tire size for lightweight touring?
 

rider=160-165 lbs
gear=20-25 lbs

With my existing bike frame, I run into tire clearance issues when going above 25 mm front and 28 mm rear. I would like to think that 25 front and 28 rear would be enough for most paved roads. what do you think? How will that setup fare in south america or south asia? do they have a lot of gravel or cobbles?

South America (region-dependent) will be MOSTLY gravel, dirt roads, and trails. The paved freeways are not fun for biking. The preferred bike for that part of the world seems to be a dedicated tourer with 2-inch wide tires, or a fatbike.

Nice sidebar on your packing strategy is also included in the Adventure Cycling Magazine. Way to go Max!

Check out this month's Adventure Cycling Magazine, and see what some of the folks were riding south in the 70s. It looked like pretty skinny tires. Not saying they are optimum, but they worked. Fifty mm tires and fat tired bikes seem like a little overkill for a lightly packed, light weight rider. However, 25-28 mm tires are probably a little under-gunned.

My wife and I completed a tour 4 years ago where part of our route took us over 400 miles of dirt and gravel roads and trails. Thirty-two mm tires handled it quite well. On a tour last summer we travelled on some of the worst "pavement" I have ridden on. We also did a fair amount of unsurfaced roads and gravel. Again, we were on 32 mm tires, which handled the road, and some single track well. However, there was a period of a little over a week that caused me some anxiety. We were a long way from anywhere, no cell service, didn't know the language, and I elected not to carry a spare tire just to save a little weight. I figured that if we ruined a tire, it would have taken a very expensive week to find a replacement. Point is: IMO anything 32 mm to 40 mm would work well, and take a spare.

We have also done quite a bit of dirt and gravel on 28 mm tires in North America.

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It's a matter of a personal preference. There is no rule. Only discomfort, which is a relative term.

I've done a bit of touring on 28 mm wide tires (700x28c) and a bit - on 42 mm tires. I prefer the latter, and am not going back. Had to build a set of my own 650b wheels for the purpose, totally worth it!

lots of gravel and cobbles and brick and dirt and mud. also lots of pavement. if you plan your route
properly, you "should" be able to do a tour in most any country totally on pavement. but may not
be the most scenic or least-trafficked routes.

so based on what's suggested, it's better to just take a mountain bike, and put on slicks?

personally, I'd go with something that can take 1.5in or 38s , I've ridden a lot on 1.5s and if the paved roads are reasonable and the gravel as well, they work fine. Ive ridden on 50s and obviously on rougher stuff and looser gravel they would help to an extent, but it really depends on the surfaces.
If I were to be reasonably certain the gravel isnt too bad, 38s are great, and on smoother surfaces they are a bit faster than 50s, although again, diff tires can have very diff characteristics riding, so its hard to make a blanket statement regarding width (but I do stand by my experience of 38 regular Marathons vs 50mm Supremes.)

I too have ridden a fair amount on rougher roads on 28 slicks and do appreciate wider tires for comfort due to lower pressures as well as more footprint in looser surfaces. This comes back to the fact that there is gravel and there is gravel, it aint a uniform sort of thing, just so many variables.

i have 4 bikes right now. started this thread thinking i might sell the carbon touring bike i built and just tour on my beater road bike. i guess i'll just keep it, since it has 32h wheels, disc brakes, bar ends and 35 tires.

As a small side note, the Schwalbe marathon 37mm is the best rolling tire from the lineup for some reason, rolls better than the wider and thinner tires at same pressures.
I've also found 37mm to be a sweet spot of comfort and rolling resistance even on gravel roads. Doesn't handle loose gravel as well as 2", but rolls and corners better on harder surfaces.

Take your Race Bike on sew-ups If You wish..

For SA gravel and Rural Asia get a old pre supension MTB , or an LHT 26" wheel .

Or a Bike friday Pocket Llama (mine 406 - 47) with that 20" wheel you have the world wide Kids Bikes and BMX to find spare tires..

Glad to see that some people prefer 28mm. Thats the biggest tires my bike can take and gives me hope off doing some lightweight touring without buying a new bike for the summer.

On pavement and hardpack, 28's are just fine, even for loaded touring. I run 25's on my touring bike and like their responsiveness. 38's are good too of course, bit more comfortable I guess on a rough surface. All personal preference and dependent on expected road sufaces.

Yep, I think you'll be fine.

Unpaved I'd go minimum 32mm.

I do light touring on my old Cannondale Crit bike, and use it for day rides that hit rough dirt roads around home. I have 25mm Pasela gravel king on the front and a 28mm tire in the back.
It was enough to run some really rough trails with the fat bikes today, rock gardens were fine, but I did take it easy on the big drops:cry: I weight 225 right now.

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