Testing a oversized tyre on a rim

[slogfester]

I have Rigida Andra 30 (559-19 [mm]) rims which according to Sheldon Brown's table (http://sheldonbrown.com/tire-sizing.html) take 28-44 mm tyre widths. Compare with Rigida (now Ryde) website (http://www.ryde.nl/en/products?product=46) that says these rims will take 28-62 mm! Ummm.....
The wheels (made by Van Nicholas) came shipped with 26 x 2 inch (50 mm) Big Apples and I have run and heavy toured on 26 x 1.75 inch (c. 44 mm) Marathon Plus without issue. But I wanna go bigger and tougher. Roarrrrr....

I have just received some 26 x 2.0 Schwalbe Marathon Mondials. Wow, the things are huge beasts! My first thought was I only need 1.75, but they don't do them in 26 inch Anyway, after some massaging the tyres have fitted on the rims but I have to say it was a bit of squeeze and they kept trying to pop out when fitting. Quick ride round the block and they felt OK. Need to be 100% sure...

Will this work? How can I best test them to see if they are not going to roll off or anything else critical? Low pressure or high pressure? How best to push them to their limit? What should I be looking for?

Thanks

[Brucey]

any fat tyre on a skinny rim will probably roll around on the rim during hard cornering but this will objectively vary with cornering style, load, and tyre pressure, and subjectively with a load of other things too. I would suggest that you suck it and see, and/or ask VN.

Another thing to look out for is that wider tyres will load the rim more at the same tyre pressure. One limiting factor is the pressure at which the rim will be liable to split. If your rims don't have a max pressure rating that varies with tyre section (but do have one for a fixed tyre section), look up the specs for comparable Mavic rims and adjust max pressure in a similar fashion allowing for changes in tyre width.

Having said all this I can't see that two tyres of similar width from the same maker will be all that different from one another; have you actually measured the fitted tyre width in each case?

cheers

[Bicycler]

I think that, sadly, Sheldon's website is a bit outdated on this one.

Both Schwalbe and Ryde listtyres widths up to 62mm as suitable for 19mm rims. Schwalbe refer to the recommendations of the The European Tyre and Rim Technical Organisation (ETRTO):

Furthermore, the tire width must match the rim width. The following table shows possible combinations of tire widths and rim widths according to ETRTO.

Since 2006, the combination of extra wide tires and narrow 17C and 19C rims is officially approved by ETRTO. This just caught up with reality, because this combination has already been an every day occurance in MTBs and Balloonbikes for many years and has not caused any problems.

Often the use of a wider rim is useful because it brings additional stability to the tire. The tire pressure can be reduced slightly before the stability becomes “spongy”.

The referred to table is in this link under "which tyre fits which rim?" http://www.schwalbe.com/gb/reifenmasse.html

I've used 2.25" (60mm) Marathon Extremes and 2.15 (55mm) folding Marathon Mondials on my 19mm rims and they were okay. I decided the tyres were overkill and went back down to 2" (50mm) ordinary Marathons. I shared Brucey's concern about using the 60mm at high pressure but I also realised I didn't need the pressure very high on the 60mm tyre. I was using it for a bit of off-road though so I wasn't pumping it up to it's limit. I guess if I was always using very wide tyres I would have bought a wider rimmed wheel. I bet most tourists using the 2" Mondials are using 19mm rims (21+ are a bit more specialised) - you'll be fine