Rim width to tire fitment chart.

[spinningmagnets]

You can find these charts very easily, but I haven't found one that authoritatively shows the fatter tires that are popular with E-bikers. such as the 2.4-inch wide Cyclops and 2.5-inch Hookworms (61mm and 64mm)

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Here is the Surly tire-to-rim sizing chart for the "fat tire" 26 X 3.7...up to 26 X 4.7 inches, so...this still leaves the tires between and 2.2 and 3.7-inches

http://surlybikes.com/uploads/downloads/SUR_Tire_Geometries.pdf
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random bits of info found listed here:
44mm is about as narrow as you can go and still run a 26 x 3.8 tire

one inch is 25.4mm

 

[amberwolf]

this page is about motorcycle/car/truck tires, but may have info applicable to us
http://www.4crawler.com/Diesel/Tires.shtml

 

[Drunkskunk]

We should make a chart.

My rule of thumb is the maximum tire size should be no more than twice the bead width + 5%. But on small tires you can add another 10%. That's because the thickness of the sidewalls remains a constant, but it proportional higher on a smaller tire. If the sidewall is 3mm thick on each side, and the tire is 44mm wide ( 1.75") the sidewall is ~ 14% of the tire's thickness. But if the tire is 127mm wide (5.0"), the sidewall is 5% of the tire's thickness.
Therefore, A rim like the elsewhere-mentioned 19mm can go up to a 1.75" tire, but a big 5" tire would have a minimum of a 65mm rim.

It should be easy enough to make a spreadsheet of this. Sadly, I have no idea how.

 

[cal3thousand]

I run a 2.4" tire on a rim with 25mm inner width. I don't think I would go wider without a wider rim.

 

[MadRhino]

What fits, may be far from what's best. :wink:

 

[spinningmagnets]

thats also what I was hoping to get responses for...

What is "best"?...not necessarily what will fit. Tire pressure, and pinch-flats, handling on corners...dirt and street...so many variables

 

[Eclectic]

I tried a Cyclops (on the rear only) on a stock (IIRC) 25mm rim. It fit OK but it gave me a lot of problems so I went back to a 1.75.

The larger inner tube compressed the rim enough that all the spokes started coming loose in the middle of my 15 mile commute.

With the narrow rim, the tire was a couple of inches taller. The added diameter (on the rear) made the steering geometry a little twitchy and I was having problem reaching the ground with my feet. Slow off the line and did not handle as well in a corner.

The ride was a little bouncy.

On the up-side. I got run off the road @ 20 mph into some gravel and was able to come to a controlled stop.

 

[MadRhino]

thats also what I was hoping to get responses for...

What is "best"?...not necessarily what will fit. Tire pressure, and pinch-flats, handling on corners...dirt and street...so many variables

Try a 3.0 tire on a 65mm rim. You will love this on the street, and hard pack dirt. On lose or wet dirt, the rim need to be 2/3 of tire width, that is also the optimal all around ratio for a performance bike.

 

[spinningmagnets]

Thanks, MadRhino...It was looking like that was a good ratio from the chart (and projecting likely combos in the area that is not filled in yet), but...I was hoping to get verification from someone with experience first. Many common forks will accept a 3-inch tire (without going to a "fat" fork, but YMMV), so if we use a 3.0-inch tire in a 65mm wide rim as a target, the rest can be filled in.