rohloff chainline?



till!

New Member
Nov 19, 2004
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Ill start off by pointing out Im already confused, but that isnt necessarily a secret around here ...

Seems rohloff want a 54mm chainline, and that seems freaking wide to me. So how do you get it?

Ordinarily if you had a road double you would use a 108mm(?) bb ... and guessing ... a 46mm outer with a 41mm inner? You can get the BB in 108/113/118mm graduations.

Also, to add further complications, I probably want a 39 - 42t chainring, and only a single at that ... I can swap the inner to the outer if I want? There is a fair bit of choice around 130BCD/5-arm, you can get most of the way between 38-56t if you can swap which side the ring fits?

So I should get a 118mm BB, that would give me a 51mm ring on the inner, or 56 on the outer, not a 113mm BB, as it would only give me 51mm on the outer, or worse, 46mm on the inner?

All these numbers have been possibly misinterpreted from Sheldon Brown's site, but we can safely say it isnt his fault.

till
 
I was under the impression that Rohloffs are to be run on a single chainwheel up front?
Don't Rohlofs have 14spds, 500% variation?
http://www.rohloff.de/index.php?p=PRODUKTE/SPEEDHUB

Even though the price seems steep (@ $1600Aus), it's comes across as the most logical option for year round MTB XC race use with little maintenace & consumption of parts compared to external cassette & derailuer.

Reports have it that the Rohloff can last through more than one bike, but the price itself is basically a well optioned bike....

(I don't think I've answered you question here, just rambled really....)
 
till! wrote:

> Ill start off by pointing out Im already confused, but that
> isnt necessarily a secret around here ...
>
> Seems rohloff want a 54mm chainline, and that seems freaking
> wide to me. So how do you get it?
>
> Ordinarily if you had a road double you would use a 108mm(?)
> bb ... and guessing ... a 46mm outer with a 41mm inner? You
> can get the BB in 108/113/118mm graduations.
>
> Also, to add further complications, I probably want a 39 - 42t
> chainring, and only a single at that ... I can swap the inner
> to the outer if I want? There is a fair bit of choice around
> 130BCD/5-arm, you can get most of the way between 38-56t if
> you can swap which side the ring fits?
>
> So I should get a 118mm BB, that would give me a 51mm ring on
> the inner, or 56 on the outer, not a 113mm BB, as it would
> only give me 51mm on the outer, or worse, 46mm on the inner?
>
> All these numbers have been possibly misinterpreted from
> Sheldon Brown's site, but we can safely say it isnt his fault.


I'm running a SRAM/Sachs Spectro S7 internal-gear hub. I've
mounted the dished sprocket in the concave position, giving me
a 55.5 mm chainline.

I'm using a Shimano 104 PCD triple crankset with a single 36T
chainwheel mounted in the outmost position. I find a 110mm
bottom bracket gives me a perfect chainline (to within a mm).

John
 
Marx SS said:
I was under the impression that Rohloffs are to be run on a single chainwheel up front?
You can, and you probably want to, but that doesnt have much to do with the issue at hand. Actually if you have a real money problem you can get a shlumph(???) mountain drive as well, but that would be another $1600 probably =)

till
 
"Marx SS" wrote in message...
>

<snip>
> Even though the price seems steep (@ $1600Aus), it's comes across as
> the most logical option for year round MTB XC race use with little
> maintenace & consumption of parts compared to external cassette &
> derailuer.
>

<snip>

A bit on the heavy side for normal XC racing, but then I think gears and derailuers add to much weight. ;-) Would be handy for a
muddy Polaris or 24hr.

ParbSS
 
till! wrote:

> Seems rohloff want a 54mm chainline, and that seems freaking wide to
> me. So how do you get it?


Rohloff's marketing folks think this hub is for downhill mountain
bikes, and the 54 mm spec pretty much corresponds to the outermost ring
on a typical MTB triple chainset.

> Ordinarily if you had a road double you would use a 108mm(?) bb ...
> and guessing ... a 46mm outer with a 41mm inner?


That sounds about right.

> You can get the BB in
> 108/113/118mm graduations.


Since modern BBs are symmetrical, a 118 would put the outer ring at 51
mm. You'd want a 124 to get to exactly 54 mm. If your cranks use the
traditional square bottom bracket, you can get pretty close to that.
If they're splined, you won't find a BB longer than 118.
>
> Also, to add further complications, I probably want a 39 - 42t
> chainring, and only a single at that ... I can swap the inner to the
> outer if I want?


Yes that's no problem.

> So I should get a 118mm BB, that would give me a 51mm ring on the
> inner, or 56 on the outer, not a 113mm BB, as it would only give me
> 51mm on the outer, or worse, 46mm on the inner?
>
> All these numbers have been possibly misinterpreted from Sheldon
> Brown's site, but we can safely say it isnt his fault.


The 118 bb is only 5 mm longer _on each side_ than the 108, so those
numbers are not correct.

118, as I mentioned above, will put the outer ring at 51 mm.

If you want perfect chainline, you could install 5 3 mm spacers between
the chaining and the crank spider. This will also save you from having
to buy a set of short chainring bolts.

See: http://sheldonbrown.com/harris/singlespeed.html#bolts for a photo
of a similar setup, though in this case the spacers are used to move
the chainline inward.

These spacers are nothing special, they're standard rear-axle spacers,
10 mm inside diameter. Just make sure you get a matched set.

Another way to move chailne to the right is to put a spacer washer
under the right side bottom bracket mounting ring. Sturmey-Archer
sprocket spacers are good for this, 1/16" thick.

Sheldon "http://harriscyclery.com/rohloff" Brown
Newtonville, Massachusetts USA
+-------------------------------------------------+
| One measurement is worth 50 expert opinions |
| --Howard Sutherland |
+-------------------------------------------------+
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
 
Sheldon Brown said:
till! wrote:

The 118 bb is only 5 mm longer _on each side_ than the 108, so those
numbers are not correct.

118, as I mentioned above, will put the outer ring at 51 mm.

If you want perfect chainline, you could install 5 3 mm spacers between
the chaining and the crank spider. This will also save you from having
to buy a set of short chainring bolts.
Hmm, thanks for the reply - next time Ill measure from both ends =)

Puzzlingly there seems to be octalink BBs at 121 AND 126mm, at nashbar but only for a 73mm shell, not the 68mm Id more likely want.

The spacers you suggested are probably a better idea, provided I clear the chainstays.

till
 
till! wrote:

> Sheldon Brown Wrote:
>
>>
>>If you want perfect chainline, you could install 5 3 mm spacers
>>between
>>the chaining and the crank spider. This will also save you from
>>having
>>to buy a set of short chainring bolts.

>
> Hmm, thanks for the reply - next time Ill measure from both ends =)
>
> Puzzlingly there seems to be octalink BBs at 121 AND 126mm, at nashbar
> but only for a 73mm shell, not the 68mm Id more likely want.
>
> The spacers you suggested are probably a better idea, provided I clear
> the chainstays.
>


If you're spacing the chainring out, make sure you don't go too close to
the crank arm...

--
BrettS