Small Touring Frames & 650 Wheels

"Roy Zipris" wrote ...

Quoted message said:

Recently, I've been looking at touring bikes, and it appears that many
builders use 650 wheels on their smaller frames and 700 wheels on
larger frames. I did not see this wheel-size distinction in road bikes
until you get into *really* small frames--i.e, those for kids or
so-called "woman-specific" sizes.

I understand both the toe-overlap issue and the basic differences in
geometry between road and touring bikes, but I don't understand why
wheel size is more critical--or at least, so different--in a touring
bike. Would someone please enlighten me? Thanks. Regards, Roy Zipris

Most tourers are designed to accept much wider tires than road bikes, with
correspondingly greater sidewall heights. Tourers are also designed to
accept fenders, and frequently carry a third water bottle under the down
tube. All three take up space under the downtube that, on a smaller frame,
would not be available with a bigger (700) rim in the way.

My own feeling is that, in an ideal world, wheel sizes would be more closely
matched to frame size and intended use of the bicycle, with three or four
rim sizes being as widely available as 700 and 26" are today. Unfortunately
the economics of bicycle manufacturing make it unlikely that this will
happen any time soon.

My own tourer has 26" rims on a 58 cm frame, which definitely looks a little
odd. Were the frame any larger the proportions would definitely be
aesthetically displeasing. As it is, I rather like the way it looks right
now, but I'm a little different that way. I can run 26" x 1.75" tires and
fenders on it, and have room for a full size (28 oz) water bottle under the
down tube, which is nice. The slightly lower standover height is nice when
I'm getting on and off a fully loaded bike, and when I'm in city traffic
where I am expected to stop for stoplights, stop signs, etc. 26" tires and
rims are also more widely available than any other size, which saved my ass
when I needed a new rear rim in Oban, Scotland a few years back.

Do the bikes you're looking at have 650B, 650C or 26" wheels? 650B or 650C
might be the optimum rim size for a particular frame size and geometry, but
finding replacement tires and rims in a remote area might be a little
difficult.
--
mark

Thanks, Mark. Some are 650 (I don't recall which letter), some 26". I'm
still at the fantasy stage, so I haven't gotten too involved in
particulars yet.
Regards, Roy Zipris

Roy Zipris said:

I understand both the toe-overlap issue and the basic differences in
geometry between road and touring bikes, but I don't understand why
wheel size is more critical--or at least, so different--in a touring
bike. Would someone please enlighten me? Thanks. Regards, Roy Zipris

Toe overlap is not a big problem. And by 650 wheels I think you mean
mountain bike-or 559-wheels. I wouldn't tour any where but France on
650B wheels. The pros for 559 wheels are strength and wide tire
availability almost anywhere. Don't know any cons and I've made touring
bikes both ways. Both work well. 559 wheels look kinda odd on big
frames but who cares if they work well.
Phil Brown

Roy Zipris said:

Thanks, Mark. Some are 650 (I don't recall which letter), some 26". I'm
still at the fantasy stage, so I haven't gotten too involved in
particulars yet.
Regards, Roy Zipris

I believe you're thinking 650B (584 in bead sead diameter and ISO
width), the "weird" size that an intentional effort to repopularize is
currently being made for. This size makes some sense, especially since
you can play tricks with putting it on stupidly low-clearance bikes.
650C (571), sometimes referred to confusingly as "26"", and frequently
referred to as plain "650," is a size that only really is applicable to
roadie road bikes because the tires and rims don't really exist for
other applications, save for one tire made by Terry that's a 28.

The big reasons why touring bikes are made more commonly with variable
wheel sizes is because appropriate tires and rims basically exist in
both 700 (622), MTB 26" (559, by far more common choice for scaled-down
wheels on touring bikes), and now 650B, and also because toe clearance
becomes a much bigger issue on touring bikes if fatter tires and
fenders are used. Really no bike should have toe overlap even with a
wide tire and full front fender, and it's a ridiculous problem on some,
and 26" doesn't go all the way towards solving the problem on some
bikes - 24" sizes should be used more frequently than they are,
especially since the tires and rims are actually pretty available.

Touring bikes designed around MTB 26" make a lot of sense. The only
problem I see is that if you ever want to put light or midweight road
rims and 25-28ish tires on such bikes, there are like no good options
for rims (there are few particularly cool rims in general), with a few
single-eyelet rims in the 390 gram range being the only choice, and
only a handful of tires. It's not a big issue overall, but more
flexibility would be good here because there are a lot of very light
people who only really need roadie weight rims, especially in the case
of touring bikes used as do-everything bikes.

Roy Zipris said:

Recently, I've been looking at touring bikes, and it appears that many
builders use 650 wheels on their smaller frames and 700 wheels on
larger frames. I did not see this wheel-size distinction in road bikes
until you get into *really* small frames--i.e, those for kids or
so-called "woman-specific" sizes.

I understand both the toe-overlap issue and the basic differences in
geometry between road and touring bikes, but I don't understand why
wheel size is more critical--or at least, so different--in a touring
bike. Would someone please enlighten me? Thanks. Regards, Roy Zipris

You have the factors there, just connect the dots. With an
ample tire section and reasonable mudguard clearance, even a
slightly shorter crank becomes an issue for clearance. Toss
in a customer request for a short top tube and suddenly we
are talking small wheel format.

For the same rider on a race bike, skip the big tire section
and mudguard clearance. With less tire and mudguard in the
way a shorter front center is easier.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971