After riding my Scott Scale 29er for some time I went for a ride on my Scott Spark 26" and was really surprised how clumsy the 26" wheels felt between roots - almost like I got stuck between each roots so I decided to try and convert to 650B/27.5".

The rear is fine - lots of room:


The fork is a DT Swiss XRC RL100 WC and I have a contact that can modify the fork to fit a 650B/27.5 wheel but after mounting the front wheels I'm a little bit confused about the need for a modification. There is room - the sides is no problem but I'm a little worried about the top of the brake arch. Would you ride this?


The bike looks good but damn the 620mm handlebars feels narrow after spending some time with a 700mm handlebars


I will ofcourse mount some pedals before I ride the bike

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How muddy is it where you ride? If a big piece of flint got jammed in some mud on the tyre at speed your fork would not be a happy chappy. I don't know how realistic that is though.

That looks tight----especially for mud clearance----too bad you can't strengthen the top of the fork bridge and then carve out a more acceptable arch.

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There is mud - maybe I will just do another conversion to 650B/only dry trails bike

No serious - I know the mud will add some height to the tire but the tire is inflated to 40 psi on the picture and I never ride with this much pressure - maybe 25-28 psi so with me on the bike this must reduce with height. I read somewhere that + 5mm should be fine - don't know if that is enough?!

If I do the modification of the fork arch that is exactly what will happen - I know the carbon guy who will carve some material of the bottom and reinforce with top. He has done with before and it works fine. I'm just wondering if it's nessesary?!

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The tire is a Schwalbe Rocket Ron EVO 2.1" and the rims is a BOR XMD 333 650B.

From between the knobs to the underside of the fork arch is about 10 mm and from the top of the knobs to the underside of the arch is about 5-6 mm. Fully compressed there is no problem with the arch.





I think it might be alright for riding.

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Maybe some heli-tape layers, to protect from the myriads of small pebbles and dust, that orbits a tire in speed.
Interesting experiment, up-sizing the Wheels !
Please report how it works out.

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You are probably right - that would be a good idea with some protection tape.

Also forgot the most important part:


Without pedals and with a heavy rear qr

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Wow! I've been wanting to convert my Spark too! I have read that someone did a conversion and I was worried about the fork clearance and have been waiting for someone to show pictures. Thanks a lot for these pictures. Now to come up with some money for new 650B wheels...

Mads, could you check rear tire clearance with seat tube at full compression of the rear suspension? Thanks!

A Fox fork at the front will give more clearance

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Scott Foil Di2 2012
Scott Scale 35 2010

Seattube clearance fully compressed - no problem!


Talked with the carbon/fork guy today - he suggested to try it. He would ride it!

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I ride a 26" Fox Fork w/ a Nobby Nic 650b x 2.35" with about the same amount of clearance. I get the occasional leaf that gets stuck in there and buzzes, but other than that, it's been great.

Hey Ricerocket - thank you very much for your comment. Makes me more calm - now it's just to testride it

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The main issue to be concerned about is the bottom of the crown touching the tire. You need to let all the air out of the fork and compress it all the way to check it and make sure it doesn't hit! The last thing you want is for the fork to bottom out and completely stop the front wheel, sending you over the bars!

Did that - picture also posted

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Some people have been stuffing some huge tyres into some Fox and RS forks recently - not exactly a huge amount of breathing room but no catastrophic stories - yet!

If you're really worried, have any decent suspension shop make you up a travel spacer and you'll never have any problems.