Lightweight touring bike?

[bikemig]

Once you get into 20 pounds or less on a bike, the bike is likely to come with short reach brakes. At that point, you likely top out at 25c on a tire. I wouldn't want that narrow a tire on a bike I ride all day. I'd want at least a 28c and that means you likely need a bike that takes long reach brakes (assuming you're running calipers).

I'd be concerned about 2 factors more than weight--gearing and the size of tire that will fit on the bike. You can change the gearing but the frame geometry dictates how large a tire you can fit.

For example, take a look as the Soma ES frame. http://www.somafab.com/archives/product/es

It takes a long reach brake and has eyelets (so you can run a rack if you like) and will fit a 28c tire. You can run a carbon fork up front (or steel). The point is that the bike has a geometry somewhere between a full out racing bike and a touring bike. You may find that a bike with that kind of geometry is ideal for the kind of lightweight touring you are doing.

[staehpj1]

If you don't mind my asking, which mountains?  I found the Rockies and Cascades much easier than the Ozarks and Appalachians.

That is true for the Trans America.  On the TA I found the Appalachians and Ozarks to be much harder than the Rockies and Cascades, but depending on your route that can be far from true.  For example I found the Sierra Cascades to be exceedingly difficult when we rode the Southern half of it.

[staehpj1]

At what point of youth, fitness, and light load does a 27-30 gear inch low become a viable option for touring?

Just one data point.  I did the ST with a 25" low gear.  I was 60, not especially fit, and carrying 14 pounds of gear (base weight).  The 25" gear was okay.

[DaveB]

[quote author=staehpjJust one data point.  I did the ST with a 25" low gear.  I was 60, not especially fit, and carrying 14 pounds of gear (base weight).  The 25" gear was okay.
[/quote]
Doesn't the ST route avoid the high mountains of the west and the steepest hills of the Appalachian/Blue ridge/Smokies if TN,KY and VA?

[staehpj1]

Just one data point.  I did the ST with a 25" low gear.  I was 60, not especially fit, and carrying 14 pounds of gear (base weight).  The 25" gear was okay.

Doesn't the ST route avoid the high mountains of the west and the steepest hills of the Appalachian/Blue ridge/Smokies if TN,KY and VA?

The ST avoids the Appalachians altogether and crosses the Western Mountains by what is probably the easiest route.  It does still cross the mountains, has some fairly long steep climbs, and tops out at a little over 8200'.

Given that the OP was asking about the Underground Railroad route, I am guessing that there was more climbing on the ST than what he is proposing doing, but I have not done the UGRR and have not looked at elevation profiles for it.  While it apparently crosses no mountain ranges it may have steep hills, so I have no idea how two compare the two.

FWIW, I did the Trans America some years earlier (when I was 56), carrying a fairly heavy load (about 50 pounds base gear weight), and using a low gear of almost 22".  It was OK, but I wouldn't have minded slightly lower gearing.

[zzzz]

I have used a road bike (Ti) on the 5 long tours I have taken. The first two I had a 32 in low gear (34/28)  and the last three a 28 inch low gear (34/32). I have carried between 15-20 lbs of gear. That said, I weigh 145 lbs and the one (and only) thing I've ever been exceptional about on a bike was going uphill.

I have a couple of observations on using a road bike.

1) My bike can only take a 25mm rear tire. If I was going to do it over again I would have made sure that the bike could take at least a 28mm. Most days on most roads the narrower tire is fine but then you will get on a road that is littered w cracks big enough to eat that skinny tire or you need to ride a few miles of gravel and you'll wish you had a bigger tire.

2) I think road bikes are susceptible to handling issues as you add weight and the more concentrated and higher it's placed the more likely it is to be problematic. My bike got funky going down the big passes out west where I was cold and at high speeds when I had more than 15 lbs all in my rear panniers with the short wheel base it has. On my last 2 trips I added a frame bag to my set-up to spread out the weight and the problem went away. Because I'm only 5'6 the frame is too small for the bag to add any volume capacity to speak of but I put in everything thats small and relatively heavy in there (tools, spares, toiletries bag) and it helped a lot.
 
3) I would recommend that you look past just this trip when considering what to buy. I believe the Underground RR route is relatively flat with a fairly narrow weather window but there will be (we hope) future trips. I got my bike thinking I was going to do one 30 day blitz across the country and never tour again and got a bike specifically for what I would need on that specific trip. Then I got the bug and I realize I should have gotten something a little different.

Russ Seaton said on a previous post that 18lbs is not considered lightweight touring. I actually don't know how you could get down to his noted 10-12 lbs w/o going REALLY spartan and knowing that your route was never going to go thru any cold weather. I have read with interest Pete's (staehpj1) article on CGOAB about lightweight touring multiple times trying all I could to get below 15 lbs and I haven't been able to do it. This years trip to Alaska w rain and cold weather gear I couldn't get below 20 lbs. Still, with my bike coming in at a svelte 17 lbs that still had me at a combined total weight of bike + gear at under 40 lbs total and it has never felt onerous to pedal.

Pete

[Pat Lamb]

That said, I weigh 145 lbs and the one (and only) thing I've ever been exceptional about on a bike was going uphill.

I hate you. 

I excel at going downhill and recovery rides!

[dancingcyclist]

A friend of mine has an aluminum frame w/carbon fork and pulls a BOB trailer fully loaded along with a handle bar bag. He's runs a triple crank and had the bike shop put on an extra low (lg. cog) gear on his cassette. He uses a Mt. bike rear derailleur and can still use his STI shifters. Tires are 700X25. His bike with two bottle cages, small seat bag, rear fender weighs about the same as my Specialize Allez Comp at about 21lbs. He rode the length of the PCH a couple years ago with no trouble. I think his bike is about 10 years old and has high milage as he rides about 3000-4000 miles/year if not more now that he's retired.

I was going to try this combination myself but after weighing a loaded trailer along with my own weight of 185lbs. I thought it might be pushing the bikes limit a bit so I changed my mind. After breaking the right chain stay at the drop out while on an everyday ride on my Allez I'm glad I didn't go that route. I also prefer panniers over the trailer and most aluminum road bikes don't come with braze ons.

You might think about heavier built wheels with more spokes also as most road bikes go with light weight and aren't designed to carry much more then just the rider.