Nightmare with Shimano intermediate ratios.

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Valbrona
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Re: Nightmare with Shimano intermediate ratios.

Postby Valbrona » 11 Aug 2011, 10:35pm

Colin 531: Why do a thousand word post about gearing but not mention what front gearing (chainset) your cassette is being run with? Maybe you think it does not matter.

You seem to have fallen foul of this CTC Holy Grail that dictates in order to get lower gearing you have to fit 30 something tooth sprockets at the back. PS Chainrings aren't welded onto chainsets.
I should coco.

reohn2
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Re: Nightmare with Shimano intermediate ratios.

Postby reohn2 » 12 Aug 2011, 8:34am

Valbrona wrote:Colin 531: Why do a thousand word post about gearing but not mention what front gearing (chainset) your cassette is being run with? Maybe you think it does not matter.

You seem to have fallen foul of this CTC Holy Grail that dictates in order to get lower gearing you have to fit 30 something tooth sprockets at the back. PS Chainrings aren't welded onto chainsets.


Look at the thread title.
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531colin
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Re: Nightmare with Shimano intermediate ratios.

Postby 531colin » 12 Aug 2011, 4:45pm

Found my ideal cassette........here http://forum.ctc.org.uk/viewtopic.php?f=5&t=40807&start=30
Buy a 10 speed SLX cassette, ditch the top sprocket! (11) 13 15 17 19 21 23 26 30 34.

Seriously though, I will buy a tiagra HG50 9speed 13 14 15 16 17 19 21 23 25
Mix it up with my existing 9 speed ................11 13 15 17 20 23 26 30 34
To get my ideal........................................13 15 17 19 21 23 26 30 34
with all the important shifts ................................17 19 21 23 ............not disturbed from the same cassette!

I reckon I will get away with using the top sprocket without a recessed next-to-top, the recess is shallow, the gap behind the top sprocket will be fractionally greater than ideal.

Grateful thanks to everybody who has contributed to this somewhat agonised decision!

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531colin
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Re: Nightmare with Shimano intermediate ratios.

Postby 531colin » 14 Aug 2011, 6:46pm

OK, so I've had a ride now.
It all works very well, I can detect a slight hesitation/clunk at the gearchange on the "join" between the 2 cassettes, ie the 23/26 shift, its not quite as slick as the 17/19/21/23 shifts, which are all un-disturbed from the 13/25 cassette. Not quite as slick, but thats all....its much better than the leg-stopping 17/20 jump that was the original problem.
And the 13t top sprocket (from the 13/25 cassette) doesn't expect to seat in a recess in the next-to-top sprocket, so thats OK too.
I have put the sprockets and spacers loose on the hub body without the rivets...got 'em out, couldn't get 'em back in!
I used top gear but not bottom, its nice to have one in reserve for real hills, theres one or two of them in Yorkshire.

Valbrona
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Re: Nightmare with Shimano intermediate ratios.

Postby Valbrona » 14 Aug 2011, 9:10pm

Someone wanting a 34t sprocket at the back (assuming a 34t front chainring on a double chainset) is probably better off with smaller chainrings at the front, as with a triple chainset. But most people are only able to think in terms of 'bigger sprockets' in order to get lower gears.
I should coco.

reohn2
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Re: Nightmare with Shimano intermediate ratios.

Postby reohn2 » 14 Aug 2011, 9:55pm

531colin wrote:OK, so I've had a ride now.
It all works very well, I can detect a slight hesitation/clunk at the gearchange on the "join" between the 2 cassettes, ie the 23/26 shift, its not quite as slick as the 17/19/21/23 shifts, which are all un-disturbed from the 13/25 cassette. Not quite as slick, but thats all....its much better than the leg-stopping 17/20 jump that was the original problem.
And the 13t top sprocket (from the 13/25 cassette) doesn't expect to seat in a recess in the next-to-top sprocket, so thats OK too.
I have put the sprockets and spacers loose on the hub body without the rivets...got 'em out, couldn't get 'em back in!
I used top gear but not bottom, its nice to have one in reserve for real hills, theres one or two of them in Yorkshire.


Glad you're all sorted,I've never really been concerned about the "out of sequence" change or slight "clunk" and as you say its much better than thinking someone put the brakes on when a 3tooth gap surprises the knee caps :shock: .
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reohn2
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Re: Nightmare with Shimano intermediate ratios.

Postby reohn2 » 14 Aug 2011, 9:59pm

Valbrona wrote:Someone wanting a 34t sprocket at the back (assuming a 34t front chainring on a double chainset) is probably better off with smaller chainrings at the front, as with a triple chainset. But most people are only able to think in terms of 'bigger sprockets' in order to get lower gears.


But the thread is about "intermediate" ratios or when the over large gap between ratios is unacceptable,which doesn't have anything to do with bottom gear or chainrings.
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531colin
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Re: Nightmare with Shimano intermediate ratios.

Postby 531colin » 14 Aug 2011, 10:58pm

Valbrona wrote:Someone wanting a 34t sprocket at the back (assuming a 34t front chainring on a double chainset) is probably better off with smaller chainrings at the front, as with a triple chainset. But most people are only able to think in terms of 'bigger sprockets' in order to get lower gears.


I'm not most people....
I'm old and weak, I like the small roads and the rough tracks in the Dales. I'm running 24, 34, 46 on the front. When 24 front 28 rear is getting marginal, your options for a significantly lower gear are a bit limited.

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frank9755
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Re: Nightmare with Shimano intermediate ratios.

Postby frank9755 » 15 Aug 2011, 9:00am

Glad you've got sorted, Colin. Very satisfying to have beaten the system and got the gears you want!

Valbrona
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Re: Nightmare with Shimano intermediate ratios.

Postby Valbrona » 17 Aug 2011, 1:42am

531colin wrote:I'm old and weak,I'm running 24, 34, 46 on the front. When 24 front 28 rear is getting marginal, your options for a significantly lower gear are a bit limited.


Me too. There are only cissy hills in my part of the world (not like Yorkshire), and I manage with a 26/34/42 front and 11-23 rear. Just thought for a minute you were running a double.
I should coco.

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531colin
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Re: Nightmare with Shimano intermediate ratios.

Postby 531colin » 17 Aug 2011, 7:34pm

Oddly enough, fitting the "tea plate" 34 to the back has changed the way I use the gears.
On most of my local hour-or-so circuits I can now keep off the granny ring.........almost like riding a double :wink: The middle ring is now geared to unity (1:1, or rather 34:34) so I can get up most stuff on the middle ring....the granny is only needed for the real hills. The local "double arrow" hill is now a piece of cake, drop onto the granny, sit and spin. I don't even have to work at keeping the front wheel down!

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deliquium
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Re: Nightmare with Shimano intermediate ratios.

Postby deliquium » 18 Aug 2011, 7:00pm

531colin wrote: The local "double arrow" hill is now a piece of cake, drop onto the granny, sit and spin. I don't even have to work at keeping the front wheel down!


Sorry to venture off topic - I wonder how much rider weight affects this? "Double arrow" hills in these parts on a touring bike are mainly a fight with the front wheel lifting and the rear wheel not getting traction ie balance of rider weight - plus going so slow as not to fall off with the resultant panic of SPD cleat disengagement and which wall to fall into!

Maybe another post?

ps never had a problem with a tandem trike - although a solo trike would give the same weight distribution problem but minus the falling off panic.
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531colin
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Re: Nightmare with Shimano intermediate ratios.

Postby 531colin » 18 Aug 2011, 7:34pm

I can get up this hill with a 28 sprocket, if I'm really determined to do it, but the front wheel lifts.
Obviously I have to push harder in a higher gear....you might think the wheel would lift more in a lower gear....is it because I pedal smoother in the lower gear?.....the wheel only lifts momentarily as the cranks are at 3 and 9 o'clock.

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deliquium
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Re: Nightmare with Shimano intermediate ratios.

Postby deliquium » 18 Aug 2011, 7:48pm

I think you have hit the nail on the head Colin - a lower gear means less effort and time between the 3 and 9 o'clock front wheel lifting window/envelope/opportunity.

Good - it's not that you are lighter than me?

Damn, I've just bought a shed load of 12-28 7 and 8 speed cassettes - could be in the For Sale section soon :roll:
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reohn2
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Re: Nightmare with Shimano intermediate ratios.

Postby reohn2 » 18 Aug 2011, 8:23pm

When its getting frontwheel airborn time, have you tried climbing on the drops?
Theres a couple of bridleways I ride that have little 20m long,25%(?) jump ups that with 24x26 (24inch) the front wheel starts to lift,if go to the drops and crouch (more weight over the front wheel) its controlable :),I dare not get out of the saddle as the dirt/gravel surfase is too loose.
On a similar tarmac gradient its a doddle out of the saddle but in a higher gear,unless its wet :shock: .If you want to climb sloooowly a tandem is great,very stable at 2mph :) but we stuggle to get up anything over 20% :oops:
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