Wanted to go up in tire width from 25c to 30c. Bought a set of Good Year Eagle Sports. Noticed they looked even narrower than the old ones and behold, they measure barely 25mm.
I want to return them but is there something I'm missing here??
EDIT: Thank you everyone. A combination of narrow rims and too low pressure seems to be the cause.
by weatherxreport
18 Comments
Its hard to tell, but is the bead seated? Pump those baby’s up!
It’s like how in some brands I’m a 10.5 shoe and in some brands I’m a 11. It also will heavily depend on what rim width you have with how the tire sits within the rim.
Not uncommon on cheaper tires. They could bloom out a few more mm after some rides.
Also, if the internal width of your rims is narrow, it can cause them to sit tall, too.
Internal rim width plays a huge role in inflated tire width. I run 28mm GP5000s on 17 mm internal width rims and they only blow up to 26.5-27mm measured
They stretch a bit when you ride them. But also, weight doping is a thing. People shop by grams.
Goodyear follows the ETRTO guidelines very strictly (which are not publicly available, which is super cool).
If I remember correctly from my days working for a tire distributor, under the current (then, circa 2023) guidelines, a 30mm tire is measured on a 21mm internal rim (after resting at full pressure, for 24hrs, around room temperature (70f / 20c).
Your rim brake wheels almost certainly have a narrower internal width – 19mm or less, and possibly as narrow as 15-16mm. This narrower width has a direct impact on the measured width of a tire.
Also, your tire does not appear to be fully seated in the second picture. When a Goodyear tire is fully seated, you would generally see a clear mold line 1-2mm above the rim, where the sidewall begins transitioning into the bead.
(Yes, the rim width specified for measuring tire width has increased over the last few years as wider rims have become common. In turn, yes, this means that a modern 30mm tire is actually smaller than an old 30mm tire that would have been designed to measure at 30mm on a 16-17mm internal rim.)
What works for me is to pump the tires up to the max pressure on the sidewall (or for the wheel – whichever is less) and leave them that way until I’m ready to ride. This way the tires stretch out and relax to whatever size they’re going to be and I also find out how well they’re retaining air over time.
My GP 5000 tires in 32mm measure 28.5mm with my caliper.
Good year tires seem to run narrow. I had a pair and they ran super narrow and were almost impossible to mount. Overall I did not like anything about them
25-30mm… not “c”. It’s 700c
There are multiple conditions that should be met together to get a measurement that matches the tire specs. It’s almost impossible.
The industry sizing is ridiculous. At least you didn’t pay much from them.
When you’re trying to get maximum footprint and you pay for a decent brand and it’s smaller than advertised. That’s what pisses me off.!!!
Not unusual. I have an aero bike with pretty tight tolerances that was designed to support 23s… One time I had a tire blow out and all I had was 28s… decided to give it a try out of desperation and was surprised to find that it worked.
Busted out the calipers and found the measured sized to be…. 23.
I had the same with good years from ali express. Claimed 30mm, measure 19mm on the rim. Useless
Some variation should be expected, primary from rim width variation. But that is extremely.Â
hm… gp5000 or pirelli prace rs 30mm measure ~32mm on 24mm IW rim.
I guess it’ll stretch a bit over a few days, but 1-2mm ? not 10 …
With narrower and smaller tires this isn’t such a big deal, but on the other end of the spectrum, somewhere between 40-57c tires, the design of the carcass that the tread is built on affects the overall size as well. If you get a 2.0/50C tire, it might be the same as a 1.9/47c tire or about the same as a 2.15/55c tire – the carcass and buildup will make the overall size bigger or smaller than you expect.
I know that narrow road tires are basically a carcass with a lick or rubber over the top, but maybe their carcass choice that the tire is built on will always end up being smaller or larger than you expect, which varies by manufacturer and the carcass they are building up – and I guess with cheap tires, the big choice is to lie and save material cost where they can.
Narrow rim will under size your tires. Also, don’t be a Fred, just buy Conti and be happy.