I have a Trek FX7.3, frame size 22.5 inches. I'm looking to swap the frame out for a Surly Cross Check. Has anyone done a similar build? Also, what frame size would you recommend that I go for?

Just an idea at the moment - I'm not too sure how compatible more of my parts would be with the Cross Check frame.


  • You're likely to have a lot of incompatible parts. The headset and seat post for sure. Possibly the fork, depending on whether the steer tube has been cut too short. Maybe the bottom bracket too if the shells are different and he bb doesn't accommodate spacers, which could mean the crankset as well. It's kind of hard to tell from just the specs. If all of that stuff was incompatible, you'd be better off just buying a complete Cross Check and selling the Trek.
    – jimchristie
    Apr 22, 2016 at 11:22
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    I would recommend you save your money until you can buy the complete bike. That way you have a trek as a spare bike, or you can sell it as a complete bike to offset some of the cost.
    – Criggie
    Apr 23, 2016 at 0:41

1 Answer 1


You could compare the geometries of the FX and the Cross Check. Matching the standover, 56cm matches. Comparing the effective top tube lengths, between 58cm and 60cm match.

Bottom line the geometries are different.

On another note, the FX doesn't seem to be a particularly high-end bike, so purchasing a complete Surly could possibly provide more economical than moving the parts to a new frame.

  • Thanks for the reply, You raise a good point - whether it's worth me moving across everything from the Trek to the new Surly frame. Bottom line is a don't have the money to buy a built Surly so I figured I could get the frame and, over time I'll swap things out. i.e. I'll get better wheels, derailleur, brakes etc. etc.
    – old jimmy
    Apr 22, 2016 at 11:15
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    86cm sounds like a typo. In my opinion, with sloping top tube standover height is not useful measurement. The ones that matter most are top tube length and fork length + head tube length + headset stack height. Trek does not specify their fork length but it looks longer than Surly's, all put together 58cm and 60cm are probably close.
    – ojs
    Apr 22, 2016 at 15:39
  • Thanks for the replies! I'm definitely reflecting on whether simply moving all the Trek parts over onto a new Cross Check frame is a viable option at this point. They are certainly very different beasts in terms of geometry, thats for sure.
    – old jimmy
    Apr 22, 2016 at 21:59
  • @oldjimmy, keep in mind that a complete bike usually costs maybe* 30% less than purchasing the parts and assembling it yourself**. ///////////// * - a rough estimate off the top of my head, don't trust the number ** - id est without the cost for a bike shop to assemble the bike
    – Vorac
    Apr 23, 2016 at 5:27

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