What chainring and rear cog for Rohloff?

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tommydog
Posts: 278
Joined: 11 Feb 2017, 6:48pm

What chainring and rear cog for Rohloff?

Postby tommydog » 18 Dec 2020, 7:49pm

With my 26" wheel Rohloff touring bike, I currently ride with a 42 tooth chainring at the front and a 16 tooth cog at the rear. I know a lot of people have this setup, but I find I want something a little quicker. I tend to tour very light and have never used any of the gears 1-3, even on very steep hills.

What combination would people suggest? Whatever I choose, I will want to stay with it for a while, as money is tight at the moment and I can't really justify experimenting too much. I have decided to do this now, as my current chainring is worn out, so it's a good time to do this.

Also what is the best value to quality chainring to buy? I purchased the Thorn chainring before:
https://www.sjscycles.co.uk/chainrings/ ... nch-black/

Along with this:
https://www.sjscycles.co.uk/sprockets/1 ... ket-steel/

Are the above products still the best bet? About 50% of my riding is offroad so it needs to cope with mud / grit relatively well.

rotavator
Posts: 563
Joined: 6 Jun 2016, 9:50pm
Location: North Wales

Re: What chainring and rear cog for Rohloff?

Postby rotavator » 18 Dec 2020, 8:27pm

Have a play with this gear calculator:
[url]
http://xldev.co.uk/bgc.html[/url]

Deselect Brompton compatible data only.

If you don't use gears 1-3 it sounds as if you don't need a bottom gear lower than ~25" so you could go for a chainring with say 48-54T, however, check that it will not foul your chainstay first. If it will, then go for a smaller sprocket at the back.

Oggi
Posts: 34
Joined: 27 Sep 2012, 12:13pm

Re: What chainring and rear cog for Rohloff?

Postby Oggi » 18 Dec 2020, 8:35pm

All of the gear options are detailed in here.

http://www.sjscycles.com/thornpdf/Thorn ... _LoRes.pdf

slowster
Posts: 1791
Joined: 7 Jul 2017, 10:37am

Re: What chainring and rear cog for Rohloff?

Postby slowster » 18 Dec 2020, 8:44pm

This is much better:

http://www.gear-calculator.com/?GR=RLSH&KB=42&RZ=16&UF=2120&TF=90&SL=2.6&UN=KMH&DV=gearInches

For touring I would have said a 102" top gear was more than sufficient, and therefore would keep the three currently unused bottom gears. If you continue never to use them, it's no loss.

With regard to the chainring the Thorn chainring has a 104mm bolt circle diameter, so unless you are also changing your cranks any replacement chainring will also need to have a 104mm BCD.

jb
Posts: 1044
Joined: 6 Jan 2007, 12:17pm
Location: Clitheroe

Re: What chainring and rear cog for Rohloff?

Postby jb » 18 Dec 2020, 8:57pm

Go for a 48t chainring if it's not quite right you can adjust it with a new sprocket which you will need at some point.
Cheers
J Bro

PH
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Joined: 21 Jan 2007, 12:31am
Location: Derby
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Re: What chainring and rear cog for Rohloff?

Postby PH » 18 Dec 2020, 9:05pm

I've always followed the advice to get gear 11, direct drive, as close to the most commonly used gear as possible, for me that tends to be around 70" so I've geared accordingly. Then as there's more than one combination to achieve the same result, I followed the argument that the bigger the rings the less wear, which seems obvious though I waited 15 years for someone to point it out :oops:
So on 700c wheels I have 47 x 19 on one bike and 49 x 19 on another with narrower tyres, they both come in about 20 - 105". I use all the gears, though there might be days when I don't go lower than 8, I occasionally think I miss not having anything higher, but the reality is on a bike where I do it's hardly used.
I don't know about best chainrings, I like the Thorn ones, they last well enough to seem decent value. The only other type I've tried on my hubs was a Surly SS one, it looked great, but it didn't last me any longer.

PH
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Re: What chainring and rear cog for Rohloff?

Postby PH » 18 Dec 2020, 9:10pm

slowster wrote:With regard to the chainring the Thorn chainring has a 104mm bolt circle diameter, so unless you are also changing your cranks any replacement chainring will also need to have a 104mm BCD.

Although the link goes to a 104, Thorn do them in other size/s
Thorn ST cranks only come 104, though the OP hasn't said that's what they're using.
Last edited by PH on 18 Dec 2020, 9:13pm, edited 1 time in total.

colin54
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Joined: 24 Sep 2013, 4:34pm

Re: What chainring and rear cog for Rohloff?

Postby colin54 » 18 Dec 2020, 9:12pm

There's a twenty (!) page thread on this subject on Thorn forum.
I see from there some folks use a Surly stainless ring as it's a bit thinner below the teeth than the
Thorn aluminium one so rubs less on a Hebie chainglider if fitted.It's reversible as the Thorn one is .
http://thorncyclesforum.co.uk/index.php?topic=4412.0
Surly chainring:-
https://surlybikes.com/parts/stainless_steel_chainrings
I bought a steel one off ebay from Germany( bike-prof) as I couldn't get a Surly one to match with my rear cog to fit a standard chainglider.
Linked here, NOT reversible, up to 46 teeth available.

https://www.ebay.co.uk/itm/PB-Single-Sp ... 0290.m3507

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Tigerbiten
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Joined: 29 Jun 2009, 6:49am

Re: What chainring and rear cog for Rohloff?

Postby Tigerbiten » 18 Dec 2020, 9:18pm

Do you have a "screw on" or a "splined" sprocket ??
It may make a difference in how much it costs/ how easy it is to change it.
If you don't have a splined sprocket carrier then it may be worth it to get one now with a new sprocket while at the same time changing your chainring and chain.
That way you'll have a completely new transmission

Luck ......... :D

tommydog
Posts: 278
Joined: 11 Feb 2017, 6:48pm

Re: What chainring and rear cog for Rohloff?

Postby tommydog » 18 Dec 2020, 9:40pm

Tigerbiten wrote:Do you have a "screw on" or a "splined" sprocket ??


It's the splined one. I changed out the screw one when I purchased the bike a few years ago.

One other thing to mention is that since I have had the bike, I have broken quite a few chains (much more than on any other bike). I have used this chain:

https://www.amazon.co.uk/gp/product/B07 ... UTF8&psc=1

Funnily enough it happened both times on the same hill. I really don't understand it, as I even had a professional bike shop check my chain setup and they said everything was perfect.

tommydog
Posts: 278
Joined: 11 Feb 2017, 6:48pm

Re: What chainring and rear cog for Rohloff?

Postby tommydog » 18 Dec 2020, 9:42pm

jb wrote:Go for a 48t chainring if it's not quite right you can adjust it with a new sprocket which you will need at some point.


I am tempted to do this. Would would you suggest running on the rear with the 48 on the front?

PH
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Re: What chainring and rear cog for Rohloff?

Postby PH » 18 Dec 2020, 9:59pm

tommydog wrote:One other thing to mention is that since I have had the bike, I have broken quite a few chains (much more than on any other bike). I have used this chain:

https://www.amazon.co.uk/gp/product/B07 ... UTF8&psc=1

I'm surprised by that, it's my chain of choice and I run them till the sprocket is worn out without any problems.
Did you buy from a reputable source? Apparently there are some fake KMC chains around.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: What chainring and rear cog for Rohloff?

Postby Brucey » 18 Dec 2020, 10:13pm

I agree with PH.

I would say that you definitely need a bigger chainring. In 104mm BCD they are available up to 50T. You should forget Surly stainless chainrings (unless you are going to buy a 110mm or 130mm BCD chainset too) because in 104mm BCD they only go to 36T. I suggest a 48T chainring might suit you; 48/18 gives you the same gearing as you have at present (but will be more efficient, longer-lasting, and less likely to break), a 16T sprocket is +1 gear. A 14T sprocket will give +2 gears.

In your shoes I would go with 48/18 or 48/16; I don't care how strong you think you are, if you are using a gear over 100" properly, you are doing over 30mph too and going downhill. If you adopt the 'I need to pedal, always' line then you end up wanting a gear that allows you to pedal at 50-60mph or more, i.e. one that is at least twice as big as the one you have at present. You have to ask yourself how much benefit you are going to get by flogging yourself to death trying to go a few mph faster when you could be freewheeling instead and saving your energy (the answer is 'not much' BTW).

Both chainring and sprocket are reversible and the thing that determines when you should do this (over and above stuff like cleaning and lubing, and using larger sizes sprockets and chainrings to start with) is the quality of the chain. IMHO it is a false economy to run a cheap chain on a Rohloff, unless you are scrupulously going to change the chain when it is worn by about 0.5% (which no-one does, pretty much). Most people with IGHs run the chain out to at least 1% wear and by that time the chainring (esp if it is aluminium) and sprocket need to be turned too.

If you use half the life of a chainring and sprocket this costs about £25; spending at least the same amount on a wear-resistant chain makes sense.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

KM2
Posts: 580
Joined: 23 Oct 2008, 5:38pm

Re: What chainring and rear cog for Rohloff?

Postby KM2 » 18 Dec 2020, 11:31pm

I was told, and it worked for me.
Set up normal/favourite gear as number 11, then use the biggest sprocket/ chainring combination to achieve that gear. As I had an 18 sprocket , I went for a 45 ring. I pedal.
I always wanted to try a 45/42 chainring set up to achieve a one tooth effective jump .But I never did.

jb
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Joined: 6 Jan 2007, 12:17pm
Location: Clitheroe

Re: What chainring and rear cog for Rohloff?

Postby jb » 18 Dec 2020, 11:56pm

tommydog wrote:
jb wrote:Go for a 48t chainring if it's not quite right you can adjust it with a new sprocket which you will need at some point.


I am tempted to do this. Would would you suggest running on the rear with the 48 on the front?

Actually a 50t chainring with a 16t sprocket gives you a 22 ins gear which is low enough for anybody on the road, and a top gear of 120 from your present 104 ins.
Cheers

J Bro