Mystery front shifting problem solved
04-23-16 | 09:49 AM
#1
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Senior Member
Joined: May 2008
Posts: 9,102
Likes: 6,009
From: Zang's Spur, CO
Mystery front shifting problem solved
This was driving me mad, and now that I've solved it, I thought I would share;
Some years back I built a bike I use for touring/winter rides. Originally it was a 3x9 drivetrain, upgraded several years ago to 10s on the rear w/o changing the front. Crank is an XT crankset from the 9s era, (22/32/44) with the 44T swapped out for a 48T before installation. FD is an IRD Alpina-D. I have no idea how many chains it has gone through, but both small & middle rings have been replaced over the years when they started chain-sucking on a new chain. Large ring is still the 48T installed when new.
Anyway, over the past winter, the shifting from middle->large ring has become gradually worse. Since I clean/overhaul it every spring, I just put up with it until the annual overhaul a week ago. So I did the overhaul, then after re-assembly went half crazy trying to get it to shift properly: Varying height/yaw/low-limit/high-limit of the FD cage did not solve the problem. It was nearly impossible to get the chain to climb from the middle to the large. If I adjusted the high-limit to allow the cage to move further out, it would throw the chain right over the ring, and onto the crankarm.
However, once I finally got it on the large ring, it would work fine.
After closely watching what was happening on the workstand, I developed a theory;
I went to eBay and found a NOS 48T for $22.
It arrived yesterday and I installed it this morning.
Shifting again works like a charm.
The conclusion: The edges of the little pins/rivets on the backside of the large ring have worn to a rounded profile, so they can no longer catch the chain to lift it onto the large ring. It is maddening to replace a ring with perfectly good teeth that is virtually unusable just because I can't shift onto it.
Some years back I built a bike I use for touring/winter rides. Originally it was a 3x9 drivetrain, upgraded several years ago to 10s on the rear w/o changing the front. Crank is an XT crankset from the 9s era, (22/32/44) with the 44T swapped out for a 48T before installation. FD is an IRD Alpina-D. I have no idea how many chains it has gone through, but both small & middle rings have been replaced over the years when they started chain-sucking on a new chain. Large ring is still the 48T installed when new.
Anyway, over the past winter, the shifting from middle->large ring has become gradually worse. Since I clean/overhaul it every spring, I just put up with it until the annual overhaul a week ago. So I did the overhaul, then after re-assembly went half crazy trying to get it to shift properly: Varying height/yaw/low-limit/high-limit of the FD cage did not solve the problem. It was nearly impossible to get the chain to climb from the middle to the large. If I adjusted the high-limit to allow the cage to move further out, it would throw the chain right over the ring, and onto the crankarm.
However, once I finally got it on the large ring, it would work fine.After closely watching what was happening on the workstand, I developed a theory;
I went to eBay and found a NOS 48T for $22.
It arrived yesterday and I installed it this morning.
Shifting again works like a charm.
The conclusion: The edges of the little pins/rivets on the backside of the large ring have worn to a rounded profile, so they can no longer catch the chain to lift it onto the large ring. It is maddening to replace a ring with perfectly good teeth that is virtually unusable just because I can't shift onto it.
04-23-16 | 03:13 PM
#3
Senior Member
Joined: Aug 2005
Posts: 935
Likes: 46
From: Las Vegas, NV
Bikes: '04 LeMond Buenos Aires, '82 Bianchi Nuova Racing, De Rosa SLX, Bridgestone MB-1, Guerciotti TSX, Torpado Aelle, LeMond Tourmalet 853, Bridgestone Radac
A couple months ago I bought my dream crank - Campagnolo C-Record in 180mm. It has a 41T inner ring and, despite the closer range to the 53T, is a bear to upshift.
On the other hand, on my commuter I have Vuelta 36T and 48T rings on a Deore XT crank. The 48T doesn't have any pins or ramps and always shifts great.
On the other hand, on my commuter I have Vuelta 36T and 48T rings on a Deore XT crank. The 48T doesn't have any pins or ramps and always shifts great.
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