PTbiker

According to https://sheldonbrown.com/tire-sizing.html#width, my 559-21 rim can have a 44-559 tire (up to 50-559). However, another website says that my rim can only fit 47/54-559 tires.

Is it safe to use a 44mm wide tire on a 21mm wide mountain bike rim?



Source: sheldonbrown.com



Source: https://www.wtb.com/pages/tire-rim-fit-chart

jadmt

I have Velocity Dyad 26's which are 18.6mm inner width 24mm outer and have many miles with 37mm and 41 mm panaracers and also 53mm (RH rat trap pass 26x2.3) tires and all do great. also run those same tires on a some mavic 231 and 217's with no issues either.

FBinNY 

There's plenty of latitude in rim/tire width ratios. The published guidelines are just that "guidelines" and can safely be taken with a grain (or more) of salt.

It's a question of purpose and desired benefits vs.performance. Generally overly wide tires have a greater tendency to flex sideways (wallow) when cornering, and increased risk of "snake bike" flats, especially at low pressures. OTOH- narrower tires tend to offer harsher rides and possibly lower traction at higher pressures.

So, think about what you're trying to achieve, then be ready to fine tune inflation pressure to maximize the benefits while minimizing drawbacks.

Iride01 

Sheldon's recommendations are only generalizations that you can use when you have no better information. Just guidance only and not regulations that you must follow or else you die.

The other page you linked seems to be from someone that is selling a specific brand of tire. You might should go by their recommendation if you are using their tire. However you might get away with going outside theirs or even Sheldon's recommendations if you aren't putting your tires through H E double toothpicks every time you ride.

Bill Kapaun

I'm more conservative then Sheldon and I wouldn't have any problem.
I presume you mean inner width? That's usually "about" 5-6mm less than outer.

Hondo6

I think you're misreading the WTB chart. And you didn't include both WTB charts - they have a different chart for urban/hybrid/cyclocross/gravel/road plus/adventure tires.



There's considerable overlap between these two WTB charts.

Per the WTB site, the solid black blocks on the WTB charts are recommended for "optimal performance". Those with dots are "compatible". Only those that are solid light grey are "not recommended" by WTB.

After looking at both WTB charts, it appears that WTB considers anything between 30mm and 54mm tires to provide "optimal performance" with a 21mm interior width rim and that WTB considers 28mm and 55mm to 65mm tires to be "compatible" with a 21mm interior width rim. This agrees fairly well with the late Sheldon Brown's info (Brown's is more conservative); the two sources are fairly consistent.

In both cases, a 44mm tire appears to be considered perfectly acceptable for a 21mm interior width rim.

cyccommute 

More like a truckload of salt. My mountain bikes are using Mavic XC717 rims that have a 17mm internal width. I use 50 to 55 mm tires on those rims without issue and have regularly for more than 20 years. On my touring bike I have Velocity Deep V which have a 13mm internal width on which I use 35 to 38mm tires. Again, no issues.

The “guidelines” aren’t!

icemilkcoffee 

A lot of the Mavic MTB UST rims have 17-19mm internal widths. If you go by WTB's guideline, you pretty much can't run any MTB tires on these MTB specific rims.

PTbiker

The problem is that I thought I had an "MTB only rim" (since it's from a mountain bike), but what matters is where I ride. So, in conclusion, I can use 30 to 50mm tires, as I've been riding on road only. If I use my bike for MTB, I should use at least a 47mm tire to protect the rim, right?

One more chart:

Source: https://www.schwalbe.com/en/reifenmasse

Hondo6

I'm road only when it comes to riding, so I'll defer to those with MTB experience. But since I understand that gravel, cyclocross, and adventure riding often involves riding conditions somewhat similar to less arduous mountain trail riding, I'd guess you'd be OK with somewhat smaller tires than 47mm.

How much smaller? Dunno. Maybe someone with more expertise in the relevant riding discipline(s) can give an informed answer based on experience?

djb

Ive ridden with 2.5 inch mountain bike tires on 21mm internal width rims AND on 17mm internal rims.
Ive also ridden and toured with a fairly hefty load on some long trips using the same 17mm internal width rims with 2in slick tires, and at the proper pressure, this combination was rock solid. At lower pressures over super rough roads or loose surfaces, the bike handled fine, and at higher pressures (we're talking 42 psi front, 45 psi rear) my loaded touring bike handled extremely well cornering rather fast. I had four panniers, a rackpack on top of the rear panniers and a handlebar bag, and I was carrying a minimum of 45lbs, often more with more water, food etc.

Lombard

^^^This.^^^ Those ratings are very conservative. Nobody will die a fiery death if you go outside that range by a few mm here and there. I too used to have 17mm rims on my mountain bike with 55mm tires. At the other end, riders now run 21mm rims with 25mm tires on their road bikes.

DT Swiss has a chart on their website that is a better guideline.

Iride01 

If you are looking for the utmost in safety. And if you are going to go by recommendations, then go by the recommendation of the tire manufacturer for the tire you are looking at. And if they also specify a specific model of rim then use that too. To go by any others recommendation would seem silly if utmost safety is your concern.

However, many of us would just put the size tire we wish to use on the rim and see if it works for us. If it does it does, if it don't, then we change to something else.

And unless you are riding your bike like they do in the x-games or some of those wild BMX races, then you probably won't be pushing the limits with any thing.

SkinGriz

^ This.

Bike tires are bias ply. Bias ply tires can get away with pretty extreme differences in rim widths.

If you were taking corners downhill at 50mph it might matter.

SkinGriz

If the worst you’re doing is gravel or fire road type of dirt roads I bet you can get away with 35mm. If you’re doing something where you know the tire will hit a sharp hard edge like a boulder or tree root then bigger tires can help.

grumpus

Tyres don't protect rims, it's air that protects rims (unless you're using a rim insert). You get better control on loose surfaces by running at lower pressure so you need a wider tyre to compensate for that lower pressure. You need the same support from the tyre whether it's narrow and hard or wide and soft: tyre pressure * tyre contact area = force keeping the rim off the floor.

Lombard

135 years later, Mr. Dunlop's invention still lives!

FBinNY 

Hmmmmmmmm! an opportunity for thought.

Interesting, so which is it? and how? Think about that and sort it out in your own head


Kind of chicken and egg here. Does gravel call for lower pressure? Why? Or do we need wider tires to "float" rather than furrowing on dirt, gravel, or sand? and the lower pressure follows form that change?

I offer both questions not to correct Grumpus, and actually thank him for setting this post up for me. My intent is to get people to think about how systems work on systems rather than individual elements within those systems.

IMO - engineering is like impressionist art. You have to step back and look at the big picture to appreciate the beauty.


PLEASE do not post answers to the questions above. My intent is to stimulate thought and thereby improve resistance to dogma.

Camilo

You should always research until you find an expert or recommendation you agree with. Plenty of room for that in tire-rim compatibility charts.