rekmeyata

I'm glad you mentioned that because I have an old Specialized Armadillo All Condition tire marked 700x26 but it measures right at 25 (I checked because of your post), so it could be as you mentioned the Specialized brand under size their tires. I know a lot of companies build their tires smaller than the label size, I have a set of Hutchinsons that are marked 700x25 but their actually 700x23. I'm not sure why the huge discrepancy though, I guess it's like shoes I sometimes wear a 10 1/2 sometimes an 11, and sometimes a 11 1/2. All this makes me wonder if car tires are the same!

Sierra

Since it was nominally called a "touring" bike, I bought 27" x 1 1/4" Panaracer Paselas for my '71 P15 Paramount. They are BIG!

Kind of wish I'd bought the 1 1/8" instead.

Darth Lefty 

And this oldie but a goodie I've posted a few times already

rekmeyata

Think of that closeness to the fork as a cheap thorn flicker...

Anywho, yes the Panaracers are a taller tire but not all that much wider like I said only 1/16th of inch wider than marked, the Specialized Armadillo All Condition tires are a taller tire too.

The Golden Boy 

I like having that cushion on there- a 27 x 1 1/4 tire with a recommended tire pressure of 95- I usually inflate them to 85 and that's comfortable to me.

I have two bikes that have issues with 1 1/4 and 32 tires- at the brake bridges, so I went with 1 1/8 and 28s respectively.


I had bought some wheels that came with a set of Specialized tires- a "Touring" on the front- that was 27 x 1 1/4 and the "Expedition" which was 27 x 1 3/8. They were so cushy- but they were dangerously old- I didn't want to ride farther than 5 miles from home just in case. But they were cool tires.

The Golden Boy 

Sierra

Yes, that reminds me of another reason I went with the larger tires. I'm running the original Weinmann rims which do not have hooked beads. The tires want to blow off at 90 psi, so I keep them at 80 psi.

rekmeyata

run mine at less then even 80 but I weigh 165 with cycling clothes on...but I run more when I put a load on to tour and my touring kit weighs around 35 sometimes 40 (weekend only tours) plus another 25 pounds for the bike so say 230 pounds total I only put in 80 (I like about 5 psi more which I do all around) in the rear and 65 on the front. This calculator: Bicycle tire pressure calculator shows how to figure it, I use the 700x32 size for my 27" tires and since most of my touring weight is on the rear I change the F/R% to 45/55. Anyway the point is if you are riding with more or less weight you need to adjust your pressure accordingly, so if I ride with just my body weight and the bike's which would be about 190 and change the F/R % to 40/60 then the PSI drops to 55 front and 66 rear (again I like 5 psi more).

The above figures keep the tires drop ratio to around the idea 15% drop that has been widely recognized as the best drop to use for most types of riding and for most types of tires. Some tires may require more psi than the calculator shows so you have to look at the tire packaging and see if they recommend anything different. The reason why some tires require more psi and tell you so is because one, they know about the 15% drop rule, and two, their tires drop a bit differently than most and thus using the standard calculation will cause their tire to drop too much.