Thorn Sherpa Mk2 Max Tyre Width

[CecilCunninghammer]

Hi there,

I inherited my dad's Thorn Sherpa (he’s not dead—he just upgraded to a Thorn Mercury Rohloff). I wanted to find out whether the Sherpa Mk2 would fit some Vittoria Mezcal 2.1-inch tyres. I can only find info on the Mk3 online. If anyone has experience with this tyre or a similar-width tyre on the Mk2 Sherpa, please let me know what your experience was! I’m planning to do some off-road touring and would love to fit the chunkiest tyres possible on the bike.

Many thanks,
Cecil

[mickeg]

I am not sure what version Sherpa I have, I bought the frame and fork from someone used in 2010.  But I think I recall concluding years ago that mine is a Mk III.  The seller said mine was a 2008.

The brochure on mine is from May 2009.  And it only refers to it as a Sherpa, no Mk designation.

I have run 50mm wide Schwalbe Dureme in front and on the rear 50mm Schwalbe Extreme while also had fenders (mudguards).

Photo attached from 2011.  Tires in the photo are Continental Town and Country 50mm.

I suspect 2.1 would be too wide on mine.  I think I was at the max with the tires in the photo.

If you can tell me the difference between Mk II and Mk III, I can tell you if my frame matches yours.

[RonS]

The first thread in the “Thorn General” section of the forum has a historical archive of Thorn brochures. Perhaps the info you need will be there if no forum members are able to assist.
Good luck and happy riding.

[CecilCunninghammer]

Thanks for your help mickeg and RonS!

From a Google search I found someone on this forum who said the mk3 has a bigger tyre clearance but I just wanted to confiirm that.

I will consult the archive of Thorn brochures in the Thorn General section!

[Andyb1]

I found that a 26 x 2.0 Dureme actually has a smaller wheel diameter than a 26 x 1.75 Marathon plus……
If you have the Sherpa to hand then it might be best to measure the fork width yourself.  Then only the diameter of the tyre to worry about.   If you have mudguards those will of course limit tyre sizes.  Brochure figures will probably be for a bike without mudguards.

[mickeg]

If your tire clearance is marginal at best, rim width could be a factor too.  Thorn has often used fairly narrow rims for wider tires, that may make the tire width a few mm narrower.  My Sherpa, I used wider rims than Thorn typically used.

[Danneaux]

I have two Sherpa Mk2 forks, one fitted to my DB Transporter, the other of a different offset in a box. When I'm home a bit later, I'll measure maximum clearance between the bare fork blades. I'll also take a look at clearance with my 26 x 2.0 labeled Innova Swiftor on the T-porter; as I recall, it is a bit wider than my 2.0 Duremes when inflated to the same pressure.

Remember, bike tires tend to have a 1:1 (1.0) aspect ratio, so a fatter tire will also be taller and have less clearance at the fork crown and chainstay/seatstay bridges, mostly a consideration if you also intend to run mudguards with adequate clearance. Fatter/taller tires can also affect standover and cornering clearance if either of those are marginal for your needs. As Andy pointed out, not all tires of the same labeled size have the same physical dimensions, including width or diameter.

A quick search of the archives brought this to light, hopefully helpful to you...
https://thorncyclesforum.co.uk/index.php?topic=6389.0
...perhaps even more helpful than me measuring a bare fork, as it is based on some practical experience with tires wider than mine?

Best, Dan.