Shahmatt

I need some advice on my Nexus 7 hub model: SG-7R50. Specifically on dust caps 10 and 11 in the parts breakdown in image below:



After disassembling, replacing a bearing ring and regreasing, I am now trying to put together the outer assembly.

The wheel turns fine with dust caps (10 and 11) inserted. The problem is when I install the sprocket (33) and snap ring (34). I find that the dust caps possibly come into contact with the sprocket. If I turn the wheel and hold the sprocket the wheel slows down in quick time.

The sprocket is a smaller (than recommended) 14T size which came stock with my bike.

The rubber dust cap (10) shows slightly 'wobbly' when viewed in profile while turning the wheel. The wobbliness is probably due to the dust cap not being seated fully. I've tried my best to push it in, and it's as far as it can go in now on thumb power, but it still shows some slight wobbliness in profile.

I watched a youtube video in which removal of dust cap 11 is suggested for sprockets less than 16T (recommended) size. I reassembled without dust cap 11 and contact with sprocket is much lessened. I tried reversing the sprocket so that the indented bits are towards the inside (facing the hub) instead of outside. This seemed to help as well.

But the wheel still does not move as freely as without the sprocket installed - i.e. mounted only on its bearings. Sprocket induced friction is a problem isn't it? Or is it just that the hub is designed this way.

So what am I doing wrong? Has anyone else faced this problem? Any help is much appreciated.

I'm not sure how dust cap 11 was even part of the hub before I started disassembly. It looks as though there would have been significant friction and this would have slowed down the bike while coasting. But the trouble is I don't remember it being this way. As far as I could recall before disassembly, when coasting the bike moved fine. But on the other hand I didn't do this kind of wheel turn test that I am doing now so I can't do a scientific comparison.

Full parts link:
https://www.google.com.sg/url?sa=t&r...awZ7pQ&cad=rja

Shahmatt

Based on the second to last response in the forum below, the dust cap-sprocket friction is a design issue with this hub.

Nexus Hub Gear Query « Singletrack Forum

rensv

Hi Shahmatt,

Have you been able to fix this issue?

Thanks!

maddog34

if you are also having excess drag issues, i'd advise starting a new thread...this one is several years old, and the OP may not be a regular participant here.

and FYI.. The Nexus hubs i've dealt with ALL have some drag. I'd try some Tri-Flow PTFE lube on the seals.. I've had some luck using Zep 45, which is similar.

The Coaster Brake nexus hubs are worse, and even with the seals removed, there is still drag noted.

I have also found one hub that had the Bearing tension set too tight... it took some fiddling, but it improved. that was some time ago. though... i can't recall exactly What finally worked ... it might have involved leaving one seal off... like the Two Seals are really supposed to be one, or the other, not both???? one for a larger sprocket, and one for a smaller one??like i said, it's been a WHILE since that adventure.. and that MAY have been a A Sturmey Archer hub...

i just swapped a Nexus8 off of a Rans Fusion Recumbent, and built it back up as a freehub/derailleur setup for a customer.. the Nexus 8 began skipping in several gears even though it was adjusted by THREE different mechanics... we took the opportunity to upgrade to disc brakes too since the rear wheel assy. was being swapped anyway...
He called a week later to tell me that he LOVED the new setup... that felt great since us mechanics usually only hear the complaints...

good luck, and post a new thread.