Do you have the N360?

I have the previous model, and I find that setting the shifter up is a pain, but you only do that when you change the cables. Once it's set up, it stays adjusted well (maybe a spin of the barrel adjuster if there's cable stretch at the beginning). But removing the wheel remains a pain. That's why I put my Marathon Plusses on -- no flats in recent memory. Pre N360, the drive side bolt is awkward to deal with. There a very shallow section that's hard to get a hold of. Then below the attachment point for the shifter is another, more generous area to grab on to. Unfortunately the rack and fender attachments and the shape of my dropouts make for very little turning room. I usually have to at least remove the fender stay. It looks like the N360 has a significantly different shifter attachment, so I'm wondering if it facilitates removing the rear wheel.

Welcome to the new golden age of IGHs.

The SRAM Automatix centrifugal shifting two speed has hit the after market (no connection with retailer - for illustrative purposes only). SRAM has said they'll be debuting new 7- and 8-speed hubs @ Eurobike.

It may be true of some, but I don't think it's true of the Nuvinci. It's supposedly a very robust hub. I had to send mine in once early on for servicing because there was a bad seal and it was leaking fluid. I think this was a known issue with a minority of hubs and was fixed quickly and under warrantee. Manufacture's specs say a minimum ratio of 2-to-1 front to back rings. On my bike that gives me a low end of about 24 gear inches. It was originally a little higher than I wanted, but I now routinely ride with a much larger front ring and save the 2-to-1 set up for when I'm hauling a lot. Even so, I've heard of folks ignoring the specs to get a lower low gear with no ill effects, and the current model can go a little lower within the specs. Somewhere on these forums is someone telling about talking to Nuvinci about the lower gear limit, and while Nuvinci wouldn't condone running it outside of the specs, it sounded like they expected it to be less efficient at that range, but still not prone to failure.

Don't know if the new ones are as "bomb proof." I figure those weight savings had to come from somewhere, but I haven't heard of any issues with the current model. Seems to be 100% improvements.

The SRAM iMotion3 and Sturmey RS-RF3 both detach/reattach in seconds w/o tools.

And out on the cutting edge:

http://bikeforums.net/attachment.php...hmentid=214031

Hello all I contacted Sturmey Archer, asking them if they could provide gearing in inches for their 5 speed internal hub. I acknowledged that I
saw their chart that lists % for each of the 5 gears, They did respond quickly, however, telling me that my question could not be answered because
no tire, crank size had been provided. I found their response off-putting. I did find Sheldon Brown's gearing chart that is helpful.

Was this a reasonable request to make of SA?

Thanks.
sindlero

gear inches cannot be calculated without knowing the tire size.

to calculate the gear inch range of an IGH bike, the tooth count for both the chainring and rear cog must also be known.

crank arm size is only relevant to calculating gain ratios; it does not factor into gear inch calculations.


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as for the poll question, i can't answer because i've only ever used one IGH, the alfine 8 on my new hybrid, and i've only had it for 2 months now, so i won't be able to comment on it's long-term quality until i at least get several seasons under it. up until this point though, i've been quite pleased with it.

It was not. You need to know the tire size, rear cog and front chain ring to calculate gear inches.

Voted for the Alfine 8. I've had 2 nexus 7s and my current commuter has the Alfine. Nexus 7s were fine, but in the winter one would "lock up" and refuse to shift. This was only when I left the bike outside exposed to the elements (something that many of you don't do). I haven't had the alfine 8 enough to test it in sub 32degree weather.

You didn't give them enough information answer your question but it sounds like they could have been a lot more helpful than they were. If they had given you a link to a site (like Sheldon Brown's) that let's you plug in the different options and give you an answer that would have been better.

Gear inches are fine but for a lot of people they're even less meaningful than the percentages the IGH manufacturers give you. Once someone tells you that pedaling at 90 rpm with 74 gear inches moves you at about 20 mph, then I think it starts to click.

How does the NuVinci do in sub-freezing temperatures?

Follow-up please
 

Hi I left out that my motivation is to find out how a 3 or 5 speed would work in Philadelphia that has varied terrain. I guess I need to ride my new 3 speed and find out.
Thanks. sindlero

gear ratios and percentages can stand on their own.. like 3 speed hubs 20:60
internal gear .. 4/3rds or 3/4. depending on the input and output.
the roles are reversed , a 1.33% overdrive, or a 0.75% reduction gear.

gear inches is adding the diameter of the wheel,
throw in circumference around
and you get development rolled out on the ground, length..

etc.:rolleyes:

This should answer your questions

http://www.bikeforums.net/showthread...!!!?highlight=

I must protest the absence of the old SRAM P5 and S7. They are very common here, durable, efficient and cheap. The shifting is crude and (on the S7) the 4 to 5 shift is too large (strangely the 3 to 4 shift never bothers me, but is the same size).

Nexus 7 shifts better but I can't see any other advantage.

I'll vote SRAM IM9 because it was the best hub in the list on paper. I wanted to buy one but apparently it is not available in Europe anymore (possibly discontinued). Nine lovely gears, evenly spaced and obtained by using only a single planetary gear set at a time (rather than up to two at a time as Shimano often does), available with coaster brake. Near perfection, in my opinion.

SRAM has announced they will discontinue production of the P5 and S7 hubs over the next year or two. Their new 7- and 8-speed IGHs will debut @ Eurobike later this month.

Bah, that doesn't mean Nexus 7 is better. :)

I'm not happy to hear they have 7 and 8 speed parts on the way, sounds like they will just copy Shimano, which in my opinion is pretty crappy. Not that the hubs break or anything, but Nexus 7 is nothing to aspire to, and Nexus/Alfine 8 could stand to be less bizarre.

I like the SRAM 5, 7 and 9 speed designs because they are basically just a series of 3-speeds where only one is driving at a time, and with a shared direct drive.

I'm one of the votes for the S3X, but I need to qualify that vote by saying that the S3X is the only (recent) experience I've had with an IGH.

I have this same set-up on my commute bike. I like the shifter on the seat stay 'cause it's cleaner to my mind. It's not more efficient, that's for sure and fits with a comparison I made somewhere about it being similar to the suicide-shifter on motos. I'm in direct drive 99% of the time, but due primarily to a prearthritic condition in my left knee (trauma induced), the ablity to shift to a lower gear on occasion during my commute is very much welcomed.


:love:

The Sturmey 8-speed is even simpler than that, it has only 3 set of planetaries. The downside of this design is that first gear is 1:1 but other than that, it's extremely simple. I still want to build a road bike with one.

The 1:1 first is great for folding bikes with small wheels, OTOH.

Oh, ok so you're the guy...:thumb: Now I remember the 'suicide shifter' comparison. My fg is 79.1 GI and w/a 500 ft elevation climb on the way home it'd be nice to have the lower gears to go to. Been wanting to get one of these for a while now, but no fundage is opening up. There's a Mercier on BD for a reasonable price, but still things are tight. Oh well, some day. :p

Memo from the Dept. of Redundancy Dept.:
IGH hub = internal geared hub hub. Like saying "PIN number". :p

Well that depends on your definition of simple. To get 8 speeds out of three sets of planetaries with 1st being 1:1, I imagine that many gears use 2 sets at once, and 8th uses all three at once. Do you know if that is correct?

I imagine it goes 0-1-1-2-1-2-2-3 sets in use at once. Shimano's 8 speed goes 1-2-2-2-0-1-1-1, Shimano's 7 goes 1-2-1-2-1-2-1 I think, and the SRAM 7 goes 1-1-1-0-1-1-1.

You could in theory get 9 speeds from two planetaries, and it would drive 2-1-2-1-0-1-2-1-2 sets at once. Not sure why no one has tried that, but I suspect its cheaper to just use more planetaries of a lower quality.

Cycling Magazine mentioned how simple an all-up IGH could be in their big comparison test (in 1907).

The Sturmey Archer 8(W)s have three sets of planetary gears:

1st gear: direct drive, 100%
2nd gear: stage C, 130%
3rd gear: stage A, 148%
4th gear: stage B, 169%
5th gear: stages A x C, 192%
6th gear: stages B x C, 220%
7th gear: stages A x B, 250%
8th gear: stages A x B x C, 325% overall

The all-overdrive Sturmey 8 does not have a traditional IGH clutch coupling (and Seward T. Johnson rolls over in his grave) or any sliding elements.


The Shimano 8s have four sets of planetaries:

1st gear: gear set one, 52%
2nd gear: gear set one + gear set two, 52% x 122% = 63%
3rd gear: gear set one + gear set three, 52% x 142% = 74%
4th gear: gear set one + gear set four, 52% x 162% = 84%
5th gear: direct drive, 100% (clutch coupling locks out gear set one)
6th gear: gear set two, 122%
7th gear: gear set three, 142%
8th gear: gear set four, 162%, 307% overall

A single stage compound gear uses planet gears with two different sized ends - the planet is a single part that's two little gears side by side. One end meshes with the sun gear and the other meshes with the ring gear.

This is done for two reasons: to achieve a finer gear ratio step than would be possible with a simple epicyclic, or to achieve a particular ratio within the constraints of the hub's form factor.

The classic single stage compound IGH is the old Sturmey AM medium range three speed hub. Its planet gears (part# K654) have 14T on one end and 25T on the other. The 25T end meshes with the 15T sun, and the 14T end meshes with the 54T ring. This "trick" allows the hub to have smaller gear steps (~15%) than can be achieved with a simple epicyclic (maybe down to about 22%, depending on several things).

In addition to the old AM, single stage compound gears are used in the SRAM S7 and iMotion 9, S-A XRF8(W) and the Rohloff IGHs.

NOTE: In bicycle IGH, single stage compound gears are not normally considered "compound gearing". When bicycle gear heads talk about compound gears, they mean dual or triple stage compound gears.

A dual stage compound gear inputs into the ring or pinion of one epicyclic, then outputs into the pinion or ring of a second epicyclic. The power runs through two sets of planetaries on its way to the hub to propel the bike.

A triple stage compound gear would of course run through three sets of planetaries.

The unique Nexus Seven IGH dual stage compounds to create gear ratios 3, 4 (the pseudo unity ratio) and 5.

The Shimano 8s dual stage compound to create gear ratios 2, 3 and 4.

The Sturmey 8s dual stage compound to create gear ratios 5, 6 and 7, and triple stage compound to create gear ratio 8.

Did you ever wonder how the Rohloff 14 creates all those wonderfully even gear steps? This hub dual stage compounds to create gear ratios 1, 2, 6, 7, and 14, and triple stage compounds to achieve gear ratios 3, 5, 10 and 12.

The SRAM S7 and iM9 do not use dual or triple stage compounding (as mentioned, they both make use of single stage compound planets.)

Fun fact: the planetary gear train was invented by James Watt.

All good info. When I say the Sturmey 8 is simpler, it is referring to fewer parts and a mechanically simpler layout (not to mention ease of use and serviceability) but as noted, it comes at the cost of being less efficient, i.e. in 8th gear you're engaging all 3 sets of planetaries. In practice, it's not really noticeable.

I still say that for the price and features, it's a great value. They seem to have fixed the reliability issues with the older ones, I would have no qualms about using one for touring if I had the right bike to put it on.