Postby Chris Jeggo » 4 Nov 2019, 1:29pm

Yes, rubbery worms, some smooth, some knobbly.

Yes, as Brucey says.

In addition, there is a table of not-too-uncommon tyre sizes and their multifarious markings at
https://www.cyclinguk.org/cyclists-library/components/wheels-tyres/tyre-sizes, but note that some entries like 13/8 should be read as
1 3/8, i.e. one inch and three eighths.

scottg
Posts: 866
Joined: 10 Jan 2008, 8:44pm
Location: Highland Heights Kentucky,, USA

Re: Tyre/wheel sizes

Postby scottg » 4 Nov 2019, 1:32pm

AASHTA*...

https://www.sheldonbrown.com/tire-sizing.html


As Always Sheldon has the answer, plus I like the olde timey web page look,
9s era.
+++++++++++++++++++++++++
Deutsche Luftschiffahrts-AG
+++++++++++++++++++++++++

Darkman
Posts: 144
Joined: 30 Aug 2019, 8:46pm

Re: Tyre/wheel sizes

Postby Darkman » 4 Nov 2019, 1:40pm

Ooh, reminds me of Geocities! :mrgreen:

So the bottom line is, 28" and 29" tyres are both 622mm??

700C is a French sizing term, but the same.

Therefore, any of the above should fit my rims (within reason re width)... :?: :?

Brucey
Posts: 42167
Joined: 4 Jan 2012, 6:25pm

Re: Tyre/wheel sizes

Postby Brucey » 4 Nov 2019, 2:01pm

Darkman wrote:Ooh, reminds me of Geocities! :mrgreen:

So the bottom line is, 28" and 29" tyres are both 622mm??

700C is a French sizing term, but the same.

Therefore, any of the above should fit my rims (within reason re width)... :?: :?


28" = 622, always....? oh no, if only it were that simple, I would have said so.

The reason why some 700C tyres are marked 28" is because they pinched one of Mr Dunlop's many 28" tyre/rim sizes. That still leaves plenty of others. For example 28" x 1-1/2" is a size which is still used and fits to a 635mm rim, so ~40-635 in ISO. There are other (now rarer) sizes too, which in some cases the French also pinched and called 700A, 700B, 700D and so forth, all using different rim diameters. 28 x 1-1/2" tyres are 700B by the way.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Darkman
Posts: 144
Joined: 30 Aug 2019, 8:46pm

Re: Tyre/wheel sizes

Postby Darkman » 4 Nov 2019, 2:12pm

I think I might take up rowing.... :(

sukuinage
Posts: 96
Joined: 20 May 2008, 1:18pm
Location: Germany

Re: Tyre/wheel sizes

Postby sukuinage » 4 Nov 2019, 2:42pm

Brucey wrote:
Darkman wrote:Ooh, reminds me of Geocities! :mrgreen:

So the bottom line is, 28" and 29" tyres are both 622mm??

700C is a French sizing term, but the same.

Therefore, any of the above should fit my rims (within reason re width)... :?: :?


28" = 622, always....? oh no, if only it were that simple, I would have said so.

The reason why some 700C tyres are marked 28" is because they pinched one of Mr Dunlop's many 28" tyre/rim sizes. That still leaves plenty of others. For example 28" x 1-1/2" is a size which is still used and fits to a 635mm rim, so ~40-635 in ISO. There are other (now rarer) sizes too, which in some cases the French also pinched and called 700A, 700B, 700D and so forth, all using different rim diameters. 28 x 1-1/2" tyres are 700B by the way.

cheers


Whilst Brucey is, of course correct, the "usual" definition of 28" (certainly in Germany) is 700C, ETRTO 622 and it's unlikely you'd encounter anything different which wasn't clearly identified.
The new MTB and gravel bikes, as previously stated now use 29" for 700C, usually with decimal imperial sizing e.g. 1.75 or 2.1. They may well be marked on the tyre with the metric dimensions e.g. 622x54
To get back to the original question I would say most 700C (622mm) tyres fit a 20mm internal rim and certainly a 1.75 could be used to replace a 2.1. There is no difference between wired and folding bead as far as fitting is concerned but be aware that, despite the standard there can be big differences in ease of fitting between certain tyre/ rim combinations

hamster
Posts: 3715
Joined: 2 Feb 2007, 12:42pm

Re: Tyre/wheel sizes

Postby hamster » 4 Nov 2019, 5:11pm

[quote="sukuinage"There is no difference between wired and folding bead as far as fitting is concerned but be aware that, despite the standard there can be big differences in ease of fitting between certain tyre/ rim combinations[/quote]

Especially with tubeless tyres on very shallow rims.

Brucey
Posts: 42167
Joined: 4 Jan 2012, 6:25pm

Re: Tyre/wheel sizes

Postby Brucey » 4 Nov 2019, 6:00pm

sukuinage wrote:
Whilst Brucey is, of course correct, the "usual" definition of 28" (certainly in Germany) is 700C, ETRTO 622 and it's unlikely you'd encounter anything different which wasn't clearly identified.


ha! You would be amazed at how many 28 x 1-1/2" wheeled bikes there are knocking around, and how many times folk leave the bike shop with the wrong tyres.... old tyres tend to lose any markings they might have once had when new, and rims are often not marked in any way. 700A (642) and 700D (587) sizes are not quite extinct either. The only way to be sure is to try the tyre on the rim.

Just to add even more fun there are sizes that are still used in parts of scandinavia like 27 x 1-1/2". These tyres fit onto 609mm rims. I've been fiddling around with bikes for decades (in the UK) and I have only ever seen one wheel that size, and no tyres.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

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Chris Jeggo
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Location: Woking

Re: Tyre/wheel sizes

Postby Chris Jeggo » 4 Nov 2019, 9:54pm

Brucey has mentioned ISO bead seat diameters of 584 and 590 above. These sizes were common in the UK for many years, but under another name. 26" wheels were in the majority, and their overall diameter, including the tyre, was pretty close to that nominal 26". The two common sizes were 26 x 1-3/8" and 26 x 1-1/4", but a tyre so labelled would only fit on a rim identically labelled. So we had a standard wheel diameter, which has a certain logic, but not a standard rim size, which was a bit of a pain. The difference of 1/8" in tyre width gave a difference of about 3mm in tyre height so a difference of a mere 6mm in rim diameter, as above. The French had a similar system - a 700 wheel was 700mm in overall diameter, not far off 28", and there were four different tyre widths labelled A, B,C and D, so there were four different rim sizes. To add to the confusion the Americans went their own way.

Nowadays we know better - rim diameter is more important than wheel diameter because we like to change tyre widths without buying new wheels. Except that we finish up buying new sizes anyway because the cycle industry makes it gradually more difficult not to by exploiting built-in obsolescence, sometimes masquerading as fashion, or for spurious technical reasons. There was nothing wrong with 27 x 1-1/4" (ISO 630), but 700C, only 8mm smaller (ISO 622), has taken over. Something similar has taken place in recent years in MTB tyres - a 559mm rim became a well established standard, and then became obsolescent in just a few recent years.

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The utility cyclist
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Re: Tyre/wheel sizes

Postby The utility cyclist » 4 Nov 2019, 11:06pm

Darkman wrote:I think I might take up rowing.... :(

Sadly typically over complicated answers from the posters here to a very simple question.

Yes you can fit narrower tyres of the same size 28 or 622 or 700C whichever you want to use to your rims, even down to 28mm on those rims.

Folding tyres, they will fit fine, they tend to be a bit lighter and roll nicer, also they are a few quid more expensive.

If you're not going off road that much then you don't really need much if any tread pattern, the less tread pattern the quicker you'll be in the road but will have less grip on say grass/mud/loose surfaces, the trick is getting an optimum for what you're going to use the bike the most for which is a compromise but that's always the case so don't sweat it.

So, as an example these will fit the profile you're looking for, not outright slick road tyres and aren't folding but could be an inexpensive solution at £19 for the pair delivered
https://www.ebay.co.uk/itm/1-Pair-Schwa ... Swdb5duuBG
or these. a pair with two tubes for £30 delivered (£26.50 without) which are a bit lighter and probably a bit faster rolling https://www.ebay.co.uk/itm/Schwalbe-Sil ... iIZeMt2NXg
or if you want something ridiculously fast on the road but might need to be a bit more careful off road then buy these https://www.ebay.co.uk/itm/Panaracer-Gr ... Sw7pldUgr3

tim-b
Posts: 1674
Joined: 10 Oct 2009, 8:20am

Re: Tyre/wheel sizes

Postby tim-b » 5 Nov 2019, 5:31am

Hi
Sadly typically over complicated answers from the posters here to a very simple question.

Agreed. Work through each of the four sections here (link) and all should become as clear as cycling "standards" can be. The second section is Schwalbe-centric (as you'd expect) but useful nonetheless
Folding tyres, they will fit fine, they tend to be a bit lighter and roll nicer, also they are a few quid more expensive.
If you're not going off road that much then you don't really need much if any tread pattern, the less tread pattern the quicker you'll be in the road but will have less grip on say grass/mud/loose surfaces, the trick is getting an optimum for what you're going to use the bike the most for which is a compromise but that's always the case so don't sweat it.

Simples
Regards
tim-b
~~~~¯\(ツ)/¯~~~~