Heatherbikes

Not sure if this is a mechanics thread or gidget gadget thread....BUT, does anyone have that bloody hub yet? I ordered the hub with a front drum brake hub a few months ago. The front hub came within days but the 8 speed hub is hopefully coming in mid December. I wanted to get my commuter ready for the winter/monsoon season. Luckily it has not been that bad weatherwise, but my bike is in pieces. My back up mountain bike has bit the bullet so I have had to get out my sunny weather ride a raleigh sprite with 4 working gears!
I have heard bad things about the sturmey archer 8 speed hub, but it is so cheap(in Canada at least) compared to the nexus or srams and I can't afford to spend too much on a cheapish bike. I still do not understand what direct drive means and why it is in 1st gear. I have also read that the sa 8 speed hub runs too high and works better on small bikes. I was intending to set it up on a hybrid with 700 cc tires or else an old raleigh with 26 inch wheels. Does anyone have any recipes for cogs and chainrings that would work for either wheel size? I have contacted Sunracer quite a few times with no response!
I really want to try an internal geared hub because I am so tired of derailleurs getting mucky, dysfunctional and dead. Despite having a bike mechanic husband our bikes still end up in a pile waiting for the day we can clean up and replace the derailleurs.
I live in the pacific northwest in a rural area so deal with old highways and mucky roads, there is much rain and moisture and the highway crews LOVE to put salt on the road at any sign of frost. It is very hilly and I do live up a steep dirt road. I am always climbing or descending hills with occasional relative flatness. I have been riding my sprite lately on my daily commutes and found that the 4 derailleur gears are quite sufficient except for the big hills which gives me some confidence that I would manage just fine with an 8 speed internal hub.
I keep obsessing about what internal geared hub I should have ordered. Nexus or Alfine seem to get rave reviews, but the sram i motion has a higher range. I might order a better hub to put on the bike I will probably use most.
So my question? Any experience with the new SA hub, how to best set it up, does it suck and should I have gotten something else?

Berre

According to the specs, this SA 8 speed hub has direct drive in first gear. This means one rotation of the cog equals to one rotation of the wheel. The ridden distance with a 28 inch wheel (700 c, 622 ETRTO) is about 2.25m. (The exact distance depends on the size of the tire.)

Gears 2-8 all make a longer travelled distance per cog rotation. The exact figures are on the SA website.

For climbing, first gear may be to hard when used with a 28 inch wheel. Obviously, your strenght and condition as a rider is the important factor.

tatfiend 

I believe that the input gear ratio should be watched with all gear hubs. Rohloff, SRAM and NuVinci are all very specific about minimum input ratios which are clearly specified. Sturmey Archer, prior to the Sunrace buyout, also had ckear specs on this. Rohloff hubs for instance specify a minimum ratio of 2.35 to 1 chainwheel to input sprocket. In other words a 38 tooth chain ring and 16 tooth input sprocket minimum. A smaller chain ring with the 16 tooth sprocket invalidates the warranty. NuVinci specs an input ratio of 2 to 1 and SRAM varies from 1.73 to 1 to 2 to 1 depending on the particular gear hub. If the ratio is set too low then the hub is subjected to higher input torque.

Shimano and Sunrace are less clear on input ratio specifications and list sprocket combinations that give quite low input ratios. As noted this subjects their hubs to higher input torques. I have seen enough reports of hub failures from both so that I suspect that they are not spec'd for strong riders and those who climb or accelerate hard while out of the saddl frequently. A recent post from a 235 pound out of saddle rider from San Francisco reported destroying two 7 speed Shimano hubs in less than a year. Shimano apparently indicated their hubs were not designed for his type of use!

The 1 to 1 first gear ratio makes it difficult to gear for a reasonable low first gear while trying to keep the input ratio reasonable if using 26" or 700C tires. To me the ratios of the SA 8 speed suit it for small wheel bikes such as folders rather than normal wheel size street bikes. The SRAM iMotion9 has direct drive in 5th gear and the Rohloff has it in 11th. These allow a lower first gear with more normal size sprockets. The only other gear hub I know of with a 1 to 1 first gear was the Shimano 4 speed, now discontinued.

From your description of steep hills and a dirt road I would expect that the Sturmey Archer will not be suitable for what you want it for. I could well be mistaken though as the new version is supposed to be stronger than the older one, at least that is what is being claimed.

joejack951

What are the working gears left on your Raleigh? You said you can climb ok in them aside from the really steep stuff. If you can give us the ratios, we can figure out what chainring and rear cog you would need to get those ratios with the SA hub. If the ratio ends up unsuitable for the hub, it sounds like you might need to go with a different hub.

tcs

I don't believe the SA8W (W for wide, as in 325% vs. 305% for the older design) has been released to the public yet. Latest word is "early '09". The few Taiwanese-redesign prototypes folks have tested have run well and been far less fussy about gear shift alignment, but AFAIK no one has had one long enough to know if there has been the necessary durability improvement over the original British design.

Heatherbikes, from your description of use, I'd recomend the SRAM S7 hub. This robust model is less expensive than the Alfine or i9, has fairly even gear steps, a broad range, and is relatively easy to overhaul (clean and lubricate) when that time comes - as it does for all bicycle components, including IGHs.

HTH,
tcs

Squeazel

+1

The 1:1 low gear makes the SA 8-speed impractical for anything but small-wheeled bikes. I have one on my Raleigh 20 with a 44 front chainring and a 25 back cog giving me a low gear of about 30 inches and a high of about 90. This is pretty good for the hills we have around here, but I would hesitate to put one in a 26" or 700c wheel- the front chainring would be about 30 teeth to get the same gearing, which would put a lot of stress on the internal parts. You don't want the planetary gears to go bang as you're standing on the pedals in third. Get a Shimano 7 speed.

LWaB

I wonder why SA make cranks with 30T and 33T? https://www.sturmey-archer.com/cranks__FCS80.php
Perhaps the SA hub is designed to be used with small chainrings.

It is only difficult to get the gear range you want on a 26" or 27" wheel if you stick to using excessively large chainrings (for the hub). I've had no problems with a couple of SA 8sp hubs on small wheeled Audax bikes, other than getting the cable tension just right after a flat tyre. YMMV.

tatfiend 

The small chainrings you mention subject the hub to high torque loads internally. High to excessive input torque can damage gear hubs or at least increase wear rates on parts.

I would like Sunrace Sturmey Archer, an Shimano, to clearly list minimum input ratios, and input torque limits, for their gear hubs. Both Rohloff and NuVinci list both and SRAM lists minimum input ratios for all of their hubs. The Rohloff warranty can be invalidated by using too low an input ratio per the manual.

No problem if used on a 100 mile per year cruiser bike ridden gently on bike paths but from posts I have seen hub failure can be a problem for strong riders using them.

Squeazel

Maybe the new hub is stronger- I've heard of a number of people who have had problems with the old hub. Jur from the folding bikes forum destroyed one even on a 20" wheeled bike: https://www.bikeforums.net/showthread...873&highlight=

But I had also heard that the first bunch out of the factory had some quality control issues. It is auspicious that SA make a 30 and 33 tooth crank- the only reason to do so is to run with the SA 8 hub.

tcs

A common 110BDC crank will take 33T chainwheels.

I've always thought stated minimum input ratios would have to have a large safety margin to cover heavy, powerful mashers. Maximum input torque is far more logical, but less intuitive.

tcs

tcs

I should hope - otherwise the cost and time of redesign and the beef that got added was hardly worth the effort!

tcs

tatfiend 

I agree that it should take into account even strong users and the Rohloff spec apparently does. They also spec a 2.5 to 1 minimum input ratio for riders over 100Kg or tandem use in addition to the normal input ratio spec of 2.35. It is also approved for mountain bike use, the only gear hub so approved per my understanding. Also the only one with a wide enough ratio spread for such use.

Heatherbikes

I'm confused-still. Thanks everyone so far. My raleigh sprite from the late '60's has a 5 speed derailleur and the lowest gear isn't working. No idea on ratios. It's good for short jaunts into town where it is relatively flat, but I have had to use it go get to work where there are some big hills.
I had been thinking of getting the sram 7 geared hub so I might order one to get my commuter going. Can I use it with the sturmey archer's front wheel drum brake? Shouldn't matter right?
So, would the SA 8 speed hub work on a regular sized bike with the 30 or 33 chainring? Aren't the rear cogs at least 20? At least I can cancel the order if things aren't looking good.

tatfiend 

Heatherbikes;

Count the teeth on the chainring, the smallest chainring if more than one.
Count the teeth on the largest rear sprocket.
Divide the sprocket teeth into the chainring teeth.
Multiply the result by 27 or measured wheel diameter.

This will give you your lowest gear in gear inches.

17" to 21" is typical for a MTB or a loaded touring bike.
27" to 33" is a common low for a road triple.
40" to 50" is typical low for a road double.

The SA 8 speed hub has 23 or 25 tooth sprockets listed. If presume a 27" diameter wheel then with the 25 tooth sprocket and a 33 tooth chainring the low will be approximately 36". With a 30 tooth sprocket this becomes about 33".

Per the SRAM manual the S7 has a minimum input ratio allowed of >1.83 or a 19 tooth sprocket and 35 tooth chainring for example. Low is a .574 ratio. With a 27" wheel this calculates to a 28.5" low gear.

The SRAM iMotion9 lists a minimum input ratio of >1.73 and a low gear internal ratio of .542. This allows a 19/33 combination of input sprocket and chainwheel. The low gear will be 27" with a 27" diameter wheel.

Either SRAM hub will allow a lower low than the SA 8 speed hub while staying within SRAM input ratio guidelines.

How low do you need? That is for you to determine. Can you borrow a mountain bike in close to your size and use it to determine the lowest gear you need for your route up the hill?

tcs

If SRAM's guidlines are to protect the hub, then they must surely cover use by heavy mashers. Light spinners should be able to gear much lower.

"We had more conversations about how low you could gear the hub, Rohloff have calculated that the maximum torque, that the hub will reliably withstand, is slightly more than could be produced by two world class athletes on a tandem using a 38 tooth chainring and a 16 tooth sprocket. This is the lowest gearing that they will sanction (which is equivalent to a 22 tooth chainring and a 32 tooth sprocket in a derailleur system.) I use very low gears and I wanted even lower ones! Whenever I get the opportunity, I like to travel on dirt roads, over high mountains, with medium-weight camping and cooking kit and up to 1 week’s supply of food... I reasoned that, as I was certainly not a world class athlete, not particularly strong or heavy and there is only 1 of me (!) that I should be able to use a lower gear than would be safe for the two world class athletes on their tandem! Rohloff product manager, Carsten Geck, agreed with me..." - Andy Blance of Thorn Cycles

tcs

Grand Bois

I'd cancel the order if I were you. The SA 8 speed hub was designed for folders with 20" wheels. I looked into them myself. There was no way to make it work on a road bike. I ended up buying a SRF3 for $53. I love it, but it's not suitable for steep hills. The next one will have a Shimano Nexus 8 speed. I'm going to strip off the paint and polish it before I build the wheel because I think the silver paint looks cheap.

tatfiend 

TCS, I agree. I just prefr to use the manufacturer's listed recommendations. The gearing listed by SRAM is enough lower than Rohloff's that I suspect that due to the much more limited range of the iMotion9 they may have listed closer to the strength limit to allow a reasonable low gear. My Swobo Dixon iMotion9 is geared 2 to 1 from the manufacturer.

Seen enough posts regarding heavy agressive riders damaging SA and Shimano gear hubs that I prefer higher input gearing for them too than the factory allows. They seem to have minimal reserves of strength when geared low.

ogbigbird

had this big post to respond with but my computer kicked me off!!! bottom line, a 36tooth front ring with a 20 or 22tooth rear cog should be fine. i ride a single speed cruiser to work everyday and smoke too, run a 46front with a 20rear and have no problems. cadence, just having your rpms up when you approach a hill will help. when i head to a hil, i spin it out and fly right up. the 8speed s.a. igh with the 1:1 1st gear is sorta impractible with 26" or 700c wheels, cancel if you can or just run a 36/22 combo. as for maximum input torque, i have been riding older s.a. 3speeds for years, can mash the heck out of the pedels and have had no problems. a strong rider who can really pedel hard sort of makes a ring size limit impractical.

p.s. as for your raleigh with only 4 working gears, no low and ect, check to make sure your limiter screws on the rear der are allowing you enough travel to get into 1st. also make sure you don't have too much slack in your gear shifter wire to make sure you can shift full range. maybe that'll fix your 2nd string bike, since you mentioned it.