Rear derailleur options
 

My wife and I both own vintage bikes, I've had lots of "practice" on the mechanincs. I'm doing well. My question is this, if her bike (80's Nishiki Landau) has a 6 speed freewheel could I use a rear derailleur that were say 5 or even 9 gears and just adjust the limit screws? And how do I know what will or won't work with friction shifters?

Thanks,
Joe


Edit: Bike is full Suntour. Originally had an ARx but that was replaced with an older Honour. She drops her bike a lot.

ANY derailleur will work with friction shifting. Also there is just about no limitation regardless of the number of speeds, BUT more modern derailleurs built for 7 or more speeds will have narrower cages (9+ speeds narrower yet), and the narrow cage can sometimes create problems with wider chains, especially when feeding at an angle. If you're running 5or 6s, try to buy a derailleur advertised for 8s or less, though if you find a 9s bargain go ahead.

I thought 5-6-7-8 all used the same chain width? single speed is thicker, 9 speed a little thinner, and 10 speed even thinner chain ?

I have used 9 speed derailleurs like early 2000 vintage Ultegra with 6-7 speed bikes no problem, with friction shifting, using standard 6-7-8 speed chains. worked /great/ in fact.

http://pierce.smugmug.com/By-Date/20...MG_8176-X2.jpg

Excellent. Thank you for all the help. If I tell you that she often rides small cog/small chain wheel does it change things?

Probably not unless you're using a 9s RD with a 5/6s chain. Generally you'll only get some rubbing where the chain enters the RD cage at the lower loop. It's easily fixed by filing a bit of entry angle on the front lip at the bottom of the cage.

thats tough on the rear cog and the chain is all. I'd suggest staying on the big ring most of the time, and only using the small ring for bigger hills. big+big is less harmfull than small+small.

REALLY? That is exactly the opposite of what I thought. Good to know.

Count the teeth on the front chainwheels and rear cogs, Google bicycle gear chart, and plug in the tooth counts. Then encourage your wife to ride the front/rear combo that is closest in gear ratio to the small/small. As noted that combination will wear the drive train faster than any other, and it's actually quite a high gear ratio.

the reason small-small is bad is, the smaller front cog puts more force on the chain for a given pedalling effort, and the smaller rear cog puts that force on fewer teeth.

Small/small is 42/15. She's only recently gotten comfortable shifting with downtube shifters. I shudder to think what might happen if I tell her she'll need to "adjust the left side too".

wow, 15 is an unusually large small rear cog. 13 was more typical in the 70s.

assuming that 42T small front is paired with the classic 52T big, then 52:18 or 52:19 is nearly the same gear as 42:15....

If small-small is the favored ratio, get rid of the big ring and put the small one on the outside. ?

or perhaps make a 3 speed IGH conversion .. 42 : 15 the center gear..

phew, if she's using a 42:whatever as her high gear, I bet shed be happier with something like a 34:50 compact double, maybe reduced to 46 or 48 big ring.

Not unusual for a Junior division racer, though.

I toured for 10 years (60s-70s) with a 47-51/13-29 10 speed (5x2) drive train. I set it up this way, trading away a rarely used (though sometimes missed) high end, for better mid-range gears.

That's very different from the normal situation. A 15 will not wear near as fast a a smaller one, and that's not a terribly high ratio.

Hi,

Running the lowest front gear and highest rear gear as a typical gear
is not good as you then don't have a close higher gear easily available.
(Well you do, but involves double shifting, up font, down rear.)

The front high gear and a medium back gear should be nearly
the same and may be more a flexible way of riding that gearing.

Not saying you cannot do it, but most of the time the highest
rear gear should only be used with the highest front gear,
and the lowest rear gear with the lowest front gear.
(For two front rings and a close ratio set on the back.)

Sounds like the front big ring is never used. Probably
because double shifting is not understood properly.

Going to more gears on the back either gives you
closer ratios or more range, for the latter you need
to make sure the derailleur can handle the lowest cog.

(Mine can't handle a bigger lowest cog than the one fitted.)

rgds, sreten.

Thanks everyone. She has 42/52 up front and I don't think she has ever used the large ring. She never needs to put it higher than the 42/15 but there are some big hills here so she needs to quickly drop down to the largest rear cog. I'm going to be doing an overhaul on the bike and am considering not even using the larger ring and making it a 6 speed. For all I know she may not even be keeping it on the smallest cog anymore. She crashed a few months back and so she has been riding at a more commuter pace since then.

on my 1xN (it was 5, later 6, and now is 7), I ended up settling on a 44t front, and a rather wide range rear (13-32, I think) and this gave me a rather good range of gears, albeit rather widely spaced. this bike uses a mountain derailleur (originally an old Suntour, now an Altus since the Suntour got completely worn out)


edit: disclaimer: above bike is a 'cruiser', heh. a fast light weight geared cruiser I built up in the late 70s

Now a Big conversion would be a Mountain compact Crankset. the Big ring is a 44t at most.
the other 2 are smaller..

hey, I like flatbar bikes with ergon style grips, and trigger shifters. 3x8 or 3x9 works great. had one I built up with a homebrew 2x8 system that worked pretty good too, using a 50:34 compact front. I'm not real big on twist grip shifts, tho.

true. both my wife and daughter like them :-/

if I leave my wife's bike (3x8) in 2-5 or so, she'll never shift it. she's happy to just toodle along. its a sit-up-n-beg style comfort stepthrough.

Guys. I have no idea what you mean by grippies.