Why wouldn't this work?

Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.

Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of
the reasons..

Jasper

 

On Tue, 27 May 2003 12:58:39 GMT, Jasper Janssen <[email protected]> wrote:

>Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
>frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
>rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.
>
>Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of the
>reasons..
>
>Jasper
First off it would but the wheel out of line in the frame making it difficult to adjust the brakes
... and having the tire rub against the stays... even if you were to realign the frame to make use
of this if the tire is not centered then the bike gets really tough to ride.... lots of wasted
energy kind tough to balance..

 

Jasper Janssen <[email protected]> wrote:

>Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
>frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
>rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.
>
>Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of the
>reasons..

It would work, as long as you also moved the brake mounting points accordingly. I suppose there
might be some assymetrical movement in the rear triangle if you were really torquing the frame in a
sprint - but would guess that wouldn't be a real issue.

The bottom line is that wheel dish isn't a huge issue at all if your rear wheel is simply built
correctly. It's certainly not a big enough "problem" to make it worth the hassles of riding a bike
that has a wider than necessary Q factor (due to the chainline), and that can't use any
off-the-shelf wheels, ever.

There are easier ways to reduce dish, such as using an off-center rim or building the wheel on a MTB
hub (or by adding a longer axle and 5mm spacer on the left). Of course, going with a 135mm hub is
going to make it hard to buy off-the-shelf wheels as well, and will kick out the chainline 2.5mm -
but at least everything else is "standard".

Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame

 

Jasper Janssen <[email protected]> wrote in message
news:<[email protected]>...
> Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
> frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
> rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.
>
> Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of
> the reasons..
>
> Jasper

Some bicycles have been built this way- earlier Vision recumbent bicycles had offset frames and
undished wheels.

One this that you'd have to deal with is frame alignment- it's quite easy for your average bike
mechanic to measure and align a frame to a centerline. I've done it with a string and a ruler. To
align everything to a given offset is a somewhat tougher job and would require a frame plate and
good measuring devices.

Another thing is that you'd mess up the chainline- the chain has to curve further to the right with
an offset frame. That's less of an issue with a recumbent, where the chain's 3 times as long as an
upright, but it would get real messy on a short-chainstay racing bike.

FWIW: Vision's current recumbents are symetrical.

Jeff

 

I don't think it would work at all because the rear wheel wouldn't be tracking directly behind the front wheel. I can't believe a bike like that would be rideable.

 

Going off topic, on 28 May 2003, DiabloScott wrote:

> wrote:
> > Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think
> > of the reasons..
>
> I don't think it would work at all because the rear wheel wouldn't be tracking directly behind the
> front wheel. I can't believe a bike like that would be rideable.

Try before you comment -- it's easy to ride a bike with offset rear wheel, but may be difficult to
ride no hands. If the offset is huge, then the steering is noticably asymmetric (I'm thinking of a
criuser bike I rode years ago that had been bent ~4 inches sideways when run over by a car). Even
severe offset like that is easy to ride--the kid who owned that bike rode it all summer after the
damage, we all had fun riding a bike that "dog-tracked".

-- Doug Milliken www.millikenresearch.com

 

Off topic? How is that off topic? I gave the OP something he hadn't thought of, a direct answer to his question.

OK, change my comment from "I can't believe a bike like that would be rideable." to
"A bike like that would ride like it had been run over by a car."

 

On Tue, 27 May 2003 15:50:46 -0400, Doug Milliken <[email protected]> wrote:

>Try before you comment -- it's easy to ride a bike with offset rear wheel, but may be difficult to
>ride no hands. If the offset is huge, then the steering is noticably asymmetric (I'm thinking of a
>criuser bike I rode years ago that had been bent ~4 inches sideways when run over by a car). Even
>severe offset like that is easy to ride--the kid who owned that bike rode it all summer after the
>damage, we all had fun riding a bike that "dog-tracked".

Wow, that's a lot of offset. Mine always leaned a little bit, and when I measured it I found that
the strings passed 3.5 and 4 cm from the seat tube, so that works out to.. only 2.5 mm offset. Of
course, this was not a bike with relaxed steering. It's downright jittery, almost. But that degree
of offset is already enough in that bike to be significantly uncomfortable for longer rides, because
you're *always* pushing the bars to keep the damn thing straight.

Jasper

 

On 28 May 2003 03:32:57 +0950, DiabloScott <[email protected]> wrote:

>I don't think it would work at all because the rear wheel wouldn't be tracking directly behind the
>front wheel. I can't believe a bike like that would be rideable.

But, actually, no. What I'm proposing is a dishless rear wheel, where you put that tracking behind
the front wheel, and base the rest off of that --so you bend the rear of the frame (particularly the
right side) in such a way that your cogset fits in.

Jasper

 

I believe I remember that an Orbit bicycle (built in Britain) is built with an offset rear triangle
to reduce the dish in the rear wheel. I read about it in the CTC magazine in a test article by
Chris Juden.

Bob Taylor

Jasper Janssen <[email protected]> wrote in message
news:<[email protected]>...
> Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
> frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
> rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.
>
> Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of
> the reasons..
>
> Jasper

 

jasper-<< Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear
of the frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than
just the rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.

Aslo buy lots of padded clothing so when the thing starts to shuck and jive down that hill, you
don't get hurt to much...

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

Jasper Janssen <[email protected]> wrote:

> Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
> frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just
> the rim?

Some frame makers have done just that. An example is Orbit Cycles:

http://www.orbit-cycles.co.uk/techspecsolo.shtml (The heading "offset rear triangle" is partway down
the page.)

Chalo Colina

 

On 28 May 2003 13:07:32 -0700, [email protected] (Bluto) wrote:
>Jasper Janssen <[email protected]> wrote:
>
>> Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
>> frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just
>> the rim?
>
>Some frame makers have done just that. An example is Orbit Cycles:
>
>http://www.orbit-cycles.co.uk/techspecsolo.shtml (The heading "offset rear triangle" is partway
>down the page.)

So, to sum up, the main thing keeping this back from being standard is non-standardness?

If enough bike makers start doing it, it will of course eventually become standard..

Jasper

 

Jasper Janssen <[email protected]> wrote:

> So, to sum up, the main thing keeping this [rear frame offset] back from being standard is
> non-standardness?
>
> If enough bike makers start doing it, it will of course eventually become standard..

Actually, I think the main thing keeping it out of the mass market is that it negates the subtle but
significant advantages of symmetrical construction. Comparative measurements between one side and
the other save both bike makers and bike mechanics from having to make a lot of painstaking absolute
measurements and keep a lot of references on hand.

Bicycle framebuilding is a lot more rudimentary a craft than many people think, with stretched
strings and meter sticks frequently used to check alignment. A maker who doesn't use industrial
inspection techniques or at least pretty elaborate purpose-built measuring tools would not be able
to yield as straight an offset frame for a similar amount of time and effort.

Likewise bike shop mechanics are able to do a lot of frame diagnostic work on a bike that's presumed
to be symmetrical. Not as much with an offset frame. In the worst case, an offset frame would get a
costly "straightening" by a thorough but ill-informed mechanic!

Similarly, offset built wheels pose a tiresome measurement chore to verify proper dish, a task
that's thus not likely to be repeated between successive wheel builds.

Something else to consider is that an offset frame (say a dishless 9sp
130mm) poses all the same clearance, chainline, Q-factor and related issues as does a 160mm dishless
rear, just all on one side. Meaning that the wider hub size possesses all the advantages of
both a dishless rear wheel and symmetrical frame construction, with no more complicating
issues than the offset rear already has.

Chalo Colina

 

On 29 May 2003 12:54:12 -0700, [email protected] (Bluto) wrote:

>Something else to consider is that an offset frame (say a dishless 9sp
>130mm) poses all the same clearance, chainline, Q-factor and related issues as does a 160mm
> dishless rear, just all on one side. Meaning that the wider hub size possesses all the
> advantages of both a dishless rear wheel and symmetrical frame construction, with no more
> complicating issues than the offset rear already has.

Except for the position of the bearing on the left side, putting more stress on the axle. Well,
unless you use a hub that takes that into account, I guess.

Jasper