29+ tyres and 'normal' rims

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This topic has 5 replies, 5 voices, and was last updated 8 years ago by ajantom.

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29+ tyres and 'normal' rims
jimfrandisco
Free Member

I know there’s lots about this all over the internet – but struggling to find out just the very basics.
I know 29+ tyres like the knard are designed for rims 35mm+ and running them on narrow rims can mean they fold over or need higher pressure…but what do you class as a ‘narrow’ rim, and is that internal or external rim width?
Eventually i’ll change rim, but in the short term looking for a larger tyre for more comfort on a rigid bike, which is pointless if i have to still run it at higher pressures.
cheers

Posted 8 years ago

cokie
Full Member

I’ve seen someone run a Knard on a Stans Crest rim 😯 !
It works in the sense that it doesn’t burp and rolls, but it loses all of it’s benefits- by pinching the tyre you don’t get the large footprint and it make the tyre an odd shape.

Posted 8 years ago

mos
Full Member

The extra pressure needed to stop it from rolling off the rim kind of negates some of the benefits such as comfort. Plus they can get extra bouncy in the rough.

Posted 8 years ago

jimfrandisco
Free Member

Thanks mos/cokie – yep, that’s what i expected.
So without a 35mm+ rim there’s just no point bothering with a + tyre.

Posted 8 years ago

thisisnotaspoon
Free Member

I think the rule of thumb is a minimum 2:1 on tyre size to rim width with fat bikes (4″ tyre on a 50mm rim etc). So a 3″ tyre is going to struggle on anything narrower than 35-40mm.

Posted 8 years ago

ajantom
Full Member

I have been running a Knard on the back of my Krampus on a Pacenti DL31 (31mm outer, about 27mm inner) for a year.
Maybe have to put a couple of PSI more in it – I run the front on a 50mm rim at 13/14 PSI, so the rear is at 15/16 ish. Had zero problems with roll, and comfort is fine.

Posted 8 years ago