No one seems to know the answer to my question, so I’m hoping someone here can help!

Can I presume that with a triple front, and 8 speed rear say, there will always be a sweet spot whereby if the chain is on the middle chainring there will be no chain rub irrespective of which rear gear is selected?

I want to be able to move through the full range of rear gears, up and down, without encountering any chain rub on the insides of the front derailleur, and without having to re-adjust the front derailleur for as long as the chain remains on the middle chainring.

My present setup, which has friction levers, 5-speed rear block (Suntour), triple front Shimano Claris derailleur, and 8-speed chain, produces no chain rub at all when using the middle chainring, but then the rear block is only about 25mm wide, whereas a new 8-speed Shimano cassette would be 35.4mm. I would like to upgrade(?) to have the extra rear gears, but not at the expense of having to keep trimming the front derailleur.

No, you can't presume that. Depends on front derailleur design (manufacturer must choose a middle line between less adjustment needed and crisper shifting, and probably other constraints if designed for index shifting, chainstay length (longer = less rub) and range of rear cassette (larger range will be more likely to rub).

Thanks for that, which is what my own measurements appeared to confirm.

I think I'll stick my current setup and keep the 5 speed block. It fully avoids the chain rub, without having to fiddle with front middle ring trimming, and the range on the middle ring is actually spot on, although a couple of extra gears within the range would have been preferred.

Rub on what? if the FD cage (?) friction shifting lets you adjust its location so it wont.

Or dump the whole drive train for an IGH, and be done with derailleurs entirely .
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Happy enough with my Old 6 by Triple drivetrains .

the minor FD adjustment is just part of the operating the bike quietly..

happier with my IGH since Most of my riding is around Town Which is far from flat.

Yes, the FD cage.

The point I'm making is that once the chain is on the middle front, and adjusted to an optimum position, I don't then want to continue readjusting the chain position on the middle front as I move up and down the rear rings. This works perfectly with my current 5 speed freewheel, but not it seems if it's going to entail the thicker freewheel/cassette of an 8 speed.

Too bad , that is just your Wish. get over it.

recenter the FD cage after your rear shift .


the 5 speed freewheel is narrower than any With more ..

its the angle, off center, that causes the chain to have to flex sideways to reach

Typical Triple Crank setups , rather Than Middle to smallest , you shift to the Big Ring.

likewise Middle to largest rear, its time to shift to the granny gear.

Best to do a tooth count and make a gearing grid chart to know the ratio pattern of your drivetrain.



want to not be involved in operating your bike. A NuVinci 360 continuously variable hub is a great product ,

you just rotate the shift grip till the gear feels right.

If you are using friction shifting, you can use a narrower chain than is optimum for the number of cogs on your rear wheel. So you might get away with a 10 speed chain on an 8 speed cassette and possibly avoid chain rub. However, you might then have to deal with replacing your chain more often. It is all about tradeoffs. If you want to make gains in one area, you may lose something elsewhere. Having to trim your front derailleur isn't the end of the world, the more often you do it, the easier it becomes

Strange comment! No need to get over anything here, since retaining the present set up is preferred.


Believe it or not, I've actually been doing this for many years now!

But thanks for you latter comment.

Yes, thanks for this. I actually tried a narrower chain some time back for different reasons, but it caused the chain to sometimes ride between front chaninrings.

Attributed to some Italian 'cycling with indexed shifting is like Sex with Rubber Boots on'

That is about it. Strange to see a post like this from someone using friction shifting. If you want no fuss shifting, you need to simplify your drivetrain

You must not know much about sex. Do you know anything about bicycling?

You Dr. Ruth or what? kid.

Well I think that the author failed to realize, that in Venice it's recommended at high tide.

Back to the task at hand;
The whole idea of having a tripple is to have a wider range of gears. Now my opinion would be that if you want it to not rub, and to use the whole rear cassette, go to nine speed and loose the front derailleur altogether. on my commuter, I'm running a 7 speed mega range cassette with the front derailleur dummied with the limit screws as a chain watcher. No rub.

Sex is recommended in Venice, even at High Tide ?