(Nothing) New discussion about tire width and different sizes between manufacturers
12-12-18, 07:55 AM
#1
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(Nothing) New discussion about tire width and different sizes between manufacturers
I found a great deal at performance on a pair of Michelin Pro endurance 700x 28c to replace my very worn and fantastic Rubino Pro III that have been nothing but fabulous.
I had tried thw Michelin size 23c with similar positive experience except for a shorter life than the rubinos. No flats between the two in more than 6k + miles.
I was worried that the 28s would be too wide for my 2013 Fuji Gran fondo but when I got home and mounted the tires they are exactly the same width mounted on the same rim. WTF? I know manufacturers sizes vary a bit and sometimes within the same brand and different models but there is a big (or should be) difference between a 25mm and 28mm.
I used a digital caliper to measure but the batteries were dead and I was unable to get the rear measurements. I'll replace the battery and measure again.
Another thing it caught my attention was the Vittoria tire recommends a min of 100psi and a max of 130psi while the Michelin recomends a max of 100 iirc.
What's the point of this post? Nothing really as it has been discussed before.
Post your experiences with sizes and pressure recommendations.
01-23-19, 10:19 AM
#2
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I'm interested in the replies to this too. My new bike has 28mm tires (700x28c), but my digital calipers clearly show them to be 30mm wide.
01-23-19, 10:29 AM
#3
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Leave the tires on for a few days and remeasure.
As an example, Panaracer Gravelking SK tires will increase in size over the first few days. Brand new 43 mm tires measured 41 mm but grew to 43 mm over the first 48 hours. Similarly, 38's grew to 41.
-Tim-
As an example, Panaracer Gravelking SK tires will increase in size over the first few days. Brand new 43 mm tires measured 41 mm but grew to 43 mm over the first 48 hours. Similarly, 38's grew to 41.
-Tim-
01-23-19, 02:42 PM
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I use Conti GP4K tires on all but one of my road bikes and though I love the tire, the sizing is comical. There is never going to be some standard that all follow, but it should be fairly easy for a brand to measure based on a 17mm inner width rim and use the tire width based on that. 17mm internal is an incredibly common/acceptable road rim width at this point.
No 28mm tire should measure 32mm as that screws with the clearance on a lot of bikes. No 25mm tire should measure 28mm, especially when the model tire already comes with a 28mm tire. Thats just dumb.
But its reality. Dumb reality, but reality nonetheless.
In the grand scheme of things, wrong tire width is pretty minor. Actual tire width is pretty well documented for the bigger models I have looked up, so a little google time will tell you what you need to know.
01-23-19, 07:22 PM
#6
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Unknowingly, this kind of thing in the TT and triathlon world can render a really expensive wheel setup about as aero a 32 spoke boxes.
Tubulars don’t tend to see this as much, or so the Internet told me.
Tubulars don’t tend to see this as much, or so the Internet told me.
01-23-19, 08:17 PM
#7
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Enjoy..!
https://fitwerx.com/how-bicycle-rim-...contact-patch/
Some further elaboration.. ETRTO defines a tire's width based on some standards, eg. a 23mm tire should be labelled as a 23mm tire if it is inflated to 87psi on a 15mm internal rim. Depart from that and all bets are off. A 28mm tire is defined by size inflated to 87psi (6 Bar) on a 17mm internal sized rim, etc. Oh, and the standard dictates measuring 24 hours after inflation. And.. size is just the casing.. don't include knobbies, etc..
https://fitwerx.com/how-bicycle-rim-...contact-patch/
Some further elaboration.. ETRTO defines a tire's width based on some standards, eg. a 23mm tire should be labelled as a 23mm tire if it is inflated to 87psi on a 15mm internal rim. Depart from that and all bets are off. A 28mm tire is defined by size inflated to 87psi (6 Bar) on a 17mm internal sized rim, etc. Oh, and the standard dictates measuring 24 hours after inflation. And.. size is just the casing.. don't include knobbies, etc..
Last edited by Sy Reene; 01-23-19 at 08:34 PM.
01-23-19, 10:18 PM
#8
Non omnino gravis
...and there is no standard within the industry. As has been mentioned, Continental puts up numbers as they see fit-- I've seen 25s mount to 28 on narrow 15mm internal Shimano wheels. On my 19mm internal wheels my 700x25 Giant Gavias mount to exactly 27mm-- so presumably on a 17 internal wheel they would be "true to size." Schwalbes mount to ~4mm wider than stated on my wheels-- 25 were over 29, and 28s were 31.5. Same wheelset, 700x35 Hutchinson Overides mount to exactly 35mm wide.
In my experience, I haven't seen pressure make a huge difference in mounted tire width. At most, in the neighborhood of 0.2mm.
In my experience, I haven't seen pressure make a huge difference in mounted tire width. At most, in the neighborhood of 0.2mm.
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01-24-19, 05:31 AM
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The 25mm Vittorias that came stock on my Fuji measure 26mm on 19c rims, and the 23mm GP4KS2s I have measure 25mm on 17c rims, they'd be even wider if I put them on the stock rims. I'm getting ready to order a set of 21c rims, and plan to run 25mm GP5Ks, which from what others have reported, measure more like the 23mm GP4Ks, so I should get around 27mm on the new rims.
