Bicycle Mechanics - Smallest Width Tires for 21c Rim?

I've got a Giant Cypress with 700X40C tires on there now (stock). Since I am 99% on the road, I want to go with a smaller width on these tires. The rims are not branded, but Rainman has referred to them as "Hoopsters" and they are 21cm measuring from inside to inside width of the rim.

Sheldon Brown's article recommends 35cm as the smallest:
http://www.sheldonbrown.com/tire_sizing.html

but his source, written in German, (which I don't read so well !), seems to leave some fudge down to 28 or 32cm .
.http://tandem-fahren.de/Technik/Reifentips/REIFEN.HTM

Does anyone have experience with this? I'm just trying to avoid as much trial and error as possible, and still have a fast safe tire

I ride 700c hybrid style wheels on my commuter with 28mm tyres.
Some of the narrower 28mm are too narrow, and some of the narrower 32mm (Panaracer Pasela) are as small as I want to go.

The Rivendell RolyPoly is a good tyre for you.

700x35 sounds about right. I have a specialized crossroads with 700x38 and the same size rims. I really can't see putting road bike tires on those rims or road bike rims on that bike. One option is to look for slicks or near slicks at 700x35 that run 80psi, another option is to buy a road bike. Road bikes won't bounce over curbs and are lousy on pot holed streets and cluttered sidewalks. I'm running a no suspension mountain bike with 1.5" city slicker tires and a nice touring bike at 700x35. Takes the in town rough stuff without sacrificing too much speed. On downhills they do up to 30mph no problem.

One rule of thumb:
Never use tyres narrower than the outer width of the rim. You will end up gouging the braking surfaces.

I agree with D*Alex!!!!!, and I'm going to take the opinion a bit further. You will have a BETTER ride, cornering durability etc., if the tires you run are a bit WIDER in diameter than, ( width of ), your rim, you should be able to see the sidewalls sticking out a touch to the outside at least. Why?, a slightly wider tire will be ROUNDER. A a rounder tire keeps it's geometry as the bike leans into the turn and is therefore more predictable than a small ovalized tire that will make the bike feel as though it's "diving". The wider tire will absorb more road shock giving less damage to you and the bike. Many experts including those at a very respected tire company think that the slightly larger tire ROLLS BETTER. I know from years of experence and expert opinion the larger tire corners FAR better.

The downside?, The larger tire accelerates a bit slower because of the larger mass.

Ride Fat Ride Happy
Pat

Sounds like some good advice to me. Thank you all. One thing about the BFs, there's someone that has looked into nearly anything having to do with bikes!

My outer to outer rim width is 26cm, so I guess either a 28 or greater would work. I guess I'm leaning toward a 32, but haven't looked into availability yet.

My thanks to you all. I have the Panaracer Pasela 700X32s on and WOW what a difference from the original equipment 700X40s. For anyone with a bead width of 19, I can attest that 28 is the minimum you want to go!

MichaelW, you're right the Pasela 32, sure looks like a 28 to me!

Somebody's 32 is someonelse's 28, her 23 is his 20, that company's 25 is this company's 28 etc etc etc.......

Ride the size by sight and feel
Pat