Tire clearance when using 26" rims on a road frame



P

Pilgrim

Guest
Hello, I have a 1975 Schwinn Sports Tourer frame which would have
originally been equipped with 27" wheels. The chainstays seem rather
narrow, but I would like to put 26" mountain bike wheels and tires on
it. What is the maximum tire width that will fit this bike, or how
should I measure it myself to determine this?
 
Pilgrim wrote:
> Hello, I have a 1975 Schwinn Sports Tourer frame which would have
> originally been equipped with 27" wheels. The chainstays seem rather
> narrow, but I would like to put 26" mountain bike wheels and tires on
> it. What is the maximum tire width that will fit this bike, or how
> should I measure it myself to determine this?


Stick a mountain bike wheel in it and look.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
 
On Oct 10, 6:22 pm, "Paul Borg" <[email protected]> wrote:
> "Pilgrim" <[email protected]> wrote in message
>
> news:[email protected]...
>
> > Hello, I have a 1975 Schwinn Sports Tourer frame which would have
> > originally been equipped with 27" wheels. The chainstays seem rather
> > narrow, but I would like to put 26" mountain bike wheels and tires on
> > it. What is the maximum tire width that will fit this bike, or how
> > should I measure it myself to determine this?

>
> You will need long reach brake calipers for sure (unless you're planning on
> making this a fixed gear, in which case the hand brakes are optional)
>
> How could you not have access to a 26" though, to just try it out for real?
> They're a dime a dozen.


That's the plan for when the bike shop opens. I'm just trying to do
some pre-search until then. They have a few MTB wheels that I can try
on for size, but I'll be building my wheels from scratch, so I'll
still need to know which rim and tire widths to look for on ebay.
 
On Oct 10, 5:05 pm, Pilgrim <[email protected]> wrote:
> Hello, I have a 1975 Schwinn Sports Tourer frame which would have
> originally been equipped with 27" wheels. The chainstays seem rather
> narrow, but I would like to put 26" mountain bike wheels and tires on
> it. What is the maximum tire width that will fit this bike, or how
> should I measure it myself to determine this?


You can measure for yourself by finding the point roughly 12 1/2" from
the axle on the chainstays and then measuring the distance between the
chainstays. IIRC, you should be able to fit a 1.75" wide tire in
there- but that'll be a tight fit. A 1.5" tire might work better, but
it's not much fatter than the original 27 x 1 1/4" tire.

Also, you'll be dropping the bottom bracket by almost 1 1/2". This is
drastic, particularly since the Sport Tourer didn't have a high BB to
start with. I'd expect to be banging pedals on the ground in even the
mildest turns. If you can put up with that (I did, for a while), fine.
It's just a consequence of building a mongrel bike like this.

A better choice would be to convert the bike to 700C wheels, which are
almost the same diameter, and have a much wider range of tire sizes
available. 700 x 40C tires should fit, and you might be able to use
your original brakes.

Jeff
 
"Pilgrim" <[email protected]> wrote in message
news:[email protected]...
> Hello, I have a 1975 Schwinn Sports Tourer frame which would have
> originally been equipped with 27" wheels. The chainstays seem rather
> narrow, but I would like to put 26" mountain bike wheels and tires on
> it. What is the maximum tire width that will fit this bike, or how
> should I measure it myself to determine this?
>


You will need long reach brake calipers for sure (unless you're planning on
making this a fixed gear, in which case the hand brakes are optional)

How could you not have access to a 26" though, to just try it out for real?
They're a dime a dozen.
 
On Oct 10, 6:05 pm, Pilgrim <[email protected]> wrote:
> Hello, I have a 1975 Schwinn Sports Tourer frame which would have
> originally been equipped with 27" wheels. The chainstays seem rather
> narrow, but I would like to put 26" mountain bike wheels and tires on
> it. What is the maximum tire width that will fit this bike, or how
> should I measure it myself to determine this?


How about going somewhere, like to a bike shop and slide a front
wheel(rear is 135mm) kinda in there and see??
 
On Oct 10, 6:18 pm, JeffWills <[email protected]> wrote:
> On Oct 10, 5:05 pm, Pilgrim <[email protected]> wrote:
>
> > Hello, I have a 1975 Schwinn Sports Tourer frame which would have
> > originally been equipped with 27" wheels. The chainstays seem rather
> > narrow, but I would like to put 26" mountain bike wheels and tires on
> > it. What is the maximum tire width that will fit this bike, or how
> > should I measure it myself to determine this?

>
> You can measure for yourself by finding the point roughly 12 1/2" from
> the axle on the chainstays and then measuring the distance between the
> chainstays. IIRC, you should be able to fit a 1.75" wide tire in
> there- but that'll be a tight fit. A 1.5" tire might work better, but
> it's not much fatter than the original 27 x 1 1/4" tire.
>
> Also, you'll be dropping the bottom bracket by almost 1 1/2". This is
> drastic, particularly since the Sport Tourer didn't have a high BB to
> start with. I'd expect to be banging pedals on the ground in even the
> mildest turns. If you can put up with that (I did, for a while), fine.
> It's just a consequence of building a mongrel bike like this.
>
> A better choice would be to convert the bike to 700C wheels, which are
> almost the same diameter, and have a much wider range of tire sizes
> available. 700 x 40C tires should fit, and you might be able to use
> your original brakes.
>
> Jeff


Good points Jeff, I hadn't thought about the effect on the ride
height. That could be annoying. I don't have to worry about using the
original brakes because I got the frame bare, and I actually kinda
prefer a coaster brake. Don't worry, I'll have a front brake. Just
bought a Surly 1X1 fork with canti pivots for 26" rims so that
shouldn't be a problem. Gotta admit, part of me wants to scrap the
Schwinn, and just finish the job with a Crosscheck frame, but lets do
this cheap. After all, it's a mongrel :-D

So is chainstay bending an option? A friend of mine said that he had
managed to spread his a bit to fit a wider axle, but could the same be
done at the seatpost to increase tire clearance? I know somebody's
gonna jump my case about this, but let me put it this way. I live in
San Francisco, and I frequently dash between cars at intersections. If
this is less dangerous to my health than that, it probably won't
bother me. I paid $35 for this frame, and I can always take a bus
home. So lets get experimental!

One thing to note is that I've already cut off the crossmember that
holds to chainstays together at the seatpost, it was a kickstand. I
plan to braze another piece of metal in there for strength, but before
I do that it should make bending the chainstays a little easier.




"Mongrel bike", I like the sound of that :-D