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expedition frame sizing - coming from touring frame

nickm321nickm321 Posts: 33
edited January 2015 in Tour & expedition
Hi all,
I've currently got a 700c 531st steel framed touring bike. The rims are worn out, and it can't take more than 32mm wide tyres, so I'm looking to migrate to a 26" steel mountain bike frame with cable disc brakes.

At the moment I'm trying to work out the geometry to best get a comfortable fit, translating my road bike sizes. My road bikes all have a 56cm c-c effective top tube, which feels right for me (5'10"). Having looked at the modern Orange P7 frame geometry, the model with that effective top tube is the smallest, the 15". This seems odd as my mountain bike (17" Giant Trance) feels right as a mountain bike, but I run a 50mm stem on that! I was wondering if anyone had any thoughts on translating road to mtb geometry? How much effect does the seat tube angle have, as I'm sure a slacker angle that might be on an mtb could make the distance from bum to bars longer for the same effective top tube length?

Here's the orange P7 geometry chart: (current models have much more compact geometry, the older ones seem more traditional. I couldn't find a geometry chart for older ones, and I don't think there are many of the older ones with disc mounts).

P7_geo.png

Thanks in advance!
Nick.

Posts

  • MichaelWMichaelW Posts: 2,226
    Total reach includes stem and bars, from saddle to hand-grip. Flat bars have less reach, so for the total reach you need a longer ETT.
  • andymillerandymiller Posts: 2,856
    nickm321 wrote:
    At the moment I'm trying to work out the geometry to best get a comfortable fit, translating my road bike sizes. My road bikes all have a 56cm c-c effective top tube, which feels right for me (5'10"). Having looked at the modern Orange P7 frame geometry, the model with that effective top tube is the smallest, the 15". This seems odd as my mountain bike (17" Giant Trance) feels right as a mountain bike, but I run a 50mm stem on that! I was wondering if anyone had any thoughts on translating road to mtb geometry?

    It looks to me that you are in the territory of either the small frame with a longer stem or the medium frame with a shorter stem.

    I'd use as the benchmark the ETT plus the length of the stem on the bikes you feel comfortable on (including the Giant).

    The 15" would require quite a long seatpost, so I'd check that you can get the total length you need before deciding.
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