I found that my newly purchased WTB Nanoraptor 29" tyre doesn’t fit on my 28" rim. 
It is too small for the rim. The rim says “28 x 11/y” on it where y is unreadable. The original tyre has the size “28 x 1 1/2” on it.
I wonder if I’ve got some odd, old fashioned or non-standard 28" rim? Can anyone help me out here in identifying which rim size I’ve got?
Tony
I’m confused. How can a 29" tyre be too small for a 28" rim? Are most 29" tyres meant to fit on 28" rims? Then why would they have different sizes?
Andrew
hmmm that sux. could it be a 27" rim? those are a little bigger than 28"s.
I think that 28" rims are a different size to 700c rims, maybe 29" tyres are designed to fit 700c’s.
Rim sizes are a pain, it’d make things a lot easier if the stated size matched the physical dimensions: -
my 20" rim measures 16.5"
my 24" rim is 20.5"
my 700c(28"?) is 24.5"
no 28 and 700C are usually the same thing, and 29’s are made to them, or at least the 622mm versians.
Yeah, no kidding the rim and tire size thing is a source of confusion for me as well. Today I went to MEC to try get a spare tube for my new 29’er. What turmoil I created.
First of all there were all these tubes with presta valves, well I passed on those as I can’t be bothered with the extra hassle of the prestas.
Then there were bins with metric labels for tubes that were packaged with labels in standard measurements. Once I added to the mix the sales clerk who was trying to make sense of me telling him I had a 29’er uni with a 700 cm wheel that needed a tube for a ‘fairly narrow’ road tire… mayhem ensued.
When I finally arrived home with the 700 X 28 spare tube for my uni, my brother, who knows nothing about uni’s but is a pretty keen cyclist, informed me that I really should have snagged the 700 X 35!
I really don’t know what this all means… except that I think I shall just have to pedal back to MEC tomorrow and get the other tube… cause, well, if nothing else, I usually listen to my brother… not matter what the numbers say on the package!
Erin
It’s a 28x1+1/2 rim, which is really ancient technology used on dutch style bikes with rod brakes. The bead diameter is 635mm, which is too far off from the standard of 622mm to fit the tyres.
Okay, what’s happened here is you’ve been sold a uni with an old 28" rim on it. These are like 50 years out of date (pre decent brakes) bicycle technology. Is it a very old unicycle, or one that’s been sitting in a shop for 20 years? No-one should sell these size rims any more as everyone has standardized on 700c rims for 28/29 riding.
The good news is you can get spare tyres from a shop specialising in old european bike bits, some shops may have one 28x1+1/2 tyre hanging around for people with ancient road touring bikes. The other good news is that the rim size is bigger than a 700c, so you might have okay tyre clearance if you rebuilt the wheel with a decent rim.
The bad news is that your rim size is obsolete, the standard 28" / 29" size nowadays is the 700c size, so you can’t put any of the more pimpy tyres or off-road tyres on it. You might be able to pick up an ancient cyclocross tyre for it if you’re lucky. The other bad news is that rebuilding the rim would need a whole new set of spokes unless you luck out and can build with one more crossing or something.
Note to anyone buying a 28" or 29" unicycle, before you buy, always check that it is a 700c rim (622mm bead diameter) which you are buying as anything else is a con.
Joe
Yes, my unicycle is very old and of dubious origin. I bought it from a bike shop mechanic who made it from various bits he found. The rim is very heavy and made of steel. The edges are rolled over to form a lip to hold the tyre bead. As it is 635mm diameter (bead to bead) it won’t fit 28/29" tyres which are 622mm.
Hurrah for Sheldon Brown! This guy is a fantastic source of information. Thanks for the link, Joe.
The upshot is that I’m getting the wheel rebuilt with the widest 700C rim the bike shop had: a Mavic designed for touring bikes.
Joe, I’m not sure what you mean by “rebuilding the rim would need a whole new set of spokes unless you luck out and can build with one more crossing or something.” The new rim has the same number of spoke holes as the original, so that’s no problem. While you can get away with re-using old spokes, I thought it was a good idea to use new spokes when rebuilding a wheel. At least that’s what bike shops will tell you. Not sure what the reasoning is, though.
Erin - I think 700 x 35 would be the inner tube size of choice for a 29" tyre without buying an inner specifically designed for a 29"er. The 700 x 35 looks very skinny compared to the volume of the 29" tyre, but it will blow up OK. 29"er specific inners are expensive (NZD$22 = USD$11 apprx) and I’m not convinced that they’re necessary.
Tony
All bike shops I’ve ever had wheels built at have refused to use the old spokes.
When asked why they’ve muttered something about the spokes being under different tensions in an old wheel and hence a new wheel built with old spokes will never be as strong.
Anyone got a better/fuller explanation than this? Is the real reason bike shops want to sell more spokes (or maybe it is easier to build a wheel with new spokes)?
somtimes using the same spokes is perfectly ok. bike shops on the other hand dont want to spend the labor time unthreading and extracting each spoke so its mostly a job for the “do it yourselfer”
What’s wrong with Presta’s huh? Beats a car valve anyday, IMHO, especially on narrow rims.
Ken
(presta-boy)