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[Bill822]

This video kind of spooked me. Has anyone else broken an SR/F belt or even heard of one breaking?
The worrying part was that he was on a flat and level road, not jumping curbs or hitting a pothole. Start carrying a spare belt? Maybe so.

[DonTom]

This video kind of spooked me. Has anyone else broken an SR/F belt or even heard of one breaking?
The worrying part was that he was on a flat and level road, not jumping curbs or hitting a pothole. Start carrying a spare belt? Maybe so.

Read reply number 13 here.

But many belts last many thousand of miles.

Also, a small rock can get between the belt and the sprocket. Even while on payment.

But belts do not always break the same instant they are damaged. The damage can be done even before the belt is put on the bike. There are many ways to mishandle a belt. Such a prying on it, or even bending it smaller than the smallest sprocket that it will be used on. Such a belt may even last a few thousand miles before it snaps from the damage done months ago. Belts out of alignment can also cause problems. Many possibilities, and many of the reasons  are just based on pure bad luck. A belt can snap in it's first 50 miles just like it's possible to get a flat tire in the first 50 miles. And that did happen to me on my DR200SE!  That was two days after I purchased it, hard to say when it  picked up the screw that I found in the tire. Could have happened right on the dealer's lot!  I will never know. Belts can be like that also.

The SR/F has a thicker belt than any other Zero motorcycle. I doubt them breaking will be more  common  than on  the other Zeros, and they really don't break that often. I put a poll here to find out for myself, see here.

I have around 7,000 miles on each of my Zeros and no belt problems yet (as I knock on wood).

-Don-  Auburn, CA

[ESokoloff]

This video kind of spooked me. ..........
The worrying part was that he was on a flat and level road, not jumping curbs or hitting a pothole. ..........

I watched the video & saw that the road was quite bumpy.
How many times was that poor belt subjected to that rough road/strong exceleration combo?

I'm not saying that the belt design is not faulty, just trying to play devils advocate.

[NEW2elec]

I'm starting to wonder if a spring loaded dampening belt tensioner pulley added with a larger belt to absorb some of the stress of take off and pothole free spin and reload is needed.

[Shadow]

That silly sounding pop and whir when the belt snaps made me chuckle a good bit...     Anytime I've shredded through a DSR belt it sounded more like angry godzilla.

Rotational mass on the SR/F drive wheel is quite a bit more (at a guess?) from S/DS.

Wild conjecture: The motor drive logic really ought to have some kind of feedback loop with the ABS sensor so we're smoothly applying the desired torque within limits the belt can withstand.

Also see above written while I was posting. Mechanical or electronic, something has got to give?

[DonTom]

This video kind of spooked me. ..........
The worrying part was that he was on a flat and level road, not jumping curbs or hitting a pothole. ..........

I watched the video & saw that the road was quite bumpy.
How many times was that poor belt subjected to that rough road/strong exceleration combo?

I'm not saying that the belt design is not faulty, just trying to play devils advocate.

I would think traction control would solve the problem of bumps. If the rear wheel  spins freely (faster than the front), the motor should stop for that instant, releasing any belt tension.

-Don-  Auburn, CA

[JasonHC]

The fix is painfully easy.

Pontiac sold a million Grand Prix's with the slogan.

Instead of a 17mm itty bitty baby belt.

How about a nice wide one like any Indian or HD has.
22mm is about as small as they use, 25mm is very common, I think 38mm is the most commonly used size now, and there are millions of them on the road, and it's VERY rare for them to "snap" or "pop" off.

Wider is Better!

YES, ZERO designed the swingarm with no room for a wider belt. That was just dumb.

Honestly, I expect a complete recall for every SR/F. Since there is just no space for a wider belt, do just like the FX did, and put a chain on it.

[Moto7575]

A friend broke a belt twice in a row with a Zero S. The problem was the dealers mistake (excessive tension on the belt). That might have been the case for the S/R you bought.

[stevenh]

A friend broke a belt twice in a row with a Zero S. The problem was the dealers mistake (excessive tension on the belt). That might have been the case for the S/R you bought.

When I took delivery on my DSR in 2016, the belt was WAY over tight, I think this was common for a while (several of us had to decrease the tension after taking delivery around that time).  Once adjusted to the lower side of the specification, the belt lasted fine for over 10K miles, and 3.5 years.

Steve

[alko]

I'm starting to wonder if a spring loaded dampening belt tensioner pulley added with a larger belt to absorb some of the stress of take off and pothole free spin and reload is needed.

I've wondered the exact same thing. A tensioner pulley would be a great improvement!

[Richard230]

Don't forget that the motor sprocket is concentric with the swingarm pivot. That should prevent any changes in belt tension as the swingarm moves up and down. So I am not sure if a spring tensioner is going to help much while riding over a bumpy surface.  Also, don't forget that there have been a lot of DR Zeros riding around on very bumpy off-road tracks over the years and I can't recall anyone ever mentioning that they were stranded in the boondocks due to a broken belt.  So my guess is that belts are most likely to break due to over tightening, incorrect alignment, or environmental damage (rocks, chemicals like road salt, etc.) - all of which can be checked and corrected by the owner.

[alko]

Don't forget that the motor sprocket is concentric with the swingarm pivot. That should prevent any changes in belt tension as the swingarm moves up and down. So I am not sure if a spring tensioner is going to help much while riding over a bumpy surface.  Also, don't forget that there have been a lot of DR Zeros riding around on very bumpy off-road tracks over the years and I can't recall anyone ever mentioning that they were stranded in the boondocks due to a broken belt.  So my guess is that belts are most likely to break due to over tightening, incorrect alignment, or environmental damage (rocks, chemicals like road salt, etc.) - all of which can be checked and corrected by the owner.

I disagree with your assumption that belt tension doesn't change with movement of the swingarm. Under heavy acceleration, sharp bumps and potholes can hugely increase stress on the belt. Whether it's enough to snap a belt, It's probably a combination of other factors as well, but under the right conditions it can happen. A belt tensioner would prevent it even if it's a rock, twig stuck in the belt.

[NoMoreIdeas]

This could have been a lot of things that werent Zero's fault. Overtightened belt, mis-alligned rear wheel or just a faulty belt. Its the dealers responsibility to go over the bike between the time its taken out of the crate and into a customer's hands. In my experience, my zero was delivered with a mis-alligned wheel which created an awful noise for quite some time before I figured it out.

[DonTom]

This could have been a lot of things that werent Zero's fault. Overtightened belt, mis-alligned rear wheel or just a faulty belt. Its the dealers responsibility to go over the bike between the time its taken out of the crate and into a customer's hands. In my experience, my zero was delivered with a mis-alligned wheel which created an awful noise for quite some time before I figured it out.

I have noticed on my 2017s, that Zero over-tightens everything. Nothing near their own suggested torque values.

-Don-  Auburn, CA

[NEW2elec]

 A few tests meant to snap the belt under a spin up and wheel stop under load while filmed with a slow motion camera to confirm where the belt snaps would be needed.
For now I'll assume it's at the top near the rear sprocket.  That seems to be the point where the sprocket is no longer holding the belt's teeth in place and so that part of the belt is under the most stress while the motor pulley is still spinning and a point where the belt can stretch and break.
A tensioner pulley would attach to the swing arm in my mind.  The belt would have a larger circumference and the added slack would be taken up be the tensioner pulley at the (assumed) weakest point.  As the added tension of a spin up and reload happens the belt would pull against the pulley and the extra slack would be used as a cushion until the pulley rebounded and takes the slack back out of the belt line.

Could the correct spring tension be found that works with the set up?  That's the hard part.

As it is now I would think that "this" bike's problem is likely having the belt at the wrong tension to start with but if a tensioner pulley could work it gives you a greater margin of error.