Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

For discussions about bikes and equipment.
Freddie
Posts: 2329
Joined: 12 Jan 2008, 12:01pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby Freddie » 19 Aug 2019, 1:02pm

Is there good data for chain efficiency at differing angles. I suppose a triple allows you the same spread of gears, but with shallower angles than a double, but does this produce meaningful differences in drivetrain efficiency?

Freddie
Posts: 2329
Joined: 12 Jan 2008, 12:01pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby Freddie » 19 Aug 2019, 1:15pm

CJ wrote:But what about the downshift? You can't make the outer plate any deeper than it already is, since has to completely clear the outer ring. So the mech will always be working at a severe disadvantage when it comes to deflecting the chain off the middle ring, because it can't possibly get as close to the action as it really needs to be! And the middle to inner shift is THE MOST IMPORTANT shift a tourist ever makes, it's the "Goodness me this hill is steeper than I expected" shift, the leg-saving "{FFE - family-friendly edit } give me some lower gears" shift and the "Oh no I've left it too late" shift! So it's no good when the only way this shift works is with the pedals spinning fast with zero pressure on them, because neither of those things are going to happen on an unexpectedly steepening hill!
What is wrong with using a 3 speed hub (+ cassette) to achieve what the front mech does? In theory you have instantaneous changes on the downshift you describe, are there any problems in practise? I suppose remembering to briefly stop pedalling when shifting the 3 speed hub could be confusing, but other than that...

The front mech has always struck me as a very slow and agricultural changer, most of all precisely when you need it not to be (in the situation you described).

NetworkMan
Posts: 715
Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby NetworkMan » 19 Aug 2019, 2:20pm

Freddie wrote:Is there good data for chain efficiency at differing angles. I suppose a triple allows you the same spread of gears, but with shallower angles than a double, but does this produce meaningful differences in drivetrain efficiency?

Yes, some info and discussion here. Also Bicycling Science, third edition, Wilson et Al.
viewtopic.php?f=5&t=132147

Bmblbzzz
Posts: 3075
Joined: 18 May 2012, 7:56pm
Location: From here to there.

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby Bmblbzzz » 19 Aug 2019, 3:21pm

Freddie wrote:
CJ wrote:But what about the downshift? You can't make the outer plate any deeper than it already is, since has to completely clear the outer ring. So the mech will always be working at a severe disadvantage when it comes to deflecting the chain off the middle ring, because it can't possibly get as close to the action as it really needs to be! And the middle to inner shift is THE MOST IMPORTANT shift a tourist ever makes, it's the "Goodness me this hill is steeper than I expected" shift, the leg-saving "{FFE - family-friendly edit } give me some lower gears" shift and the "Oh no I've left it too late" shift! So it's no good when the only way this shift works is with the pedals spinning fast with zero pressure on them, because neither of those things are going to happen on an unexpectedly steepening hill!
What is wrong with using a 3 speed hub (+ cassette) to achieve what the front mech does? In theory you have instantaneous changes on the downshift you describe, are there any problems in practise? I suppose remembering to briefly stop pedalling when shifting the 3 speed hub could be confusing, but other than that...

The front mech has always struck me as a very slow and agricultural changer, most of all precisely when you need it not to be (in the situation you described).

Doesn't Tigerbitten otp have a 10-speed cassette on an 11-speed hub... with a front triple as well?

User avatar
Tigerbiten
Posts: 2008
Joined: 29 Jun 2009, 6:49am

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby Tigerbiten » 19 Aug 2019, 3:49pm

I opted for twin hub gears, Schlumpf HSD and Rohloff, with twin chainrings to get my range of gears.
It's Mick F who has a triple and SA hub with a 9 block on one of his bikes.

I looked into that combo but with only one hand the three controls would have been too cramped on a single handlebar.
Plus that combo also didn't give me the gear range wanted , 10"-> +130", without going for a very wide range cassette which gave irregular jumps between the gears.

With my combo, one of the controls is under my heels, so I only need two on my handlebar.
And very regular jumps, 13.6%, between all 24 unique gears.


YMMV ........ :D

CXRAndy
Posts: 45
Joined: 18 Aug 2019, 1:45pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby CXRAndy » 19 Aug 2019, 5:06pm

I have a Kinesis Tripster V2 ATR with a a triple crankset 48/36/26. I use XTR triple Di2 front derailleur with Di2 hydraulic road shifters.

Its great all-rounder for touring, climbing mountains

I use a 11-32 cassette for general riding and a 11-40 cassette for mountains. gear inch range 18"-115"
Last edited by CXRAndy on 19 Aug 2019, 5:08pm, edited 1 time in total.

pwa
Posts: 11611
Joined: 2 Oct 2011, 8:55pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby pwa » 19 Aug 2019, 5:08pm

CXRAndy wrote:I have a Kinesis Tripster V2 ATR with a a triple crankset 48/36/26. I use XTR triple Di2 front derailleur with Di2 hydraulic road shifters.

Its great all-rounder for touring, climbing mountains

So that is using drop bar levers but still managing a tourer type (48/36/26) chainset? Sounds useful.

CXRAndy
Posts: 45
Joined: 18 Aug 2019, 1:45pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby CXRAndy » 19 Aug 2019, 5:13pm

Yes. drop handle bars
Image Attachments
20180929_071807.jpg

Brucey
Posts: 37242
Joined: 4 Jan 2012, 6:25pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby Brucey » 19 Aug 2019, 5:36pm

Freddie wrote:Is there good data for chain efficiency at differing angles. I suppose a triple allows you the same spread of gears, but with shallower angles than a double, but does this produce meaningful differences in drivetrain efficiency?


Image

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

pwa
Posts: 11611
Joined: 2 Oct 2011, 8:55pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby pwa » 19 Aug 2019, 6:28pm

CXRAndy wrote:Yes. drop handle bars

Nice. I have a mistrust of electronic stuff on bikes, but apart from that, very nice. Attractive frame too.

User avatar
CJ
Posts: 3004
Joined: 15 Jan 2007, 9:55pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby CJ » 20 Aug 2019, 10:30pm

Freddie wrote:What is wrong with using a 3 speed hub (+ cassette) to achieve what the front mech does?

Efficiency, dear boy, efficiency.
Chris Juden
One lady owner, never raced or jumped.

User avatar
CJ
Posts: 3004
Joined: 15 Jan 2007, 9:55pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby CJ » 20 Aug 2019, 10:56pm

Freddie wrote:Is there good data for chain efficiency at differing angles. I suppose a triple allows you the same spread of gears, but with shallower angles than a double, but does this produce meaningful differences in drivetrain efficiency?

There is a lot of bad data, and only one good study that I am aware of, done on a very elegant rig (the only one I've seen that I can believe truly capable of measuring the tiny - but physiologically significant to the puny human engine - differences in losses between competing bicycle transmissions) by a German university on behalf of Fichtel & Sachs in the 1980s. This found that small tooth-count sprockets (13 or fewer) were much worse than any amount of out-of-line running. It also found that hub-gears were indeed less efficient than derailers (Fichtel and Sachs had just bought Maillard and Huret, so made both at that time, so the person paying the piper had an honest interest in an honest tune) except in direct-drive of course. I have all the references somewhere, but nobody pays me to know this stuff any more so I'm afraid I simply can't be bothered looking it up.

In a nutshell: derailers are better than internal gears unless you have energy to spare or are mechanically incompetent. And more teeth is always better. And provided you're not much further out of line than an old-school single-ring 6-speed, you shouldn't really worry about that factor. So a double is pretty much state-of-the-art efficiency wise, so long as the big ring aligns as close to the centre of the cassette as it can be and you don't use the small end of the cassette with the inner ring (which you won't need to, and in that case will be reminded not to by the chain making an awful noise against the outer).
Chris Juden
One lady owner, never raced or jumped.

Brucey
Posts: 37242
Joined: 4 Jan 2012, 6:25pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby Brucey » 20 Aug 2019, 11:29pm

Nearly all tests I have seen have been carried out at constant torque, which is a very bad simulation of 'the human engine'. If the % losses vary with torque load then any constant torque testing is going to contain errors. Thus you might be OK comparing like with like, but otherwise there is likely to be some doubt.

Some things that are worth reading from the IHPVA archives

http://www.ihpva.org/HParchive/PDF/hp50-2000.pdf

http://www.ihpva.org/HParchive/PDF/hp51-2001.pdf

http://www.ihpva.org/HParchive/PDF/hp52-2001.pdf

but all of these tests/reports have flaws of various kinds.

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

keyboardmonkey
Posts: 667
Joined: 1 Dec 2009, 5:05pm
Location: Yorkshire

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby keyboardmonkey » 20 Aug 2019, 11:38pm

CJ wrote:I have all the references somewhere, but nobody pays me to know this stuff any more so I'm afraid I simply can't be bothered looking it up.

Ha ha. Fair enough :lol:

User avatar
CJ
Posts: 3004
Joined: 15 Jan 2007, 9:55pm

Re: Audax Bike (Spa?) with Tourer Gearing & Double vs. Triple

Postby CJ » 20 Aug 2019, 11:40pm

And in reply to the suggestion that the Audax and/or Touring bike is dead (sorry, but I don't visit here often nowadays), I would say that it's more like the roadies have come around to our way of thinking! For now they are adopting bicycles they call road bikes or gravel bikes that have tyres of similar breadth to that which we always held to be optimum for audax or touring respectively! And since UCI were dragged kicking and screaming into acceptance of disc brakes, these road and gravel bikes do not have any reason to skimp on tyre/frame clearance. Yes, there is often room to fit a proper mudguard!

The one area (apart from gears, still stupidly high on all off-the-shelf bikes) where the roadie still has to learn some common sense is front centres. There is no good reason for this dimension to be so short as it remains on a modern road bike, to the detriment of basic road safety. A bicycle already has a worse braking performance than almost every other vehicle on the road, not because its brakes are bad (nowadays they aren't) but because its centre of gravity is high in relation to its wheelbase, so it tips over forward before it slides. The roadie's obsession with a short wheelbase thereby runs counter to basic road safety. A modest lengthening of the front would do no harm and some good to the all-round performance of the bicycle. It would still tip over before sliding, but at a quicker rate of deceleration. If the UCI are really interested in safety they should legislate on that. A simple rule that the tyre miss the rider's toe by at least 1cm would make bikes that can be raced faster in safety and that Joe Public can fit a mudguard onto without kicking it to bits - or worse!
Chris Juden
One lady owner, never raced or jumped.