Broken 373 Bolt

The head of the bolt 373 is broken
I need to know how to unscrew this bolt without making any damage
Do you have any idea if this is a commercial part?

It should be possible by removing the axle (340-08), ,coming from the other side (bolt 379) I guess ?

373 bolt dimension:
M8 x 16 mm (pitch 1,25 mm) wrench size 13 mm

Usual bolt, but beware of the strength class, shown on the bolt’s head ( 8.8 )!

Please do not use bolts without class number.
Please do not use bolts classified below 8.8, they are too weak and might break ( 4.6 or 5.8 )!
Of course you can use bolts classified above 8.8 ( i.e. 10.9 ).

Recommended torque: 18-20 Nm
according to page 14 of the OM 2008
“+rite-lok TL70” means you have to secure the bolt by using a thread locking compound :wink:

Thanks …
Finally I was able to remove the broken bolt on a lathe
I could find a 8.8 bolt and will try to get a harder one
As you said recommended torque is to be 20 Nm
Be aware to follow this and avoid any damage
Good ride :wink:

Happy you solved the problem,
further questions always welcome :smiley:
Good ride!

Actually StridaSilver, stick to the exact OEM bolt (8.8 grade).

Putting in a higher strength bolt does not make for a higher strength joint: the existing recommended torque will not be enough to stretch the higher strength bolt into its elastic clamp region. Paradoxically, it may fail in bending fatigue through not being “stretched”.

All the best.

I’ve installed a 10.9 bolt @ 19 Nm using locktite
In order to install the 8.8 bolt I need to unscrew the previously installed bolt
The bike is working fine for now and I am afraid of breaking the bolt again
I will keep it like that and in case it fails I will submit feedback
What do you think?

Hello Minkair,
Hello StridaSilver,

last week I’ve spoken with a bike-mechanic about the strength classes.
He said that Minkair’s explanation is absolutely correct, if you are looking at an “ordinary” screw connection.
(“Ordinary” means : Part B contains a thread, Part A a drill hole. By mounting the parts together will the bolt pass the hole.)
Appearing shear forces will take effect directly to the bolt.

But, as you can see below, the special construction of the Strida rear joint (in conjunction with the rear wheel axle) cannot be seen as an “ordinary” bolt connection.

For the first, because the axle 340-08 wents completely through the bottom tube - any appearing shear or bending forces would be transferred to the axle, not to the bolt.

For second, please note that the big, second “washer” below the bolts head is actually not a simple washer. The big corrugated disc is a cup spring (disc spring, spring collar), which is strongly pressing the bottom and seat tubes together.
Regarding the construction details, we do not think that there will be any shear force applied to the bolt.

(Both of my Stridas are, against the drawing, equipped with one cup spring, therefore I don’t know the correct part number, 363 or 367)

Might it be possible that the pictured bolt connection is different from older Strida versions?

Dear Minkair, what do you think about it?

If you are unsure, fix the original bolt class, as Minkair suggested.
However, a 10.9 bolt is for sure a better choice than a bolt without class number (or 4.6).

Btw, does your Strida make clicking noises sometimes?
(like mentioned here: [url]Strida 5.0 "clicking" noise] )
Would be a good reason to change the bolts…
Both Stridas had these noises, by braking the sharp edges of the cup spring they were gone :wink:

The bolt will not break by carefully mounting or unmounting… :slight_smile:

better quality here:

Thanks for your replies Minkair and BlackStrida,
I could hear an annoying sound every pedal turn.
This was solved by increasing the clearance between the bolt 464 and the rear wheel.
What I do have is a weird clicking sound between the seat base and the seat tube.
It feels like it is too loose even after tightened it.
Cheers and thanks again,

BlackStridaAustria makes some good points, this is actually a rather complex bolted joint with the disc springs. I do have 2 Belleville springs (cup springs) on my 2009 strida, they appear identical so are just two springs in series.

Regarding creaks, i have just solved an annoying rythmic creak when pedaling hard, the noise was coming from the lower steering joint (where the bottom tube drops onto the spigot on the steering tube).

Loosened the two allen screws that hold the spigot, went for a short ride. creak was gone. Tightened the spigot in its new relaxed position and repeated the ride -creak permanently gone.

Maybe us hi-milers should put together a ‘book of creaks’ to supplement the bare manual?
The one joint that seems to give no trouble is the spherical joint at the handlebars, at least noise-wise.

Hello Minkair,

many thanks for your reply.

Very interesting to hear about the spigot bolts, you presented another noise problem solution -thanks again!

As we all know, the manual is outdated for a long time, if Ming does not release a new edition, we will have to do that ourselves, I want to suggest here.
It would be great, especially for newbies, to find concentrated information in a (online) manual.
(Btw, what about an update of this site:

The last noise source, discovered on both Stridas, is the chattering of the rear brake hose in the seat tube (usually at higher speed or bumpy roads).
Does anybody know a solution for that?

Kind regards,


The last noise source, discovered on both Stridas, is the chattering of the rear brake hose in the seat tube (usually at higher speed or bumpy roads).
Does anybody know a solution for that?

easy :smiley: push the cable in (from top or bottom) so it rests on the inside of the tube surface, or vice versa (pull it to tighten) … this is the flip-side to a ‘cable-less’ appearance … which is now pretty fashionable :wink:

also … Still out dated, but more candid is mark’s Tips: … ge=manuals
also check out manuals on same link going back to Mk1. This includes a good guide to selecting spring washers for the bottom to rear tube joint under 373 Bolt - the aim is to have a stack of washer thickness’ from the large diameter nylon washer between the tubes to the 373 bolt, which bottom out on the axle. The aim is to get a joint which is stiff, and does not fall to the ground, jet also OK to fold.

good luck - all you axle fiddlers :mrgreen:

Dear guest,

many thanks for your worthwhile hints :smiley:
I’ll try the cable trick ASAP.

Best regards,


Old thread, but I can confirm that this was a solution also for me. I had a similar rythmic creak on my Strida LT and after much tinkering and pondering found out that the issue was exactly as Minkair describes. Cheers!