I tried a search here, but didn't have much luck (or maybe it was too much). Anyway, I adopted a couple of road bikes and am going to try cleaning them up and making them functional again, but the first thing I noticed is that they have 27" by 1 1/4" Araya? rims. Can I put 700c tires on these rims, since that seems to be what all the stores carry today? I know, to a regular road rider this is probably one of the dumbest questions put forth, but I've always been a MTB enthusiast and this is all new to me. Duh! My 27.5's are shorter than these 27's. That's just wrong... Thanks in advance for any and all comments.

No they are 4mm smaller in diameter.

Most of the C&V guys will recommend Panaracer Pasalas for 27" wheels.

https://www.thebikesmiths.com/produc...SABEgLzz_D_BwE

Thanks dedhed. I just read where someone tried putting the new 700c on a 27" rim and it rode in the center groove and wouldn't seat to the outwalls, and that was after he fought with it forever. Thanks for the link.

Lots of 27" tires available. You can change wheels to 700C. I once bought a bike with a 700C on a 27. I literally had to cut the tire off to get it off the rim.

A 27" rim is ISO 630 meaning the bead seat (where the tire bead seats) is 630 mm in diameter. A 700c rim is ISO 622 or 622 mm in diameter. So, the two are 8 mm in diameter different and the tires do not interchange.

Tire sizes make no sense except the ISO/E.R.T.R.O. system: https://www.sheldonbrown.com/tire-sizing.html
Use the ISO sizes and there will be no confusion.

Well, "27.5" and "27" both refer to the wheel diameter including the tire, so yes, a complete 27.5" wheel is taller than a 27" wheel. You gotta use different measurements if you want to just compare the rims.

The ultimate 27" tire reference thread!

Welcome to the arcane world of bicycle tire sizes. The best article ever about tire sizing and how a 29" tire fits on a rim too small for a 27" tire and how a 28" tire needs a rim too big for either

​​​​​​https://www.sheldonbrown.com/tire-sizing.html

They are 4mm smaller in radius, 8mm smaller in diameter.

700c (622mm) tires will not fit on 27" (630mm) rims. I would love to watch someone manage to get a 700C tire onto a 27" rim, and if they managed to stretch it over the rim sidewalls, try to have it inflate properly - but I only want to see this for the comedic value.

If the 27" rims are damaged, you can often upgrade to 700c rims if your brakes can be adjusted 4mm down in their slots on the brake calipers. This also gives you an extra ~4mm of tire clearance, so a bike that originally came with 1-1/4" (~32mm) wide tires can often fit up to 35mm or 38mm with 700c wheels. If you can't adjust your brakes that much, 27" rims are still available, both new cheap replacement rims and better quality ones on the used market.

And Panaracer Pasela tires are the best option in my opinion. I think there are also a couple options from Continental, and a few others. I use Paselas on my 700c wheels, not because there are few options, as with 27", but by choice because they are excellent performers and good value.

I'd just switch the wheels and tires to 700c then make sure the brakes reach.

Nope. Thanks to dedhed's first link to Bike Smiths, I'm going to stay with the 27". Their prices and selection on everything I think I'll need for these 2 bikes is better than I'd first anticipated.

They also make the PT version, with added flat resistance. It costs a bit more, however.

Correct, I thought about that later. The 4mm came into my head from the brake reach issue.

Yeah, that's really dangerous. As a datapoint, I have a couple of 27 inch bikes. I just respoked one wheel, using the old Weinmann rim. I believe that the Araya rims are better. If you have a bike with 27inch wheels and are considering changing over to 700c, a couple of things

For keeping 27 rims: cheaper (no changeover expense), is per the original design (brake arms are proper length, etc.), tire selection is decent but certainly more limited than for 700c, rims are probably not as good as what's available today.

For changing over to 700c: changeover expense, not OEM or original design (must at least adjust brakes, may need different brakes with longer arms), great selection of tires, great selection of rims of higher quality.

Having just respoked two wheels (which was fun) I can say that it's certainly easier just to buy new 700c wheels and probably not much more expensive than just rims. Before you change, check to see if you have 4mm of travel in the brake shoes (that is, can you move the brake shoes 4mm down on the existing brake arms). Else, prepare to find new brakes.

I kept the 27 inchers because both bikes (Schwinn Superior 78 and World Voyageur 73) are semi-classics.

For now, you can just find some good 27 inch tires (I use Panaracer Pasalas, too) and go for it if you want to ride. Good luck!

Something else to keep in mind about switching from 27" to 700c is that the further away from the brake pivot you move the brake pads, the less braking power you get for any given amount of force you put into the lever. For a 'short pull' brake, the 4mm movement will cut your braking power by about 10% compared to what you would get with 27" wheels.

I just refurbed a bike with 27" wheels, and I went with Continental Super Sport Plus tires in 27 x 1 1/4. They are smooth and fast, and the puncture resistance is top notch! I live in thorn country and need a super tough tire, these are working out great!

That's correct but not a show stopper (or wheel stopper, pun intended). I converted an '83 Trek 400 from the stock 27" rims and a freewheel rear hub to 700c rims with a 8/9/10-speed freehub rear wheel. The original owner had upgraded the OEM Dia Compe 500 single pivot brakes factory brakes to long reach 105 dual pivot brakes and these would adjust down the required 4 mm. Braking power didn't suffer noticeably.

tl;dr version: just use the ISO/ETRTO tire and rim designations instead of the various arcane numbers.

An ETRTO tire designation will look something like this: 35-622, where the first number is the nominal width of the tire and the second is the tire bead seat diameter. If you're trying to figure out what tire will fit on your rim, the second number is the one to look at. If the bead seat diameter doesn't match, the tire won't fit your rim. Period. Full stop. Rims can accommodate a fairly wide range of tire widths, with the limiting factor usually being frame clearance.