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Why 27" / 630 mm wheels?

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Why 27" / 630 mm wheels?

Old 07-14-14, 06:13 PM
  #76  
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The Rigida AL 1320 was one such hooked rim available in 27" in the 70s. Easy enough to make 700C & 27" versions of a given extruded & formed shape, once it is tooled. This rim, and the Michelin Elan (IIRC), mentioned above, are original equipment on my 1978 Motobecane Grand Jubilé.
Regarding the demise of 27" on new bikes, my 1987 Miyata brazenly sports 27" Araya rims that I assume are original.
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Old 07-14-14, 06:36 PM
  #77  
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Originally Posted by old's'cool View Post
The Rigida AL 1320 was one such hooked rim available in 27" in the 70s.
The 1320 was Rigida's second generation of narrow clincher rim, after their 1319 model. The latter was what I chose for converting my Gitane Interclub from tubulars to clinchers around '76. At the time I decided to go with 27" instead of 700c since the former tire size was more readily available throughout the US. It also turned out to have the right ERD so I could reuse the spokes. The 1319 rim (and the Mavic Mod-E) were already using the hooked design, but some users had issues with certain tires so Rigida came out with the slightly wider 1320 rim as a replacement.

BTW, the link in the post above gives the outside width as 28mm which is clearly too wide. My recollection is that the 1319 and 1320 nomenclature referred to the inner and outer rim widths (i.e. 13mm inner and 19 vs. 20mm outer).

Last edited by prathmann; 07-14-14 at 06:39 PM.
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Old 07-14-14, 09:10 PM
  #78  
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Originally Posted by dddd View Post
There were many brands offering hook-bead 27" rims, in both racing and touring widths, and both single- and double-walled styles.

These seemed to have been sold from about '75 to '89 as O.E.M. spec on road bikes.

The 27" Pasela tires in each of the three widths are among the widest 27" tires, almost fully up to their listed widths.
Only the Michelin gumwall (1-1/4" only) seems to measure as wide at 32mm (1.25") on a decently-wide rim.

Older 1" tires were the same width as 25c tires from the same period, up through the 1980's at least.

These 1" and 25c-labeled tires also carried molded-in designations of 20-630 and 20-622, respectively, during the later years of the 27" era.
The molded-in dimension was the more accurate.
I also bought "TurboSport" tires labeled as 27x1-1/4" which carried the (accurate) molded-in size designation of 26-622, made by Cheng/CST and sold by Specialized.

Current standard 1-1/4" gumwalls from Kenda, Cheng, etc. seem to measure 28mm wide on 22-23mm-wide rims after overnight inflation to rated psi.
But on the Varsity, with 28mm-wide steel rims, they measure 31mm after overnight inflation.

Performance sold 27x1" tires up until a couple of years ago that measured 21.5mm on 22mm-wide rims.

The IRC Triathlon was widely distributed in 27x1" width until recently, and was a very sporty tire with a tread thick enough to be called durable.

Current 27x1" Pasela tires measure about 26mm wide on a 22mm-wide rim, fully as wide as tires that some companies label 1-1/8"
Paselas in 1-1/8" size are easily as wide as most 1-1/4" tires from other brands, and I've had clearance issues after this full width took me by surprise.
My 1975 Raleigh came with straight sided rims, and I seem to remember that the old Sekine had straight sided rims, and that would have been closer to 1978 or 1979, both were Canadian made bikes with Chromed Steel rims. It's possible that the then new AL clincher rims were hooked and the steel ones were not. A 1" tire should be a hair wider then 25mm, in that 1" is 25.4mm, a 1 1/8 should be around 28mm and a 1 1/4 should be around 32mm. What is interesting is that although a 27" uses a larger rim (630mm) then a 700C (622mm), the tire is larger for the 700, in that 27" is actually 685.8mm. However realistically 700C is actually a fairly wide tire, in that 700-622 is 78mm cut that in half you get a tire that is 39mm high, since tires are essentially round, I expect that the original French 700C size represented a tire around 39mm wide. A 25mm wide tire is going to be roughly 25mm high, double that you get 50, add 50 to 622 and you get a tire that is 672mm in diameter. The question as always, when buying tires, is will a given tire for a given rim, fit a given bicycle.
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Old 07-15-14, 07:53 AM
  #79  
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Originally Posted by Pompiere View Post
I keep seeing this statement repeated, but both pairs of Paselas that I have measure exactly what the sidewall says they should. The 27x1 is 1 inch wide and the 27x1 1/8 is 1 1/8 inches. I have tires from other companies that are a full size narrower than advertised, as in a 700x25 that is really 23mm and a 27x1 1/4 that is really 1 1/8".
I agree. I have 5 bikes with Paselas and they all measure spot on.
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Old 07-15-14, 08:09 AM
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I thought 27 was standard when in high school. My first exposure to 700c was in Frankfurt, Germany, when I purchased a Peugeot and an extra set of wheels with sew-ups.
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Old 07-15-14, 11:52 AM
  #81  
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Originally Posted by Road Fan View Post
On triathlete bikes, that is the 650c's.
Yes, but not for many, many years, right? It was a fad with the Tri-geeks.

Some smaller-framed (non-tri-specific) road bikes also are out there, but with the (recent) exception of the Terry Telus 28, your tire choices are usually 23, 23, 23, 23, 23, 23, or 23.
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Old 07-15-14, 03:47 PM
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And the 26X1.375 For pre war American L/W bikes or 26X175 for M/W bikes or Schwinn 26X1&3/4
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Old 07-15-14, 07:40 PM
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Originally Posted by trailmix View Post
I agree. I have 5 bikes with Paselas and they all measure spot on.
I think the issue is that SOME tire makers decided that marking a 27mm tire a 28mm, and using the slightly lower weight as a selling feature to the weight weenie set. Then someone else decided to take advantage and sell a 26mm tire as a 28mm, then it becomes a race to the bottom. In some countries like Canada this kind of marking a size larger, could be considered a violation of the acts regarding advertising, and a company could be fined thousands of dollars for pulling this kind of stunt. Canada isn't the only country where a company could get a hefty fine for this kind of nonsense. Moulding a tire differently for different markets does not make economic sense, so some of them don't do it.
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