I'm sure this has been asked before but I have a 2003 62 cm Jamis Aurora I'm very comfortable with. It has an effective top tube length of 590 with a 72.5 head tube angle and 72 seat tube angle. I've put together a 62 Surly LHT with an effective top tube length of 610 and 71.5 head tube angle and 72 seat tube. I put a 120 stem on the Surly which the same I have on the Jamis. The Surly isn't as comfortable, I get shoulder fatigue after about 1/2 hour. I'm thinking I need to change the stem length on the Surly to 100 which to me would be the same as the combo on the Jamis (590 + 120 = 710 & 610 + 100 = 710). Does doing this make sense, is that how it works? I run my bar height on the same on both. Thanks

And So? get more stems and try them .. maybe your cities bike shops have several for you to try?

varieties in length and angle are amongst your options ... and stem raisers.

divide top reach/setback at a plumb line over BB axis..

done enough push & sit-ups to support your upper body better, by strengthening the core supporting muscles ?







...

I can always do more upper body work, especially at my age. I may just go with the shorter stem length and see how it feels. My Jamis is very comfortable on long rides, I just want the Surly to feel the same way.

Well this may not be addressing the question or flat out wrong way to approach this, but you can try this link:

Enter the head angle of the Jamis with current stem angle and length. Do the same with the Surly keeping in mind the difference in effective top tube length. Thus you will take into consideration the head tube angle. Also, do you know the stem angle? Keeping in mind head tube angle, stem angle and length should help you mimic the Jamis position. Again, I don't really know what I am talking about and I am sure smarter and more experience folks will chime in.

Sorry I just looked at the link I posted again. It may not help too much as this is comparing stems on the same bike (thus having the same head tube angle). You may have to resort to pencil, paper and old school geometry to determine how long of a stem and at what angle to use to duplicate the Jamis

No, not head tube angle. It is seat tube angle that makes a difference. Head tube angle makes a difference of a couple of millimeters in bar height. Seat tube angle makes a difference of roughly a cm per degree. Think about it. A steeper seat tube means the top tube starts further forward and hence the whole headtube, stem and handlebars are that much further forward.

Edit: Same seat tube angle on the bikes. Yes, the 100 stem ought to get you in very close. From there you can add or subtract stack spacers. (I find the ratio of 1/2 cm spacer = 1 cm less (horizontal) stem length for a near identical fit and comfort for me.) I'm hoping you haven't cut the steerer yet.

Ben

Nope, I left the steerer uncut precisely for this reason. Thanks!

Yes you are correct, wasn't think through this very well. Thanks for clearing this up.

Plug all of your numbers in here. The calculations are centered around the bottom bracket so you can transfer fit from one bike to another pretty easily.


-Kedosto

Thanks, awesome tool, I'll see what it tells me.

Start by moving your Surly saddle back to the limit of travel. Ride that and see how it feels. No cost.