Designing adventure touring frame, feedback appreciated!
Hey there! I'm currently working on a project for an adventure touring bike, one that i'd like to use for long off-road rides like sections of the great divide, trans Canada trail, and visiting remote locations which may not have high quality road, if any road at all.
Here's what i've got so far, which was designed using BikeCAD after doing some drawn drafts and research.
The seat tube angle was hard to see when I put it on there directly. It's 73 degrees at the moment.
This will be TIG welded from 4130. I'd like to make this my project at the UBI frame building class this coming March, so long as they don't have any problems with technicalities in making this there. I called and asked about it, didn't experience any information that anything here would be a problem so far.
The bike in this picture is sized for myself. It's designed for use with an internal gear hub by default, but will have a derailleur hanger. Tensioning for the IGH is done via an eccentric bottom bracket. I have decided on this in order to have a drivetrain that is more resistant to mud, after speaking with a friend who had extensive great divide experience and stated that their derailleur was always troubled by so much mud.
Disc brakes will be featured, and I have some dropouts which have a chainstay disc mount on them. Are there any particular downsides to having a chainstay mounted disc brake to look out for? I'd like these in particular in order to use a heavy duty rack like a Surly rack or a Tubus stainless steel one, without the need for special adapters or jury rigging. I think that between a large rear rack and an expedition sized frame bag, the bike should be able to carry enough things.
I'd like to use the 100mm Surly Pugsley fork. The intent is to use a 29" mountain bike rear wheel, and then run a Surly Endomorph / Large Marge tire and rim on a normal width dynamo hub. If not being used in primarily off-road conditions, the bike could then have the wide Surly wheel replaced with a standard 29" wheel and tire.
I did not want to design a dual super fat tire bike because:
1. It requires odd sized bottom brackets and restricts choices
2. It did not seem like it would be an easy bike to make as a first time project, even with UBI's help - if they even said yes to doing it at all.
Regarding 29" rear, fat front:
I think that this could give the bike a lot of versatility - it can be run for a heavy duty off road situation offering a lot of flotation on the front, but a normal 29" wheel can be equipped - or even mid width touring tires front and back if the tour will have a lot of road.
To be honest too, I just want one of those super fat tires because they're awesome. I could go mountain biking too!
Or is this just being naive?
Things I am most concerned about:
The rear chainstays were made a bit longer in order to facilitate fenders and large amounts of mud clearance. That this will make the wheelbase longer is understandable, are there any severely negative consequences otherwise?
Should I use a 135mm non-offset Surly Pugsley front fork instead of the 100mm unit? That would give the bike the bike the ability to swap front and rear wheels if normal 29" wheels were being used, although not if the Pugsley wheel was installed. Are there downsides to this otherwise? The only problems I could think of were that this would disqualify the use of a dynamo hub, and if a 29" wheel was used, you probably could not use the cantilever mounts on the Surly Pugsley fork - but I was thinking that really there aren't many rim brake compatible 29" mountain bike wheels anyways, are there?
Have I messed up severely on the geometry anywhere? Should it be tweaked somewhat? I am 5'10" with a 33" inseam, and find that my personal favourite ETT is about 585 - but to keep the front center from being super short, the plan is to make the ETT a bit longer and to use a shorter stem. I would like to use an On-One Mary bar, this is a personal favourite.
Any feedback would be really appreciated. I have about 6 weeks to tweak the design outside of school.