“TL:DR - it can't make the bike more agile, it can make the bike bike less agile”
I’m really busy running my own business so don’t have time for an essay, which is why my previous post was written very quickly, and that phrase was technically incorrect even though that phrase could mean exactly the right thing because of the actual words in it!
(Consider the definition of “inertia”)
My point was about moving mass towards the BB, not adding mass. Lowering the CoG of a bike reduces the distance it has to move when you lean the bike over, therefore meaning less force is required, therefore you increase agility.
So many people saying “lowering the shock in the frame makes the bike more stable” but it doesn’t. Obviously added mass doesn’t increase agility.
I still think that it makes more sense for gearbox bikes to have the drivetrain fully enclosed. Similar to the Millyard bike. Totally isolate it from mud and debris.
I think gearbox DH bikes make 100% sense a friend has had a Zerode Taniwa for a few years and it’s been faultless.
My point was about moving mass towards the BB, not adding mass. Lowering the CoG of a bike reduces the distance it has to move when you lean the bike over, therefore meaning less force is required, therefore you increase agility.
So many people saying “lowering the shock in the frame makes the bike more stable” but it doesn’t. Obviously added mass doesn’t increase agility.
another can of worms opened here...
while there are two different issues on CoG - system CoG including the rider, and bike CoG.
Overall bike CoG is probably most important to overall speed etc.
But bike CoG maybe more important for "feel"
You are moving the bike around underneath you (or having it moved by external forces).
Realistically that is felt through the feet - so at BB height. So if the CoG of the frame is further above that point, it will feel like it takes more effort to move. Also the gyroscopic effects of the wheels are going to have an effect, and one that is applied at axle height.
The waffle about weight/CoG and geometry is 'interesting' enough I suppose but coming back to the original question about how the current lot of Gearbox DH bikes being ridden at 2025 WC rounds might influence the wider future market for MTBs, I suppose the question is more what appetite do privateers and muggles have for gearbox bikes?
Offhand I'm sure everyone who's ever owned and had to maintain any MTB (especially a DH bike) would be very enthusiastic about the idea of not having a gear dangler on the back to catch rocks, But I have to question the reality of it. Gearboxes have been on the horizon for 20 odd years now, but the available solutions have always come with compromises and price tags that never quite seem appealing enough for mass adoption.
These days I still think there's a problem with common mounting standards, or a lack thereof (correct me if I'm wrong here). I see a similar issue with mid-drive E-bikes and there is some potential to help align all the miscellaneous things people might want to bolt into a frame instead of a BB and nudge the world a bit closer to gearboxes that way...
I also question the inherent loss of efficiency in most gearboxes, but I think a fair few would accept that compromise if pricing was on par and maintenance burden was reduced... But is that what we'll be offered?
Then there's the issue of just how many DH bikes are being sold each year, or not. Is there really the worldwide market now for relatively "non-standard" (and therefore more expensive) DH bikes? Is DH really a growth market? or should the effort be expended on Enduro and E-MTBs where more punters seem inclined to throw their money now...
Do Gearbox DH bikes necessarily translate to Gearbox Enduro and Trail bikes? Yes they exist, but they're not a product for the masses still...
Despite a WC DH field full of fancy new toys, I'm not sure the bike buying public are any closer to affordable Gearbox bikes today than they were five years ago...
Despite a WC DH field full of fancy new toys, I'm not sure the bike buying public are any closer to affordable Gearbox bikes today than they were five years ago...
Well the Zerode is £8500 and the Gamux is about £10500. Both are expensive yes, but not completely insane in the current market of elite level bikes.
I always wondered why singlespeed DH bikes never became a thing.
If I was in the market for an out and out downhill bike I'd definitely be giving Starling a call to see if they would make a Sturn 🙂
More and more oldies are running SS conversions on their DHs, 3 out of 4 of my regular DH riding mates have gone SS on theirs, various bikes/manufacturers.
I also question the inherent loss of efficiency in most gearboxes, but I think a fair few would accept that compromise if pricing was on par and maintenance burden was reduced... But is that what we'll be offered
I suspect some people would.
Roadies are the often looking for the most efficient solution, but in any club (or Audax) there's always someone with an Rohloff. They'll be semi retired and easily doing 10,000miles+ a year so they're easily that 5% fitter than the weekend warriors to offset the drag and get the maximum benefit from the reduced maintenance.
Same will be true on MTB's. Someone who turns up once a week on a Tuesday night (and probably not at all for most of the winter) and sits in the bottom third of the group isn't going to buy it. Someone who rides 5 days a week year round in the Peak probably would (hardly a surprise that 18bikes make a gearbox bike).
It's the opposite end of the bell curve from the guy who buys an e-mtb to keep up.
These days I still think there's a problem with common mounting standards, or a lack thereof
I think part of that problem is the inevitable miniaturization that's ongoing. A DJI is tiny compared to an early Bosh CX for example. You could probably mount a DJI and a Pinion in the space early motors took up. But DJI won't want to give up one of their USP's that it integrates so neatly into frame designs, and vice versa others won't want a 'universal' standard they can't adopt.
More and more oldies are running SS conversions on their DHs, 3 out of 4 of my regular DH riding mates have gone SS on theirs, various bikes/manufacturers.
Well, if nothing else comes from the interest in gearbox DH bikes maybe it'll lead to manufactures making more jack drive DH frames.
Brooklyn Machine Works, ftw.
I think part of that problem is the inevitable miniaturization that's ongoing. A DJI is tiny compared to an early Bosh CX for example. You could probably mount a DJI and a Pinion in the space early motors took up. But DJI won't want to give up one of their USP's that it integrates so neatly into frame designs, and vice versa others won't want a 'universal' standard they can't adopt.
All well and good, but Gearboxes are kinda useless if frame manufacturers don't adopt them and really that needs a common mounting standard.
For all their flaws part of the reason that derailleurs are so ubiquitous is that the mounting interface has historically been common, customers don't generally end up rejecting a frame out of hand because they can't bolt their preferred SRAM/Shimano/Microshift/Campag mech on there... Even UDH recognises the need to allow cross compatibility...
Look at it another way would anyone buy an MTB in 2025 that used a proprietary brake mounting standard? Post mount is the defacto standard (for any modern MTB at least) and using anything else is a huge gamble for the frame manufacturer... Why should gearboxes be any different?
What the respective Gearbox manufacturer's would like is actually a bit irrelevant, they're not really in the driving seat here.
"Overall bike CoG is probably most important to overall speed etc.
But bike CoG maybe more important for "feel"
You are moving the bike around underneath you (or having it moved by external forces).
Realistically that is felt through the feet - so at BB height. So if the CoG of the frame is further above that point, it will feel like it takes more effort to move. Also the gyroscopic effects of the wheels are going to have an effect, and one that is applied at axle height."
My point (and I believe Seb's too) was that lowering the CoG of the bike makes it more agile because you're reducing the torque required to destabilise it. That also fractionally lowers the CoG of the whole system which means the system won't need to lean as much to stay balanced in a corner but it's a very tiny change - so much of the mass of the bike can't be moved (like the wheels and tyres) and even a small female rider is almost triple the weight of a DH bike.
Ebike motors aren't at all standardised but they seem to sell well. Gearboxes are heavy (which is a huge deal when trying to sell a bike even if it doesn't matter in the real world), expensive and apparently quite high drag. And it's only very recently that I've seen ones without gripshift. Derailleur gears do work rather well. I don't like them on my ebike because of how fast I wear out cassettes but changing that requires a new ebike with a gearbox too which are super rare and expensive.
