Belt drive wading through treacle

steelyinterests · February 2020

I have been riding around in a Cube Hyde pro 2019 for about year now. It has a Gates carbon belt drive (CDN) coupled to a shimano alfine 8 hub. It came with 28" - 55mm balloon tyres because it has a rigid aluminium (?) fork to help with some suspension. The bike also weighs quite a bit: 13.7 kgs which I, stupidly, did not check when I bought the bike. I have added a pannier rack (0.5kg?) and mudguards (0.5kg?) to it. The major attraction was the touted low maintenance which it has largely been apart from tyre flats. The hub has been brilliant.

The big issue I have is that I feel this drag while riding the bike. It feels very inefficient and I get tired in a way that my cheap £100 second hand Giant GSR trekking bike with a chain drive doesn't, inspite of its shattered components. I fear that this load due to drag is wrecking my knee a bit which was already not up to scratch; I separately created another post asking for advice on bikes for bad knees and received a few, much appreciated, tips. I am thinking of getting rid of the cube bike and getting a light bike with gearing to support high cadence riding. Sadly, that might mean no alfine.

Have people who have owned belt drives experienced the same thing? Does anyone think that the belt tension is incorrect? I will probably take it to the shop for an annual service and explain the problem, and ride it around a bit more before I get rid of it.

Any thoughts would be much appreciated.

Mad_Malx · February 2020

It’s not the belt drive per se - the round the world record was set on a belt drive rolhoff a few years back. And vin cox did it with a chain drive Alfine I think, so I suspect the problem is something else. alignment ok?

fenix · February 2020

Tyres too low pressure ?
Brakes rubbing ? Lift each wheel and spin them.

thecycleclinic · February 2020

Tyres make a huge difference
13.7kg that's luxury. My commutor weighs in a 17.3kg with panniers. I can shift that at an 15 mph average without too much difficulty.

So the issue is likely to be a combination of factors. Position is number one. If your upright on this bike the any speed is going to be a battle unless gravity assisted.

mercia_man · February 2020

As someone with owning experience of bikes with hub gears and belt drive, I recognise the OP’s description of “riding through treacle”. There’s plenty on the internet spelling out the slightly better efficiency of a well maintained, properly adjusted, clean and lubricated chain and derailleur system compared with belt drives and hub gears. This advantage of chain/derailleur systems is negated if you don’t look after them, however.

In practice, I could feel the difference in efficiency when riding our Rohloff hub tandem. This was most noticeable in a couple of noisier lower ratios when the clockwork whirring sound of the teeth meshing together made you think you were working harder than you probably were. I can feel an even bigger “treacle” effect when riding my wife’s e-bike (power off) with Gates belt drive and Nexus hub gear.

To my mind, the advantages of hub gears and belt drive outweigh chains and derailleurs for certain applications such as all-weather commuting and round-the-world rides because they are reliable and virtually maintenance-free. They also make a lot of sense for e-bikes where any loss of efficiency is not noticeable when you have the power on.

But if you want that glorious feeling that every bit of effort from your legs is being transmitted smoothly and quietly into forward motion, nothing can beat a clean and well lubricated chain and derailleur system on a lightweight bike.

steelyinterests · February 2020

Mad_Malx said:
It’s not the belt drive per se - the round the world record was set on a belt drive rolhoff a few years back. And vin cox did it with a chain drive Alfine I think, so I suspect the problem is something else. alignment ok?

Looks fine to me. I checked again. Nothing weird.

steelyinterests · February 2020

fenix said:
Tyres too low pressure ?
Brakes rubbing ? Lift each wheel and spin them.

The tyres are pumped up to 50psi - max for the tyre. It rolls quite well and contact patch is quite small. I have tried other pressures too - trade-offs between comfort and speed.

My ride position is fine, I think. It is almost the same as the derailleur bike. Thigh to ground plane, saddle position etc., all seem to be fine as suggested by loads of videos and sites on the interwebs.

The front wheel spins quite well. The rear wheel, is another story. The nexus hub comes in to play here. It is no where near as the fluid spinning of a derailleur setup. I can quite clearly see the drag. But, I don't see the rear wheel rubbing the disc brakes; I could be wrong; needs a skilled pair of eyes here. As @mercia_man suggests, the drag is there and I clearly feel it. Somehow, it feels like a lot of drag!

The gates phone app seems to think that the belt tension is correct (measures the low frequency vibration of the belt using the mic when the belt is twanged). I think there needs to be huge error bars here.

I am pretty much at the limit of what of I can tweak with my limited tools and skills. I will book it in for service this week or next, and see what the mech has got to say.

asprilla · February 2020

I used to have a Civia Bryant with belt drive and Alfine hub. It's a heavy set-up and makes the bike heavy at the back end too. Adding a rack wont help that feeling either.

I found the hub drive to be inefficient too. That treacle feeling didnt go away, no matter what I did.

I changed mine for a fixed gear. Complete pendulum swing.

steelyinterests · February 2020

asprilla said:
I used to have a Civia Bryant with belt drive and Alfine hub. It's a heavy set-up and makes the bike heavy at the back end too. Adding a rack wont help that feeling either.

I found the hub drive to be inefficient too. That treacle feeling didnt go away, no matter what I did.

I changed mine for a fixed gear. Complete pendulum swing.

Hmm. I am going to get my cheapo Giant fixed up again just to be sure. Also, I have booked the Cube in for a service next week. We'll see what happens then.

raymondo60 · February 2020

I had a similar issue some years ago with a Trek Soho. After buying (and loving) the single-speed District, I was sold on the belt-drive set-up and thought the Alfine-geared Soho would make a good winter commuter. After several months I just gave up - I couldn't describe my issue as 'drag' specifically, just an overall feeling that the specs and weight of the bike were working against me. There were times when I had to stop and check my rear wheel wasn't fouled or something. In the end I just decided the bike wasn't for me.

N0bodyOfTheGoat · February 2020

I used a Saracen Pylon 8 alfine hub 26" hybrid as a commuter from 2008 until ~2014, it was a heavy beast to slog up the incline on the way home at ~14Kg back then when I was far less cycling fit than I've been for the last few years, but the easiest gears got me up there everyday eventually.

There's no getting away from heavier bikes are harder work up hills. The Alfine hub itself adds a fair bit of weight to the rear wheel compared to a cassette and rear derailleur, but on traffic light laden streets being able to change gears while stationary can be very handy.

Side pannier loads give you extra carrying capacity at the cost of a lot of extra aero drag, without googling isn't it reckoned to be ~20W power loss per side?

Wide tyres give you extra comfort, but at the cost of extra aero drag, especially the front tyre.

It will be intresting to see what you make of it after the service, especially if they do an oil change on the hub.

steelyinterests · March 2020

Here is some post mechanic's review info.

He thought that there was some minor brake rubbing on the rear wheel but not enough to cause the drag I talked about. He suggested higher tyre pressures. But after some more testing he reckons that there is nothing wrong with the bike. And the drag is the nature of the belt drive + hub gear bikes. The bike doesn't freewheel well either.

On his advice, I decided not to have it serviced it further to save me some money. It's a pity; the bike has been quite low maintenance except for flat tyres. All I can conclude is: think twice about belt drive.

The Giant has now been fixed with a full replacement of the drive train and some hard work by the same mechanic. I took a short ride on it - all seems well and much improved even. Returning to this bike for a while.

Thanks for all the help and suggestions.

Belt drive wading through treacle

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