Belt twisted twice

My 5 cents to put in. Belt twisted during starting on a green light:

Caught between snubber bolt and brake disc:

Some facts:
The belt is (relatively) new.
The freewheel is almost worn out, but there was no slipping yet.
The freewheel is contaminated with dirt, it is possible to rotate the rear wheel in both directions using pedals when the bike is upside down (and the pedals rotate when I walk the bike).
The snubber bearing is turning freely.
Belt tension was rather low (after belt snapping I have returned to ā€œnormalā€ tension).
I am far from weight limit for strida - my weight is ~75kg.

Part #338 is bent indeed (both the disc part and the stem - it now has partial internal thread from the bolt =))):

Since the belt is now doomed(?) anyway I think of replacing just the part #338 - to see if it is the only culprit or not.

Or I could replace part #338 and the freewheel and see if the once twisted belt is prone to subsequent twisting even if the culprit is removed.

What do you think?

Iā€™m sure that Bietrumeā€™s meaning is absolutely trustworthy:

Of course, we all would like to find out whatā€™s the initial reason for the twisting of the belt - if you change part nr. 338 and leave the old belt it couldnā€™t be verified if the initial reason was 338, because the belt might fail due to the above quoted reason.

If you replace 338 and freewheel itā€™s the same situation.

To find out if the culprit is really the 338 part youā€™ll need to replace the belt - and keep the old 338 part to see if the twisting happens again.
But doing that means also to damage a new belt (very probably), thatā€™s an ugly double windmill (translated with different words: ā€œto be caught between devil and blue seaā€ or ā€œcatch-22ā€).

Iā€™m really sorry but I canā€™t help to decideā€¦

However, one thing should be mentioned: The bolt 379 must not be overtightened, but it must be secured with bolt adhesive.
I mean the overtightening is the initial reason for the bending of the ā€œwasher sectionā€ (the narrow piece with the bigger diameter) of 338.

This belt is (was =) relatively new, so I think Iā€™ll:

  1. replace #338 and leave the current belt - to see if it will continue to twist. After it snaps/twists/exhibits some other abnormal behavior, Iā€™ll:
  2. replace the belt and see if it twists (with new part #338, but old freewheel).

That sequence should give more data about the problem.

What is the recommended torque for bolt #379? I was unable to find it in the manual.

You are right - it might have happened during rear wheel removal and installation in the field, when torque wrench is unavailable.

Sorry, no idea, usually I tighten the bolt very gently by hand, meanwhile Iā€™ve damaged two of the 338 parts :unamused:

Missing 379 torque was added to the improvement wishlist draftā€¦

Did you check it immediately after tightening or after riding?
Could it be that is it damaged not by tightening, but by the wheel movement?

Iā€™ve replaced #338 part and tightened #379 bolt with 5Nm torque - #338 part still looks good after unscrewing =) Will see what happens after riding thoughā€¦

On the black Strida Iā€™ve destryoed the 338 part definitely by too much force -
Iā€™ve mounted the wheel and wondered, while tightening the bolt, that it didnā€™t become firm.
Therefore the bolt was unscrewed again and I saw the deformed 338 partā€¦

On the silver Strida Iā€™m not 100% sure, but I believe it was the same reason.
I guess that any force, applied to the wheel via the tyre in axle direction, should be absorbed by the wheels flexibility.

Hmmm, here Iā€™m also unsure, sorry, but I think that the very gently tightening will be below 2 or 3Nm.
2Nm are the lowest amount which can be set on the BBB torque wrench, I do not trust the wrench at this range limitā€¦
Iā€™ll try to figure out a safe torque amount asapā€¦

According to Mingā€™s customer support the torque should be 6-8Nm.

Many thanks to Sara for the fast reply!

Ok, the belt still twists with new #338 part (3 times in a row today!), so now Iā€™ll replace the belt with a new one.

ā€¦and youā€™re sure that the 338 part (magnet spacer) is still OK?

Yes, #338 part is ok.

Long term feedback: No belt problems since the repair service in Vienna.
As I use my Strida about 11 km per working day - This means about 1.000+ km.

Now Iā€™ll have a problem with my rear break, but this is another story and yet to be investigated.

For comparison, stridahdā€™s freewheel next to a brand new one:


1600 x 1200


1200 x 1600


Wow, it wears very quickly (only 1000km!). Ming Cycles should definitely improve the freewheel design: better surface hardness and better sealing/friction of the bearings.

Is it a visual effect or is the outside diameter of the new freewheel really bigger than the OD of the used one (look at the size of the flanges)? I
f this is the case then the number of teeth is not similar :question:

No Bietrume, thatā€™s a misunderstandingā€¦sorry, my faultā€¦

The above shown freewheel is stridahdā€™s first one, the one weā€™ve changed together with Mike.

But, in fact, 3.000 km are also not that muchā€¦

Indeed, yes, hereā€™s a similar pic, taken 90Ā° to the left of the cam position before:

Interesting photographs :slight_smile:

You also have to add the fact that I am not lightweight and I used it throughout two winters without much cleaning.

PS: I fixed my break problem for now. The brake pads were worn and I had to adjust them. However I guess I will need some new within this year. Any suggestions for a shop with reasonable prices?

Maybe interesting:

Re: Rear disk brake wearing fast on 5.0

Re: Disc brake caliper lever bumps into caliper body

Just google for ā€œHayes MX2/MX3ā€, guess youā€™ll find these locally :wink:

Pic from Chainreactioncycles:

http://www.chainreactioncycles.com/Models.aspx?ModelID=8656

http://www.bikestore.cc/bbs47-hayes-mx2mx3-mechanical-scheibenbremsbelaege-p-119656.html

http://www.ebay.com/itm/DISC-BRAKE-PADS-HAYES-MX2-MX3-MX4-SOLE-/320604132340

Compared to the above, the original Strida pads are not that expensive, at least at Vanmoof; youā€™ll get 2 pairs for 20 ā‚¬:

http://vanmoof.com/shop/catalog/product_info.php?cPath=112_126&products_id=213

Thanks. They are even available with reasonable prices in the famous internet book store :slight_smile:

:laughing: yes!

After 2 years riding in the snow and rain the belt also twisted and torn.
Initially, I though it was due to excessive torque, so I could manage by avoiding steep slopes.
Now I need to replace my broken belt and it seems that I need to adjust the tension after getting a new belt.
I donā€™t know exactly how to do this, additionally my rear disk is also bent.

Well, beginning at the brake rotorā€¦
Unfortunately can a common brake rotor (without heavy mods) not be used, you will need an original brake disc.
At this opportunity to order spare parts you might also take a closer look at the snubber bearing, the 338 part (magnet spacer) and of course the freewheel.
The rear rotor is clamped by the freewheel, a special tool [size=200]T[/size]is required to remove it - do you have such thing?
As always, Iā€™d recommend the purchase of a hook key [size=200]A[/size] for proper belt tensioning
For convenient belt changing you might use the step 13 of this thread.
(There should be also a few hints for belt, snubber and rear brake caliper un/remounting :wink: )

Did you already check the local parts availability?