How many teeth on a Rohloff rear sprocket?

[StuntPilot]

The post in the previous thread (rohloff world tour - what spares to take?) from Dave at 'Bored with I.T.' is an excellent read ...

http://www.tiredofit.ca/2011/03/10/thorn-nomad-mk2/

I am a little confused however when he talks of the Rohloff sprocket size. He mentions his as being a 17T Rohloff sprocket. In the picture of the sprocket shown on his site, I count 16 'teeth' and 16 'holes'.

This is exactly the same as the sprocket on my Raven Tour. When I purchased the bike, it was stated as having a 17T sprocket so I was suprised when it arrived that there were only 16 'teeth'.

Am I missing something or does 17T mean 16 'teeth' on the sprocket?

[il padrone]

No, the 16t is what is normally  supplied with a Rohloff hub. Strange that you have 17t but did you specify the gearing with Thorn or something?

The 17t does give noticeably longer wear life than the 16t, but that all depends if it gives you a suitable set of gear ratios.

[StuntPilot]

Hi il padrone! The bike was bought second-hand from Thorn so I did not specify the gearing. I took it as it came.

Its just that the documentation and the eBay advert mentioned it had a 17 tooth Rohloff rear sprocket and when it arrived I counted 16 teeth!

If you look at the Tired of I.T. post, you can count 16 teeth in the photograph yet the text mentions that he has a 17T Rholoff sprocket. Hence my original confusion and question.

[Danneaux]

Richard,

My 17T sprocket has 17 teeth and 17 holes.

On the bright side...you're stronger than you thought! 

Best,

Dan.

[Andre Jute]

It may just be an impression, but I've always thought that the Thorn default Rohloff sprocket was 17 teeth, i.e. what they fitted unless you asked for another tooth count. If I'm right, it is probably just a reflex to say glance at a used bike, say it is all standard, and assume that it has a 17T sprocket.

Elsewhere in Rohloff land, a 16T sprocket is what comes on a Rohloff setup by default. 16T is what leaves the factory on Rohloff kits.

16T sprockets were also cheaper to replace, the last time I looked, though I wouldn't let a couple of bucks every 20K determine so important a transmission decision.

I have a 16T sprocket with 38T chainring on a luxuriously equipped touring/utility bike, used on 622mm wheels with 60mm Big Apple tyres in very hilly terrain, and I love the combination.

Andre Jute

[IanW]

I read a couple of Sheldon Brown's articles about chain and sprocket/chainring wear

http://sheldonbrown.com/chains.html

http://sheldonbrown.com/chain-life.html

which would seem to indicated that,
if you are careful with chain reinstallation after after dismounting (for whatever reason),
then an *even* number of teeth on *both* the rear sprocket and the front chainring
would allow a longer chain life
at the expense of probably having to replace all 3 at the end of the chain's extended service life.

So maybe that is why the 16t sprocket is the default option?

--
Ian

[Danneaux]

Hi Ian!

These threads may be of interest as well:
http://www.thorncycles.co.uk/forums/index.php?topic=4655.msg22907#msg22907
http://www.thorncycles.co.uk/forums/index.php?topic=2480.0

Best,

Dan. (...who hopes to even the odds with an even-odd 36x17 combo)

[Dave Whittle Thorn Workshop]

As of around mid 2011 the default sprocket on all our bikes is 17t, all come from the factory to us with 17t.

Sorry about the eBay bike being listed incorrectly, if it causes you an issue get in touch,

Regards, Dave.

[StuntPilot]

Dave

Thanks for wading in! No, not a problem at all with the 16t sprocket! I would have contacted SJS Cycles on delivery if it was an issue.

Having trekked up and down the border hills here since getting the bike, the 38x16 is a fine combination. Very happy with my Raven Tour Dave!

Cheers

Richard