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.