Frame Sizing: Going from 26" to Fatbike

[Aushiker]

I am seeking advice on frame sizing. I currently have a Giant XTC 2 which is a large frame (chart below) and going by the Salsa Mukluk geometry it seems that my Giant XTC 2 falls between their medium and large frames. I also tried using Sheldon Brown (RIP) revisionist theory of bicycle sizing but that gives much the same result.



I also worked out my stack and reach measurements on the XTC which are a stack of 590 mm and reach of 460 mm which of course does not fit nicely with anything that Salsa has. The XTC top tube length is 610 mm.

My thinking is a medium Salsa Mukluk. Does this sound reasonable? Interestingly with Surly frames such as the ECR or Pugsley my XTC pretty much matches the ECR/Pugsley large frame.

The bike will be used mainly for fatbike loaded touring and also at times fitted out with 29er wheel set for more dirt road/black top touring. The bars will be Jones H-Bar Loop bars.



Thoughts?
Andrew

[eldavo]

I'm more concerned with standover offroad, I had a medium 17" fat bike frame previously and with uneven sand it was uncomfortably at the high end for standover.
On road I have frames up to large 58cm seat tube and 80cm standover, but am very glad to have a 16" small frame fat bike now.
On Australia Day I rode the beach in the afternoon with the tide coming in, with the bike floating between my legs after having to give up getting around some rocks, other times on uneven rocks stopping to figure out a line, it was fun instead of in the drink on the rocks, shaken.

[Mugglechops]

My old 26in hardtails ranged from 18-20in. My 29er is a 19 and my Fatbike is a 19.

If you are going to use it for touring a bigger frame allows you to use a bigger frame bag.

[RonK]

Given the quite short reach of the Salsa geometry, I think you should choose the large frame. You may even need a setback seatpost, which seems common on many Salsa bikes.

Oh, btw, I can't find one for the Mukluk, but this Salsa document about sizing the Fargo which has similar geometry may be helpful (bearing in mind that the Fargo is designed for drop bars and has an even higher stack).

How To Pick The Proper Size Fargo

[Aushiker]

Thanks everyone. I have thrown the numbers around every which way including using Ron's linked document and still undecided ... nothing jumps out and ticks the boxes. One aspect I am curious about but and that is on my XTC I have 110 mm stem, so that is a TTE of 610 + 110 mm = 720 mm. The large Mukluk is TTE of 625 mm so if I am reading this right I wouldn't be over stretched with the large Mukluk. Reach BTW is 460 mm on the XTC versus 435 mm on the large Mukluk.

Seat post length is 2" shorter on the Mukluk so I don't think stand-over will be an issue.

The other noticeable difference is the head-tube angle ... 68.5 degrees on the Mukluk versus 71 degrees on the XTC so it is a slacker angle on the Mukluk which is probably good anyway.

Thanks
Andrew

[RonK]

Thanks everyone. I have thrown the numbers around every which way including using Ron's linked document and still undecided ... nothing jumps out and ticks the boxes. One aspect I am curious about but and that is on my XTC I have 110 mm stem, so that is a TTE of 610 + 110 mm = 720 mm. The large Mukluk is TTE of 625 mm so if I am reading this right I wouldn't be over stretched with the large Mukluk. Reach BTW is 460 mm on the XTC versus 435 mm on the large Mukluk.

Seat post length is 2" shorter on the Mukluk so I don't think stand-over will be an issue.

The other noticeable difference is the head-tube angle ... 68.5 degrees on the Mukluk versus 71 degrees on the XTC so it is a slacker angle on the Mukluk which is probably good anyway.

Thanks
Andrew

I think there is something wrong with your reach calculation for the XTC. I'm struggling to understand how the Mukluk can have a longer ETT yet a shorter reach when both have the same seat tube angle. Could the slacker head tube angle and extra stack height really make that much difference?

Also, since you are planning to use the H-bar, Jones recommendation is to use a longer frame with a short stem.

I think you could well find the medium frame a bit cramped.

[Aushiker]

I think there is something wrong with your reach calculation for the XTC. I'm struggling to understand how the Mukluk can have a longer ETT yet a shorter reach when both have the same seat tube angle. Could the slacker head tube angle and extra stack height really make that much difference?

I just rechecked my measurements:

BB to Wall 1015 first time, today 1010 so an average of 1012.5.
Middle of headtube top (as seen from the side) distance from the wall - First measurement I have recorded as 555 mm but rechecking today I have at 585 mm ... ugh I must have missed read my notes.

So this means as I understand it the reach is 1013 - 585 = 428 mm on the XTC versus the reported reach on the large Mukluk of 435 which is logically as the ETT on the Mukluk is 625 versus 610 on the XTC. Reach of 428 mm is seven mm more than the medium framed Mukluk and seven mm less than the large Mukluk ... man I cannot win .

Also, since you are planning to use the H-bar, Jones recommendation is to use a longer frame with a short stem.

I cannot find where Jones talks about fitment. Do you have a link? I did find a comment by Vik where he suggests:

If you are retrofiting to an existing bike keep the larger dimensions in mind and if you are buying for a new bike you may want to size up the frame.

I think large it is ...

Andrew

[RonK]

Sorry, I can't find it again - I can't remember if it was in his blog or a video clip.

I'm pretty sure that Aidan followed this advice when building his Ogre - perhaps he remembers where it came from.