MoodyBlue

Hi Folks

I'm having an issue with a Kuwahara mountain bike I picked up on Freecycle a few weeks back.

When I collected it, the former owner said that there was an issue with the gears, and he was right.

Basically, I couldn't engage the large front sprocket at all, regardless of which rear sprocket was engaged. Also, it was difficult to shift down to the small front sprocket unless the largest rear sprocket was engaged - the chain also had a tendency to pop off the small front sprocket as I went up the gears.

All in all, not great

I've not got a lot of experience with adjusting derailleurs, but have been able to adjust and index the gears on my hybrid road bike successfully, but am struggling to do the same with the Kuwahara. I don't know if there are any differences with mountains (I suspect, however, that the principle remain the same even if their are).

I've tried to adjust both the high and low positions but what I seem to have found is that, as far inboard as the cage will sit, it seems to me that it is still too far out for the small sprocket to be engaged while, at the same time, in the furthest outboard position (pretty much up against whatever thing outside the sprockets is called), I cannot engage the large sprocket.

I'm happy to accept that I lack knowledge and skill here, so am hoping for some hints, so I get back on track, and on the bike.

MB

DorkDisk

Perhaps the bottom bracket was swapped out and the new one is too wide, causing the crankset to be too outboard.

cyccommute 

It sound like you may have a number of issues. Pictures will always help. Your most immediate problem sounds like the bike has a spindle that is too long. That pushes the crankset out board so that the inner ring is where the middle should be, the middle is where the outer ring should be, outer ring is somewhere around Saturn. If someone changed the crank at some point, they may have put on a more modern crank that sits further inboard than the older cranks do. The old cranks used 120mm or wider spindles while more modern cranks use spindles around 115mm or less. Since your chainring is derailing when in the smallest ring, I suspect you need something closer to the 115mm spindle. Here’s a somewhat dated database with spindle lengths for various cranks. Check to see if your crank is on it.

You may want to release the cable and adjust the stops so that the derailer can move as far inboard and outboard as it can. Move it by hand and see if the derailer can reach the outer ring. If not, it’s a spindle issue.

Your problem could also be related to cable pull. You may not be winding up enough cable because it is slack when in the lowest position. Check to see that the cable has a little twang to it when in the lowest position. The derailer should be adjusted so that the chain just clears the inner plate of the front derailer. With a tight enough cable, the outer ring should just clear outer plate of the derailer.

You might also want to replace the cable and housing just to ensure that it isn’t sticky.

My money, however, is on the spindle being too long.

MoodyBlue

Hi CC, and Thanks.

I can't post pictures yet - being a newbie, I need a couple more posts first.

I'll have a look at the crank.

I did think about rotating the the derailleur anti-clockwise and then correcting the angle, as this would move the cage further inboard (but also move it forward as well).

I'll check the cable which my recollection says was slack at the lowest level (by which you mean the derailleur at its furthest point inboard).


MB

70sSanO

First thing I would check is to check which cog the chain lines up perpendicular to the rear axle. You can check large and small chainrings (double) or if it is a triple just use the middle chainring. The chain should be approximately in the middle cog and perpendicular. If it is in the one of the higher (smaller) cogs, the crank spindle is probably too long; as has already been noted by others.

John

MoodyBlue

Hi John

The chain appears perpendicular to the rear axle when it is on the middle chainring, and the fourth (i.e. middle) rear cog.

It will have to look more closely at the crank spindle.

MoodyBlue

Hi CC

The front derailleur cable has just enough tension to be able to say it is not slack - any more tension on it moves the derailleur outboard.

This image shows the derailleur inboard as far as it will move, with the chain on the inner of the 3 chainrings, and the smallest rear cog. The chain clearly touches the derailleur cage and curves inwards to reach the small rear cog (and won't move off the cage until I shift out to the 4th cog).





This pic shows the view from above, with the derailleur fully inboard. I had to move the chain on to the first chainring manually.


This view shows the derailleur in the fully outboard position (but which will not move the chain on to the 3rd chainring).



I have also checked the click shifter and cable for freedom of movement.

cyccommute 

That says to me that the spindle is too long.


Clean that derailer! A bit of lube on the pivots wouldn’t hurt.

Again, says spindle is too long.