[El Caballo]

First Impressions: Technical Data and Installation Issues

If you just want to know what it's like to ride one, skip forward to the next message. I'll update this thread as I get more riding time, so keep checking back.

I just got my 29" rigid bike set up with a Shimano Nexus 8 "Red Band" gearhub, SG-8R25-VS, with no rollerbrake. This is the premium level gearhub that is purportedly rated for off-road use: it is distinguishable from the regular version only by a small red band next to the drive side hub flange. GT uses this hub for an internal transmission on their iT1.

Sheldon Brown's website (http://www.sheldonbrown.com/harris/shimano-nexus.html) has a lot of good information about this hub, and makes good background reading. However, it is out of date in a couple respects, which I'll note throughout the review.

Claimed weight is 1550g. The bike shop scale showed 1590g without the rear sprocket or axle nuts, but with the rear axle. It only comes in 36H. There is a black version available in Europe, but I was unable to get anything but silver here in the USA.

The 305% gear range is roughly equivalent to a 1x9 with an 11-34 cassette. Sheldon's website claims only a twist shifter is available: this is wrong. You can also get a two-button shifter/brake lever: each thumb button moves one gear up or down at a time. There is no independent button shifter, so if you want to run hydros you'll need to run the twist shifter. The shifters are not compatible with anything else: SRAM ESP 8-speed shifters pull just about the right total amount of cable, but the Nexus shifter has exactly equal cable pull between gears and derailleur shifters don't.

Installation is tricky, especially if you or your shop hasn't done it before. The hub is 130mm OLD, so to use it on a standard 135mm MTB frame you'll have to add spacing washers, or do a funky trick with the non-turn washers. "What are non-turn washers?" you ask. They're little metal bits that sit in the dropouts and keep the axle from spinning. Shimano provides three pairs of them for different angles of slotted horizontal dropouts, but if you have vertical dropouts, you'll need to order the appropriate pair separately.

And then comes the funky bit. The approved method of assembly is for the non-turn washers to go on the outside of the dropouts. Well, if you don't have or don't want to find spacing washers, you can use two of the same washer (instead of one R and one L) and flip one so it goes inside the dropouts, then dish the wheel slightly to keep it centered. I think you have to do it this way, with the hub slightly offset to the non-drive side, if you want to run a rear disc brake -- but I can't yet verify this.

This took about a week for the local bike shop to figure out. But finally it was done, and I had a rigid 29er with an internal gearhub.

My bike now weighs between 2 and 2.5 pounds more than it did as a singlespeed: bathroom scale weights aren't exact, even if they are the nice doctor's kind with the sliding weights. This is less than a pound heavier than going 1x9 with LX.

Now you might say "The Nexus doesn't allow a disc brake, just those crappy Rollerbrakes that weigh three pounds, make it impossible to fix flats, and don't actually stop." Not quite. You can get a disc adapter here: http://shop.cnc-bike.de/catalog/product_info.php?products_id=988, and possibly from Cannondale, who make one for this bike: http://gb.cannondale.com/bikes/06/ce/model-6BR1.html
But I am running V-brakes right now and have not tested either of these.

Next installment: I ride it.

 

[dhpimp]

I also have this exact hub and LOVE it. I can't say enough great things about internal gears. The shifting is fast, effortless and quiet (except in 5th gear where it changes to the 2nd clutch mechanism - but that's normal). I've been riding one for about 18 months solid and haven't had to touch it at all for any sort of adjustment. It is recommended to service it once every 6 months (intense use) but I opened it up after 1 year and it still looked normal. What awesome sealing for year round commuter bike use! :thumbsup:

I just got my 29" rigid bike set up with a Shimano Nexus 8 "Red Band" gearhub, SG-8R25-VS, with no rollerbrake. This is the premium level gearhub that is purportedly rated for off-road use: it is distinguishable from the regular version only by a small red band next to the drive side hub flange. GT uses this hub for an internal transmission on their iT1.

A little correction here - this hub is NOT designed for offroad use on the rear of the bike. The only reason GT is allowed to use it is because it is mounted inside the frame of the bike and does not put torsional loads on the axle (where the gear change is made). If you use this on an MTB offroad then your probably going to scrap the internals after a short period of time of riding. :madman:

Shimano's got a DISC Brake verison of this hub coming out next year, but again it's only for commuter use

 

[Speedub.Nate]

Looking forward to your next installment. I've got a Nexus 8 on a street bike and like it for what it is, and have heard good things about the Red Band.

Personally I'm holding out for Sram's upcoming i-motion 9 with a 340% gear range. However, it's at least a few months from release, and I'm very curious about your experiences with your install.

 

[El Caballo]

First Ride Report

But first, a couple more tech notes.

Wheel removal is easy if you don't have the Rollerbrake. First you disconnect the shifter cable. Shift into first gear (no riding required!) and get down near the rear wheel. You'll see the rotating collar that pulls the cable. Push it back down and around with your thumb, putting slack in the cable, and then pull the little nut out of the slot. There's a trick to it but it's hard to describe: once you figure it out it's very easy. Then you loosen the axle nuts, just like with any singlespeed. Remember that the non-turn washers aren't solidly attached to the hub, so they might migrate a bit, and you'll have to push them back into place before it'll go back into the dropouts.

The chainline is slightly adjustable because the cogs (it comes with 18T and 21T, I think) are dished. Flip them over for several mm of adjustment.

OK, first riding impressions.

Shifting is uncanny. You feel the cable pulling and then you're instantly in gear, as if by magic. No grinding, no noise, no delay, and it happens as fast as you can push the button. If you're really cranking hard on the pedals while you shift, it won't grind or crunch, it'll just not shift until you let up the pressure some.

Sometimes the 4 -> 5 transition requires more lever effort than the other shifts, but it's not a problem, just something you notice. Also, it seems like the freewheel makes more noise in some gears than others. It's not loud, and I don't notice at all unless I'm listening for it.

Freewheel engagement is the same as every other mountain or road hub I've owned. I feel 32 clicks.

The big complaint I hear about gearhubs is that they're less efficient. Some people claim clearly perceptible drag, particularly on cheaper hubs with lots of gears (like the Shimano 7-speed) or new Rohloffs that haven't broken in yet. I think I have a decent basis for comparison, since the bike is rigid, and was a singlespeed before I added the gearhub.

I was really looking for drag. Well, I put it in 1:1 (5th gear) and couldn't decide if it felt any different from before, or whether I was just thinking what I expected to find. I rowed up and down through the gears, trying to figure out if there was extra effort involved with some of them versus others. I'm still doing it, and all I can say is that if there is a loss of efficiency, it's subtle enough that I can't clearly pin it down.

This jibes with the article in issue #52 of "Human Power" magazine (put out by the IHPVA), which shows the results of exhaustive efficiency testing on several gearhubs and a standard Ultegra drivetrain. The article was written in 2001.
http://www.ihpva.org/pubs/HP52.pdf
They showed the Shimano 4, Shimano 7, Sachs 7, and Rohloff 14 to all be within half a percent of each other, and 2%-2.5% less efficient than an Ultegra drivetrain. Since the Nexus 8 is claimed to be substantially more efficient than the Nexus 7 (described by one as "pedaling through oatmeal"), and the "Red Band" is supposedly even better, I can easily believe that the efficiency is comparable to a derailleur-based drivetrain, if not superior under less than ideal circumstances.

Anyway, I don't find drag to be an issue.

Next installment: I ride it on trails.

 

[steevo]

I also just set up my bike with the red strip hub this weekend. I put it on my cross check commuter. I'm glad there is a thread on this hub as there is hardly any info about it anywhere.

My first impressions: installation was a little confusing to me. I've never worked with an internal hub of any kind, so I was immediately confused by the installation of the cog. The directions show the cog already on the hub, and then to install the dust cap. What they don't show is that there is a split ring that holds the cog firmly in place, so at first I couldn't figure out why my cog had play in it. It's probably common knowledge to use the split ring though. ONce I figured that out, the rest was easy.

I had to buy the hub-bub adaptor ($54.00!!!) in order to use the twist shifter with my on-one midge bars. It's a little funky having the extra length in the drops on one side. I do not want to cut the bar shorter because the shifter indicator takes up a lot of real estate in the drops and it would hit my hand. It works fine, but I think a flat bar would work better with this shifter.

My first ride on it today was my 8 mile commute to work. Formerly my Cross Check was fixed gear/single speed, so it was a completely different experience having the gear range. I'm using the 19t cog and have 44t chainring up front. Shifting felt a little vague at times, like I would make the shift and there would be some hesitation before I felt it in the pedals, sometimes it took me by surprise. I read somewhere on line today that I may need to tension the shifter cable some--beyond the point where the yellow indicators line up.

El Caballo -- I'm anxious to hear your impressions of this hub off road. Also, can you post your cog/chainring combo? I bought it with the idea in mind that I would use it on my SS karate monkey someday. I'm hearing conflicting reports on whether it is actually suitable for off road use though. [ dhpimp, can you confirm this hub is not suitable for offroad use]

I'll also post my impressions with it as I get some more time on it.

 

[El Caballo]

Trail Ride Report

I took the bike out to my local singletrack, which takes anywhere between 45 to 90 minutes for my usual loop. It begins with a couple hundred feet of steep uphill grind, which I could never clear on a SS. Well, with the gearhub in "1" I scooted right up, only dismounting once where I lost traction in a bunch of loose, freshly cut dry grass. (I'm still running 30-18 on a 29er, so "1" is about 30-34, or about 32-34 on a 26er.)

I head through some swoopy ups and downs, most smooth, some rooty. Actually I can pretty much spare you the details of the ride, because everything worked just like you'd hope. I push the button, it changes gear. Nothing made grinding noises, the chain didn't skip (even though it's a tensioner setup, not sliding dropouts), and the ride was free of mechanicals. It felt like a singlespeed, except without as much suffering.

However, I have to say that I really, really don't like the Nexus "3-finger" brake levers, which are designed for ham-fisted use on comfort bikes. I want my two-finger levers back, but that's not an option unless I use the twist shifter. (The pushbutton shifter is integrated with the brake lever.) I can make them work if I carefully adjust the brakes so the lever doesn't hit my other fingers when I squeeze it, but it's still not what I want.

So far, here are the good and bad points.
+ No drivetrain issues. Feels like a singlespeed but with gears
+ I'll say it again: no issues. No dropped chains, no bent hangers, no bashing derailleurs on rocks, nearly impervious to mud
+ Excellent, well-protected shifter cable routing will never snag on anything. No click box, Speedbone, or anything external required
+ Over a pound lighter than a Rohloff or the upcoming SRAM iMotion 9
+ Gear range equivalent to 1x9 (11-34)
+ No obvious drag issues, unlike some other gearhubs
+ Maintenance. I think once a year I'm supposed to squirt some grease in there.

- Disc brakes require expensive, hard to find adaptor
- No separate button shifter. Brake levers on integrated button shifter aren't designed for mountain biking
- Weighs more than 1x9. Gearhubs not the best solution for suspension bikes because of unsprung weight, but this is the lightest solution out there
- Why doesn't it come with the non-turn washers for vertical dropouts?

? Durability. No one really knows how it'll hold up to trail riding. I'll try to find out.

 

[El Caballo]

Second Ride Report

I jammed a couple laps around Demo Forest, which involves some fast, moderately bouncy trails, quite a few log crossings, and -- yes -- I took it off some sweet jumps, including about seven times off the 2.5 footer before the photos finally came out. I'm also working on my urban, and finally cleared the double stage curb to 3 steps up that I could never quite get before. So I'm not making any attempt to be nice to this thing.

I'm debating going to the 21T rear, which would let me sit down more on steep climbs, but at that point it's usually faster to walk anyway.

If anyone thinks of any way to get a real trigger shifter on this thing, speak up. (I want to disassemble a SRAM ESP trigger someday and see if there's a way to modify it to work...if you have a spare 8 or 9 speed 1:1 pull trigger shifter for cheap, PM me.)

At this point I don't have a lot to add. I'll let people know if anything breaks or needs maintenance, but other than that, you can assume I'm out riding.

So far, I'm glad I made the switch.

 

[Speedub.Nate]

At this point I don't have a lot to add.

How about pictures?

 

[LTS]

Second Ride Report
If anyone thinks of any way to get a real trigger shifter on this thing, speak up. (I want to disassemble a SRAM ESP trigger someday and see if there's a way to modify it to work...if you have a spare 8 or 9 speed 1:1 pull trigger shifter for cheap, PM me.)

You don't need to mess around with modified derailleur triggers. Your wish will be fullfilled when the Shimano Alfine group is released.

picture: alfine rapidfire

 

[El Caballo]

Your wish will be fullfilled when the Shimano Alfine group is released.

Thank you for the news! I guess I can suffer until then.

The Alfine looks pretty much exactly like the Nexus 8...at least the cassette joint, axle, hub shell, and non-turn washers look identical. Maybe that means the disc adapter is the same and we can order it through Shimano...? Let's hope so.

Differences I can see: the cassette cog has a chainguide around it, and it's clearly drilled for less than 36 holes (maybe 24-28).

 

[danielhaden]

Another neat trick of a fully broken in Nexus 8, is the 4 pawl freewheel likes to make the occaisional little slip, same as most tandem hubs. This is quite alarming, although unharmful. Also, it takes a very long time (about 500 miles) to break in gears #4 and #8. Once they're broken in, riding at very high speeds in #8 is great fun.

In fact, the efficiency in the top several gears is simply stunning! This is best seen when the cog, chainwheel, and chainline are all perfectly straight.

It is greatly helpful not to locate the gap in the cog's circlip directly onto a spline gap. Instead, center the gap of the circlip directly between the spline gaps (under the ridge/lip). You'll see.
Now, press all around the circlip with a screwdriver to make sure it is all nicely even.

For either single speed or for gearhub use, one should use evenly numbered gears for high efficiency. I've used 20 against 46 for flat country or 20 against 42 for rolling hills (that was a 26" bike--reduce chainring or increase cog by 2t for a 700c bike).

24 against 42 is necessary for mountains on the 26" bike or 24 against 40 for mountains on the 700c bike.
However, at this point, it is probably wise to install a "dingle" adapter ($65 simplified rear derailleur) and a smallish front crankset with no more than a 20t difference between highest and lowest. Perhaps a "compact double" would be of great benefit.

A dual-chainring setup is unnecessary for all but mountain dwellers. It is possible to get a lovely low gear, that is lower than a typical road bike, road "triple" setup while still able to run along at 24 mph should the desire arise.
And the gear range of the Nexus 8 is so very easy to change with just one front chainring or just one rear cog.
The inexpensive $11 Rocket multi-fit chainring is highly efficient as a mate to the Nexus 8 because there are no tooth effects for shifting. Anything from the BMX sport also works.

The high-efficiency setup for the Nexus 8 will use a 7 speed chain. The Shimano HG 70 is perfect for this task.
Yes, it looks like a tight fit, but it isn't a tight fit at all because the chain always runs in a straight line. That HG70 is a very efficient mate for the Nexus cog.

To fit vertical drops despite a possible mismatch, you can use chainrings/cogs with just 1t more or less, or if you are serious about avoiding odd-tooth gearing, KMC has a 7/8 speed chain compatible half-link for about $5. There's one on my bike.

The chain does not go extremely tight. When you apply crank pressure, you should see a very slight droop.

The easy way to get the cable out to change a tire is to shift to first gear and then pull the cable jacket right out of the rear cable attachment. This will slack the cable enough to easily remove the little metal bolt from its plastic hanger with no risk of damage to the hanger or your thumb.

The Nexus 8 has been approved by Shimano for mountain bike and off-road use.

The revo+brake combination and the trigger+brake combination shifters are both more accurate than the revo-only shifter. This isn't bothersome in practice, but I'd really suggest using the more accurate shifters for competition use.

 

[20.100 FR]

Do you think a 2 rings front - nexus rear would be interesting fot a MTB ?

The need for a tensionner would bring the same weight as a derailleur, so the whole thing might be on the heavy side...

 

[danielhaden]

Actually, the "dingle" idea was a very bad idea--unless you've already invested in a Nexus system and you're getting:
1: "Stuck" going up hills
or
2: No high gears

If you're living in a mountain area, just avoid the Nexus alltogether.
$980 isn't too high a price to pay for the high performance Rohloff that wins competetions frequently, has low gears and has high gears.

If you're in a mountain area and on a budget, still continue to avoid the Nexus because a traditional system will serve you better. Check out the SX5, 8 speed cassette, PC58 (strongest chain available), SX5 shifters from SRAM along with an inexpensive Deore derailleur. This all costs much less than a Nexus and will seriously outperform it.
Although, it will not put you ahead in competition like the Rohloff gearhub.

 

[El Caballo]

I don't think gearhubs are a smart idea with rear suspension, because they add so much unsprung weight -- and you need a chain tensioner anyway, so most of the benefit is lost. Same with any setup that involves gears + a gearhub.

The point of a gearhub, to me, is that I feel that quiet, direct drivetrain like I'm riding a singlespeed, and I don't have to maintain a complicated bunch of shifters and gears -- except that when I get to the brutal climbs I don't suffer.

Yes, Rohloffs are cooler and have a larger gear range. But they cost $1000 vs. $170 for the Shimano, weigh a pound more, and don't fit on all frames.

Maybe I'll blow mine up or it'll start skipping and my opinion will change. But for now, I'm just riding it and waiting for the Alfine trigger shifters to appear.

 

[El Caballo]

Pictures!

Here are some pictures.

Still to do: clean up cable routing (right now it's just full housing zip-tied to the frame).

 

[r1Gel]

El Caballo - - - Nexus price?

Great thread, very informative :thumbsup:

You mentioned lower down you got the Nexus hub for $170. Do you know of any e-tailers selling at this price? Harris Cyclery has it at $200. I'm assuming your price is for the hub only; no brakes or shifters, right?

I'm seriously considering converting my rigid mtb to Nexus...

 

[r1Gel]

danielhaden, some questions for you

For either single speed or for gearhub use, one should use evenly numbered gears for high efficiency.

Without getting too technical, would you please explain why this is so?

The high-efficiency setup for the Nexus 8 will use a 7 speed chain. The Shimano HG 70 is perfect for this task.

Why would that be better than a dedicated single-speed chain, say a SRAM PC-1? Wouldn't a 1sp chain fit better and be more durable?

The revo+brake combination and the trigger+brake combination shifters are both more accurate than the revo-only shifter. This isn't bothersome in practice, but I'd really suggest using the more accurate shifters for competition use.

Why do you think this is so? Does this mean you've tried all the shifter types for the Nexus 8? When you say "more accurate" does that mean the revo-only shifter has a tendency to mis-shift? Which do you prefer between the push-button and Revo shifter?

Pardon my questions. I'm researching on everything I could on the Nexus components as I plan to convert my rigid mtb to internal gearing.

 

[El Caballo]

You mentioned lower down you got the Nexus hub for $170. Do you know of any e-tailers selling at this price? Harris Cyclery has it at $200. I'm assuming your price is for the hub only; no brakes or shifters, right?

Yes, $170 is just the hub itself. Since Harris is so expensive, I just had my LBS do it.

This will cost about $170 for the hub, $30 for spokes, $25-40 depending on what shifter you get, plus tax and wheelbuilding labor. My bike came with 36 hole rims, but if yours aren't, you'll need to buy a rim too. Add another few bucks for the non-turn washers, and probably a new chain.

Plan on about $300 if you build it all yourself, $400 if you have a shop do everything.

I'm using a KMC singlespeed chain. I don't know why a 7-speed chain would be more efficient -- if anything, I figure you'd drop it more since it's designed to shift.

rigel: let us know if you do it. We don't have good reliability data on this thing yet...we need a few out there on the trail to figure out whether it'll stand up to abuse.

 

[Cloxxki]

Awesome thread El Caballo, great project!
But it looks like your tension might still be improved upon for a couple bucks? I worked on the 10-quid On-One Otherdoofer yesterday, and it seems on par with but much more practical than the 50-bucks Rennen Rollenlager. It's worth to get a halftlink that fits your chain when buying one to improve tensioner position. A halflink might do a lot for your setup already?
When a friend used a similar tensioner in simlar position to your's due to chain length, his chain would skip under the slightest loads, even with a Shimano DX cog. Tensioner pushing up makes a huge difference, even in drivetrain "feel". When yesterday I swapped gearing and corrected chain length on someone's SS road setup to make the Otherdoofer work as push-up, he immediately notice the improvement in "directness".

 

[El Caballo]

Where to buy them

http://www.aebike.com

Search on "Nexus". They have all the parts, including the non-turn washers. Anyplace that has the QBP catalog online will work, but I think aebike is the cheapest.

$140 for the hub (SG-8R25 Premium Hub)
$10 for non-turn washers (unnecessary if you have SS or track dropouts)
$16 for the revo shifter, or $37 for the tapfire brifter
$53 for a "Quality Wheelhouse" wheel build
(I don't know how well they will cope with something like this...let me know if you find out)
$16 for a new chain
$??? for a 36H rim

Theoretical total: $245-$266 + rim + tax/shipping + your labor to install (but not build the wheel)