SRAM 36h Automatix 2 Speed Rear Hub Reviews

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I installed this hub on my drop bar steel commuter bike. Using a 21t rear cog and a 38t front chainring, I get a good 48 gear inch low gear for starting out and climbing steep hills, and a 67 gear inch high gear that isn't too hard for the frequent wind advisory days we have around here. The hub shifts at 11.5 mph with my 700c wheels, making a great shift point when sprinting through intersections. If I need to climb a steep hill, I simply slow to just under 11mph and spin my way up the hill. The gearing is perfect for my commute. The automatic shifting feature is a great asset in stop-and-go city traffic. My normal cruising speed on this bike is 17-20 mph when my headwind is below 25 mph.

If you build this hub into a smaller wheel, the shift point will be lower than my 11.5 mph. This may be problematic for use on a folding bike, which would otherwise be an ideal use for this hub.

EDIT: I have located an online forum thread that describes how to adjust the shift point in the hub. I'm not saying you should do it. Any modification is at your own risk, and will certainly void the warranty. You can locate the forum thread by searching "ctc forum automatix" in Google.

The good: Easy to use, predictable shifting, and very little drag (noticeably less drag in high gear than the Nexus 3 hub it replaced)

The bad: When coasting at a speed above the 11.5mph shift point, the hub drops back into low gear. It shifts back up as soon as you start pedaling. You get used to it, and don't notice it after a while. Also, with my hub you can hear a light rattling noise when coasting over bumpy surfaces. I venture to guess its a result of the centrifugal weights not being engaged, but I haven't taken the hub apart to investigate. It's not a loud rattle, and it doesn't sound like anything's wrong with the hub. When pedaling over bumpy surfaces, the light rattle is not present.

All in all, I really like the Automatix hub. It has its minor imperfections, but it's simple and works well for city riding.

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I have a Sram automatic on my retro 87 fuji with 700c rims. First thing to note is that a normal size chain ring is to big for the gearing. I have reduced my front to a 38t which works perfectly.

One odd thing to note is the hub is preset at the factory to automatically shift at 7 or 11 mph. There is no way to determine the configuration before purchase or easy way to adjust the shift points.

Overall I'm impressed with it. Reducing the front chain ring to a 38t made a huge difference.

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Pros: gives you an added gear while commuting; clean looking; fairly quiet

Cons: Heavy. Shifts WAYYYY to early. Shifts going uphill. Downshifts when coasting.

As shipped, it is basically a granny assist gear and will shift after a few pedal revolutions. I took apart the hub and followed internet instructions to modify the shift point. The modification worked, but it was a real pain in the you know what. Little info from SRAM about this hub on the web.

Honest reviews on SRAM 36h Automatix 2 Speed Rear Hub

Like this hub a lot am using on a bike i ride to work. It is very smooth in how it shifts and very reliable, no messy shifts leaving you hanging in a intersection .A slight pause in the peddling is all it takes to shift into low gear The only maintenance i have had to do is tension the chain and keep it lubed . The key to be happy with this is to select the proper gearing . What worked for me was to find the highest gear that i could ride my whole commute in with my derailed geared bike mashing up the hills. Determine the gear inches using a chart and then making this my mid range for this hub. Then set this up by buying the optimum front chain ring. This gave me a low gear i am not going to blow my knees out with and a much better high gear so no spinning like mad man on the flats. This winter i want to set my mountain bike up with one of these.

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The shift point is set so low that it shifts after 3-4 slow easy revolutions. My attempt to follow internet instructions to change this resulted in destroying the pins holding the commas in place. SRAM customer service was polite in stating no parts are available. The wheel is a total loss, so beware.