Ideal gearing with three-speed hubs

[OnYourRight]

My girlfriend’s bicycle has a Shimano Nexus Inter-3 SG-3R40 hub. The hub, like other Shimano three-speed hubs, has ratios of 0.733, 1, and 1.364. I believe most other three-speed hubs have fractionally closer ratios.

The bike came with a 42T chainring and 18T rear sprocket. These produced gears of 47, 64, and 87 gear inches with the 27.4" diameter wheels. I always found that top gear too tall to justify its effect on the climbing gear, and more importantly, so did the owner.

So I recently replaced the 18T sprocket with a 21T sprocket, producing gears of 40, 55, and 75 gear inches. This makes the top gear useful on flat roads, albeit mostly with a tailwind or while following someone (that would be me!) while haring along for short periods. The top gear is still tall enough to be useful on some downhills – at least the kind it’s worth pedalling on.

The middle gear is useful in many cases in the city, and I’m hoping it will be a good cruising gear for all-day rides at low intensity (we’ve yet to test this).

The new low gear makes climbing steep hills a more viable proposition, albeit obviously not always at a racing cadence of ~90 RPM.

You could argue for a larger sprocket still, but my fear was that the middle gear would then be too low for any kind of riding on the flat.

What do you think? I realise I should have asked this before changing the sprocket!

[mjr]

Sheldon Brown advises having top gear for flat cruising.

My 3speed came with a knee-popping 50/66/99ish gearing which I've lowered to 45/60/80. I can just about climb railway bridges - almost as steep as any local hill plus slalom barriers mean it's a standing start - but I'd rather not. I'm tempted to go one step more to 40/54/72 but 80 is surprisingly doable as a fair condition flat gear for me.

Wikipedia says London hire bikes are 32/44/60 which seems too low, so I think the ideal is the middle gear somewhere in 50-60.

[sreten]

Hi,

My folder does 33 to 66 gear inches, my road bike 40 to 100.
I'm 50+ so take of this what you may, given I'm a old duffer.

You certainly went the right way. FWIW I can do hills
better on the road bike than the folder, and in good
conditions to go fast I have to really spin on the folder.
And never go as fast as the road bike, but that doesn't
matter as it improves the spinning on the road bike.

Say I had only only one 3 speed full size bike,
I'd certaintly go for about 40 bottom end and
wouldn't miss much the 75 to 100 gears

rgds, sreten.

[Brucey]

these days for utility riding, anywhere hilly, I'd advise a top gear of 65-72" (but could be different depending on cadence preference) and let the others fall where they will. Basically if you are spun out on your top gear you are doing more than ~20mph and for that kind of riding anything faster is a rare event (or downhill).

However I have also had a bike I used for hard training with an IGH and on that I set the middle year to about 68", reckoning that I'd have gears that I could be working hard with more of the time, especially on hills. Part of the logic was also that the middle gear is most efficient, and I'd be using that one most of the time.

cheers

[barrym]

these days for utility riding, anywhere hilly, I'd advise a top gear of 65-72" and let the others fall where they will. Basically if you are spun out on your top gear you are doing more than ~20mph and for that kind of riding anything faster is a rare event (or downhill).

However I have also had a bike I used for hard training with an IGH and on that I set the middle year to about 68", reckoning that I'd have gears that I could be working hard with more of the time, especially on hills. Part of the logic was also that the middle gear is most efficient, and I'd be using that one most of the time.

cheers

I often 'pretend' I'm living the dream of a 3 speed SA, and just use 3 of my 7, (I have a 1 x 7) which equates to 49.60.72. These are pretty close to a SA I think, and I find quite practical in all but extreme cases.

YMMV.

[pioneer]

I had a Sturmey' three speed on my Raleigh for a while and geared it a 40,54,72. This was because I wanted the top gear to be in the region of 70/75" and the direct drive gear of 54 is the lowest you can get without ignoring Sturmey's advice about a two to one ratio for chainring and sprocket (in this case a 40 chainring and 20 sprocket). Don't know if Shimano offer the same advice though. And the direct drive of 54 is pretty good for most of East Anglia's hills with the 40 gear as a reserve.

I think it's a pity that you can't get a close ratio 3 speed. My prefered gears are only in the range of about 50-70. On the few occasions these days when I ride a derailleur geared bike (last time was about five months ago), still didn't use anything above about 75".

[MartinC]

You want 1 gear that's your pretty much you preferred cruising gear rather than having this fall between 2 of the gears. For me that's about 5m roll out (I think that's about 60-65" in old money). I normally make this the middle gear giving me an uphill gear and a tailwind/downhill gear too. If you're happy to forego the high gear you can make you cruising gear the top gear and a lower gear for climbing. This all depends on you knowing what your ideal cruising gear is for the bike.

[Brucey]

I think it's a pity that you can't get a close ratio 3 speed. My prefered gears are only in the range of about 50-70".

If you can find an SA 'AM' hub (or just a centre in fact, it will go into a pre ~1990's AW shell) you can have say, 52.9", 60", 69.3" gear ratios.

[You can use this hub with a standard 3-speed trigger, and although the normal control rod is a strange one, you can convert the hub to run a standard AW toggle key and control rod, too, if the original one claps out.]

cheers

[resus1uk]

I found my standard M3 Brompton too highly geared (50t, 13t) producing 48/63/85.
Changing to the 44t chainwheel gives 42/56/74; which is more comfortable for an older rider.
On my trike I rarely change from 65" gear in town.

[OnYourRight]

Thanks for the comments.

You want 1 gear that's your pretty much you preferred cruising gear rather than having this fall between 2 of the gears. For me that's about 5m roll out (I think that's about 60-65" in old money). I normally make this the middle gear giving me an uphill gear and a tailwind/downhill gear too. If you're happy to forego the high gear you can make you cruising gear the top gear and a lower gear for climbing. This all depends on you knowing what your ideal cruising gear is for the bike.

Your first sentence is the advice I’d give to anyone who asks (and I’d tell them to make the third gear the cruising gear), but in our case we really wondered about that. As things stand there are essentially two cruising gears: one suitable for slow riding (55") and one suitable for fast riding (75"). I can’t see how any other arrangement would allow this.

Of course many people have no need for a slow flat gear. But she uses this bike for both city commuting and riding out of the city with me. Any third gear as flat-cruising gear that would be satisfying on short rides would be just too high for cruising in all day. This thread suggests to me something in the 55" region may be ideal for all-day rides (and being the second gear, it happens to be the hub’s most efficient one).

On the other hand, the owner pedals slower than I do. The new arrangement works well in the city, but we’ll see how it all pans out on our first long ride. I’m hoping to get the new Voyager Hyper tyres on before the weekend, testing both gears and tyres at the same time and flying in the face of the scientific method!

[pioneer]

My old Raleigh (originally 21 speed, then fixed, then 5 speed hub, then 3 speed hub,then 64 freewheel, now 60 freewheel) is my mainly off road bike. Though provided I remember it's only a 60" gear, is also fine at gentle road pottering. And it's good to ride slower sometimes too.

[mjr]

This thread suggests to me something in the 55" region may be ideal for all-day rides (and being the second gear, it happens to be the hub’s most efficient one).

That thread seems to be more about the inevitable 10mph daily average (faster moving average speed meaning longer stops) so how do you work that out?

One complication I've spotted is that my cadence seems to vary far more on a 3-speed hub geared bike than the 3x7, yet it's still comfortable. I don't know if it's something about the simpler drivetrain, the more upright position (probably not, else the folding bike should have that effect too) or something else about the frame, but it may be why a 80" gear seems usable for stretches of route where I use 72" on other bikes. On the flip side, it feels best to almost be spinning a gear out before changing up, but that's similar on the 1x6.

So I'm not sure whether what feels nicest on derailleur gears is more than a vague indicator for what feels nice on hub gears.

[OnYourRight]

This thread suggests to me something in the 55" region may be ideal for all-day rides (and being the second gear, it happens to be the hub’s most efficient one).

That thread seems to be more about the inevitable 10mph daily average (faster moving average speed meaning longer stops) so how do you work that out?

Well, I reckoned a 55" gear at a comfortable (?) 75 RPM would produce about 12.3 miles per hour, which seems like the kind of pace we’d be capable of sustaining, being slightly below the moving averages on the last page of that thread. We’re not hardened touring cyclists, obviously. I’m the stronger cyclist and I’d be carrying all our gear.

I know what you mean about cadence. I feel the same when I ride her bike. There’s an attractive simplicity to not worrying about cadence and gears as much. I wouldn’t mind an IGH bike myself.

It may turn out that my girlfriend can manage the 75" gear at lower speeds than I imagine, much as you seem to get good use out of your 80" gear (but you’re undoubtedly a stronger cyclist). As I already mentioned, she tends to prefer a slower cadence than I do.

I’m pretty confident 40", 55", and 75" will be better than the original 47", 64", and 87" anyway.

[MikeF]

What gearing you need depends very much on the rider and also the bike. Some bikes inherently seem to be "faster" with the same amount of input. I've never ridden a "Boris" bike but I suspect the gearing has been chosen so that pretty well anyone can ride one whatever their fitness and that's why the gearing appears low. I wonder how the person who rode one on the recent ride 100 found it? I don't think you can say what the gearing should be without counting other factors. You can only really try and see.

Out of interest I note my most used range (on derailleur) is 38-83, but I'm sure some other riders would use something very different. It's so long ago since I've ridden a SA 3speed that I don't know what the gearing was, but It would have been on the old type 26" wheels though.

[mjr]

I've never ridden a "Boris" bike but I suspect the gearing has been chosen so that pretty well anyone can ride one whatever their fitness and that's why the gearing appears low. I wonder how the person who rode one on the recent ride 100 found it? I don't think you can say what the gearing should be without counting other factors. You can only really try and see.

Sorry if it wasn't clear but I have ridden them many times and found the 32/44/60 to be rather low. 32 was only needed for the cobbled climb of Back Hill - and I felt that was because of the stonking weight of the bike (Wikipedia claims 18kg for the frame alone - I'm sure I've read they're over 25 on the road) and the rather stiff little M+ tyres lurching over the cobbles, rather than the climb as such.

I'm sure the ride 100 would be fine on one. The climbs are something like 13% at worst and not that long. Someone's done Mont Ventoux on one anyway. I guess most of the ride would be spent spinning in 60. The usage charge would hurt, too!

Oh and the 45/60/80 SA 3speed I rode today is on the old type 26" wheels still.