Do carbon belts stretch?
 

Hi,

I'm thinking about buying a belt driven bike. But all bikes I've seen, have vertical dropouts. Like that:
https://www.boc24.de/images/products...457_0252-2.jpg

With chains, it doesn't matter how cautious you are, they always stretch and either the derailleur keeps the chain tensioned or you have a horizontal dropout to keep it in the proper tension.
I don't know much about carbon belts, so I'm worried if with time it will stretch and loose tension.
Anyone knows about that?

Also, recommendation on belt driven bikes until €1000 are welcome. But since this is going to be a daily use bike, eyelets for mudgards and racks are important. Also disk brakes are welcome.

in a metal chain, "Stretch" is a way of describing accumulated wear of its metal surfaces as a total increase in length.

bikes, in the eurozone? (I am in the US) German Tout Terrain is more than €1000, Especially with VAT included in that total.


Gates carbon drive-train components come to $500 alone, so i doubt you will find anything at your price,

unless its an Asian copy of the belt drive idea.



...

Drive belts are very sensitive to tension in that too little is a bad thing. But as a well designed belted bike has an ability to adjust the belt's tension so if any "stretch" does happen it's easily corrected for. Have you ridden a belted bike yet? They do feel a bit different IMO. Andy

Something that might contribute to premature stretch is the fact that too many people run cog belts way too tight. I worked with them on office machines for 47 years, and many made them way too tight.

The one I'm thinking about right now is this one:
https://www.boc24.de/shop/fahrraeder...cycles-cx-1000

No, I have never ridden a belted bike. I'm thinking about it because of the low maintenance. Specially considering the snow, mud and salt I'll have to face during winter.
What difference did you notice?

There's probably an eccentric bottom bracket to adjust belt tension.

IME, belts don't stretch- auto fan belts often run for their service life without being tightened.

That bike has an eccentric bottom bracket to tension the belt correctly therefore horizontal dropouts aren't needed.

Also, horizontal dropouts with disc brakes are... difficult to say the least. The caliper needs to move with the wheel. Therefore it's easier to put a eccentric bb into the bike instead unless you want to take surly's approach and have a way overengineered dropout.

We don't live in a dystopia like 1984.

Gates belts are polyurethane. A toxic NOT environmentally friendly concoction of man's modern excess. There is a marketing gimmick to refer to Gates belts as carbon, but they are what they are.

The belts don't stretch. They are very reliable.

However, from an efficiency perspective belt drive is significantly less efficient than chain drive. Nothing is as efficient as chain drive.

Do you want nearly maintenance free but less efficient?

I worked as a conveyor mechanic for 30 years (now retired..thank God). I never saw any of our "carbon" drive belts stretch. But, I've seen many of them snap. I wouldn't worry though, you won't be trying to drive a 24" belt from a dead stop with 500+ pounds of product on it. As for the ones that weren't marked "carbon", I've seen many of them shear off their teeth.

Efficiency is not my main concern. This is going to be a daily use bike, so I'm not worried about speed.
But low maintenance is very important to me. Bike shops are VERY expensive here and I want to go there as little as possible until I finish buying all the tools needed to be self sufficient.

Gates says that their belts use "Advanced no-stretch carbon cord technology."

Not sure how much of that phrase is engineering and how much is marketing.

Gates Carbon Drive? System for Bicycles | Gates Carbon Drive?

If you have 1,000 euros to spend on a bike, you can spend another 100 on tools. You really only need a 4,5,6mm allen, crank remover, pedal wrench, and normal screwdrivers for a modern bike. Since this bike has an eccentric bb, you'll need a pin spanner as well.

Everything else isn't really necessary until you have to do serious maintence to the bike (bearings etc.)

I find this statement particularly interesting.

I wonder why? Not for fixed gear bikes? Really? Not for high mileage bikes? Seems like they know their belts don't last long and can't stand up to lots of force.

With that said, the strongest mountain biker I know rode a single speed belt drive off road up significant hills, so it seems to work fine even in those situations.

they would perhaps be used and/ or Stolen . bring more money, or buy on credit.

or be able to repair a cheaper chain drive bike. while you look for a job that pays much better.

then get the higher end bike of your dreams..





....

Translating into engineer-speak:
"Recent low-stretch carbon cord technology."

So not radically different in this case.

I wonder if the fixed gear prohibition is because the belt won't tolerate the torque reversal during braking. As to the other disclaimers, it seems the belt has a lower torque limitations then a chain and, as you noted, long term durability issues.

That was my thought as well. It seems those belts have a directionality associated with them as one of the warnings is "don't reverse" but in more ambiguous terms. I wonder if the tooth shape isn't symmetrical.

IDK where you get your assumptions, Because, they make a threaded cog for fixies

21T Thread-on/Fixie CDX

Very interesting. I pulled my info from their "tensioning and handling" page where it clearly states that

I can only assume the "CDN" system is the carbon... drive....something. CDN isn't referred to elsewhere on the page.

Handling & Tension

EDIT: I got it. They have two different lines of products. A "rugged" product designed for fixies and off-road, and a normal product not "designed" for it.

Sounds like marketing hogwash to me.

Is reverse torque higher than forward torque? If so, how?

They are belted with carbon fiber cords. Obviously they must use a flexible poly as a belt material rather than rigid epoxy, but it is still a carbon fiber composite material just like the less flexible stuff they make airplanes and bicycle frames out of.

Took this guy 19,000 miles to break his first belt: Review: Gates Carbon Belt Drive Centertrack - CyclingAbout

Can't remember the brand but I've seen an LBS selling belt-drive single speed and 3-speed commuters for ~$600. So they're out there.

CDN belt is for urban/city riding which "offers a lower-cost option for the casual rider."
CDX belt is for "high-mileage touring, competitive racing, or rugged off-roading" and "performs in the harshest conditions."

Bicycle Belt Drive Products Overview | Gates Carbon Drive?

FAQs

My Priority Continuum uses the CDN belt. I've stood on the pedals and pushed hard to get up a few hills, and haven't had any problems. Granted, I've only had it a few months and am just now coming up on 500 miles, but so far no problems or concerns with the belt.

IKEA sell a belt drive bike and it is £400 in the UK. I doubt they sell many in the UK market because it is an unconventional design to British eyes (coaster brakes for example). Perhaps an easier sell in Continental Europe.

I think there is merit in the belt drive from an engineering perspective (it's not just marketing), but the fact that market share for belt drive is tiny (I think I have only ever seen one belt-drive bike being ridden) suggests that chain drive is doing a pretty good job.