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  1. #26
    Senior Member Wogster's Avatar
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    Quote Originally Posted by scopinusa View Post
    You are spot-on about aesthetics. As you know also, 27"ers are smoother than 700's due to the increased radius just as 27.5 and 29" are smoother, among other things, than 26" tires. I feel the difference readily. That's why you see 27"s on my Ironman (previous post) rather than 700's. Weight differences are only found in set designs, so that's not a concern for me. There are more tire choices with 700's, but only in the higher priced, lighter and more puncture-prone designs that I don't want as a general statement.

    I was disappointed when the industry moved to 700's and still see it as a negative.
    You do realise that 27.5" is not a real size, the actual size is what has been referred to as 650B for decades, and they can be as small as 650mm in diameter which is actually less then 26".... 29" is simply a marketing name for a wide 700C tire. It get confusing when you look at tires outside the normal use. For example I have a mountain bike that is used as a foul weather road oriented bike, if it had 29" wheels instead of the 26" wheels it has, then there is no such thing as a 29x1.5 or 29x1.75, those tires are actually 700x38 or 700x42 respectively. If we refer to them by their ISO (or ETRTO designation) then they would be 38-622 or 42-622 which means that technically you could install a tire as narrow as 23-622 or as wide as 60-622. The other issue is, that a 27" tire can actually be smaller then a 700C tire..... A wide 700C tire can be as large as 706mm and 27" can be as small as 680mm. 27" itself is 685.8mm......

    I switched my Raleigh from 27" to 700C, because I like having more tire options, and it's not just the expensive tires either. 27" is a dying size, every year there are fewer bikes that originally came with 27" wheels, rust and crashes, will continue to dwindle the supply. Conversions will also dwindle the supply, and that will make it harder to justify continuing to make replacement rims and tires in that size. If you want a new 27" wheel, even today, you need to get it custom built, and that is expensive, there are few decent tires made in that size, and for some dealers they are special order. I expect in the next 20-30 years you will need to take advantage of the NOS parts to keep that size, and they will not be cheap.

  2. #27
    Senior Member DiegoFrogs's Avatar
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    Quote Originally Posted by scopinusa View Post
    As you know also, 27"ers are smoother than 700's due to the increased radius...
    I feel the difference readily. That's why you see 27"s on my Ironman (previous post) rather than 700's. Weight differences are only found in set designs, so that's not a concern for me. There are more tire choices with 700's, but only in the higher priced, lighter and more puncture-prone designs that I don't want as a general statement.
    You can "feel" the difference in "smooth" where the BSD circumference is 1.29% greater? Have you considered working for the space program?

    I've switched several bikes over from 27" to 700c rims, but haven't done any controlled experiments where I used an otherwise-identical rim, hub, spoke and tire, but my engineering-brain has a hard time believing this statement. All of the 27" rims I've come across have been the single-walled, non-eyeletted variety which thus can't handle the higher spoke tension. In all cases, I've switched to double-walled rims, and only one did not have eyelets.

    On only one occasion did I make the switch partially for the issue about tire availability: I was moving to Europe and would have to order 27" tires from overseas, and wanted to switch my 37 year old touring bike to a modern cassette hub and dynamo hub.

  3. #28
    Ride, Wrench, Swap, Race dddd's Avatar
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    Quote Originally Posted by AAZ View Post
    Seems like this type of thread is initiated once or twice a year.
    I found the Specialized All Condition Armadillo to be excellent at 27".
    Yes, the Armadillos are well made, tough and flat-resistant.

    Slightly narrower than the 27" Gatorskins I've used, but more resistant to cuts from any angle and of course with a stiffer casing.

    So many more choices with 700c, such that I can find more of the exact style of tire I want and usually at a better price, basic tires excepted.

    I actually do about half of my riding on 700c discards, usually un-worn front tires or new-looking rear tires with a small, boot-able hole in the tread region. At the pressures I run (I weigh 145), such booted tires are still entirely reliable.

  4. #29
    reg
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    Senior Member reg's Avatar
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    Quote Originally Posted by garage sale GT View Post
    I had a 27x1-3/8 set of cyclocross knobbies for a while. I don't recall who made them, wtb I think.

    You could consider changing your bike over to 700c. There's only 4mm difference in rim radius so your existing brakes may have enough reach.
    cavet: your brakes will probably fit- the old single piviot sidepulls- but if you want to upgrade to dual piviot- go long reach Tetkro's finding out the expensive and hard way myself.

  5. #30
    old and fixed... clubman's Avatar
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    Quote Originally Posted by scopinusa View Post

    I was disappointed when the industry moved to 700's and still see it as a negative.
    Well, the 622 mm bead/700 size predated the 27" Dunlop size by at least 4 decades. The industry re-embraced 700c clinchers as the standard for road bikes.

  6. #31
    Ride, Wrench, Swap, Race dddd's Avatar
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    Quote Originally Posted by clubman View Post
    Well, the 622 mm bead/700 size predated the 27" Dunlop size by at least 4 decades. The industry re-embraced 700c clinchers as the standard for road bikes.
    I read just today that Dunlop introduced the 27x1-1/4" tire/rim size in 1935, and it was an entirely new set of dimensions not based on any other of the numerical "A, B, C, etc" versions of metric or other existing standards.

    It was also stated that the 700c/622 bead seat diameter did precede this 27" standard, using fat tires of 1-5/8" and 1-3/4" to yield rolling diameters in the 28" range.
    Likely this is how "700c" racing tubulars came to be referred to by tire maker Continental as 28", not that these thin tires measure anywhere close to that rolling diameter.

  7. #32
    old and fixed... clubman's Avatar
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    Quote Originally Posted by dddd View Post
    I read just today that Dunlop introduced the 27x1-1/4" tire/rim size in 1935, and it was an entirely new set of dimensions not based on any other of the numerical "A, B, C, etc" versions of metric or other existing standards.

    It was also stated that the 700c/622 bead seat diameter did precede this 27" standard, using fat tires of 1-5/8" and 1-3/4" to yield rolling diameters in the 28" range.
    Likely this is how "700c" racing tubulars came to be referred to by tire maker Continental as 28", not that these thin tires measure anywhere close to that rolling diameter.
    The 622 bead was a Canadian standard from around the turn of the century albeit on wooden rims. I mistakenly thought the Dunlops were early 50's. Still, I was wondering when the tubular racing wheel took over the peleton.

  8. #33
    Senior Member trailmix's Avatar
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    I hope they don't stop making 630s anytime soon, most of my bikes still roll on 27s. Tire selection is somewhat utilitarian but not too many people still racing these bikes anyway. On my 630 wheeled bikes, I use Panaracers, Continental and Vittoria and they seem to fit my needs.

  9. #34
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    Hi Wogster and all; Yes I know all the actual rim numbers well. The post I replied to didn't need an exhaustive explanation; just the descriptive terms generically applied to wheel/tire sizes. I wish the industry would use actual rim measurements too, but they generally don't. There are, and will be countless "27"" rims for many years to come. Longer than I'll care. I only use double wall (Araya) rims in this size. Very well manufactured and roll "true". BTW, there are newly manufactured "27"" rims available on Amazon. Millions of bikes with this rim are still in service all over the planet. However, if the Martians arrive and vaporize all "27's", new, used and otherwise, then I'll adjust to something else, no big deal.
    Also, for DiegoFrogs comments; Yes, You, I and anyone else can tell the difference in "rough surface" rolling characteristics of the"27"" vs. the "700". It's not only a rim radius/diameter ratio, but spoke length, hub flange radius vs. rim radius and can include dish variation based on the cluster/free wheel width, tire inflated profile, etc. Numbers can tell a story, we just have to include them all. You may remember the move to larger flange diameters, and then down again. Stiffer ride with little or no appreciable gain in performance and other things.
    Also the remark about working for the space program: I did manage an aerospace R&D metallurgical lab for my humble career, but that work was absolutely no help for sensing cycling vibration or lots of other things.

  10. #35
    Gearhead old's'cool's Avatar
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    I'm with DiegoFrogs on the controlled experiments question. 1.29% is a lot to ask from measurement capability in such a subtle and complex parameter as "smoothness", and not very easy to meet in a system with so many confounding and/or uncontrolled variables, e.g.: tire pressure, individual rim variations, individual tire variations, spoke tension, spoke length; to name the ones that first come to mind.
    Speaking for myself, I wouldn't bother going after or worrying about a 1.29% difference in "smoothness" between 27" and 700C wheels. Now, if there is a difference greater than that being perceived or measured, it must be due to something in addition to or besides the difference in rim diameter.
    Geoff
    "I think that I think, therefore I think that I am"

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