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Various webshops use the following names:

  • Sachs Torpedo 3 gear
  • SRAM T3
  • SRAM i-motion 3 gear

There are many inconsistencies in what exactly they call them, and for a long time I thought it was exactly the same product, but now I know that at least Sachs Torpedo and i-motion 3 gear are different. I don't know how though, except that the shifter looks different, and the shifters are incompatible.

I don't know how T3 fits in, maybe it is the same as one of the others.

What are the technical differences between them? Any reason to buy one over the others? I am tempted to buy the Torpedo because I hope it will last longer, since family's bikes with Torpedo lasted forever in my childhood.

The webshop I'm buying from is selling both Sachs Torpedo and SRAM i-motion 3 gear, I asked them for the difference, but they were not really helpful.

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up vote 3 down vote accepted

SRAM acquired Sachs in 2000. The main visible difference between the (Fichtel &) Sachs Torpedo 3 hub and the SRAM T3 is that the SRAM T3 comes in an aluminium body, whereas the Sachs Torpedo 3 comes in a chrome plated steel body and the brake design has been changed (but is compatible). There appearantly was a successor model to the Sachs Torpedo 3 called Sachs Spectro T3 in between the SRAM T3 and the Sachs Torpedo 3. Around 1996 the coaster break mechanism was changed by Sachs. So the timeline is ~1977: H3111 (Sachs Torpedo 3) -> ~1996: MH3111 (Sachs Spectro T3) -> ~2000 MH3115 SRAM T3.

For the (Fichtel &) Sachs Torpedo 3 (H3111) speed hub see: http://www.scheunenfun.de/f+s_h3111.htm (german)

For the Sachs Spectro T3 (MH3111) and the SRAM T3 (MH3115) see: http://www.scheunenfun.de/sram-t3.htm (german)

So those mentioned above are internally compatible, at least if your willing to replace some parts.

I am not exactly sure about the i-motion 3, but SRAM states that it is the successor of the T3 hub (see http://www.sheldonbrown.com/harris/pdfs/sram-internal-gears.pdf) it has a different shifting mechanism (a broken cable leaves it in low gear (opposed to high gear on the T3) among and some other differences, as far as i can see (see http://cdn.sram.com/sites/default/files/techdocs/sram-techmanual-my10-gearhubsystems-english-reva.pdf) and the internals are not compatible to the t3.

Some people have noted to have had problems (broken axles) with the i-motion 3 hub, whereas the old Torpedo hubs rarely break, which should be the case for the T3 as well, as it is mostly the same design (see http://www.bikeforums.net/archive/index.php/t-394516.html).

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