Single chain ring !

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whoof
Posts: 1882
Joined: 29 Apr 2014, 2:13pm

Re: Single chain ring !

Postby whoof » 2 Sep 2018, 9:53am

Aqua Blue Sport pro cycling team have been running a single chain ring bike all season. This week the have abruptly stopped the team. One of the reasons stated was the quality of the bikes in particular the gappy gear ratios and the tendency to drop the chain.

Brucey
Posts: 35572
Joined: 4 Jan 2012, 6:25pm

Re: Single chain ring !

Postby Brucey » 2 Sep 2018, 10:58am

whoof wrote:Aqua Blue Sport pro cycling team have been running a single chain ring bike all season. This week the have abruptly stopped the team. One of the reasons stated was the quality of the bikes in particular the gappy gear ratios and the tendency to drop the chain.


long before this the riders were complaining of 'feeling like lab rats' (i.e. they were being experimented on) and following a spate of basic mechanical issues that deprived his riders of any chance of victory, even the DS was saying that the bikes were 'not good enough'. That such comments were made public indicates some sort of combination of bike problems / unhappiness in the team.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

landsurfer
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Joined: 27 Oct 2012, 9:13pm
Location: Rotherham

Re: Single chain ring !

Postby landsurfer » 2 Sep 2018, 11:24am

gaz wrote:
Peter W wrote:I fail to see how with either of those options you could be able to pedal at a sensible cadence, hence speed, on a flat or gently falling road with a welcome following wind?

What's a sensible cadence/speed? Assuming a nominal 27" wheel I'd be comfortable at 20mph in that gear, given the circumstances you outline.


The options work for me (I shouldn't have used the "liar" word, sorry ).
I was spinning out at 16mph with the 26 so freewheeled a lot of the downhill sections, i ride high cadence / low effort to protect my damaged knees, which i have found to totally effective. Started LEJOG with the 26 fitted planning to move to a 34 or 38 as we entered the flatter areas, but the reality check was that i was comfortable on the 26. I'm back on the 34 as it suites my local area better ... not a particularly hilly area. With a 34 i spin out at 20mph .... how much faster do i need to go .. my TT days are over by choice .... i enjoy cycling my 100 - 150 miles a week ..... at high cadence :)
Last edited by landsurfer on 2 Sep 2018, 7:20pm, edited 1 time in total.
The Road Goes On Forever ...

NetworkMan
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Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Single chain ring !

Postby NetworkMan » 2 Sep 2018, 11:37am

I’ve considered this before and threw the idea out for a touring bike. I’ve just done it again, working below.
Top Gear
Years ago IIRC Tim Hughes (used to edit Cycle) wrote that for touring you don’t need anything higher than (IIRC) 75 inches. The rationale is that at a cadence of 80 rpm you are going at nearly 18 mph and that going faster is a waste of energy. You might say that even less that 75 is OK but lets take that as a start. Riding downhill for fun is a bonus we'll have to throw out. edit: As is using a tailwind to exceed 20 mph.
Bottom Gear
My old Dawes Horizon came with a 25 inch bottom gear and I still find that pretty good. YMMV but I’ll take that.
Minimum Sprocket Size
Most people reckon that 11T wears out pretty fast and we are going to be using all the sprockets so lets say 12T although 13T might be better.
Maximum sprocket size
Easy – it’s 12*75/25 = 36 T which is OK with modern RD’s and it’s not too huge.
Chainring
A 32 mm tyre on 700C is 27 inches diameter. So we need 12*75/27 = 33T. We might have to buy 34T?
No of Speeds
I was fairly happy with the 13-30 7 speed on my Horizon though the 17-20 tooth jump is starting to be annoying. Lets go with that spacing anyway and see where it take us. We need the 6th root of 30/13 which gives us 1.15 or 15% between ratios. How many speeds do we need for a range of 36/12 with 15% between gears? It turns out that 9 does it almost exactly since 1.15^8 is 3.06.
Which Sprockets
Starting with 12 multiply by (almost) 1.15 as you go, rounding up or down:-
12, 14, 16, 18, 21, 24, 28, 32, 36. The jump of 21-18 (16.7%) is better than the 20-17 (17.6%) on my Horizon.
What’s wrong with it?
The steps between gears are rather large and 10 speeds would give us 13.0% jumps and 11 speed 11.6%. The biggest issue is chainline and sprocket wear. Probably the most used gear will be gear 2, 33/14 or 64 inches with an awful chainline and 14T is pretty small too. 10 or 11 speeds won't help here either; the problem is that the most used gears are at or near the end of the cassette. I doubt you can buy a 12-36 cassette.

Now look at my 8 speed triple with 13-26 cassette and 48/38/24. Top gear is 100 inches and bottom is 25. The most used gears are closer to the middle of the cassette and have more teeth. The cassette gives closer ratios with an average of 10.4% and with a simple mod. I can probably make the cassette into a 13-30 and get a 22 inch bottom. I suppose it’s heavier but the biggest sprocket is 26T not 36T, the 24T ring weighs little and the 48T is alloy. Oh, and the 13-26 only cost £11.50.
Last edited by NetworkMan on 2 Sep 2018, 1:02pm, edited 4 times in total.

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meic
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Location: Caerfyrddin (Carmarthen)

Re: Single chain ring !

Postby meic » 2 Sep 2018, 11:48am

The rationale is that at a cadence of 80 rpm you are going at nearly 18 mph and that going faster is a waste of energy.

That forgets tailwinds.
Some of my best days touring are holding 20mph or more for a few hours while surfing a tailwind.
"Make hay while the sun shines".
Yma o Hyd

cycle tramp
Posts: 533
Joined: 5 Aug 2009, 7:22pm

Re: Single chain ring !

Postby cycle tramp » 2 Sep 2018, 12:00pm

Peter W wrote:100% with Brucey on this one!

Quite Landsurfer, 'I run a 34 front chainring with a 12/32 cassette and have experienced NO ISSUES.' You immediately contradict that claim by stating that you changed to a 26 front ring for a specific journey.

I fail to see how with either of those options you could be able to pedal at a sensible cadence, hence speed, on a flat or gently falling road with a welcome following wind? In what way is your single ring system (nonsense of changing to suit different kinds of days riding) superior to a 'normal' double, which covers both speed and climbing, with the not unwelcome benefit of a non twisted chainline?


H'mmm.... having read and re-read both Landsurfer's posts and your own comments i wonder if there is a degree of misunderstanding. Using a 34 tooth chain ring for most journeys and then switching to a 26 tooth chain ring is not an indication that the orginal choice of chain ring was some how a mistake or error any more so than changing the rear cog by derailleur to suit the nature of the gradient, but rather a recognition thst the topography of tour may be different to that which is normally encountered
...i understand the sentiments to change the size of the chain ring by replacement, rather than have lots of sizes of chain rings bolted together and using a front derailleur to choose which change ring to use as 'nonsense'... but it is what some cyclists chose to do,, whether they run a fixed wheel, hub gear or whatever... when you get very good at changing the chainring, it takes less than 10 minutes, allows you the chance to probably clean the chain ring and allows you the chance to remount the chain ring in a different position to even the wear :-)

NetworkMan
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Location: South Devon

Re: Single chain ring !

Postby NetworkMan » 2 Sep 2018, 12:09pm

meic wrote:
The rationale is that at a cadence of 80 rpm you are going at nearly 18 mph and that going faster is a waste of energy.

That forgets tailwinds.
Some of my best days touring are holding 20mph or more for a few hours while surfing a tailwind.
"Make hay while the sun shines".

Exactly and doing that is a luxury you'll have to do without if you want this design of single chainring transmission. I'll edit to make that clearer.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Single chain ring !

Postby Brucey » 2 Sep 2018, 12:20pm

interestingly one of the objections that is levelled against some (mostly simpler) IGHs is that the gear ratios are not evenly spaced. Well IMHO they look rather good in that respect vs the intervals in a typical 11s cassette that you might want to use in a 1x11 setup.

For example
http://ritzelrechner.de/?GR=DERS&KB=36&RZ=11,13,15,17,19,21,24,28,32,37,42&UF=2215&TF=90&SL=2.6&UN=MPH&DV=gearInches

shows that what looks like a nice even progression when you eyeball the cassette is actually giving you intervals that vary from 11% to 18%. In other words some of the gear intervals are getting on for twice as large as others!

You can't avoid this entirely; you can have 1T, 2T, 3T, 4T, 5T (etc) intervals only and these are a variable percentage of the sprocket you start with.

Simply by having another chainring or two, and a FD, you can have a gear setup that gives you more evenly spaced ratios (as well as a wider range) that you can use. The 'weight penalty' is largely imaginary; say a couple of chainrings and a FD weighs 0.4kg. This might be 0.5% of the all up weight, so might 'slow you down' by up to 0.5% whilst climbing. Well, if the resultant transmission is also more efficient by 0.5% or more, you have 'won' and you will go faster and/or exert less effort.

IMHO having a 1x transmission is like having a little thief aboard, that steals some of your effort, for no real benefit. The inefficiency (in road use, less so in MTB use) arises from two main sources

1) you are liable to be using smaller chainrings and sprockets than otherwise. This generates greater chordal losses in the transmission. The GB cycling team at Rio used larger chainrings and sprockets than normal (by just a few teeth) and they got a ~0.5% improvement in efficiency for (basically) nothing. If you have a choice of 36/14 vs (say) 49/19 then the difference in efficiency will be greater than that (*).

2) chainline. Poor chainlines in many of the most used (by time or mileage) gears are unavoidable with a 1x11 setup. These losses are comparable in size with chordal losses. [Thus it is not unusual to find that the efficiency of all the gears on (and to the left of) the big ring is roughly constant; as you move to larger sprockets (which are more efficient with lower chordal losses) these gains can be almost exactly offset by larger cross-chaining losses.]

A conservative estimate of the average losses (in road riding) is about 1% each, so about 2% overall. However in a long climb it might easily be more than this. Even 2% is a fair amount; on an hour-long climb you will be ~1'12" behind your buddies even if you are trying just as hard.

(*) and the 36/14 combo will wear out faster too. And the 1x chainrings and sprockets required are ludicrously expensive; for the cost of them you could buy a complete triple chainset, and several (say 8s) cassettes and chains....

BTW the idea of using 1 x setup and carrying a spare chainring around in your bag just in case the gear range isn't quite right is surely some form of madness; why not have it bolted on the bike? It'd be like having, er, a double chainset.... :roll:

cheers
Last edited by Brucey on 2 Sep 2018, 7:53pm, edited 2 times in total.
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LuckyLuke
Posts: 221
Joined: 10 Jun 2010, 11:54am

Re: Single chain ring !

Postby LuckyLuke » 2 Sep 2018, 12:25pm

Hi, I can see the appeal of a single chainring. My commuter has a Nexus 8 hub & a single ring. It sounds daft but not having to switch between rings up front feels more convenient. (I have triples on two other bikes.)
One compromise, as stated, is the limited range. Plus bigger gaps between sprockets on the back, if that's an issue for you?
I wonder if a compact double could be one answer? E.g. a 42-46T big ring, 26-30T small ring & 11-34T on the back?
Most of the time you ride in the big ring, with a bail out inner ring. I've tried it with a TA Pro Vis 5 crank & 46,30; 42,26 & 42,30. The latter worked best for me, the former two combos had too great a jump between rings.
I swapped back to triples though, as I preferred smaller jumps between sprockets.
Best wishes,
Luke

landsurfer
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Location: Rotherham

Re: Single chain ring !

Postby landsurfer » 2 Sep 2018, 1:12pm

Brucey wrote: And the 1x chainrings and sprockets required are ludicrously expensive; for the cost of them you could buy a complete triple chainset, and several (say 8s) cassettes and chains....

BTW the idea of using 1 x setup and carrying a spare chainring around in your bag just in case the gear range isn't quite right is surely some form of madness; why not have it bolted on the bike? It'd be like having, er, a double chainset.... :roll:

cheers


34 tooth chain rings £7 - £14 from SPA.

Carrying spare sprockets in your bag .... agree ... idiots !
The Road Goes On Forever ...

Brucey
Posts: 35572
Joined: 4 Jan 2012, 6:25pm

Re: Single chain ring !

Postby Brucey » 2 Sep 2018, 1:19pm

landsurfer wrote: ....34 tooth chain rings £7 - £14 from SPA....


I have not looked recently but the last time I did the 'narrow-wide' ones as stipulated for 1x11 use were somewhat pricier than that....

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

landsurfer
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Location: Rotherham

Re: Single chain ring !

Postby landsurfer » 2 Sep 2018, 1:23pm

Brucey wrote:
landsurfer wrote: ....34 tooth chain rings £7 - £14 from SPA....


I have not looked recently but the last time I did the 'narrow-wide' ones as stipulated for 1x11 use were somewhat pricier than that....

cheers


Thats the price i paid last month from SPA for a replacement 34, £14 plus p&p, I run 9 speed. Occasionally they have sales ... last time i had a 33 and a 34 for £7 ea. 110BCD.
The Road Goes On Forever ...

Brucey
Posts: 35572
Joined: 4 Jan 2012, 6:25pm

Re: Single chain ring !

Postby Brucey » 2 Sep 2018, 1:56pm

what I'm trying to point out is that you are probably (you have not said) buying chainrings that are really meant for use in a double or triple chainset. These are the least suitable chainrings for single chainring use in a modern 1x setup, which is why they make different chainrings for that very purpose.

in order of increasing suitability for 1x11 use (say)

a) - modern derailleur chainrings ('not very suitable': The teeth are not full height; the chain is basically designed to fall off these easily, and it does....)
b) - a 3/32" chainring (with full height teeth) designed for fixed gear/singlespeed use
c) - a modified 1/8" fixed /SS chainring with full height teeth
d) - a 'proper 1x' narrow-wide chainring.

Image
a narrow-wide chainring meant for 1x11 use

Option d) is likely to cost about £30 or £40 per chainring. They are more expensive because the chainring cannot be made without some milling to give the tooth profiles. Option a) is very likely to unship very often and drive you berserk unless you fit a chain guide of some kind (and TBH you might as well fit a FD and be done with it....)

Option c) won't confer 100% reliability but it is a pretty good option for road use (on a MTB it is not so good-mud tends to foul things up); basically you file the teeth so that the chain is a snug fit (snugger than with a typical 3/32" chainring) on the teeth; this dissuades the chain from unshipping. Unlike a narrow-wide chainring you can put the chain back on any way you want to.

Regarding cassettes any that will give you a wide range for 1x11 use (so 40T or larger big sprocket) are likely to be expensive. Prices start at about £60 per cassette (for a cheap, heavy one like a sun race or sram 1130) and go up from there. You can easily spend x3 as much on one that is 'just right'.

Good 11s chains are expensive, but you can buy a cheap one (like a SRAM PC-1110) for as little as £10 or £12. Shifting won't necessarily be great and it will be worn out within 1000 miles (so you need to check it for wear every week if you are trying not to wear the cassette out) but at that price they are throwaway items.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

cycle tramp
Posts: 533
Joined: 5 Aug 2009, 7:22pm

Re: Single chain ring !

Postby cycle tramp » 2 Sep 2018, 2:31pm

landsurfer wrote:
Brucey wrote:

BTW the idea of using 1 x setup and carrying a spare chainring around in your bag just in case the gear range isn't quite right is surely some form of madness; why not have it bolted on the bike? It'd be like having, er, a double chainset.... :roll:

cheers


34 tooth chain rings £7 - £14 from SPA.

Carrying spare sprockets in your bag .... agree ... idiots !


Possibly right on both accounts, but then i was using a 3 speed hub on a two day tour of about 50 miles per day... and i knew that i'd be up against riders with carbon framesets, disc brakes and a full set of gears... ..i needed every chance i could get so the 36 tooth was fitted, with a 34 tooth and a 38 tooth were packed, just incase... i needn't have worried as out of all the riders i was fourth up the steep climb to the hotel... after getting off and marching my way to the top :-)
As for the price of chain rings, the last five i've bought second hand from this forum... i simply turn them over.. i use a chain guard (from SPA cycles) to keep the chain on board & the cuffs of my trousers clean... double bonus..
.. would i take two chain rings of different sizes if i toured on my 5 speed?.. i don't know, if someone has a couple of spare months they could lend me, i'll let you know :-)
Last edited by cycle tramp on 3 Sep 2018, 7:16pm, edited 1 time in total.

Peter W
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Joined: 10 Apr 2018, 4:22pm

Re: Single chain ring !

Postby Peter W » 2 Sep 2018, 3:44pm

Quote, 'He just gets his kicks calling people liars.'

Says more about your inability to understand a logical point, than about me. You claimed no issues with using a single 34 front yet found it necessary (why else would you do so) to change to a 26 ring for a particular ride.

I note you did not answer the question. i.e. 'In what way is your single ring system (nonsense of changing to suit different kinds of days riding) superior to a normal double ...etc' From where, or from what, do you draw your accusation of me being a liar who is just out for kicks??