Schlumpf Advanced Belt Drive System

Schlumpf introduced a new belt drive system at this year’s Eurobike show. Dubbed the Advanced Belt Drive System (ABDS), the claimed benefits include:

  • Using only a few standardized parts, any belt line can be achieved.
  • Any belt width for any type of use (heavy-duty applications, light-duty city bikes) can be supported using the same standardized parts.
  • A bigger radius at the rear sprocket allows the use of industry-standard belts with a 14-mm pitch.
  • Belts with a 14-mm pitch offer a better fit, and need no pretensioning.
  • The lack of pretensioning increases overall efficiency, and avoids power losses and wear on the bearings.
  • The greater freedom of design makes it possible to design in scoops for mud relief.

The $64 question is whether the large diameter rear sprocket will necessitate the use of a geared bottom bracket like the Schlumpf Speed Drive; the literature seems to imply so.

ABDS Tech Manual (PDF) →

15 Responses to “Schlumpf Advanced Belt Drive System”

  • Fergie348 says:

    Well, the examples that Schlumpf gives in it’s technical brochure are a final drive of 40 x 16 for the competitor (presumably Gates) and a final drive of 40 x 26 for their setup. The final drive might be necessary for a user to attach to a single speed hub in order to obtain a sufficiently high gear for road riding, but if I’m not mistaken all the IGH sprockets that Gates sells are 24 tooth so not much difference there.

    The larger benefit seems to be the use of standard belts using a 14 mm pitch (as opposed to 11 mm pitch of the Gates drive) of varying widths to suit the application. Narrow for city bikes, wide for MTB or cargo bikes, etc. The larger pitch should allow the belt to run at a lower tension, which may make setup easier.

    It seems kind of hokey to me – you have to stack up to 5 or 6 pieces of metal together, holding it all together with ‘Module-assembly bolts’ to form a belt adaptor for the crank or for the rear hub. It’s also not clear what adaptors for hubs are available. It looks heavy and failure prone to me. Time will tell.

  • Pete says:

    Very interesting. It could be problematic, as Fergie says, but if done right it could also be a way to retrofit a wider variety of existing cranks and hubs for belt drive. Obviously, if you are trying to use many different belt widths then the “sandwich” construction has benefits. The bolts at least look like pretty standard crank bolts.
    I’m also encouraged that they are looking at using existing standards. On reason I’m reluctant to use the Gates system is that it’s so proprietary. A few more players in this game can only help.

  • Michael says:

    Don’t know enough about it (the Schlumpf) to form an opinion. However it’s nice to see some R&D money being spent on bicycles. And some creative stuff at that. Being very familiar with toothed belt drives and their strength/weaknesses I feel they are particularly well suited to cycling applications and am interested in knowing more about this one in particular. And by more companies joining the fray the price will come down to earth sooner than later.

  • Bob B says:

    I think Schlumpf is fully capable to pull this off. I got a chance to try out their 2 speed bottom brackets back in my recumbent days. They are pretty amazing and work really well. Tap the bottom bracket dust cap button and it shifts down into a new range.

  • David says:

    I don’t know about failure prone, it’s just 5 bolts holding the thing together, but it looks like it requires their Speed Drive which adds ~$650 in cost and you’re right back to proprietary.

  • jamesmallon says:

    I find this to be a convincing ‘head-check’ on belt drives:

  • Paul M says:

    Surely you don’t have to use a Speed-Drive, you could stick a standard internal gear hub on there to cope with the reduced primary ratio.

    I’m very interested in the capability of using indusry standard belts. I’m just putting together a mountain bike with a Gates Carbon Drive and have found the belt-length/available sprockets quite restrictive. I have managed to just about find the magic combination for my frame though (I fitted it last night). But in the long term, the idea of a Belt-Drive, hub-geared cargo bike really appeals. Watch this space…

    The Schlumpf system does look heavy though, compared to the Gates. Any idea on weight?

  • Tom T says:

    My interest in this scheme is high, but it it that of a naive consumer excited with the idea of a cleaner and quieter low-maintenance drive train on a touring bike. From this perspective, the idea of retrofitting an existing bike is intriguing, but it would appear to require something like a “Frame split for belt drive compatibility” as mentioned in the Civia Bryant product page. I am under the impression that few bicycles are set up this way, so it seems like a showstopper for the aftermarket.

    Using this belt drive in anything other than a fixie implies an IGH and apparently a Schlumpf front end. That and an Alfine-equipped wheel would go for perhaps $1200. Adding in the belt-drive bits would drive the price — if not the efficiency or reliability — well into Rohloff territory.

    The price and complexity of this drivetrain frighten me away from an immediate upgrade. Call me gullible, but I’m waiting for some reputable manufacturer to incorporate the Schlumpf solution into its product line before I find it credible.

  • David says:

    I wouldn’t put too much weight on a couple of developmental issues from four years ago. There’s been a lot of thought, money, and effort spent on this product since then and thousands of bikes have been fitted with it. I’ve got my own issues with how Gates is promoting and pricing their system, but I will give them their due that it seems to work as advertised at this point, even on single speed mountain bikes.

  • Thor says:

    checked it out last week. Every new idea is good and should give time to ripe and get the wrinkles out. To my understanding it only works with Schlumpf transmission in front, which makes the system expensive and unobtainable for most. Compared to my gates equipped Dahon it looked somewhat clumsy and the belt felt sloppy. The gates sytem just looks more elegant but of course that is in the eye of the beholder.
    the gearing of the Schlumpf might or might not work on 20 inch folders due to the larger than usual rear drive and simply not enough room for super large front “sprockets”
    time will tell but a good new fresh approach

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  • Andrew says:

    While I appreciate that they’re trying to go with a more standardized format _if_ it does require a Speed Drive it’s a complete non-starter. That aside, the modular design itself seems to give up some of the functionality of a Gate’s Carbon Drive (e.g. the lack of pass-through ports on the sprockets to shed mud) that I think would limit their application on bikes used in adverse conditions.

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  • Richard Masoner says:

    It doesn’t seem like the Speed Drive is exactly *required*, but it’s pretty obvious Schlumpf came up with this to try to increase demand for their 2 speed cranks. Otherwise, you have a ridiculously low gear with the 27T cog on their Belt Drive attachment.

    @JamesMallon: “Guitar Ted” is a pretty big dude. I’m a lighweight, but I’ve also managed to ratchet belt drives a time or two. It’s not a dealbreaker for me, though: I still like belt drive SS bikes.

  • Alan says:


    “To my understanding it only works with Schlumpf transmission in front, which makes the system expensive and unobtainable for most.”

    I hope that’s not true, but I’m afraid you’re right. If so, that will severely limit its application.

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