Tire Sizes

It may be time to lace in a 700c rim where the bead seat diamerter is 622mm, your 27" is 630mm. That will give you acess to all the "modern" tyres.

Meanwhile I will look for some 27x1" tyres in my catalogues.

Edit: Harris Cyclery seems to have all 27" tyres listed here: http://sheldonbrown.com/harris/tires/630.html
Including:
25-630 27 x 1" Panaracer
22-630 27 x 7/8" Avocet

Collegefour said:

I have an 18 year old Centurion Elite RS. The Specialized 27 X 1 & 1/8 tires have worn out and need to be replaced. I checked the Specialized website and could not find any tires in this size. I bought two Continental Ultra Sports in that size, but when I mounted them, the rear tire rubs (no problem with the front). I measured the old and new tires, and found that the old ones are 2.5mm tall, and the new ones are 3mm tall, hence the rubbing. I can solve the problem by mounting the rear tire lower in the dropouts, but the skewer is nearly out of the dropouts when the stupid tire finally clears. Is this safe? And do they still make tires in this size that are 2.5mm tall? If so, how can I tell its the correct height before purchasing?

Can you explain better which part of the tire is rubbing which part of the frame? I can't imagine how moving the axle closer to the open end of the dropouts makes the tire clearance greater. Also, what part of the tire are you measuring as 2.5mm and 3.0mm? If your Conti's are 1-1/8 they should be pretty much the same width (diameter) as the Specialized were.

No need to switch to 700c tires because 27" tires are just a website visit away... also you might not have the right brakes to make the switch.

DiabloScott said:

Can you explain better which part of the tire is rubbing which part of the frame? I can't imagine how moving the axle closer to the open end of the dropouts makes the tire clearance greater. Also, what part of the tire are you measuring as 2.5mm and 3.0mm? If your Conti's are 1-1/8 they should be pretty much the same width (diameter) as the Specialized were.

No need to switch to 700c tires because 27" tires are just a website visit away... also you might not have the right brakes to make the switch.

OK...a picture is worth a thousand words, so I'll try to attach two pics that explain what I mean.....so width is not an issue at all. The actual height from the rim to the top of the new tire (only the back tire) is the issue.

gclark8 said:

It may be time to lace in a 700c rim where the bead seat diamerter is 622mm, your 27" is 630mm. That will give you acess to all the "modern" tyres.

Meanwhile I will look for some 27x1" tyres in my catalogues.

Edit: Harris Cyclery seems to have all 27" tyres listed here: sheldonbrown.com630.htmlOpen ↗
Including:
25-630 27 x 1" Panaracer
22-630 27 x 7/8" Avocet

Thanks for the link, Clark! I'll do some studying.

Collegefour said:

OK...a picture is worth a thousand words, so I'll try to attach two pics that explain what I mean.....so width is not an issue at all. The actual height from the rim to the top of the new tire (only the back tire) is the issue.

Although it may be counter-intuitive, you have moved your rear wheel in the WRONG direction in the rear dropout.

To get MORE tire clearance, you have to slide the wheel "deeper" (i.e., away from the crank) into the horizontal dropout.

Collegefour said:

OK...a picture is worth a thousand words, so I'll try to attach two pics that explain what I mean.....so width is not an issue at all. The actual height from the rim to the top of the new tire (only the back tire) is the issue.

OK, so the tire is rubbing on either the brake calipers or the brake bridge on your frame. It appears to me that you're using 27" wheels on a bike built for 700c wheels - the difference is about 8mm in diameter. Not sure how it was working before - maybe it was a kludge.

I'm not sure how you would know for sure that your bike was built for 700c wheels unless you had the original specs - but the last 27" wheels I saw on a new bike was about 1985.

Also, it looks like you meant 3cm instead of 3mm in your first post... that would equate to a little more than 1-1/8".

Anyway - an easy check is to borrow someone's 700c wheel and stick it in there and see if you can adjust the brake pads to fit the rim.

alfeng said:

Although it may be counter-intuitive, you have moved your rear wheel in the WRONG direction in the rear dropout.

To get MORE tire clearance, you have to slide the wheel "deeper" (i.e., away from the crank) into the horizontal dropout.

Actually not counterintuitive to me at all...that was the first thing I tried, because I thought I hadn't gotten the wheel all the way on! But when It is seated as far back as I can get it, the tire rubs. Arrrgh!

DiabloScott said:

OK, so the tire is rubbing on either the brake calipers or the brake bridge on your frame. It appears to me that you're using 27" wheels on a bike built for 700c wheels - the difference is about 8mm in diameter. Not sure how it was working before - maybe it was a kludge.

I'm not sure how you would know for sure that your bike was built for 700c wheels unless you had the original specs - but the last 27" wheels I saw on a new bike was about 1985.

Also, it looks like you meant 3cm instead of 3mm in your first post... that would equate to a little more than 1-1/8".

Anyway - an easy check is to borrow someone's 700c wheel and stick it in there and see if you can adjust the brake pads to fit the rim.

I bought this bike used (if I recall correctly) at a bike shop in Pensacola, FL in like 1987 or 88. These are the rims that came with it. I do not know if the shop, or possibly the original owner, changed the rims for any reason. And yes, you're right about the cm vs mm...sorry!
I guess I'll have to go to the bike shop and borrow a 700c....I don't have any.

Collegefour said:

I bought this bike used (if I recall correctly) at a bike shop in Pensacola, FL in like 1987 or 88. These are the rims that came with it. I do not know if the shop, or possibly the original owner, changed the rims for any reason. And yes, you're right about the cm vs mm...sorry!
I guess I'll have to go to the bike shop and borrow a 700c....I don't have any.

What? You don't know anybody with a road bike newer than 20 years old?

The 3mm thing threw me because I thought maybe you were measuring the tread thickness.

DiabloScott said:

What? You don't know anybody with a road bike newer than 20 years old?

The 3mm thing threw me because I thought maybe you were measuring the tread thickness.

:o Actually, no. My only friend that also rides has a 17 year old Peuguot (sp?) that uses some kind of weird glue on tires. 🙁

Collegefour said:

:o Actually, no. My only friend that also rides has a 17 year old Peuguot (sp?) that uses some kind of weird glue on tires. 🙁

The braking area on the rims of your friend's sew-up/tubular wheels is the same as the braking area on a 700c wheel (ERTO 622-xx), so you use your friend's rear wheel to gauge whether or not the brake calipers can be properly adjusted (they probably can, particularly if the frame was originally supposed to have 700c wheels).