rawly old

this may seem like a dumb question; i geezer my age should know, but i'm faced with
a dilemna. i just lucked into an '88 5spd raleigh mixte, (according to the yr. code on the
derailleur). i've been on mtn. bikes for the 30 yrs. my problem is this, the mixte, which
incidently has never been ridden, has 27'x1.25 tires. i have plenty of clearance; can i
put 700 x 1.5" tires on those rims? the derailleur works so flawlessly with the cassette
as it is that i hate the thought of changing it out for different rims, but i really want at least 1.5s to tour. can't seem to find 27s in any size other than 1.25.

TurbineBlade

700c is a different diameter than the old 27" tires. You can probably find 27" tires that are wider than 1.25 though just by using an internet search.

I've never seen 27's listed in decimals -- always fractions (i.e. - 27 1/4, 27 3/8, etc.) Make sure your tires actually list decimals rather than fractions, since there's some confusion in tire sized based upon which is used.

https://sheldonbrown.com/tire-sizing.html

Esteban32696

I know you can find 1 3/8 wide, but I don't think I have ever seen 1 1/2 . I, too, have only seen fraction sizes.

FBinNY 

To answer the specific question of whether you can switch to 700c wheels, the answer is probably, but you should probably pass.

The key in changing to 700c is that the radius is reduced by 4mm, meaning that you'll be lowering the brake shoes by that much. If there's at least that much room to lower the shoes on both brakes the change is possible. It'll also lower the bike by 4mm reducing pedal/ground clearance, but that's not significant for your purposes.

The reason not to do it is cost. A pair of wheels is fairly pricey, and I wouldn't put that much into that bike. These days, you can get such great value in newer bikes, that spending lots of sough to keep a an older bike alive isn't warranted unless it's something special, which yours isn't (sorry, no offense intended).

Either look for the most appropriate 27" tire or buy a new bike suited to your needs, and keep this alive as a "B" bike or commuter, or sell it to a friend for casual riding in the park.

fietsbob

To put a chubby1.5" wide tire in a 27" frame , i'd suggest going smaller , to 650b... 584 ISO
.. as naturally the wider the tire also makes it's OD bigger..
The Selection of brake caliper needs to have a longer reach, but
this is a trendy conversion, these days, so parts are out there.

Do have a replacement wheelset in this scheme, brake change, etc.

there are some high performance high volume tires for road riding
to support these wheel types , the post war French Randonneur replica bikes.

FBinNY 

This is about the only way to make something that's borderline, much worse. It's a radius difference of 23mm or almost one inch. That means definitely having to source an unusually long reach brake, and dropping the bottom bracket by one inch, which is material in terms of pedal to ground clearance. It may be trendy, but that doesn't make it smart.

Ironically, what is trendy in mtb is the move to 29" which is actually 700c with wide tires. Go figure

fietsbob

Yes its a longer reach, Tektro sells a suitable dual pivot long reach caliper .
that extra space is quickly filled with mudguards with decent clearance beneath them.

FBinNY 

The OP says the bike already has plenty of clearance with 27", which isn't that surprising given that the bike dates from '88. That might put the brake to rim distance with 584 rims beyond even the longest Tektro. Not to mention the implications of dropping the BB by 1".

To the OP, 27x1-3/8 tires are readily available, and aren't that different from 1-1/2 in section. You can save a ton of dough going with wider 27" tires, and if you get more serious about touring, or simply aren't happy with that section, can always change the wheels, or buy a new bike later. You won't have wasted much dough trying out the wider 27s, since tires are consumable anyway.

rawly old

If 4mm is all i need to worry about it's doable cuz the calipers can adjust up or down more than a
centimeter, the same for in or out. I saw sumpin' in sheldon brown's about a tire that's sold as a 700,
but is actually a 635. The problem is I've no i've no idea where to find any of the potential candidates.
I've got a pair of 26" with a 6 spd cassette that will fit just fine, but really hate messing with a vitually
new 5 spd. cassette and likewise suntour gt that are so perfectly matched for fast, precise, hassle-
free shifting. Unless you race it has all the range you need.(49f x 36/14r). The bike's a pretty rare
unit in as much as it's essentially new and fit for riders 5'8" to 6'2". I'd like to keep it as original as is
practical, but i'm definitely gettin' rid of the gramma bars and putting on a gooseneck stem and some
nearly straight gullwing bars. Oh hell, guess I'll just put on the 26s and hope for the best

ironwood

Try a set of Panaracer Paselas on the 27" rims. Its a good touring tire that has a wider cross section tha most 27x1/4 tires.

If you really want 700c rims and tires, you will have to lace up a new rim on the old hubs.

I don't see how you can fit a 26" MTB wheel and have enough caliper reach. But then there are four differe3nt 26" rims and tires. The ERTRO size should be stamped on the rim and tire. It might be possible to put 650A( 590 ERTRO), or 650B(584) rims on your bike with long caliper brakes such as Dia-Comp 730 (I think) centerpulls. I converted an old Univega to 650B, and am happy with it. The Rivendell website gives specific instructions on how to measure your frame to see if it is a good candidate for a conversion.

rawly old

Well, for reasons unbeknownst to me, the calipers are slotted so the pads can be adjusted up
up or down a full centimeter. I suspect this was done so that individual dealerships would have
an option as to how they wanted the bikes set up. There appears also to be plenty of latitude
as to how widely the calipers can be adjusted to open. Having measured, it appears able to
receive anything, other than balloons, between 26" and 28".
As far as converting it goes, this is my reasoning. My old technium mtb
has a 35" standover which leaves any future progeny i might want about
a half inch clearance. my masculinity isn't as threatened riding a mixte as
it is by the top tube of my ovation. Stop signs and lights can get a bit
dicy>

Grand Bois

Bike Tools Etc is selling Tektro 800 calipers for $13.95 each. They extend to 78 millimeters.

rawly old

Sorry to have created such a flap; i'll just go with 27" x 1 3/8" and try
harder to lose another 20 pounds.

fietsbob

there was a convening on size between tire and rim makers, so they were all using the same data.

that is bead seat diameter , now its on most tires
27" is 630mm
700c is 622.
650b is 584.. etc.

FWIW, outside diameter of wheel is a product of tire width chosen for the rim.

rawly old

Oh, I dunno FBinNY considering new mixtes start around $600 and can go to $2500, I'd say finding
one that's never been ridden in pristine condition for $25 is kinda special.

FBinNY 

I didn't say that it wasn't a good find, but you'll negate the bargain if you put an excess amount of dough into it. My point is to enjoy it for what it is, rather than spend lots of dough to try to make it what it isn't.

Ultimately since it's your money, it's strictly your call. But be careful in comparing the cost of upgrades to new bikes.

In today's market new bikes are usually priced at close to the value of the components, if bought separately. Essentially the frame is free until you reach the high end where more value is assigned to it. The economics are such that folks often buy a brand new bike complete just for the components.

joejack951

The change to 700c wheels can be done relatively economically by avoiding the more common pre-built wheelsets which are geared towards the average roadie looking for styling and lightweight.

For under $60, you can get a set of 36H 700c wheels with a freewheel hub that should do everything you want. The wheels will likely need some tweaking (at the price, you can't expect perfection) and the hub will need some spacers moved around along with re-dishing the rear wheel (or spreading your frame). Still, the overall investment is quite low even including new tires.

Front: https://www.niagaracycle.com/product_...oducts_id=1021
Rear: https://www.niagaracycle.com/product_...oducts_id=1017