hard to find the appropriate forum for this, but touring people seem to have the mix of knowlage required.
i recently built up a soma smoothies es as a sport tour with fenders. my goal was to have a comfortable do all bike for 70% road and 30% mixed terrain riding i do. it is a requirement to have fenders. i have everything how i like it except for the tires. i am riding 700x32 paselas which is the maximum size i can fit with fenders and my surly pacer fork. i could probably get a 35 pasela on the back if i switched from sks p35s to 45s.
the problem is for gravel and dirt riding at 200 lbs i feel i really need the 35s for the extra cushion. i have a tendency to take the path less travled and push the limits of my tires
so here are the options
1. convert to 65ob and using 650x 38s. requires new wheels brakes and fenders.
2.get a touring fork. requires fork, and fenders, i already have a set of shorty 4 cantis.
is this weired cantis in front and caliper in back
3.get a cross frame. requires frameset, and another set of cantis
i am most interested in options 1 and 2 because of cost and time
I have a Bleriot that is made for 650b wheels/tires and I couldn't be happier! It really is the sweet spot when it comes to having a wheel circumfrence big enough to roll well but cushy enough to enjoy the ride. Most of my miles have been on roads, but I've had the bike on trails and it has performed very well!
Only you can decide whether the expense is worth it for you or not, but check out QBP (i usually buy through aebike.com) they stock all the 650b stuff. Right now they are out of the super long reach tektro brake (BR7303) but I think they were around 40 bucks when I bought them. I also have a set of their (QBP) wheels and have been pleased so far!
Touring on a 650b bike in the US probably isn't a big deal, because of overnight shipping and such, but I would reconsider if traveling out of the country...probably not as easy to get your hands on a new tire/rim if something were to happen!
It's a steel bike, correct? I bet you can get a 135 spaced hub in there without much trouble and certainly with no damage to the frame. You could also take it to an appropriate shop and have it spread to 135 (or 132.5 like surlys)...or DIY...I think on sheldon brown's site he explains the process. Hope it turns out well, but I wouldn't let 5 mm keep me from 650b!
Edit: Do you have a 135mm spaced wheel (even if it's 26"** to try in to see if it's possible with no formal adjustment to the frame?
i have yet to come up with a solution. going to put 32's on my front and rear and see how those work. if i am happy i will stay with it. if not i am going to the 650b. ill keep you posted. i did, however, dent my rear rim riding over a bridge with a 28 on back. so i know thats too small