A friend asked me why I don´t fit 29er MTB tires on my CX. I told him, that I don´t think they will fit, but since I don´t have any I haven´t tried. Anyone did?

Depends on your definition of a 29er tyre? CX tyres are 622 ERTO which is the same as 29er - but the two key factors are frame clearances and rim width. There aren't many CX frames that will allow you to fit a tyre wider than 40mm plus and fitting a 40mm tyre on a 20mm 700c rim is simply asking for trouble as the tyre bead simply pops-off the rim. Obviously, using a wider rim like a Velocity A23 allows you to run wider tyres safely.

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Just ride

Guess u are right... Will stick w the old griffo´s

CruX with Panracer Fire Cross 45mm with Aksium - No problem

Pretty heavy!

I have 1.75 Smart Sams on my Cube X-race. Its true they are heavier but lots of fun, they give a bit more confidence to go a bit harder through some terrain.

I used a Bontrager Jones XR 1.8 on the front of my Stevens cross bike, fit great and was fun on the MTB trails!!

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to go faster....just pedal harder!