Bicycle Mechanics - Shimano Nexus 8 speed install

Hello,

Noob here. Just got a built up wheel I'm trying to install on an old 10-speed and need help deciding between the "dust cap" and the "driver cap" as listed on the parts list. One is plastic and the other is a larger diameter and made of brass.

Main question is how to install the dust cap on the inside of the sprocket and still be able to install the snap ring to keep the sprocket on. There doesn't seem to be enough room for all of these.

Any help?

Okay, searched and found the same problem elsewhere with no luck on an answer. Does anyone know if it's alright just so skip the dustcap all together? Other posts regarding Nexus talk about the inability to overhaul the hub when old/dirty, though, so I'm hesitant.

I'm trying to recall exactly what the dust cap looks like, I don't recall that decision when assembling my Nexus 8 ride.

Ok, I'm back

Looking at an online schematic and comparing to an photo of my ride (I'm out of town), I pretty sure I have both components mounted.

Take another look at where the cog and snap ring sit, I was initially confused about it also and had them to far out.

I can take a better look at my wheel Friday.

In case you haven't seen it, here's a pretty good Nexus 8 manual posted by Sheldon Brown.

http://sheldonbrown.com/nexus8/index.htm
http://sheldonbrown.com/nexus-mech.html

Sorry that I can't help more. I've never changed a sprocket on mine and got that far inside it.

Thanks for the response. I did look through the manual supplied by Sheldon Brown, but it doesn't list the two different parts...same problem with the paper manual Shimano sent. Their website does, however include both the dust cap and the driver cap in their schematic of the hub. (Sorry about the big link)
http://bike.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/SG/EV-SG-8R25_BR-IM70-R-2315D_v1_m56577569830609192.pdf

From what I can figure, the dust cap is metal (brass?) and the driver cap is plastic. I can put the sprocket on the hub first (no dust cap) with the snap ring installed and everything fits snug, but neither ring will allow enough room to seat the snap ring.

If I had a larger diameter metal cap, it seems like it would fit...not that I'm a rocket scientist or anything, but could they have sent the wrong size?

Thanks again for the trouble...

Sending out the Sheldon Brown bat signal...

Last fall I bought and installed a Nexus 8 wheel from Harris on an old Fuji frame. I don't recall a dustcap at all. There is something on the left side (non drive side) that looks like a dustcap and I imagine it is covering where you'd have the roller brake if so equipped. There was a funny cross-sectioned hard plastic spacer that I had a hard time with but I wouldn't call it a dustcap....

I can shoot some pictures of setup tonight and post them.

(BTW, after 1000+ miles including an imperial and a couple of metric centuries, building a bike with that hub was the best bicycling decision I've ever made.)

You say "old 10-speed" frame. Is that 10-speed rear end, or total? I think that the Nexus 8 requires a 132 mm rear dropout spacing (without either type of brake?), and "old 10-speed" frames generally have 120 mm.

The Nexus-8 requires 130mm dropout. Most old 10-speeds are 126. You can either cold set the frame or just spread the dropouts 2mm on each side as I did with my Fuji.

Here are some closeups of the installation -- I think the black thingee on the left is the "dust cover":
http://www.salt2salt.com/scans/Nexus/DSC03378.JPG
http://www.salt2salt.com/scans/Nexus/DSC03380.JPG
http://www.salt2salt.com/scans/Nexus/DSC03381.JPG

Great pics, the "dust cap" I'm trying to figure out is actually on the drive side between the internal part of the hub and the sprocket. I think it's a little tight to get a picture of that, but I've got a picture of the two parts here...(*actually can't figure out how to post pictures yet. I'll search that one)

In the meantime, here's a pdf that shows what the link on Sheldon Brown's page was missing (the instructions sent to me by shimano were missing this too). The first couple steps of the instructions show the two parts in question (driver cap and "right hand dust cap B).

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Nexus/SG-8R20/34R0D-SG-8R20-EN_v1_m56577569830600211.pdf

Okay, let's try a picture. The ring on the left is the plastic "driver cap", and the right hand ring is "dust cap B". At least, that's my guess. I'm almost convinced the dust cap is the wrong size, though...or else takes a LOT of pressure to press it into place. Not sure how I'd figure it out though.

http://i181.photobucket.com/albums/x116/reido11/dustcapb.jpg
Now, about riding the wheel (occasionally on dirt trails) without the dust cap: bad idea?

Oh, that thing. I hated that thing. The directions are particularly lousy there. You can't really tell what the orientation is of it, despite the closeup. I put it in there. It doesn't "snap" in or anything. One way just seems to fit better than the other. That's about all I can tell you!

And it doesn't fit particularly WELL, but it should all fit down there. I've got a nexus hub on an old Suburban and the thing is the whip.

Welp, tried and tried.

Checked out a couple LBS mechanics and neither of them have worked on the nexus hubs. One even said he tried to stay away from them (at least taking them down to the innards). Harris Cyclery, where I bought the wheel online, assured me there was only one size dustcap (I still think it's too small!). They said just grease it up and don't worry about the dustcap.

Now the shifter cable is too short to reach my monkey bars! So I bought some longer cable today and hope to have it up and running soon. At least rode it up and down my hill a few times without the cable (stuck in 1st gear) and it seems pretty smooth. Maybe a little tall in the gearing with a 52 up front, 165mm crank arms and a 19 tooth in back. I'll have to take it somewhere flat once the shifter's all hooked up before I get a bigger cog.

Thanks for the help all supplied here on my first thread. Bummed I couldn't figure it out, though.

Yow 52/19 is pretty tall on that hub especially with 165mm crank. I run a 48/19 with 172.5 crank on a road bike frame and find it to be pretty good. With that chainring I'd at least put the 23 tooth sprocket on the rear!

Could somebody please tell me how to get the snapring on? Sheldon Brown's page says "The circlip snaps on, also most easily by levering it into position with a flat-blade screwdriver", but I could not get it to snap on.

I'm also having issues with setting up a Nexus 8. (Mine is the red-band version, non-roller brake.) In addition to the "dust cap B" referenced above, I have a similar-looking (but NOT identical) silver part. It seems no matter how I assemble the pieces, I end up either with the sprocket rattling around, or I can't get the cassette joint fixing ring to lock into place. The Shimano instructions aren't totally helpful.

My biggest questions are in reference to the snap ring. It goes on after the sprocket, right? Where? I mean, there are 2 positions where the snap ring could go. One, the first place it contacts if you set it on the hub, seems logical, but leaves a gap between it & the sprocket and seems to result in the "stack" of parts being too tall to get the cassete joint on. The other possible position is lower, closer to the sprocket, but it's going to be a bear to get the snap ring on since there is a larger-diameter area "above" it.

Any help will be greatly appreciated!

There is a rubber gasket that goes after the snap-ring, after which you install the cassette joint.

Thanks. That confirms what I was thinking, at least as far as order of the parts. What about the position of the snap ring?

The snap ring goes into the position that is closer to the center of the hub. Yes, it is a pain in the ass to put there, I took mine to a bike shop after wrestling with it for a while, they had a special tool for that. But if you are ultra-patient (and don't value your fingers highly :)), you may be able to pry it on with two small screwdrivers.

One small screwdriver is usually enough. Pry one side on by hand and use the screwdriver to pull the other side over.

For removal, on the other hand, use a cloth so the snap ring doesn't go flying.

For removal, on the other hand, use a cloth so the snap ring doesn't go flying.

He is NOT kidding! I spent some time on my hands looking for mine.

Thanks for the replies!! I could see it's going to be a real PITA to get it on there and didn't want to risk breaking the snap ring or tearing up the hub or causing a space-time continuum rift or something until I knew for sure that I knew what I was doing.


Brian
Internal Hub Noob

Final report: I got the split ring on. It wasn't nearly as difficult as it looked. The secret is having a couple of small screwdrivers and an extra pair of hands.

did a search and found this thread. I am now reviving it to say:
Death to "dustcap B"!!!! Its been nothing but trouble and i finally got rid of it and replaced it with a healthy amount of grease.
I was riding along one day, and for some reason my chain dropped off my rear cog, on the inside. As i kept pedaling, not yet realizing what had befalled, the chain got squeezed real tight, deforming the aforementioned "dustcap B" to the point where it created resistance by scraping against the hub. My chain would go slack when backpedalling and the cog was actually jammed crooked.
I tried to fix it several ways, but finally said the hell with the thing!
My bike now rides smoother that ever, it actually feels faster, and I am sure the grease will do an adequate job of keeping dirt and water out of the hub.
I may have to re-apply the grease every 6 months or so, but it is a good idea to service the hub periodically anyway.
I may actually devise a rubber gasket replacement, but for now...
Death to "dustcap B"!!!

update/bump:
since removing the infamous dutcap, my bike pedasl smoother and is faster :)
I can use an average o one gear up from before, i.e i can use gear 6 on streches where I used to always use 5, and gear 5 up hills where I always used 4, etc.
The dustcap was obviusly rubbing on the hub! i am sure it was not this way at first, but with the chain falling off just once, it deformed the dustcap in a second.
I applied grease instead and am prfectly happy!
:D
down with the dustcap!!

I know this is an old thread, but thanks to the info provided, I was able to get the cassette joint installed on my nexus 8. I had the same issues as several others where the instructions provided were vague and I was not sure how far down the snapring had to go.

It started out as a bear, until I figured out that a standard flat blade screwdriver workst he best. You wedge itbetween the snapring ends, and just gently twist while applying some outward pressure until one end clears the "ledge". As soon as you get that done, you can use the first "ledge" (the one you originally put the snapring under that resulted in a stack that is too tall) to gently pry against by using the same procedure of gently twisting your flathead screwdriver (cover with rag if you're worried about scratches) to push the snapring downward. Work your way around the hub until the snapring fully seats.

The drive sprocket will be seated and feel solid.

[QUOTE=Kevinator;10414346]I know this is an old thread, but thanks to the info provided, I was able to get the cassette joint installed on my nexus 8. I had the same issues as several others where the instructions provided were vague and I was not sure how far down the snapring had to go. QUOTE]

I kind of noticed this too.