A gearing question for you
 

I'm working on my touring conversion (1987 mtb as the subject) and trying to figure out the best gearing set up. I'm 45 and fairly strong but have never ridden a loaded bike.

The bike has an original 14-28 5 spd freewheel that I'll eventually update to 6 or 7 spd. The original crankset is was a 48-42-28. I was originally going to go with a 48-36-26. Using rings that I have on hand (i.e. low budget build) I changed my mind and set it up tonight with a 42-36-26. Based on gear inches from Sheldon's site the high is 78 and the low is 24. Does this seem appropriate for light to moderate weight touring? I don't have a lot of experience with gearing for that type of riding and I'm sure much is dependent on the route and weight of the bike/gear/rider and rider strength.

I'll have photos in the next couple of weeks as I'm waiting for some final parts to finish the conversion/build.

gearing
 

Survey the places you intend to ride and look at your load you will be carrying then you might need to get a larger gear set on the cassette. If you are going to see a lot of climbing you really can't have too low a gear. If you are going to be on rolling and flat stretches with a light to medium load sounds like you are in good shape. I know that Harris cyclery has a gear that goes to 34 with an extreme jump from the next lowest. That will give you a compound low in emergency situations. Also, check the rear spacing...if it is 135 then you could go for a new wheel and put an 11-34 cassette. This would require a MTB RD, longer chain, and new 9 spd shifter. Decide on what you are going to do first.
Last summer I spent in the Alps with some incredible climbs including the Stelvio and believe me you couldn't have too low a gear. Good luck and have fun.

Yes, your gearing seems appropriate for light to moderate weight touring. For not having a lot of experience with gearing you seem to have a good understanding of the factors influencing gearing choice. While I'm sure you'll receive all sorts of great advice from the forum, I think you aren't going to have a better idea of what constitutes correct gearing for you until you go out and do some loaded practice riding.

I don't worry much about the high end for touring since the only time I ever have much speed is when I'm coasting downhill. The low end is what concerns me the most. My lowest gear is 24 (front) and 28 (rear), and I've done ok on long tours with lots of steep hills, but would not have minded having a megarange 34-tooth option in the rear on some of the insanely steep hills. But you'll probably be fine without that. Also, just want to add that it's not only the rider's strength that's to be considered, it's how much abuse you want your knees to withstand. Having injured my knees touring in the past, I'd do just about anything to prevent that from happening again.

Your gearing looks good. A cheap option for you to get a lower gear if needed is to purchase a 24 chainring.

Second the 24 chain ring. And if you are looking at serious uphill grades, (and your rear spacing allows) you may even want to consider eventually rebuilding the rear end to use a cassette with a 36 granny gear. Talk about getting a low gearing.

Range of 24 to 78 inches is more limited than I would want to have, but you should try it for a while to see if you are happy with it. If you find that you want more on the high end, you can always put some of your other chainrings back on it.

I have a range of 19 to 122 inches. Unladen around town, I spend about 90 percent of my time in the 60 to 90 gear inch range. Hauling a lot of weight, I would probably be in the 50 to 80 inch range most of the time, but it would vary greatly for the terrain where I am biking. But, I am in a gear in the 20 to 30 inch range on the steeper hills so even though I spend very little time in those low gears, the low gears are critical to have available. While I can climb a 7 percent grade with a 30 inch gear, I am breathing pretty hard at the top of the hill with that gear. I find a 20 inch gear a lot more relaxing to use on that type of hill on a long day in the saddle.

Regarding 24t front, if you can find one at a good price and have the tools to install it, go for it. But having a 26t on the front already is pretty close to the 24t so I would not recommend that you make that change unless it is easy, cheap and convenient. You can decide later to make that change.

Your rear derailleur might not handle more than 28 teeth on the cluster, so if you go for a bigger sprocket in the back, you might need a derailleur too.

Thanks for all the good feedback. A lot of it will come down to riding the bike as several of you say. The high end is something that has me concerned - but only a little right now. It will be perfect for the gravel roads around here when the kids and I do overnight camping trips. On the road may be a different situation. Since I like to spin a higher cadence this may all work out fine.

My biggest issue is liking to keep my bikes a little more vintage - so 7 spd on the rear is the max I'll probably do unless I plan for a longer tour - more than a week. With a big family and lots of activities a really long tour may not be possible for awhile.

I would say that 24 inches is pretty high for a low gear on a touring bike if you expect to tour in the mountains or where it is hilly. So unless you want to tour in the flat lands or like to push really big gears and/or will be carrying a very light load I would get a 24 for the front and/or a cluster with at least a 32 on the back.

Pushing too big of a gear is not conducive to good knee health. I know this is just anecdotal, but take it as food for thought. We met a young man on the TA who had road bike like gearing and he seemed to be doing fine. He was usually first to the top of the climbs. The thing is he didn't make it 1/4 of the way across the country before he blew out his knee. He had knee surgery and I hear he was laid up for a year.

I think you're OK to get started. My rule of thumb is that you should aim for a range of 20 at the low to 100 at the top on a touring bike.

At this point what is limiting your range is the freewheel in back -- the spread of 14-28 isn't helping you. If you could get a freewheel with a spread of 12 to 30 or 12 to 32 you'd be fine.

My own view is that 24 is low enough for loaded touring on-road in all but the toughest terrain. I'd find a high gear of 78 to be unacceptably low, but tastes differ. When loaded - about 50lbs of gear - I generally push along at about 68/70 gear inches on the flat

I just returned from my first touring trip with a bike (a short test ride). I also used an old Mountain Bike (hardtail with rigid fork) with 46-38-28 crankset and 14-28 freewheel (6-speed), equipped with 40-559 tyres (Maxxis Xenith 26x1.5). That would give around 25 gear inches in lowest gear.

One of the clear conclusions that I drew from this test ride was that for me 25 gear inches on a loaded bike is not low enough. I already have a new transmission and rear wheel for this bike (bought before this test ride, but not yet installed) and it will be 42-32-22 crankset with 11-34 cassette (9-speed).

as you all say, the amount of weight and terrain makes a big diff.
24 gear inches is really not bad, when I toured fully loaded, I changed my gearing so that I had about a 21 low low, and appreciated it many times, not a lot, but it was sure as heck nice to be able to go down 1 more equivelant lower than what I had before.

again, probably the 24 will be fine for not overly loaded , and yes, while 76 is not very high, it is again very doable as I agree with others who say they are usually in the 50-70 range.

My old touring bike has a 7 speed cassette, with a range of 21-about 103 gear inches, and that was fine for just about all terrain I encountered. Going to a 7 speed would give you a bit more range, and I suspect would not be expensive to do. (but dont really know the tech limitations ofyour bike)

as always, the easiest thing to do is to put a bunch of National Geographics in your bike bags and see how the sucker is on some hills near you. Im sure you will find that your setup is fine for light to moderate load, so have fun. An overnight trip will still be very exiting for kids.

Go to an MTB 42-32-22 and in the rear a 12-34 alpine cog. That should give you all the gearing you need up hilly passes.