I think I found the perfect gearing at last...

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Tonyf33
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Joined: 17 Nov 2007, 3:31pm
Location: Letchworth N.Herts

Re: I think I found the perfect gearing at last...

Post by Tonyf33 »

I bought a Shorter 531 bike some years ago and it had a Campag 8 speed set up, the cassette was a specially designed all alloy 14-30, with a 46/43/24 c/set. Ideal for the tourist though with the half step plus granny It was a little low on the higher range but the Campagnolo 8 speed shifters were a dream :D

I'd mentioned on another thread about how if 12 speed gearing came about (& it was resiliant/cost effective) It would continue to alleviate the problem of having larger jumps for those that don't like them whilst increasing the range of sprockets.
As it is in 11 speed you can get 11-42, 11-40, 11-36, 12-36, 11-34, 12-34, 11-32, 12-32, 11-30, 12-30 all designed for the cycle touriste in mind but also useful if you want to run a fairly std double, compact double or indeed just a single ring and still have a great range of gear options.
I bagged a new Tiagra 11 speed chain AND cassette for £25, fitted it to one of my bikes and am currently running it with down tube shifters (Dura Ace 10 speed in friction mode)
I also run a shimano 10 speed,12-30 cassette so that I can have a 52/38 on my old titanium racer or on the audax cum tourer bike with a 50/36/24
Manc33
Posts: 2218
Joined: 25 Apr 2015, 9:37pm

Re: I think I found the perfect gearing at last...

Post by Manc33 »

The ratios I want never exist. :roll: People say get a Miche Primato but others say they don't shift as well as Shimano.

For example 8-speed, I would want: 13.14.15.16.17.18.20.23

The point is you have a 16t and a 18t. A 16t is not usually found on most 8-speed cassettes, the 12-23 doesn't have a 16t, but the 13-26t does. None of them have an 18t and could have if the above ratios were used.

Around 16t, 17t and 18t it is vital to me to have them close.

Its changed since the first post, I chopped 3t off the low sprocket and gained 2 gears. Most importantly, it now has a 16t on it whereas the 13-26t doesn't. I miss having a 16t more than I will need to be on a 26t sprocket. With a 24t granny ring and 23t low sprocket, you've basically got touring bike gearing of around a 1:1 lowest gear (27.5 gear inches).

Figures in black are overlapping gears...

Image

All the 13-26t gives over this is the 26t which in the granny ring is arguably not needed. Also with the 13-26t you will "lose" two gears compared to the 13-23t.

I'll know soon enough when I am going up a 5 mile long hill if the gearing isn't low enough, many a time I have pushed the gear lever for a lower gear and I am already in the lowest gear, sigh, but I have got a lot fitter the last few years and reckon about 1:1 aka about 27 gear inches is my safe limit.
We'll always be together, together on electric bikes.
andrewjoseph
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Joined: 17 Nov 2009, 10:48am
Location: near Afan

Re: I think I found the perfect gearing at last...

Post by andrewjoseph »

i have trouble going up steep hills with 26/36 combo when fully loaded.
--
Burls Ti Tourer for tarmac
Saracen aluminium full suss for trails.
Tonyf33
Posts: 3926
Joined: 17 Nov 2007, 3:31pm
Location: Letchworth N.Herts

Re: I think I found the perfect gearing at last...

Post by Tonyf33 »

Manc33 wrote:The ratios I want never exist. :roll: People say get a Miche Primato but others say they don't shift as well as Shimano.

For example 8-speed, I would want: 13.14.15.16.17.18.20.23

The point is you have a 16t and a 18t. A 16t is not usually found on most 8-speed cassettes, the 12-23 doesn't have a 16t, but the 13-26t does. None of them have an 18t and could have if the above ratios were used.

Around 16t, 17t and 18t it is vital to me to have them close.

Its changed since the first post, I chopped 3t off the low sprocket and gained 2 gears. Most importantly, it now has a 16t on it whereas the 13-26t doesn't. I miss having a 16t more than I will need to be on a 26t sprocket. With a 24t granny ring and 23t low sprocket, you've basically got touring bike gearing of around a 1:1 lowest gear (27.5 gear inches).


Have you thought about combining two cassettes to get your desired combinations, an HG 30/40/41 AND an HG 50 would give you exactly what you wanted?
Manc33
Posts: 2218
Joined: 25 Apr 2015, 9:37pm

Re: I think I found the perfect gearing at last...

Post by Manc33 »

andrewjoseph wrote:i have trouble going up steep hills with 26/36 combo when fully loaded.


I never will be. :)

Tonyf33 wrote:Have you thought about combining two cassettes to get your desired combinations, an HG 30/40/41 AND an HG 50 would give you exactly what you wanted?


No because the biggest 6 sprockets are a solid block.
We'll always be together, together on electric bikes.
Brucey
Posts: 44522
Joined: 4 Jan 2012, 6:25pm

Re: I think I found the perfect gearing at last...

Post by Brucey »

except for XT quality cassettes (and some very cheap ones made in china) the 'solid block' can be dismantled and sprockets can be swapped about between cassettes to some extent.

Just grind the rivet heads off (or just undo the screw on a sram one) and use the sprockets 'loose', they don't need to be in one lump, it is just easier to assemble if they are.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Tonyf33
Posts: 3926
Joined: 17 Nov 2007, 3:31pm
Location: Letchworth N.Herts

Re: I think I found the perfect gearing at last...

Post by Tonyf33 »

Manc33 wrote:
Tonyf33 wrote:Have you thought about combining two cassettes to get your desired combinations, an HG 30/40/41 AND an HG 50 would give you exactly what you wanted?


No because the biggest 6 sprockets are a solid block


Using two cassettes and filing off the heads of the bolts that keep the sprockets in place (for those cassettes that don't have the AK nut head) is a fairly well known solution.. take advice when it's offered with good grace even if it doesn't work for you :roll:
Manc33
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Re: I think I found the perfect gearing at last...

Post by Manc33 »

OK sorry I just didn't know you could file the heads off. :oops:
We'll always be together, together on electric bikes.
Brucey
Posts: 44522
Joined: 4 Jan 2012, 6:25pm

Re: I think I found the perfect gearing at last...

Post by Brucey »

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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
andrewjoseph
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Joined: 17 Nov 2009, 10:48am
Location: near Afan

Re: I think I found the perfect gearing at last...

Post by andrewjoseph »

Manc33 wrote:
andrewjoseph wrote:i have trouble going up steep hills with 26/36 combo when fully loaded.


I never will be. :)

...


"With a 24t granny ring and 23t low sprocket, you've basically got touring bike gearing of around a 1:1"

so not really touring gearing then.
--
Burls Ti Tourer for tarmac
Saracen aluminium full suss for trails.
Manc33
Posts: 2218
Joined: 25 Apr 2015, 9:37pm

Re: I think I found the perfect gearing at last...

Post by Manc33 »

That depends on the tourist.

Here's a question, if a 6600 rear mech handles up to 27t and a 6700 mech handles up to 30t (both are 10 speed) and the smallest low sprocket across both 6600/6700 is a 23t, does that mean the 6600 rear mech with its 27t max low sprocket will shift better on a cassette that only goes up to 23t?

I guess what I am asking is aside from what the b-tension screw does, does the parallelogram need to be slightly shorter on the 6600 just because its rated at 27t as opposed to 30t like the 6700? I want snappy shifting.

It annoys me that they now make 11sp road mechs that handle up to 32t, doesn't this mean they run sloppy on cassettes that only go up to 23t? The 5701 (10sp) I tried was sloppy with the b-tension screw removed altogether on a 23t and not much better on a 26t even though 25t is the smallest low sprocket in the 5700 groupset.

Maybe I should just use a mech where the smallest low sprocket was a 21t and it will give snappy shifting. Thing is I'm on a 75mm long cage now and I think a newer GS (like the 6600) has it at around 82mm allowing slightly more overall capacity. This would fix the rubbing I get on the sprockets around the middle of the cassette when on the granny, I think.

Taking a link out of the chain erm... won't that just have the same effect as having a slightly longer cage? Then big to big is probably going to be a drivetrain breaker. A 24t granny is really finicky to setup. On my other long cage mech (XT/100mm/SGS) I never got the 4th and 5th sprockets on the granny making the chain rub on the middle ring so it must be the jockey wheel isn't low enough on this 75mm cage.

Its a laugh. 8)

EDIT: Useful... http://www.celebrazio.net/bicycling/shi ... ables.html
We'll always be together, together on electric bikes.
Brucey
Posts: 44522
Joined: 4 Jan 2012, 6:25pm

Re: I think I found the perfect gearing at last...

Post by Brucey »

I think as a general rule mechs work best on the range of gears that they are intended for.

Fundamentally the two ('panta-servo' they used to call them) springs in the main pivots don't (and indeed can't) control the pulley movement perfectly. [This is because the spring forces vary with position too much, and this in turn is because the working travel of the spring is large in relation to the preload; a more constant force from each spring could be obtained if they were larger, heavier springs, with a lower rate and a greater preload.]

This is where the slant parallelogram comes in... but that works best on one angle of freewheel i.e. the slant angle is related to the capacity.

In addition to the above the guide pulley may not be centred on the lower pivot and this also changes the way the mech behaves with changing chain wrap. This aspect is in theory less satisfactory because the guide pulley will be at a different distance to the sprockets depending on the chainring size. However in practice this is often mitigated because the chain speed is higher when you are on a larger chainring, and a slightly 'delayed shift' isn't so bad when the chain speed is higher.[the same logic allows one set of gates/ramps on the small sprockets but several more -more than pro-rata- on the larger sprockets]. Shifts are more rapid when the chain is slacker which is fine, it is good if they are very quick when you are on the small chainring and the chain speed is low since these tend to be 'distress shifts' eg when MTBing.

I think it is worth noting that the main things that make 1T shifts fast are having the guide pulley close to the sprockets, and the 'gate' in the tooth pattern. By contrast if you have a 2T or 3T shift I think that the shifts can be relatively (i.e. not x2 or x3 slower) fast because the ramps on the side of the sprockets can lift the chain up to a greater extent.

FWIW if you want what folk on the other side of the pond might call a 'corncob triple' setup, using a 7s or 8s cluster, I'd suggest that you cast your horizons a little further than current shimano or campag gear. Specifically I'd suggest that you consider seeking out a Mk1 campagnolo chorus rear mech, rework the dropout to allow it to get as close as possible to the sprockets and that you use it with the slant set to the 'low' position.
Image

BTW what you propose is really not much different from using a 14-24 5s freewheel with an evenly spaced triple, but with more, more closely spaced sprockets. I'm not sure I'd get on with it at all, because I'd be running cross-chained on gears in the mid 70s, which is a 'red flag' for me.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Manc33
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Joined: 25 Apr 2015, 9:37pm

Re: I think I found the perfect gearing at last...

Post by Manc33 »

Brucey wrote:Fundamentally the two ('panta-servo' they used to call them) springs in the main pivots don't (and indeed can't) control the pulley movement perfectly. [This is because the spring forces vary with position too much, and this in turn is because the working travel of the spring is large in relation to the preload; a more constant force from each spring could be obtained if they were larger, heavier springs, with a lower rate and a greater preload.]


I think I know what you mean, sometimes I can shift from sprocket 1 to 4 and it lands smoothly on the 4th sprocket and runs quiet, but change from the last sprocket up to the 4th and there might be a slight tinkling on the chain. I can only guess thats because when the mech shifts down it quickly "snaps" down, whereas an upshift is a gentle push so it ends up with slightly tighter cable after shifting up.

Brucey the vintage Campag mech might fix it but I'm not that rich. :P

Here's a question... if my chainline is right (45mm) and I unscrew the front mech inner limit screw all the way out, even then I can't "make it" drop the chain off the granny ring, what does that mean? I mean in the lowest gear, I can set the front mech so its only just not rubbing the FD cage, but I can unscrew the inner limit screw more than this and not have the chain drop. This helps take up some of the slack cable on the shifter, but I don't actually need to do it (other than to take up that slack).

The way I set it, I did it so it can just about shift off the middle onto the granny, surely thats the right way?! I have got a chain catcher on (because of the range on the chainrings) but I have never made the chain drop, not once, ever on this setup. I don't think therefore, it could, so I might just whack that limit screw out more.
We'll always be together, together on electric bikes.
beardy
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Joined: 23 Feb 2010, 4:10pm

Re: I think I found the perfect gearing at last...

Post by beardy »

You are running a 52-38 on the two larger rings at the front. This means that your front dérailleur must be further from that 38 tooth ring when trying to knock the chain off it than it would be for a lesser gap like 52-39 or better still a 50-39. That is a part of your problem that can not be avoided.
Brucey
Posts: 44522
Joined: 4 Jan 2012, 6:25pm

Re: I think I found the perfect gearing at last...

Post by Brucey »

the middle to inner chainring shift is often the worst one of the lot; various things can go wrong including

- that you don't have enough inwards movement available on the front mech
- that the cage isn't wide enough at the back to prevent chain rub unless you use some kind of trimming (not all shifters have the right trimming functions to allow this)
- that the vertical distance to the middle ring is too great (as Beardy suggests)
- that the chain just won't derail off the middle ring

Before now I have set up triples where out of frustration -having tried everything else I know- I have changed the chain for a different model and suddenly the shift goes OK. I've often not been able to measure much difference in the chain tolerances but the shifting went differently, night and day different...

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