Road Cycling - Continental tires

I need to know if Conti tires run true to size when mounted and fully inflated.
Are 700x25c really 25c or are they more like 23c, are 28c more like 25c, etc.

I have reason to believe Conti's run smaller than marked.

All you Conti users out there in BF land, what has been your experience?

I have always been told, and feel, that they run a size smaller than others.

I used Conti's Ultra 2000 and Ultra 3000 for about a year and loved them. On different bikes I used both 28 and 25 mm. They definitely have a smaller feel than other tires nominally the same size. The only reason I don't run them now is because my commuting on trashy urban streets just shreds tires in about 1000 miles. And it wasn't the Contis' fault; I shredded a pair of Specialized Armadillos with the tough kevlar belting even faster! I hated tearing up $20-25 tires that fast. The 3000s are especially nice. The tread compound really sticks to the road.

sigh.....
OK, I guess nobody remembers last time I broke this down for all of you, so here we go again....

The number on the tyre is called an ertro number, and is in the form of xxx-yy.

The x's are the diameter of the rims (usually 559mm for 26" atb's, 597(?) for 26" road tyres, 622mm for 700 tyres, 630mm for 27" tyres, etc).

The y's are the profile height, NOT the width! A tyre that is, say, 622-28 is, therefore, 622mm+28mm+28mm=678mm diameter at the road.

Sometimes (depending on how the tread is moulded), this is about the same as the width of the tyre, but usually, the tyre width is considerably less than the profile height.

Exceptions to this rule are: Tyres with non-metric dinmensions (like 26x1 3/4"), as well as tubular tyres (where the width measurement is a width measurement). This is partly because tubulars usually have a nearly round cross-section, whereas clinchers usually don't.

sigh.....
OK, I guess nobody remembers last time I broke this down for all of you, so here we go again....

The number on the tyre is called an ertro number, and is in the form of xxx-yy.

The x's are the diameter of the rims (usually 559mm for 26" atb's, 597(?) for 26" road tyres, 622mm for 700 tyres, 630mm for 27" tyres, etc).

The y's are the profile height, NOT the width! A tyre that is, say, 622-28 is, therefore, 622mm+28mm+28mm=678mm diameter at the road.

Sometimes (depending on how the tread is moulded), this is about the same as the width of the tyre, but usually, the tyre width is considerably less than the profile height.

Exceptions to this rule are: Tyres with non-metric dinmensions (like 26x1 3/4"), as well as tubular tyres (where the width measurement is a width measurement). This is partly because tubulars usually have a nearly round cross-section, whereas clinchers usually don't.

As far as my experiences with Continental tyres are concerned:
Conti giro's are cheap junk, priced about $10 higher than other cheap junk tubulars.
Conti Sprinters ride and grip nicely, and are a decent tyre (if you don't get a poorly made one, or one in that awful orange colour), but wear quickly, puncture easily, and are waaaayyyy to expensive for what you get.
Conti Sport 1000: Forget it!!! Wears real quick, punctures just from looking at a piece of glass!
Conti TT2k's: Good tyre, but a bit heavy. Has adequate puncture protection (a rarity for conti), wears at a medium rate, but cracks easily along the tread. Considering the price, you are better off with Panaracer Paselas. Or Armadillos, if you need the puncture protection.
Summation: Buy conti's only if you need the grip, but expect to pay for it! Buy a spare, because you'll wear them out quickly.

D*Alex;
I understand what you are saying.

But, I think that question was inferring one brand to another. I feel that Conti sizes are smaller compared to other brands.

The numbers that you gave are right on, but as you said that is not all to the story.

And like shoe, shirts and skivvies, there is no overall standardization body to insure what size is what.

I wear one size in a Justin boot, another in a Nike running shoe and a totally different size in a Shamino cycling shoe.

So I guess the overall answer Is "In my option..............."

I think the tire "width" varies between Conti models also.

I had Conti Ultra 2000s (700X23). When I'd open up the front brake to remove the wheel there was plenty of space between the brake pads.
When I put Conti GP3000s (700X23) on my bike the tire rubs against the brake pads when removing the front wheel.
:confused:

Thanks for the response everyone, I am not surprised to hear the "one size smaller" leanings.

I'm not too worried about punctures; it has never been a big problem for me (he said laughingly). I am quite vigilant and wipe my tires often while riding.

If and when I buy Conti's, I'll likely order 28c hoping to get a 25c.

Don't know which model I'm interested in, but I'll remember Ron H's observation about variation between models, as well.

Thanks, Alex, for the information on the ertro numbers and the explicit findings on each model. I'm going to print it out and keep it on hand.