wheel size variations



ohfudge86

New Member
Nov 19, 2012
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Hello, was just wondering what are the different reasons for converting wheel sizes on bikes like 700c or 26" on a road bike made for 27" etc? What are the pros and cons. Thanks.
 

alfeng

Well-Known Member
Jul 23, 2005
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FYI. A reason to change from 27" wheels to 700c wheels is the greater availability of tire sizes (700-20 to 700-58+) & tread choices (smooth to various levels of knobby) ...

  • a[COLOR= rgb(24, 24, 24)] 27x1.25 tire has the same circumference as a 700x32 tire ... IMO, either tire size is[/COLOR] a-good-thing[COLOR= rgb(24, 24, 24)] if you are riding on poorly paved roads ...[/COLOR]

Unfortunately, a 27" wheel sans tire weighs more than a comparable 700c wheel even the 700c wheel also has 36 spokes and even if both are laced to the same model of hub BECAUSE there will almost always be four-or-more additional spokes on the 27" wheel + those spokes will probably be about 4mm longer (a gram here, a gram there, pretty soon you are adding ounces ... and, add enough ounces, and you're eventually adding pounds ... it ALL adds up) ...

Also, the 27" rim will have a larger circumference + be wider than a typical 700c rim ...

Consequently, the gross weight of the 27" wheel & tire will be modestly heavier than a 700x wheel with a 700x32 tire.

Now, if you were to choose a 700x28-or-smaller tire, then the rotational mass would be less for the 700c wheel ... and, THAT is something many riders (particularly, "racers") prefer ...

Regardless, in this day-and-age, a 27" rim will probably be more difficult to replace without placing a special order (I presume that HARRIS CYCLERY carries 27" rims, BTW) or scrounging.

CONVERSION to 700c wheels often requires brake calipers which have a longer reach than the bike may currently have.

  • the brake calipers on some bikes can be adjusted to accommodate both 27" & 700c wheels, but they are few unless the frame builder intended for that type of flexibility ...
  • SOME sports touring frames made circa 1980 [[COLOR= rgb(128, 128, 128)]near the end of the era of 27" wheels as the de facto standard on bikes sold in America[/COLOR]] could be readily fit with either 27" or 700c wheels while using the same brake calipers.

  • FWIW. Here is an early 70s vintage RALEIGH frame which originally used 27" wheels but which currently has 700c wheels (note the extreme location of the brake pads in their calipers) ...

It is more difficult (but, not impossible) to convert a bike which has 27" wheels to use 26" wheels due to the greater distance between the brake mounting hole & the rim's brake surface which would require an extremely long reach brake caliper (TEKTRO makes calipers for the entire spectrum) ... BMX brake calipers may-or-may-not have sufficient "reach."

However, the main problem in using a 26" wheel on a frame which was originally designed for 27" wheels would be a BB shell which would probably be too low which might result in the cranks & pedals being perilously close to the ground on the down stroke.

The "road" tire choice for 26" wheels is very limited.

The negative to making the conversion from 27" wheels to 700c wheels is the potential cost ... particularly, if it is not a DIY project ...

Figure on at least $100-to-$200 for the rims + spokes + tires-and-tubes AND possible $40-to-$70 for brake calipers ...

  • BUT, if the bike's 27" wheels currently have steel rims then the money spent will be well worth it ...

If you are a wise shopper then ready-to-ride 700c wheelsets (sans tires) can certainly be bought on eBay for ~$100 +/- ... the rear hub on many wheels will be for frames which have 130mm wide rear dropouts ... a steel frame CAN be respaced with only a little elbow-grease ... aligning the rear dropouts takes a little more time & skill, but not too much ...

  • if your plan is to implement a SINGLE SPEED conversion, then you probably won't need to worry about the frame's spacing

[COLOR= rgb(24, 24, 24)]The front fork on some bikes with 27" wheels may have slightly narrower spacing, too, than you would find on a contemporary front hub ... [/COLOR]

  • [COLOR= rgb(24, 24, 24)]a fork is NOT as easy to cold set; but, with effort you can certainly spread the legs enough on an ad hoc basis to allow you to insert a modern hub in a vintage steel fork -- it will be a very snug fit.[/COLOR]
[COLOR= rgb(24, 24, 24)]BTW. If you do opt to use a 700c wheelset in a frame which was originally designed for 27" wheels then you can probably use the wheels with another frame in the future.[/COLOR]