I bought the wrong Nexus

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ukdodger
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I bought the wrong Nexus

Postby ukdodger » 13 Dec 2015, 11:35am

I bought this one which is for a roller brake:

Image

Instead of this one:

Image

Is the first Nexus the same and the second with the addition of a sprocket and this:

Image

Both eight speed.

Thanks

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: I bought the wrong Nexus

Postby Brucey » 13 Dec 2015, 12:19pm

Hubs for roller brake use and V brake use are fundamentally the same thing but with small differences.

The last photo is of the cassette joint/fitting kit. All kits should include the sprocket snap ring. Some kits come with two (different) sets of NTWs; there is no guarantee that the blue/green set will work in your frame, so if you can buy the kit that has more NTWs in (usually white/silver in addition to blue/green) I'd suggest that you do so; when you can find it, it costs about the same as the one depicted. Normally the blue/green set work with a horizontal cassette joint and vertical dropouts. With near- horizontal dropouts and those NTWs you can sometimes run the cable down the seat stays but if you try for a horizontal cable run it will often end up being angled downwards and the cable will fill with water. Normally the white/silver NTWs work best with near-horizontal dropouts.

Also consider if you might be better off with the (better sealed once the boot is used) CJ-8S40 cassette joint instead of the CJ-8S20 version.

In addition to the CJ/fitting kit you will need (for V brake use on a bare hub)

- sprocket
- LH dust cover kit.

The last of these should come with hubs that are supplied against a hub part number that has a 'V' suffix (you can just see it in your second photo). If you have a hub without, you can buy the kit (it costs about £4 or so) from a suitable supplier (eg SJS). If you try to use the hub without it (or a roller brake) fitted there will be no LH locknut to bear against the frame and nothing to stop water from getting into the LH hub bearing.

You don't say which model hubs you depict there but if you have a choice, buying a 'premium' N8 hub will give you roller bearing pinions and improved efficiency vs the more basic models.

cheers
Last edited by Brucey on 13 Dec 2015, 12:25pm, edited 1 time in total.
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Mick F
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Re: I bought the wrong Nexus

Postby Mick F » 13 Dec 2015, 12:22pm

We have the roller brake model on our utility bike Barbarella.

The roller brake version is identical to the non-roller brake model except for the roller brake splines on the non drive-side.
The drive-side is identical.
Mick F. Cornwall

Brucey
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Re: I bought the wrong Nexus

Postby Brucey » 13 Dec 2015, 12:27pm

Mick F wrote:We have the roller brake model on our utility bike Barbarella.

The roller brake version is identical to the non-roller brake model except for the roller brake splines on the non drive-side.
The drive-side is identical.


the hubshells are identical except for the fitment of a cover on the LH side for V brake use, as per my previous post. If you remove the cover there are roller brake splines beneath.

cheers
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Mick F
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Re: I bought the wrong Nexus

Postby Mick F » 13 Dec 2015, 12:31pm

Ah.
Thanks.

That therefore means that if we ever modify Barbarella or use the Nexus on another bike, we could either forget the splines and leave them exposed, or buy a cover.
Mick F. Cornwall

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: I bought the wrong Nexus

Postby Brucey » 13 Dec 2015, 12:37pm

Definitely a better idea to buy the cover; without something fitted there, there are no seals of any kind on the LH bearing, just a shield that doesn't fit that well.

cheers
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ukdodger
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Joined: 18 Aug 2007, 5:32pm
Location: Sunny Surrey

Re: I bought the wrong Nexus

Postby ukdodger » 13 Dec 2015, 1:28pm

Brucey wrote:Hubs for roller brake use and V brake use are fundamentally the same thing but with small differences.

The last photo is of the cassette joint/fitting kit. All kits should include the sprocket snap ring. Some kits come with two (different) sets of NTWs; there is no guarantee that the blue/green set will work in your frame, so if you can buy the kit that has more NTWs in (usually white/silver in addition to blue/green) I'd suggest that you do so; when you can find it, it costs about the same as the one depicted. Normally the blue/green set work with a horizontal cassette joint and vertical dropouts. With near- horizontal dropouts and those NTWs you can sometimes run the cable down the seat stays but if you try for a horizontal cable run it will often end up being angled downwards and the cable will fill with water. Normally the white/silver NTWs work best with near-horizontal dropouts.

Also consider if you might be better off with the (better sealed once the boot is used) CJ-8S40 cassette joint instead of the CJ-8S20 version.

In addition to the CJ/fitting kit you will need (for V brake use on a bare hub)

- sprocket
- LH dust cover kit.

The last of these should come with hubs that are supplied against a hub part number that has a 'V' suffix (you can just see it in your second photo). If you have a hub without, you can buy the kit (it costs about £4 or so) from a suitable supplier (eg SJS). If you try to use the hub without it (or a roller brake) fitted there will be no LH locknut to bear against the frame and nothing to stop water from getting into the LH hub bearing.

You don't say which model hubs you depict there but if you have a choice, buying a 'premium' N8 hub will give you roller bearing pinions and improved efficiency vs the more basic models.

cheers


Thanks Brucey. They are both Nexus 8 speed

I need the black/grey combination of NTW's. So it will work if I get the fitting kit and a sprocket. I can find the fitting kit but not the sprocket!

Useful info if anyone want the same:

I bought both these from:

http://www.cnc-bike.de/

1 x Shimano Nexus 8-speed internal gear hub SG-8R36 Premium 36L -Montagespuren- (12496) = 59.00 EUR
Rear for Felgenbremse

1 x Shimano Nexus gear / brake lever combination Set SB-8S20 / BL-IM60 8 times (6503) = 15.00 EUR

I was surprised at how cheap both were especially the combination brake and gear shifter.

Cheers Brucey.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: I bought the wrong Nexus

Postby Brucey » 13 Dec 2015, 5:40pm

you can use almost any SA or SRAM sprocket on a Nexus hub. The exception is any 3/32" sprocket where the driving lugs will end up on the right side of the sprocket when fitted; if you use one like that on a shimano hub, it can wear the splines , because it won't be fully engaged.

If you want the sprocket to last well etc then I suggest a (dished if necessary) SA 1/8" sprocket, about 20T in size, with a matching chainring to give your chosen gear ratios. If it isn't quite right you can go down to 18T and up to 22T easily enough.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

ukdodger
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Location: Sunny Surrey

Re: I bought the wrong Nexus

Postby ukdodger » 13 Dec 2015, 5:53pm

Brucey wrote:you can use almost any SA or SRAM sprocket on a Nexus hub. The exception is any 3/32" sprocket where the driving lugs will end up on the right side of the sprocket when fitted; if you use one like that on a shimano hub, it can wear the splines , because it won't be fully engaged.

If you want the sprocket to last well etc then I suggest a (dished if necessary) SA 1/8" sprocket, about 20T in size, with a matching chainring to give your chosen gear ratios. If it isn't quite right you can go down to 18T and up to 22T easily enough.

cheers


Thanks. I've got a spare Sram sprocket. I'll give it a try.

While you're on Brucey any idea why I cant clamp a seatpost sufficiently tight so as to stop it moving. It's an alloy seatpost on this frame which has a different seat lug. no matter how tight I make it the damn thing moves. I've just sheared off a seat post bolt. Is it something to do with the alloy in the seat post?

The post isnt undersize. The same type works perfectly in a standard frame.

Image

Freddie
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Joined: 12 Jan 2008, 12:01pm

Re: I bought the wrong Nexus

Postby Freddie » 13 Dec 2015, 6:19pm

Given you are using the Nexus on a ladies frame, wouldn't the roller brake be a better option considering the improved brake cable run?

ukdodger
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Joined: 18 Aug 2007, 5:32pm
Location: Sunny Surrey

Re: I bought the wrong Nexus

Postby ukdodger » 13 Dec 2015, 6:22pm

Freddie wrote:Given you are using the Nexus on a ladies frame, wouldn't the roller brake be a better option considering the improved brake cable run?


Thanks but I've already fitted a rim brake. The cable run wasnt a problem. The calliper is between the laterals.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: I bought the wrong Nexus

Postby Brucey » 13 Dec 2015, 6:34pm

ukdodger wrote: .

While you're on Brucey any idea why I cant clamp a seatpost sufficiently tight so as to stop it moving. It's an alloy seatpost on this frame which has a different seat lug. no matter how tight I make it the damn thing moves. I've just sheared off a seat post bolt. Is it something to do with the alloy in the seat post?

The post isnt undersize. The same type works perfectly in a standard frame.


I'd always check and double-check the size first; if the seat pin can 'rattle' at all with the binder bolt just nipped, this normally means that the seat pin is a fraction undersize. I have occasionally had to machine them to suit a frame properly, and before I've done that they have persistently worked loose.

The other possibility is that there is something about the seat lug that is preventing it from clamping the seat pin properly. Is the slot cut deep enough? If all else fails then I'd suggest using a 5/16" or 8mm binder bolt with a nut instead of a (relatively flimsy, will fail in low cycle bending fatigue if not correctly aligned) 6mm threaded allen-headed bolt.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

ukdodger
Posts: 2992
Joined: 18 Aug 2007, 5:32pm
Location: Sunny Surrey

Re: I bought the wrong Nexus

Postby ukdodger » 13 Dec 2015, 6:43pm

Brucey wrote:
ukdodger wrote: .

While you're on Brucey any idea why I cant clamp a seatpost sufficiently tight so as to stop it moving. It's an alloy seatpost on this frame which has a different seat lug. no matter how tight I make it the damn thing moves. I've just sheared off a seat post bolt. Is it something to do with the alloy in the seat post?

The post isnt undersize. The same type works perfectly in a standard frame.


I'd always check and double-check the size first; if the seat pin can 'rattle' at all with the binder bolt just nipped, this normally means that the seat pin is a fraction undersize. I have occasionally had to machine them to suit a frame properly, and before I've done that they have persistently worked loose.

The other possibility is that there is something about the seat lug that is preventing it from clamping the seat pin properly. Is the slot cut deep enough? If all else fails then I'd suggest using a 5/16" or 8mm binder bolt with a nut instead of a (relatively flimsy, will fail in low cycle bending fatigue if not correctly aligned) 6mm threaded allen-headed bolt.

cheers


Cheers Brucey. Think it's going to have to be a nut and bolt. Shame because they arent as attractive as a binder bolt. The slot is deep enough. I think it might be that the eyes you pass the bolt through are situated right at the top of the lug and are smaller than standard lugs so the clamping 'band' is only about 7-8mm at the top. On standard lugs it's about 10-12mm.

jk49
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Re: I bought the wrong Nexus

Postby jk49 » 13 Dec 2015, 7:29pm

hi ukdodger, I've just tried to order the same, but can't work out how to pay.If you don't mind saying, how did you pay?

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Mick F
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Re: I bought the wrong Nexus

Postby Mick F » 13 Dec 2015, 8:01pm

This is Barbarella.
Barbarella 2.jpg
Mick F. Cornwall