An unfashionable gearing set up?

Ajax Bay

Veteran
Location
East Devon
I have a biopace triple just waiting for the right bike, saved when recently resuscitating for a son a bike I bought in 1997. The chainset was/is worth more than the bike (which got a MTB crankset as its replacement: for an undemanding COVID-motivated London commute).
 

matticus

Über Member
I have a biopace triple just waiting for the right bike,
Yeah, they need the right bike ...


preferably with elliptical wheels.
 

andrew_s

Guru
Location
Gloucester
PROBLEM :- Half step gearing as in the OP isn't workable.

There are no current front mechs which will shift reasonably between chainrings with such a small size difference. 10-tooth difference is as small as you'll find, and many (or even most) want a 12-tooth difference.
The basic problem is that if the mech is normally positioned, the inner plate of the mech hits the side of the inner chainring before change is complete, so you've got to raise the mech up the seat tube so there's a big gap between the outer mech plate and the large chainring. and doing that wrecks the quality of the shift. Non-indexed shifters will work, at the cost of an increased chance of dropping the chain, but indexed shifters are unlikely to be usable.

Apologies if this point has already been made.
 

Tigerbiten

Veteran
There are no current front mechs which will shift reasonably between chainrings with such a small size difference. 10-tooth difference is as small as you'll find, and many (or even most) want a 12-tooth difference.
I've raised that point in the past about a half step setup and was proved wrong.

There are no triple derailleurs that will work with a half step setup as they all need at least a 10 tooth difference.
A double derailleur is a different story they don't have to cope with as big a chainring difference so their back plates are a lot shallower.
Ideally you would want to go into a bike shop and measure the difference between the front and back of the cage.
You need 2 mm per tooth difference, so around 6-8 mm is ideal but a slight bigger difference will work.
If you cannot measure any, then go for the one that looks best based on their picture.
It may be more tricky finding a derailleur that not only has a small difference but also matches a smaller than standard chainring size.

Luck ............ ^_^
 

Ajax Bay

Veteran
Location
East Devon
No not a hoax, but an article by an extremely experienced (crazy) guy. If you want to be esoteric, don't expect it to be 'easy'. More fun if you have to work for it. Alternatively just adopt my earlier recommendation to meet an optimised balanced compromise of the criteria/context described in the OP.
 
OP
S

steveha

Regular
Location
Stroud
Thanks for everyone's input so far :-) Now have a plan for what I hope is a workable half-step 2x11 with almost granny built in :-)
Reviewing what I want:
  1. Currently have 36” low gear, want a couple of lower steps with a bottom around 24”
  2. Used to up to 17% steps when accelerating – and that’s fine
  3. For cruising, want half steps so I can get closer to the “ideal” ratio
  4. Would like a top of about 100”
Untitled.jpg


Matching this up to the requirements
  1. Bottom of 22.6” and 3/4 others under 36”. Step of 23% to reach 22.6” is quite large but that’s less important low down.
  2. Accelerating up either chainring is 17% max and usually a bit less
  3. Half steps 10% max and mostly 8% or less
  4. 97.2” is close to the desired 100” and the 106” top probably won’t get a lot of use.
Anyone think it will work? :-)

http://www.gear-calculator.com/?GR=DERS&KB=39,42&RZ=11,12,14,16,18,21,24,28,33,39,48&UF=2215&TF=90&SL=2.6&UN=KMH&DV=gearInches
 

Tigerbiten

Veteran
In theory yes, in practice no.

From Sheldon Brown's gear calc, which shows cassettes which are possible to buy.
Unless you can make them, 33-39-48 sprockets don't exist in 11 speed.
In 11 speed, cassettes go either 11-12-13-14, 11-13-15-17 or 10-12-14-16.
So to get 11-12-14-16 will take two cassettes to make, so double the cost.
Or you start with a 10-12-14-16 and swap the 10 lockring to an 11.

You also need to find out the minimum chainring difference for a front derailleur which fits your large chainring.
All the spec sheets show the maximum difference but not the minimum.
If you cannot find a find front derailleur that works with your chainring size, then this is all theoretical.

Luck ............ ^_^
 

Ajax Bay

Veteran
Location
East Devon
I don't think you quite comprehend the practicalities.
https://www.chainreactioncycles.com/shimano-slx-m7000-11sp-rear-derailleur/rp-prod148563
https://www.wiggle.co.uk/sunrace-ms8-wide-ratio-cassette-11-speed?
You will need to keep changing the front derailleur to achieve the reduced steps between available gears: and that's just not going to happen. So you may as well go for a 1x11 (or 12).
the situation and what I'm trying to achieve:
1) wide range of gears
2) Gradients change quite often so I want to get in roughly the right gear quickly
3) Occasionally ride in flatter areas and want exactly the right gear
 
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