Help with chain tension on a single speed conversion.



E

eric

Guest
I've "converted" a old road bike into a single speed.

What I've done:

Grind off all hangers on my frame. (bad idea in hindsight)
took off all brakes and derailleurs
took off large chainring.
I kept the old 6sp chain and freewheel on the rear wheel.

Its quite light looks quite good as is. However, I cannot get the
chain to stop "seizing up". I can pedel for a few seconds, and it
would seize. I can pedel backward for a quarter turn and I'll be ok
again.

I find that I cannot tighten the QR tight enough to prevent the wheel
from moving forward a little bit during hard pedelling. This frame
has a horizontal dropout. (Older type, wheel moves backwards into drop
out.

I believe the chain is seizing due to chain tension. However, I can't
simply add something like a Surly Singulator or even an old derailleur
to remedy this.

Any ideas?
 
"eric" <[email protected]> wrote in message
news:[email protected]...
>
> I've "converted" a old road bike into a single speed.
>
> What I've done:
>
> Grind off all hangers on my frame. (bad idea in hindsight)
> took off all brakes and derailleurs
> took off large chainring.
> I kept the old 6sp chain and freewheel on the rear wheel.
>
> Its quite light looks quite good as is. However, I cannot get the
> chain to stop "seizing up". I can pedel for a few seconds, and it
> would seize. I can pedel backward for a quarter turn and I'll be ok
> again.
>
> I find that I cannot tighten the QR tight enough to prevent the wheel
> from moving forward a little bit during hard pedelling. This frame
> has a horizontal dropout. (Older type, wheel moves backwards into drop
> out.
>
> I believe the chain is seizing due to chain tension. However, I can't
> simply add something like a Surly Singulator or even an old derailleur
> to remedy this.
>
> Any ideas?


Sounds like the QR is not clamping onto the dropout. How close is the
end of the axle to the outer face of the dropout?

PH
 
Check that you're using an old style all-steel quick release, and not one of
the modern aluminium abortions that is incapable of clamping tightly enough.

Nick

"eric" <[email protected]> wrote in message
news:[email protected]...
>
> I've "converted" a old road bike into a single speed.
>
> [snip]
>
> I find that I cannot tighten the QR tight enough to prevent the wheel
> from moving forward a little bit during hard pedelling. This frame
> has a horizontal dropout. (Older type, wheel moves backwards into drop
> out.
 
eric <[email protected]> wrote in message news:<[email protected]>...
> I've "converted" a old road bike into a single speed.
>
> What I've done:
>
> Grind off all hangers on my frame. (bad idea in hindsight)
> took off all brakes and derailleurs
> took off large chainring.
> I kept the old 6sp chain and freewheel on the rear wheel.
>
> Its quite light looks quite good as is. However, I cannot get the
> chain to stop "seizing up". I can pedel for a few seconds, and it
> would seize. I can pedel backward for a quarter turn and I'll be ok
> again.
>
> I find that I cannot tighten the QR tight enough to prevent the wheel
> from moving forward a little bit during hard pedelling. This frame
> has a horizontal dropout. (Older type, wheel moves backwards into drop
> out.
>
> I believe the chain is seizing due to chain tension. However, I can't
> simply add something like a Surly Singulator or even an old derailleur
> to remedy this.
>

Your diagnosis sounds very likely.

You may be trying to apply too much tension. What happens if you
reduce the chain tension a bit? Unless everything is perfectly
aligned chain tension will vary a bit on full rotation so you need to
set it allowing for this. About a half inch "slack" movement at the
tightest spot is what I would go for.

If your QR is moving due to excess tension then that is a "good thing"
as the alternative is a snapped chain.

Is your freewheel well aligned? Multiple freewheels (at least the
ones I use) are often a bit off-centre (spin the freewheel and see if
the sprockets wobble in relation to the wheel). This could cause
enough movement for a tight spot. If so you could buy a new single
speed freewheel and try that.

Is your chainring round and true? Again, this might cause a tight
spot if it is not.

You ~could~ add a derailleur (one that doesn't need a hanger) or a
chain tensioner (chain stay attachment) - if I read right you are
still using your freewheel, so there is no imperative not to. That
would somewhat defeat the object though.

Andrew Webster
 
Yeah, get a quality QR or go to bolt-on hubs. This was happening on a friend's recent SS conversion and a stronger QR did the trick.

Good luck,
Jeremy


Nick Payne said:
Check that you're using an old style all-steel quick release, and not one of
the modern aluminium abortions that is incapable of clamping tightly enough.

Nick

"eric" <[email protected]> wrote in message
news:[email protected]...
>
> I've "converted" a old road bike into a single speed.
>
> [snip]
>
> I find that I cannot tighten the QR tight enough to prevent the wheel
> from moving forward a little bit during hard pedelling. This frame
> has a horizontal dropout. (Older type, wheel moves backwards into drop
> out.
 
jtill <[email protected]> wrote in message news:<[email protected]>...
> Yeah, get a quality QR or go to bolt-on hubs. This was happening on a
> friend's recent SS conversion and a stronger QR did the trick.
>
> Good luck,
> Jeremy
>
>
> Nick Payne Wrote:
> > Check that you're using an old style all-steel quick release, and not
> > one of
> > the modern aluminium abortions that is incapable of clamping tightly
> > enough.
> >
> > Nick
> >


But the OP says that his chain seizes up. A better QR won't solve
that. Also, if the QR didn't slip before conversion, why should it
now?

> > "eric" <[email protected]> wrote in message
> > news:[email protected]...
> > >
> > > I've "converted" a old road bike into a single speed.
> > >
> > > [snip]
> > >
> > > I find that I cannot tighten the QR tight enough to prevent the

> wheel
> > > from moving forward a little bit during hard pedelling. This frame
> > > has a horizontal dropout. (Older type, wheel moves backwards into

> drop
> > > out.
 
Andrew Webster wrote in message
<[email protected]>...
>
>But the OP says that his chain seizes up. A better QR won't solve
>that. Also, if the QR didn't slip before conversion, why should it
>now?


When one is constrained to one gear, one must push harder to compensate for
the lack of availability of a lower gear. The chain pulls the hub forward
in the slots because the pulling force upon the chain is greater and so is
to overcome the friction available at the locknut.

The correct answer may be to tighten the QR, change to solid spindle, change
to a lower gear or change rear ends to rear facing. I have never found the
last option necessary after changing to solid spindle and using an
engineers spanner.

Trevor
 
"Trevor Jeffrey" <[email protected]> writes:

> Andrew Webster wrote in message
> <[email protected]>...
> >
> >But the OP says that his chain seizes up. A better QR won't solve
> >that. Also, if the QR didn't slip before conversion, why should it
> >now?

>
> When one is constrained to one gear, one must push harder to compensate for
> the lack of availability of a lower gear. The chain pulls the hub forward
> in the slots because the pulling force upon the chain is greater and so is
> to overcome the friction available at the locknut.
>

Nice try. Thanks for playing.
The higher the gear, the less tension in the chain.
You got fooled because it is harder to pedal, but it is
easier on the chain.
 
Jim Smith wrote in message <[email protected]>...
>"Trevor Jeffrey" <[email protected]> writes:
>
>> Andrew Webster wrote in message
>> <[email protected]>...
>> >
>> >But the OP says that his chain seizes up. A better QR won't solve
>> >that. Also, if the QR didn't slip before conversion, why should it
>> >now?

>>
>> When one is constrained to one gear, one must push harder to compensate

for
>> the lack of availability of a lower gear. The chain pulls the hub

forward
>> in the slots because the pulling force upon the chain is greater and so

is
>> to overcome the friction available at the locknut.
>>

>Nice try. Thanks for playing.
>The higher the gear, the less tension in the chain.
>You got fooled because it is harder to pedal, but it is
>easier on the chain.
>

Maximum tension within the chain is determined by pedal force and front
sprocket size alone and has nothing to do with gear ratio. Acceleration is
affected by gear ratio. So for a high gear ratio the bicycle accelerates
more slowly yet the force upon the pedals is usually increased, which is why
the axle slips.

Trevor
 
Andrew Webster wrote in message

>>>But the OP says that his chain seizes up. A better QR won't solve
>>>that. Also, if the QR didn't slip before conversion, why should it
>>>now?


Might be that his bike had old-style thin dropouts with a clamp on
derailer hanger. Conversions involving removal of such adaptor claws
sometimes do require shorting the protrusion of the axle on the right side.

Trevor Jeffrey wrote:

>>When one is constrained to one gear, one must push harder to compensate for
>>the lack of availability of a lower gear. The chain pulls the hub forward
>>in the slots because the pulling force upon the chain is greater and so is
>>to overcome the friction available at the locknut.


Jim Smith wrote
>
> Nice try. Thanks for playing.
> The higher the gear, the less tension in the chain.
> You got fooled because it is harder to pedal, but it is
> easier on the chain.


That's a bit of an oversimplification.

For a given amount of pedal force, chain tension is inversely
proportional to the size of the chainring. (Bigger chainring/higher
gear=less tension)

How ever, for a given amount of bicycle driving force at the tire, chain
tension will be inversely proportional to the size of the rear sprocket.
(Smaller sprocket/higher gear=more tension.)

Sheldon "Maths" Brown
+-------------------------------------------------+
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Phone 617-244-9772 FAX 617-244-1041
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Hard-to-find parts shipped Worldwide
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Sheldon Brown <[email protected]> writes:

> Andrew Webster wrote in message
>
> >>>But the OP says that his chain seizes up. A better QR won't solve
> >>>that. Also, if the QR didn't slip before conversion, why should it
> >>>now?

>
> Might be that his bike had old-style thin dropouts with a clamp on
> derailer hanger. Conversions involving removal of such adaptor claws
> sometimes do require shorting the protrusion of the axle on the right
> side.
>
> Trevor Jeffrey wrote:
>
> >>When one is constrained to one gear, one must push harder to compensate for
> >>the lack of availability of a lower gear. The chain pulls the hub forward
> >>in the slots because the pulling force upon the chain is greater and so is
> >>to overcome the friction available at the locknut.

>
> Jim Smith wrote
> > Nice try. Thanks for playing.
> > The higher the gear, the less tension in the chain.
> > You got fooled because it is harder to pedal, but it is
> > easier on the chain.

>
> That's a bit of an oversimplification.
>
> For a given amount of pedal force, chain tension is inversely
> proportional to the size of the chainring. (Bigger chainring/higher
> gear=less tension)
>
> How ever, for a given amount of bicycle driving force at the tire,
> chain tension will be inversely proportional to the size of the rear
> sprocket. (Smaller sprocket/higher gear=more tension.)
>

Yep. I was just thinking about the chainrings, forgot about the sprokets.
That'll teach me to be hasty.