Friction gears?

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mjr
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Re: Friction gears?

Postby mjr » 14 Jul 2014, 3:33pm

LollyKat wrote:Another advantage to friction shifters is that it is very easy to shift several - i.e.four or five - sprockets at once. I've used friction shifters for 40 years and know exactly where each gear is by the position of the lever. There is no need to look, I simply do it by feel. Very useful when riding with a cape, too, as it is easy to avoid cross chaining.

I've just fitted a Shimano switchable handlebar shifter to a folding bike. I'm not the only rider of that bike, but I intend to leave it in friction mode mainly because:
  • like LollyKat writes, it's easy to shift multiple gears in one move (as long as the pedals are moving forwards),
  • I'm less likely to hit the wrong one of up/down levers and
  • I can get a good idea of the current gear by feel without looking at indicators or cogs.
Sorry to disagree with thirdcrank, but I think check-by-feel is actually the best thing about friction shifters. And all of those features are very helpful for cycling in towns and cities, which is where the folding bike is used most often.

The immediate motive to change the shifter was what thirdcrank suggested, though: the indexing seems to drift out slightly each time the bike is folded. I don't really know why yet. Some have suggested that the fold is stretching the (fairly new) gear cable and it'll settle down soon or I could fit a prestretched cable. I'm bored with having to choose between rattling in some gears and short toolkit stops to adjust them, so I'll use friction mode for a while. Indexed shifting is simple but more tedious to get just-so, whereas I think I could set up friction shifting while drunk! :lol:

But I think the top reason for anyone else to try this should be friction shifting is much more fun, like the bikes I grew up riding. :-D It's rather annoying that it's now an almost-unknown minority option.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
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Brucey
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Re: Friction gears?

Postby Brucey » 14 Jul 2014, 6:21pm

re the indexing drifting out; I think it is most likely that the cable housing is taking a set and that this is messing with the indexing. It is worth checking two things here;

1) that the housing isn't coiled type (which more easily takes a set IME, and once set can go 'springy' etc, but experiment with the stuff you have) and

2) that beneath the ferrules, parallel-stranded housing isn't now 'slanty-ended' through the strands moving around when the housing is flexed.

If the bike can't be folded without putting a tight bend into the gear cable, I'd suggest that you just don't bother with indexed shifting, or that you look into fitting a short length of something super-flexy (like Nokon housing) where the fold is.

I recently rebuild a folding bike and didn't bother fitting indexed shifting; it would have been useful, but I could see it was just going to be trouble, and I don't much mind friction shifting .

I have a suspicion that a lot of trouble with SA 5s hubs on Bromptons is caused by the folding messing up the gear cable; unlike a 3s hub there is much less room for error in the adjustment.

IGHs with substantial gear intervals (i.e. mostly simpler ones) can be brilliant for urban use; an ultimate indexed system if you like, allowing almost instant shifting with no looking or feeling etc. Between traffic lights a boring old 3 speed hub beats the pants off of almost any derailleur system.

Re feel/benefits of indexing; obviously you can 'check by feel' as to which gear you are in with switchable indexed thumbshifters, bar ends, or DT levers. Since these work well in friction mode too, I think you can judge from the (very small) number of people who routinely use such in friction mode (because it is better, or the indexing doesn't work) just how useless or troublesome indexing usually is.

cheers
Last edited by Brucey on 14 Jul 2014, 6:34pm, edited 1 time in total.
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Mr. Viking
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Re: Friction gears?

Postby Mr. Viking » 14 Jul 2014, 6:30pm

Bike-Rich wrote:Many thanks, I understand now :)

For down-tube shifting, is it required for the frame to have provision for the fitting or is it braze-on type?

you can get shifters which fit braze ons or you can get band-on shifters which are attached with a contracting band

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NATURAL ANKLING
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Re: Friction gears?

Postby NATURAL ANKLING » 14 Jul 2014, 9:08pm

Hi,
Index shifting drifting.
Its possible That when the bike is folded / unfolded that the cable housing is twisting and adjusting the setting via an adjusting cable hollow screw :?:
If you were to mark the thumb screw adjusters with something like tipex or a emulsion light paint aplied with an artist brush you could see if this was the case.

It is possible that because of the configurtation which I can not see that this might not be the case, I was just putting forward a similar problem I had.
Edited - P.S. if shimanp brought out indexed deralleurs in 85 then the "Hatch plate" IIRC mechanism in 82 abouts, was friction with a ramped or notched plate on the r-derailleur which could be felt on the thumb lever, when moving cable.
Edited -
No not Hatch Plate that was something else "New Positive Shifting Mechanism" I will post a picture later.
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NATURAL ANKLING
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Re: Friction gears?

Postby NATURAL ANKLING » 14 Jul 2014, 9:31pm

NA Thinks Just End 2 End Return + Bivvy
You'll Still Find Me At The Top Of A Hill
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mjr
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Re: Friction gears?

Postby mjr » 14 Jul 2014, 10:49pm

I don't think the housing is the coiled type and the cable looked square-ended when I took the ferrule off to change the shifter, not slanty. There is a short length of more rigid housing around the cables near the bit that gets bent most when folded - it's a Dawes Jack if anyone knows it - so I feel it could well be some sort of stretching that may settle down in time as suggested in another place. I can't see any adjuster moving during the fold/unfold. The cable housing sometimes tries to rest on the inside of the chainring after the unfold, but I'm careful to make sure it's clear before riding.

I suspect a good 3-speed hub may well be better than the 6-speed derailleur Jack (gear range would probably be greater) but this was the best bike I'd seen for a while and now it's got friction shifters it's fun... so far. It'll get a couple of decent rides out in the next week or so, so we'll see how it goes. :-)
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
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drossall
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Re: Friction gears?

Postby drossall » 14 Jul 2014, 11:34pm

Possibly the point that hasn't been made is that derailleur systems involve a sprung derailleur that will, if not restrained, move itself back to (normally) the smallest sprocket (rear derailleur) or chainring (front derailleur). The gear control pulls the derailleur, against that spring, onto larger sprockets via the cable. When the gear control is moved back, the spring returns the derailleur towards the smaller sprocket, and takes up the slack in the cable.

When the rider lets go of the gear control, something needs to make it stay in the position where it has been put, or the derailleur will return to the small sprocket unexpectedly. Friction gear controls use friction in the lever assembly to hold the lever (and therefore the derailleur) where the rider put it. As others said, the rider puts the lever in a place that will line up with one of the sprockets by "feel", which is much easier than it sounds, and far easier than anyone not used to the system would have you believe.

The click-stops on indexed gears (should) line up the derailleur with the sprockets, but also serve instead of friction to retain the control in place.

The down tube was the obvious place for a gear control on the friction system. There were levers that mounted on the stem or handlebars, as alternatives.

With indexed gears, down-tube levers were available, but indexing made it easier to combine the brake and gear levers; in theory, you could do that with friction gears, but I'm not sure it would be so easy to position the gear lever accurately when just pushing at it with a finger; having click stops gets round this.

Integrated levers are however monumentally expensive compared to down-tube levers. I use and like integrated levers, but no sane cost-benefit analysis could justify them. The oddities of bike-manufacturing economics mean that the additional costs are substantially reduced when you buy a complete bike, because of the pricing for OEM sales to bike assembly companies ("manufacturers"). It is prices for such levers as individual items to the consumer that are ridiculous.

Cable stops are just guides because you are running cables all round the frame. Some cheap bikes have had cables taped in place, but that's pretty nasty. It's often convenient to switch between covered and bare wire along the cable run. Stops let you do that. They can be permanently attached to the frame, or come as bolt-on accessories.