Widening a bonded rear triangle



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John Stevenson

Guest
I have an old Raleigh Dynatech frame I'd like to press into service as a hack/commuter.

It has steel tubes bonded into aluminium lugs, though the rear dropouts are brazed into the seat-
and chain-stays.

It's currently spaced 126mm, and while I can fight a 130mm rear wheel into it, I don't want to have
to do that when I get a flat and I assume that the resultant non-parallelism of the dropouts won't
be good for the hub axle.

So, the question: does the panel think such a frame can be safely bent to take a 130mm hub?
If so, how?

Ta

John
 
J

John Everett

Guest
On Fri, 18 Apr 2003 21:13:23 +1000, John Stevenson <[email protected]> wrote:

>I have an old Raleigh Dynatech frame I'd like to press into service as a hack/commuter.
>
>It has steel tubes bonded into aluminium lugs, though the rear dropouts are brazed into the seat-
>and chain-stays.
>
>It's currently spaced 126mm, and while I can fight a 130mm rear wheel into it, I don't want to have
>to do that when I get a flat and I assume that the resultant non-parallelism of the dropouts won't
>be good for the hub axle.
>
>So, the question: does the panel think such a frame can be safely bent to take a 130mm hub?
>If so, how?

I wouldn't worry about it. A couple of years ago I upgraded on old Trek 1400 bonded aluminum frame
from 7-speed to 8-speed. In spite of dire predictions from the doom-and-gloom crowd, snapping the
130mm hub into the 126mm spaced frame works just fine. As a "put my money where my mouth is"
example, I took that bike to the Colorado Rockies last summer where I exceeded 40 mph on descents a
number of times. The bike's still together.

I also did the trig a few years ago to see what moving a dropout 2mm did to the parallelism. As I
recall (don't have the figures in front of me) the effect was negligible, probably well within the
tolerances a frame builder would accept.

jeverett3<AT>earthlink<DOT>net http://home.earthlink.net/~jeverett3
 
M

Mike Jacoubowsk

Guest
> I wouldn't worry about it. A couple of years ago I upgraded on old Trek 1400 bonded aluminum frame
> from 7-speed to 8-speed. In spite of dire predictions from the doom-and-gloom crowd, snapping the
> 130mm hub into the 126mm spaced frame works just fine. As a "put my money where my mouth is"
> example, I took that bike to the Colorado Rockies last summer where I exceeded 40 mph on descents
> a number of times. The bike's still together.

On the 1400, you wouldn't likely have a problem with the chainstay/bb junction, but many have
snapped the brake bridge loose from the seatstays by spreading those frames. It (the brake bridge)
is held in place both by a pair of rivets and glue, and generally it's the rivets and interlocking
curvature of the pieces that does the work, so it's usually not a big deal aside from some buzzing.

But a blanket statement not to worry about it isn't appropriate here. Those frame tubes are *very*
rigid, so most of the stress from spreading the stays ends up at the brake bridge, which is trying
to keep those stays in the right place. Please note, however, that later 1400s were actually made
with 128mm spacing, to accommodate either 126mm or 130mm hubs.

--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

"John Everett" <[email protected]> wrote in message
news:[email protected]...
> On Fri, 18 Apr 2003 21:13:23 +1000, John Stevenson <[email protected]> wrote:
>
> >I have an old Raleigh Dynatech frame I'd like to press into service as a hack/commuter.
> >
> >It has steel tubes bonded into aluminium lugs, though the rear dropouts are brazed into the seat-
> >and chain-stays.
> >
> >It's currently spaced 126mm, and while I can fight a 130mm rear wheel into it, I don't want to
> >have to do that when I get a flat and I assume that the resultant non-parallelism of the dropouts
> >won't be good for the hub axle.
> >
> >So, the question: does the panel think such a frame can be safely bent to take a 130mm hub? If
> >so, how?
>
> I wouldn't worry about it. A couple of years ago I upgraded on old Trek 1400 bonded aluminum frame
> from 7-speed to 8-speed. In spite of dire predictions from the doom-and-gloom crowd, snapping the
> 130mm hub into the 126mm spaced frame works just fine. As a "put my money where my mouth is"
> example, I took that bike to the Colorado Rockies last summer where I exceeded 40 mph on descents
> a number of times. The bike's still together.
>
> I also did the trig a few years ago to see what moving a dropout 2mm did to the parallelism. As I
> recall (don't have the figures in front of me) the effect was negligible, probably well within the
> tolerances a frame builder would accept.
>
>
> jeverett3<AT>earthlink<DOT>net http://home.earthlink.net/~jeverett3
 
S

Sheldon Brown

Guest
John Stevenson asked:

>>I have an old Raleigh Dynatech frame I'd like to press into service as a hack/commuter.
>>
>>It has steel tubes bonded into aluminium lugs, though the rear dropouts are brazed into the seat-
>>and chain-stays.
>>
>>It's currently spaced 126mm, and while I can fight a 130mm rear wheel into it, I don't want to
>>have to do that when I get a flat and I assume that the resultant non-parallelism of the dropouts
>>won't be good for the hub axle.
>>
>>So, the question: does the panel think such a frame can be safely bent to take a 130mm hub? If
>>so, how?

John Everett replied

> I wouldn't worry about it. A couple of years ago I upgraded on old Trek 1400 bonded aluminum frame
> from 7-speed to 8-speed. In spite of dire predictions from the doom-and-gloom crowd, snapping the
> 130mm hub into the 126mm spaced frame works just fine. As a "put my money where my mouth is"
> example, I took that bike to the Colorado Rockies last summer where I exceeded 40 mph on descents
> a number of times. The bike's still together.
>
> I also did the trig a few years ago to see what moving a dropout 2mm did to the parallelism. As I
> recall (don't have the figures in front of me) the effect was negligible, probably well within the
> tolerances a frame builder would accept.

I, too, did the trig for this, when I was writing my Web page on the topic:

http://sheldonbrown.com/frame-spacing.html

Going from 126 to 130 amounts to a measly 1/3 degree change. The direction of the change is such
that any stresses it might theoretically place on the axle are opposite in direction to the much
greater stresses from chain pull.

The chances of your stock setup being within 1/3 degree are pretty slim in any case.

BTW, due to popular demand, I've recently added some photos to that page that may make the procedure
a bit easier to understand.

Sheldon "Some Call It 'Cold Setting', I Call It Bending" Brown
+-------------------------------------------------+
| Men have become the tools of their tools. | -- Henry David Thoreau |
+-------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com
 
A

A Muzi

Guest
> On Fri, 18 Apr 2003 21:13:23 +1000, John Stevenson <[email protected]> wrote:
>
> >I have an old Raleigh Dynatech frame I'd like to press into service as a hack/commuter.
> >
> >It has steel tubes bonded into aluminium lugs, though the rear dropouts are brazed into the seat-
> >and chain-stays.
> >
> >It's currently spaced 126mm, and while I can fight a 130mm rear wheel into it, I don't want to
> >have to do that when I get a flat and I assume that the resultant non-parallelism of the dropouts
> >won't be good for the hub axle.
> >
> >So, the question: does the panel think such a frame can be safely bent to take a 130mm hub? If
> >so, how?

"John Everett" <[email protected]> wrote in message
news:[email protected]...
> I wouldn't worry about it. A couple of years ago I upgraded on old Trek 1400 bonded aluminum frame
> from 7-speed to 8-speed. In spite of dire predictions from the doom-and-gloom crowd, snapping the
> 130mm hub into the 126mm spaced frame works just fine. As a "put my money where my mouth is"
> example, I took that bike to the Colorado Rockies last summer where I exceeded 40 mph on descents
> a number of times. The bike's still together.
>
> I also did the trig a few years ago to see what moving a dropout 2mm did to the parallelism. As I
> recall (don't have the figures in front of me) the effect was negligible, probably well within the
> tolerances a frame builder would accept.

The Raleigh Technium aluminum frames with CrMo rear ends are no problem at all but the Trek 1400 is
prone to failure at the bridge when moving the aluminum rear end. Yours worked out OK but I don't do
rear alignments on that frame series. A phrase we like is "if it's steel you can move it"
--
Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971
 
J

John Stevenson

Guest
John Everett <[email protected]> wrote in
news:[email protected]:

> I wouldn't worry about it. A couple of years ago I upgraded on old Trek 1400 bonded aluminum frame
> from 7-speed to 8-speed. In spite of dire predictions from the doom-and-gloom crowd, snapping the
> 130mm hub into the 126mm spaced frame works just fine. As a "put my money where my mouth is"
> example, I took that bike to the Colorado Rockies last summer where I exceeded 40 mph on descents
> a number of times. The bike's still together.
>
> I also did the trig a few years ago to see what moving a dropout 2mm did to the parallelism. As I
> recall (don't have the figures in front of me) the effect was negligible, probably well within the
> tolerances a frame builder would accept.

My concern is less with the loads on the axle than the sheer inconvenience of a frame that doesn't
easily drop the wheel from the dropouts.

However from the other advice offered here (thanks chaps) it sounds like I can just go right ahead.
The seatstay bridge on this frame is brazed to the stays so the issues Mike raises about all-bonded
frames don't apply.

And I've just realised this thing is so elderly it has horizontal droputs. Now, if I can find a
Sturmey ACS somewhere I could recreate my favourite round-town bike of all time, stolen from outside
a pub in Leeds many years ago. I'm not, however, going to fight my way up the hills on my commute in
one gear. I'm way too unfit and fond of my knees!
 
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