Tom@WashDC
Well-Known Member
- Region
- USA
- City
- Loudoun County, VA.
Was riding last evening, not pushing my bike hard when all of the sudden I felt a snap/crack coming from the rear transmission/hub (Rohloff Speedhub 14 build thread) and my pedals began to spin freely without engaging the Rohloff hub. The chain was still on the hub axle, but spinning freely as I pedaled. It was dark, so I couldn't see well, but the chain was sitting in place just like it was on the cog. I thought it felt like something inside the Rohlof hub just snapped. I figured someting inside the hub was broken, and I was seriously bummed. Fortnately my wife called me a moment later and got in her car to come pick me up. When I got my bike home, and took a good look at it, I relized the rear cog was gone!
It must have snapped in two, or several pieces and just dissapeared. Aparently the Rohloff Chain Tensioner was keeping the chain in place right where it should be, giving the illusion of having a rear cog, but it was gone.
Fortunately I had my original 16T cog and was able to replace that in about 15 minutes.
A few months ago, I had purchased and installed a 13T rear cog to get a better gear ratio. When I first examined the new cog, I noticed that it had less steel in it's makeup, and wondered if that mattered. It seemd a bit insubstantial to me. On a regular bike, I doubt in matters, but for a mid-drive Bafang Ultra, it appears that it may matter. It was either a defective cog from the start, or it's just too much sustained stress over time for the smaller cog, made from much less steel.
I surmise that the 13T cog cannot handle the stress of the Bafang Ultra over time.
I'll keep the 16T cog, and try a larger chainring to achieve my desired ratio.
16T Cog 13T Cog
It must have snapped in two, or several pieces and just dissapeared. Aparently the Rohloff Chain Tensioner was keeping the chain in place right where it should be, giving the illusion of having a rear cog, but it was gone.
Fortunately I had my original 16T cog and was able to replace that in about 15 minutes.
A few months ago, I had purchased and installed a 13T rear cog to get a better gear ratio. When I first examined the new cog, I noticed that it had less steel in it's makeup, and wondered if that mattered. It seemd a bit insubstantial to me. On a regular bike, I doubt in matters, but for a mid-drive Bafang Ultra, it appears that it may matter. It was either a defective cog from the start, or it's just too much sustained stress over time for the smaller cog, made from much less steel.
I surmise that the 13T cog cannot handle the stress of the Bafang Ultra over time.
I'll keep the 16T cog, and try a larger chainring to achieve my desired ratio.
16T Cog 13T Cog
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