The Belt Drive and Gearbox thread

I've demo'ed the Zerode, wasn't impressed by the gearbox drive in any way. This was the older grip shift style, not the new electronic paddle shifters they have now. It was simply impossible (with my strength) to downshift when climbing. Drag was noticeable in higher gears. I think it is a great tech for commuter bikes and maybe DH, but definitely not for any discipline where climbing wattage/efficiency is important. 

The electronic smart shift is very good!   I agree and have ridden the old version and now have a new frame with an electric shift.  I think it's like e-bikes, a lot of the old tech was so bad that it put a bad taste in people's mouths.  For park and DH riding, there are no downsides to having the gearbox...  Well, the extra weight has to be worked around, but at least it's low and centered.   The Pinion 6 speed with smart shift and the small battery were about 4lb heavier than the standard DH drivetrain parts I removed.

Cool to see! The devils in the details, and we've been working out the kinks on chain drive bicycles for around 140 years now. I think a gear-mesh gearbox could would on an e-bike where there are watts to burn. But, as someone mentioned in the industry thread, hat's easier to say than do, as in the case of Pinion whose gearbox e-bike system isn't flying off the shelves.

I think for a human-powered bikes, gearboxes aren't going to be a competitive option for uphill and downhill riding until someone can nail the (many, many) details to get a derailleur-in-a-box working consistently with a wide range cassette, or two chainrings and a smaller cassette, or similar. A derailleur-in-a-box like the Honda RN01 seems like the only hope for an acceptable performance human-powered gearbox. And if you had a working, chain-driven, sealed derailleur-in-a-box, there's no reason why you couldn't send power from the box to the rear wheel using a Gates belt drive, a la the new Atherton bike.

I've been a fan of weird bike things since day 1, so im in on the gearbox/belt drive. That being said, I think these mtbs are still more limited to more specific use cases or riding areas, not wide spread adoption. 
I have a pinon belt drive commuter bike that I LOVE- the gear range and having almost zero maintence is great. I bet the thing up and it needs nothing but air in the tires. If you're going to invest in a long-term commuter bike or utility/cargo bike, you screw up not going gearbox/belt drive. On a cargo e-bike these are the best hands down. 

If i had unlimited funds, I would want a gearbox/belt DH bike.... 

Also - A buddy worked at Alta e-dirt bikes and they proto'd one with a Gates Belt, said it was scary quite. 

All of the brands that are making announcements that they are using belt drives / gearboxes for 2025 DH season are kinda setting off my marketing B.S detector.

It may be true that gearbox+ belt drives is the optimal setup for a WC DH race bike, but I find it odd that brands are switching at the same time as other sponsors are cutting back support. 

Are brands teams like Atherton switching because of better sponsorship $ from gearboxes and gates plus chasing the 100k prize from Gates? 

Maybe I'm just jaded and overly suspicious of marketing speak. Team sponsorship is marketing so it shouldn't be surprising that teams always talk about how their new sponsor is the best.

As I said in the companies folding thread, Shimano's back to back cassette patent is the only viable solution. Interestingly there was an Italian company that preceded them too. Ratio wise, two 12spd cassettes with 1 tooth steps between sprockets (so 2 11-22 cassettes) give really really constant gear ratios. I can post some graphs in the afternoon, I've been throwing around some numbers. 

The problem even with a dual cassette gearbox will still be weight (two cassettes) even if efficiency won't be an issue. The main issue weight wise is always the casing as it needs to support the mechanism and it only does that. The load carrying components for modern drivetrains double up as the parts that hold the bike together - it's the frame. 

As for derailleur in a box, put your 12spd cassette somewhere in your frame and be amazed at how big it is. There's no way to make that work outside DH. 

Just a reminder that there are tons of Rohloff hubs out there and they are used by people for bikepacking, low-maintenance MTBs, etc.. It came to market in 1999 (longest standing product?). They are super-reliable and low maintenance. While they have a little more drag when riding compared to a super clean, high-end classic drivetrain, once you figure dirt and wear, they are pretty close. It was also the "gearbox of choice" in Cam Cole's Lahar with which he won junior worlds.

Can someone explain why internal gear hubs don’t have the issues people complain about with gear boxes? Their weight and location is not ideal, but the weight would be less relevant if centrally located. 

I’ve not heard the complaints about drag and stuff with a Rohloff or Alfine. And as for shifting under load, well, I don’t find derailleurs do that particularly well (haven’t used Transmission) so a gearbox would have to be pretty terrible to warrant commentary. 

Traditional drivetrains have become amazing at shifting under load, but still not ideal. Pinion is suffering here too as the forces in the mechanism are high. It's not impossible to shift under load, you just can't as a user, you can't generate the forces needed. 

Rohloff does indeed have increased drag. Just like the classified 2spd hub. Don't know how the shifting works with it.

While I don't have experience, I am read into the issues with gearboxes and shifting under load. Pinion and effigear at least, no ideas about Rohloff (it's a niche within a niche anyway...). 

With Pinion apparently it's hard to shift to an easier gear as the shifting mechanism is loaded up. As I said, it's possible to shift under full load, you just need a lot of force to do it. Can't do it with the grip shift, but in the end of line they use a servo motor to bang through the gears with no problems. No idea how the electronic shifting works, I would hope it would improve things a bit. But in general Pinion requires letting up in the pedals a bit to make a shift. You can load up the grip shift and it will click over once you leg up in the pedals.

If it is hard to shift a Pinion to a lighter gear, it's impossible to do so with effigear as their mechanism locks up (at least as I inquired with them and as people have said ont he forums - apparently they haven't improved on this since release). The thing is with effigear you can't just let up on the pedals, you have to fully release the mechanism before a shift to a lighter gear can occur, the output has to rotate over the input (opposite of how power is transferred through the gearbox). With original Cavaliere bikes they got around this issue by having the output concentric to the (single) pivot and having a rear hub without a freehub - letting up on the pedals the rear wheel would drive the output forward and release the mechanism. This is not ideal with mutlipivot bikes (as the chain/belt is not as taught as it is with the original Cavaliere bikes) and using a freehub in the rear requires to literally backpedal to release the mechanism. I had a spin on a Kavenz with an effigear where the owner ziptied the rear sprocket to the spokes of the hub to fix it in place (he had a freehub equipped rear hub - Cavaliere originally sold a special hub without a freehub for this purpose) to remedy this, but it's still not ideal. Classic drivetrains work better in this regard.

The reason for this is simply the way gearboxes work. It's not a problem to shift to a heavier/faster gear as the neighbouring mechanism is offered up and it pulls the output over the original gear releasing it. Letting up on the pedals is also not a problem as you are usually running out of force (at higher RPMs). The other way around it's a problem as the currently engaged gear will always hold the mechanism 'to itself' and offering up a lighter one will not do anything. Like trying to start pedalling on a quickly moving bike and trying to catch up to the freehub and engage it, but you can't pedal quickly enough to do it. Plus this usually happens when you are pushing on the pedals, slowing down, raising the force, losing speed, so letting up on the pedals will slow you down even further.

This shifting mechanism is very much inline with what F1 and MotoGP seamless shift gearboxes (pioneered by Honda) were like where a heavier gear disengaged the previous one - https://f1-forecast.com/pdf/F1-Files/Honda/F1-SP2_16e.pdf

I know Pinion is similar, Effigear probbaly too, the gist of it is engagement is done radially, not axially like in a classic manual car gearbox. Therefore this kind of 'seamless shift' approach is very easy to implement, especially as we don't have 'engine braking' like cars have, so the shift mechanism is only loaded in one rotational direction. 

I think for dh it’s kind of a no brainer with the tech that exists today.  The pros outweigh the cons.  And since a new race ready dh bike is already pretty expensive I don’t think the cost would be prohibitive.

For e bikes the issue is you need to develop a motor that is competitive while building a gearbox that works and put it in a package that works for multiple frame suppliers.  That sounds like a huge investment and if someone makes a motor that outperforms yours in the same time frame then the industry isn’t going to adopt your product.  Of course if you do nail it then you will have a lot of customers.

Regular bikes I just don’t see it.  Current shortcomings in gearbox tech aside  Chain, cassette, derailleurs are too high performing for the money.  And brands need to offer value and high end builds on the same frame.  So I think in general gearboxes will be a niche product.  Just dh  is a niche where many brands could choose to go that direction.

I think there are a couple hurtles for widespread gearbox adoption. Shifting under load and drag being chief among them. Another issue I see is compatibility. I think the co's involved in gearboxes also need to come to an agreed on a standard mount interface. The idea of having a system that's near maintenance free is grand, but if something goes akimbo or someone else releases an even better performing unit, the end user is pretty much stuck with old and inferior. The derailleur system isn't perfect, but it's flexible in that regard. You will always have an option to replace at will. 

As for belts in MX, I think that comes down to a use case scenario ruling em out. The belt won't clear debris well, which could lead to failure. Additionally, the ability to swap chains in the pits without having to pull off the wheel gives a chain a helluva convenience, not that it happens much but I've seen guys do it at flat track races. Of note, if you check out any of the bikes in the King of the Baggers series, they're all running chain drives. I find that telling of what the engineers and mechs behind those bikes think of belts in race applications. I haven't poked around for any strength figures, but I would guess a belt doesn't handle sudden high torque loads quite the way a chain does.

One last thought on belts. One thing I wondered when I was setting up a customer's belt drive single speed ages ago was additional bearing wear due to the higher tension required by the belt drive. On a commuter rig this is probably negligible, but for a die-hard single speeder those drive side bearings would seem to be under an additional load at all times. Maybe much ado about nothing, but I never did receive an adequate answer when asked. 

the frame mounted gearhub is a pretty tidy solution when used in a high pivot configuration (ie, gt, lahar, og zerode). compact gearbox with a good bit of flexibility re: layout configuration (in comparison to bb integrated pinion & effigear boxes). the rohloff is bomber, relatively common, and shifts better under load than a pinion (i have a lahar & have spent time on a pinion zerode). albeit requires a bit of a bodge reconfiguring the hub to frame mount. 

People assume way too much about gearboxes and belts. 

Do not judge until your ride one. 

The reports you read about the drag or gripshift appear to be mostly from people who haven't ridden a gearbox bike and are just repeating what they heard. 

I have a gearbox bike with a belt drive, 155mm cranks. Full suspension with idler and tensioner. So lots of added "drag" beyond the gearbox itself. It's a big enduro bike that gets used for bike parks and shuttle laps too. I've beat it to hell and back for the last 3 years, broken frames, bent cranks, bent pedals, BB cased too many big road gaps. 

I also have many derailleur bikes and ss bikes so I have a decent feel for the comparison. 

I have not ridden the gearbox with a chain though. 

My experience is per below:

Pros:

-Gearbox is many times better than derailleur/cassette if you care about rear axle weight and suspension performance 

-gearbox bike may be heavier statically but rides much lighter. That rear axle weight again

-The difference from a nice 7 speed DH cassette and small cage derailleur is not as pronounced as a 12spd cassette but still noticable

-the belt removes "pedal kickback" sensations. I believe what we think is pedal kickback is actually chain and derailleur mass bouncing and tugging the chain. 

-my bike feels the same without a belt as with one. That's a huge plus!

-the drag in easy gears is not very noticable. I run 155mm cranks and the shorter cranks has more of an effect that gearbox for pedaling. 

-Idler adds more noticeable drag than gearbox

-Pinion gripshift is brilliant. Shifting to higher gears mid air is pure and utter joy. Feels like a throttle blip on a moto. 

-gearshifts are instantaneous. Doesn't matter how many gears up or down. Changed as soon as you shift. Dumping 3 years at once is very cool. You really need to ride this to notice how big of a game changer it is. Riding a derailleur bike feels so backwards on this point alone

-you can shift to a higher gear under full load. Instantly.

-shifting to a lower gear is also instantaneous. You just need to adjust your pedalling style and remove load for a split second. It becomes intuitive. Then you are instantly in the gear you choose. Dump as many gears as you want. This is so much better than a derailleur system. Getting 3 gears lower with a derailleur takes time and setup and grinding. 

-pinion gearbox is strong. I've bent cranks and pedals and all that load goes through the gearbox. Still spinning free without any service. 

Cons:

-The gearbox does have more drag. You can feel it when in high gears on flat road or when turning the cranks by hand. However, as noted above, the drag is not noticable in easy gears. 

-I would not use a gearbox for an xc bike but for anything gravity orientated, it's much better 

-the belt can hold loam and mud and add drag for the first rotation. This can be offset by routing the belt higher tighter to chainstay like Atherton or Zerode.

-Belts break. But not as often as chains but are currently harder to source. You need a spare. 

-Gripshift is not perfect. Harder to shift in rough sections etc where you don't want to twist your grip. Upshift twist is more awkward than downshift twist 

This. 

Please everyone just ride it before you speak of drag.

Based on what I read in internet forums, I would never buy one. It makes all the sense to me, but all I hear on the internet is "drag" and that you can't shift while pedalling. Then I got to ride one.. I haven't noticed any increase in drag compared to my Demo with half a day of riding on it in the park. I'd say if I don't lube a chain every day, there's more drag in that system, especially when the Saint wears out in 3 months and the chain comes off a pulley..

Also Effigear can shift one way under full load, but not the other way. Pinion Smart.Shift shifts very reliably and quickly under just about any situation. I jump between a "crude" bike and a gearbox bike all the time now, and I honestly am much more comfortable dumping gears running into a jump with the Pinion, while with a derailleur I'll just stay in the old gear in case the shift takes a bit longer.

I don't know if it's for everyone, I don't know if it's the future, but there's way too much exaggerated opinions about its downsides. No-one asks how many watts do you lose every time your chain is making your way onto the next cog and you're not doing full power (I don't care if you're on a Transmission or HG+, it still takes much longer to shift than a gearbox.
One thing I enjoy is as I'm accelerating down something steep, I can literally dump a gear with every crank revolution, consistently, with full power that I just couldn't do with a derailleur as it "syncs" with the rear cassette. 

I agree with everything you wrote besides, "Belt reduces pedal kick".  I have chain on my gearbox right now as I get things configured, but I don't see how I belt would change engament.  The pinion does have 18 degress of float + what your hub has.

I only have about a handful of days on my setup, gonna be hard to go back to standard drivetrain for a DH or park bike.

The pedal kickback sensation could be muted with a belt due to the belt being a bit lighter per section (is it? Can someone confirm?) and because it's rubber, it's damped a lot better than a chain is, so it should resist flapping around quite a bit more than a chain does.

Food for though, chains for camshaft drive in car engines have plastic tensioners and guides running the length of the free span between sprockets while belts only have a tensioning pulley on the idle (load wise) part of the belt right before it wraps around the crankshaft pulley to keep it taught and in time.

Also from what I understand the electric pinnion shifts when cranks are vertical so there is no load on the mechanism. 

I have only ridden a zerode for a few minutes on the road but I absolutely loved the instant shift, in my opinion that outweights the shifting under load as you just have to change the way you shift and while people make a lot of fuss about that it took me a minute to adjust. Riding my derailleur for the next 2 hours honestly felt like crap as the shift was not instant and you had to make a full turn of the wheel for the shift to complete and its something you dont ever think about until you ride a gearbox. It really changes the way you pedal in the way you dont really consider it untill you try. For me the real issue remains the price

Echoing a lot of what Roryb has said. Current bike is a big heavy enduro bike with pinion gearbox and chain. The worst bit about it is the chain. Not noticed any increased drag over my conventionally driven bikes but being able to shift when stationary is actually a lot more useful that one would assume. Not crunching through through gears in the wet, gritty UK weather is also a bonus.

Worst things about it are the no shifting under load and the gripshift, although I am used to the gripshift now. I can see how people would hop on the mechanically shifted gearbox bike from a normal bike and have issues. As with anything, it takes a bit of time to get used to.

I have also spent some time on the new electronically shifted pinion with a belt and it is in a different league. Shifts whenever, silent, super low maintenance. Just a joy to ride. Again, didnt notice any increase in drag. I think there are some good links to studies regarding drive train efficiency on the Zerode website. I think the takeaway is the more load you put through them, the more efficient they are.

I wont be purchasing another derailleur driven bike. 

I worked with a fresh out of college engineer to build a gearbox dh bike for my race team in 2009.

Gearboxes are the next best thing to riding chainless for dh.   We had to build a servobox so we could have push button electric shifting, because gripshift sucks unless it’s 1995 and some nice guy named Ed is giving it to you for free.

I have ex teammates who have worked for Gates for years, and deal with one of their belts on a zerode katipo I maintain for a coworker.

love me some gearboxes, hate belts.

MORE BUTTONS! 
Or just just sync up a SRAM shifter I guess. 

Im stoked to see this happening. I hope that some of this tech and development works its way down to us mere mortals. Personally, I think a 170mm travel enduro Ebike, with a gearbox and belt would be SICK. 

okay its 160mm... but for a mere 11000 euros

https://www.nicolai-bicycles.com/Saturn16MGU-en

for non electric powered enthusiasts, I'm interested if Atherton will be able to relatively quickly offer gearbox drivetrains on their other "A" models once they have sorted the mounting/bottom bracket area titanium lug.

Atherton have a pivot placement issue to fit gearboxes to their bikes as a straight drop in. They would have to adapt the kinematics to make it work. Possibly this is a part of the reason for the idler and high pivot in the DH bike. 

This was incredibly satisfying and enthralling to watch the whole development, build, and test process.

Regarding pedal kickback comment with belt; I use the term pedal kickback as that's what people refer to when taking about pedal feedback. 

I am of the strong opinion that it's pedal feedback, not kickback that's the main issue. Unless you are locked up on the brakes, your rear wheel is spinning too fast to catch. 

The very low belt mass vs. a chain is what makes the difference. That and the dynamic wave pattern of a chain vs. continuous belt. 

STFU loops dampen this feedback significantly as they shorten the free length of the chain while also allowing a soft catch. 

O Chain achieves the same feedback reduction but allowing a soft catch on the chain tug. Add STFU with O chain and you probably get close to how the belt feels while riding. 

To highlight this point, my bike feels the exact same through the rough without a belt as with a belt!

Keeping the chain short and tight to the chainstay with STFU loops top and bottom to reduce chain slap will get you pretty close to the belt feel. 

Yeah, I think chain feedback is a better word than pedal kick. Like you said with the chain or belt tight to the chain stay, I think it dramatically reduces any chain feedback. I did a test on my gearbox frame with and without a chain and the difference was virtually unnoticeable, and I feel like I’m pretty sensitive.   I’ve tested bikes with and without an ochain and it was a dramatic change to feel or even idler sizes on different I can feel(just as an example).

 I do want to try the belt on my bike at some point. I’m not against it. It’s just not as adjustable as a chain with links or like someone wrote above. If you have an issue, it’s not easily to source a belt.

 Has anyone checked the  difference between a belt and a chain of the same length?  

 Right now it seems like the biggest advantage of belt is the cleaning aspect and the sound residence.

Yeah, I think yours with the chain close to CS and lower tensioner up high, takes out most of the chain feedback. Proved if it feels chain less. That's the real test. 

Another thing I noticed hopping back and forth form belt to chain is the lateral chain movement and associated noise/feedback. Perhaps a fresh chain would reduce this. The stfu loops also catch that. 

Regarding the cleaning aspect of the belt. It's nice to never have to oil it etc, but it does pick up dirt and pine needles/little sticks etc. Especially with how I ride, rarely pedalling so the belt becomes a loam shelf. 

The rear snubber stops those derailing the belt but in doing so, crushes them into the belt. 

So you end up with a pulp under the belt. Still works fine but for sure adds drag. 

https://www.youtube.com/watch?v=8niTpTlLp5I&t=976s

The newer "development" video is on the other website and is insightful.  Seeing Gee follow Charlie down some trails then commenting on ride-feel afterwards indicates good things.  A lot of "interesting" "silent" "pushing-through" (in turns), "early days"...but a great starting success, it seems.

Looks like the gearbox bikes in Hardline Tasmania have no trouble clearing the jumps where BK says he is giving his 100% on.

Bad news for the "too much drag" crew I guess

The drag isn't rolling drag, it's efficiency loss from pedalling, after the road gap at hardline you don't pedal, so a gearbox wouldn't cause a problem there.