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#11
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Favorit hub and 35 PSI tire
I found the 609! at
https://www.sheldonbrown.com/tire-sizing.html It says: 609 mm Rare Dutch size, 27 x 1 1/2 I wonder why I have so many of the 609s. Either they are not so rare, or they are, which is the reason people dump them here... -- underground experts united http://user.it.uu.se/~embe8573 |
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#12
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Favorit hub and 35 PSI tire
Returning to the psi, on the 42-622 I just
mentioned, it says inflate to 50-75 psi 340-515 kPa 3.4-5.1 bar Some distance to the "35 psi" of the 40-609.. The 42-622 is an "Innova Flatfigher". It has a 29 tpi, 3.5 mm nylon layer to protect against the flat tire. Shouldn't matter to this discussion, I guess... Otherwise it says 700 * 40 C which is consistent with what you say (700C being 622 mm) but inconsistent with the ISO 42 mm width... -- underground experts united http://user.it.uu.se/~embe8573 |
#13
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Favorit hub and 35 PSI tire
On 6/20/2017 9:30 AM, AMuzi wrote:
On 6/20/2017 8:18 AM, Emanuel Berg wrote: Today I found an inner tube that fits according to the ISO mark, and is close enough to the inch mark - it fails on the diameter tho (tire 27, tube 28) which is the most important one. And the ISO interval is wide indeed. But should be fine, for sure. Here is what it says on the box: CST (Cheng Shin Tire) 700C 28 x 1 5/8 x 1 3/8 37/47-609/642 It has a 40 mm Dunlop valve. The 700 is the old French system or outer diameter (diameter including tire), right? But what does the "C" mean? '700' originally were large at 642mm, later referred to as 700A. The revised format 700B got smaller (625? can't recall), the current 700C smaller yet at 622m. (700D 587mm utterly failed in the late 1980s) I thought the original logic (if you can call it that) was that all 700 tires would have an outside diameter (tire+wheel) of 700 mm, but for narrow tires (700A) the rim would have to be larger diameter to produce the same outside diameter. If the tire was wide (700C) the rim would be smaller diameter. So the 700C specification was originally intended for wide tires. But marketing and fashion are even less logical, so people began demanding narrow tires to fit the smaller diameter and lighter 700C rims. Those came to dominate, and 700A and 700B went away. Is my history correct? -- - Frank Krygowski |
#14
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Favorit hub and 35 PSI tire
Frank Krygowski wrote:
I thought the original logic (if you can call it that) was that all 700 tires would have an outside diameter (tire+wheel) of 700 mm, but for narrow tires (700A) the rim would have to be larger diameter to produce the same outside diameter. If the tire was wide (700C) the rim would be smaller diameter. So the 700C specification was originally intended for wide tires. Yeah, but if A to C are narrow to wide, what is the other digit? The 42-622 I have is 700 x 40C. Did it once just say "700C", but when the "C" didn't mean width anymore but rather hinted at 622, they felt the need to specify 40, only they kept the C to still hint at 622? Perhaps they didn't use 622 explicitly at that point but you get my meaning... -- underground experts united http://user.it.uu.se/~embe8573 |
#15
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Favorit hub and 35 PSI tire
On Tuesday, June 20, 2017 at 11:52:59 AM UTC-4, Emanuel Berg wrote:
Frank Krygowski wrote: I thought the original logic (if you can call it that) was that all 700 tires would have an outside diameter (tire+wheel) of 700 mm, but for narrow tires (700A) the rim would have to be larger diameter to produce the same outside diameter. If the tire was wide (700C) the rim would be smaller diameter. So the 700C specification was originally intended for wide tires. Yeah, but if A to C are narrow to wide, what is the other digit? The 42-622 I have is 700 x 40C. Did it once just say "700C", but when the "C" didn't mean width anymore but rather hinted at 622, they felt the need to specify 40, only they kept the C to still hint at 622? Perhaps they didn't use 622 explicitly at that point but you get my meaning... -- underground experts united http://user.it.uu.se/~embe8573 Try reading this: https://www.sheldonbrown.com/tire-sizing.html Look at the chart third down from the top: --------------------------------------------------- French Sizes: 700 A 642 mm Obsolete 700 B 635 mm Rod-brake roadsters. 700 C 622 mm Road bikes, hybrids, "29 inch" MTBs. (28 x 1 1/2 F.13 Canada) 700 D 587 mm Oddball size formerly used on some GT models. ------------------------------------------------ Lots more information here. Cheers |
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