Rear Shimano gears problem.

ThisIsWeird

Hi all.

Trying to sort out nephew's bike which has a damaged Revoshift (yuck), but also summat weird going on at the back gears. The protective cage was bent and broken and pushed up against the changer, but it all looked fine when I pulled that away.

If I press the changer in with my thumb as I spin the pedals, the gears run up and down the cogs smoothly. However, if I try and activate them by pulling on the inner cable (all now lubed), it's very hard to do. The Revo control certainly doesn't move it, but I can't tell if that's because its casing is half-missing - tho' it does appear to rotate and click smoothly other than that. 

What does look wrong, tho', is the inner cable angle as it approaches the shifter - see yellow line pic. This can't be right, surely? But I cannot see anything bent or damaged that could have caused this.

Thoughts, please? Thanks.

molerat

That cable end adjuster should point parallel with / along the main body and straight at the cable clamp.

Edit that, some do seem to have them pointing a bit off https://www.bananaindustries.co.uk/products/shimano-rd-tz500-gsd-6-speed-direct-mount-rear-derailleur-black-red

ThisIsWeird

Thanks, Molerat.

Yes, that seems to be the same - quite an acute angle. Normal, then. (Good price!)

molerat

Pulling at the cable shouldn't be light work but if it is running smoothly there shouldn't be a problem at that end.

ThisIsWeird

Thanks, Molerat - I'll try just swapping the Revoshift first.

ThisIsWeird

Soooo, next Q - stick with Revo, go 'trigger', or go 'thumbshift'?!

Both existing Revos are worn/damaged to some degree, so will need to replace both in any case. Next to zero difference in cost. Personally, I dislike Revo, and have always had triggers, but what are the 'thumb's like? (for 9 year old)

Eg: https://www.ebay.co.uk/itm/305683982551?

Username03725

Late to the party again but...

As a Bikeability instructor, I'd suggest you go for the lever changers. They're more reliable than twisters and have an indicator to show the current gear, which makes it easier to explain to young riders which gear they're currently in.

On a wider point if anyone is considering buying a bike for a child I'd suggest you get one without front gears - i.e. no gear changer on the crank by the pedals and a single chain ring. 90% of kids have no idea what the front gears do or how to use them - mainly because most parents don't know either - and almost without fail they end up using the smallest of the three. The smallest is a such a low ratio that the rear gears don't provide a useful range of ratios, and for new riders spinning the legs wildly at barely walking speeds with virtually nothing to push against makes riding harder not easier.

A 7-speed block on the rear operated by thumb & forefinger levers on the handlebars and a single speed crank at the front will suit them just fine. A 21-speed (7x3) or similar setup esp one with twister grips to change gear is the worst option, unless you're prepared to a) explain properly how gears work and b) take the time to maintain the twister by keeping it active and keeping all of the cables properly lubricated. It may last a bit longer doing that.

ThisIsWeird

All good stuff, and I agree, Username.

Didn't want to take the risk of "I don't like it", if I changed too much, so played safe and bought new Revos. Fitted, but not tweaked yet.

Yup - even grown-up bikes have too many gears

Guesthouse

It may well be all lubed, but there could still be frayed cables and assorted muck/crud elsewhere in the routing that are causing problems. 

ThisIsWeird

Thanks, new cable inners now as new Revos - still to tweak them as it's too cold out in t'garage :-)

Outer cables seem to be in good order, and there's at least one short length that can be tidied up by shortening - it currently 'loops' in a manner simply not required. Every little will likely help.