Shimano Nexus 7 speed Internal Gear Hub upgrade?

[Anonsequitur]

Hi All,

I have a 700c Shimano Nexus 7 speed Internal Gear Hub(IGH) wheelset that I'm considering as one of my upgrade options for my Sofrider v2 but need some help with selecting an appropriate chain tensioner among other things.

I thought I'd just use a Shimano chain tensioner, but a user review has me confused if it's appropriate.

http://www.amazon.com/Shimano-Alfine-Chain-Tensioners/product-reviews/B003UW64N2/ref=dp_top_cm_cr_acr_txt?ie=UTF8&showViewpoints=1

"Do NOT buy this [Shimano chain tensioner] for your Alfine hub if you have flipped your cog to get a 47~ mm chainline. It will not work no matter how many spacers you put in. The 47~ mm chainline is the "normal" chainline for MTB (68/73 mm BB).

Like I said, its a fine product and if you have not flipped the cog then it will work nicely for you. But if you have a MTB with the standard 50 mm chainline, do NOT buy this tensioner."

My eyeball/scale measurement of my Sofrider with OEM dual-chainring(48x34) crankset has a "standard" 50mm chainline. That is, the measurement from the centerline of the "seat tube" to the center of the gap between the two chainrings is 50mm.

I thought I'd try keeping the Sofrider's OEM front-derailleur, and double crankset to use with the Nexus IGH instead of a single chainring as is usually specified by Shimano, but if the experience of this Amazon reviewer is correct, then the Shimano chain tensioner cited will not work with the OEM Sofrider v2.

Alternatively, if I upgrade with a triple chainring 48-38-28 Shimano M411, 170mm crankset, I wonder if that chainline will be compatible with this Shimano chain tensioner? Charles, can you confirm if your Shimano M411 chainline is 50mm?

I wonder if anyone else has tried a Shimano Nexus/Alfine IGH on the Sofrider, and what detailed modifications were necessary.

Also, the Over Locknut Dimension (O.L.D) of the Shimano Nexus 7 IGH(SG-7R46) is 132mm I believe, and the Sofrider has a 135mm front dropout. Do I just add a spacer/washer or two to make up the gap?

Thanks.

 

[Charles.Plager]

HI,
Let me tell you  what I

HI,

Let me tell you what I measured:

From the middle of the tube to the inside of the chain sitting on the granny gear, I meaured 1 5/8" (41.275mm). From the middle of the tube to the inner edge of the middle gear, I got 2 1/16" (52.3875 mm). From your own bike, hopefully you can figure out how much the chain takes away from the inner gear to the center of the tube and then you basically have the numers you need.

What I don't understand from the comment is that if the chain tensioner is to sensitive that it needs the chainline so precise, will it be able to handle shifting the front crank? If you really wanted to go with an IGH and a multiple front crankset, then I'd wonder if you could "repurpose" the existing rear derailleur as a chain tensioner (as we know that it can deal with the range you'd need). I can imagine rigging a cable that keeps the derailleur in a fixed position.

Good luck!

Charles

 

[Anonsequitur]

Internal Gear Hub with front-derailleur (double/triple) combo?

Thanks for providing those chainline observations, Charles!

I have read numerous accounts of IGH owners who've claimed that they've successfully combined an IGH with a front-derailleur, double/triple crankset, and some unspecified chain tensioner. The one Amazon review cited, which cautions against the use of the Shimano chain tensioner, unless the chainline is 47mm, seems at odds with the those who've reported success with an IGH/front-derailleur combo because the chainline must be deflected many mm "off-center" when switching chainrings.

I'll have to research this issue some more.

 

[John Tolhurst]

whatever chainline

Use a rear derailleur, it can be adjusted to smoothly direct the chain onto the sproket, whatever chainline the sproket is on.

 

[Anonsequitur]

Shimano chain tensioner compatible with multi chainring crankset

A little more research reveals that Shimano's chain tensioner is designed for use with multiple chainring cranksets, as would make sense. Amazon reviewers confirm this, but one owner of an MTB with 73mm bottom-bracket said the chainline wasn't compatible.

"If the different between the number of teeth on the chainrings is 12T or less, or if the front chainwheel has a single chainring, set the chain onto the smaller chainring, and then set the chain tensioner so that the tension pulley and guide pulley are perpendicular to the ground"

http://bike.shimano.com/media/techdocs/content/cycle/SI/Nexus/CTS500/50D0A-001_CT-S500-EN_v1_m56577569830638106.pdf

The Shimano documentation states:

Front chainwheel tooth difference: 16T (the Sofrider v2 48x34 chainrings difference (14T) meet this spec)
Largest sprocket: 20T (Shimano specs for IGH state up to 21, 22, and 23T sprockets are supported)
Smallest sprocket: 18T

 

[Doug Burton]

The Master on all things Chainline...

http://sheldonbrown.com/chainline.html

 

[Anonsequitur]

Sofrider IGH body of evidence of successes?

Thanks, Doug, for the Sheldon Brown chainline link. I've spent a lot of time on Sheldon's site, and found the chainline page useful.

For me, it would inspire confidence if there were a greater body of evidence of successful installations of Internal Gear Hubs (IGH) for the Sofrider, and other Cruzbikes.

I've discovered the Shimano Nexus 7 IGH wheelset I have, which includes drum/roller brakes might not work with the Sofrider. I have faint recollection of stumbling across a comment that the disk brake tabs on the Sofrider's front fork will interfere with the installation of Shimano's drum/roller brake.

More research is in order.

 

[John Tolhurst]

is a sofrider different?

In what way is a sofrider different to a mountain bike when it comes to mounting an Internally geared hub?