self tapping metric bolts

silva

Well-Known Member
Location
Belgium
Recently I came across a steel M5 bolt with Torx head in an aluminium part - a part of a Magura HS33 rim brake mount.
I tried to lose it and the bolt broke before it loosened.
It turned out that the aluminium part originally (new) had just a hole drilled in it, and the steel bolt then forced in along the way cutting its own thread. I've never seen this before on metric bolts.
I bought today a Magura mount set (25 euro) for just the broken part. And indeed, it comes with the bolt and the mount part as separate items.
This is thus a one way fixing. Once in (using alot force, risking Torx bolt head damage), never out.

Since I didn't want to risk forcing it in (this might need a machine doing it in once time), I decided to tap thread in the hole along a 3 tap set, one at a time, try the bolt each time, and I did have to use the last in order to get the bolt in.

Why would Magura opt for such a mount?
 

Phaeton

Grumpy Old Barstool
Location
Oop North (ish)
Cost saving
 

Moodyman

Guru
As above. It was probably the best bang for buck solution for them.

It's the same with cars. You can tell a good company when you're working on their cars.

I've had a couple of VW group cars and several Toyotas and the VW cars were a right pain to work on. They seemed to be unnecessarily complicated and not friendly for the DIY mechanic. Use of rivets where a screw or bolt would have been easier to remove.

It's one of the reasons I prefer my bikes with Shimano components.
 

wafter

Über Member
Location
Oxford
It's a cheap and nasty cost-saving solution, at the expense of the longevity of the component (as you've found).

In the applications I've experienced they come out OK, but IMO are far more prone to thread wear / stripping than a proper tapped hole.

Wouldn't touch any products with such fixings with a barge pole tbh - good work on sidestepping the issue with yours!
 
OP
silva

silva

Well-Known Member
Location
Belgium
A Magura HS33 brake set costs about a couple hundred euro's.
Cost saving 2 holes thread tapping versus drilling at such a price tag, that's beyond awkward.
 
OP
silva

silva

Well-Known Member
Location
Belgium
Nearly 2 months have passed since I replaced the broken mount of the Magura, and pre-tapped the hole in the replacement part. The dealers explanations on why not pre-tapped ranged from "no idea" to "to make the connection stronger". Well, I'm now 2 months braking with it, and no problem.
My rear brake still isn't working, the sole explanation is not enough oil in the system and there is no leak so the sole explanation for that is that this dealer didn't fill enough oil in it. And since after that 25 euro for that single broken part need, I refuse to spend any more on these so called low maintenance hydraulic brakes.

It just shows the crap they produce nowadays. That broken bolt fixes a brake cilinder. Not exactly something that never should be loosened. Still, apparently they aren't ashame to mount it like that.
And that dealer, apparently isn't either.
Contradicting himself every minute and hour. First answer on the reported problem: we have had a broken bolt a couple times over the years. Second answer when I said I didn't want an entire mount set just the broken part: "it's always the bolt that breaks and thus that part that is needed so we can't use the rest either". Sounds quite alot more frequent than that initial couple times over the years.

I said that I wanted the other cilinder / side also be removable, and proposed that HE would try to loosen the bolt, and if he breaks it too, replacement part cost his. I said I would do the rest (pre tapping, mounting, etc).
Unwillingness was next. :tongue:
 

Ajax Bay

Veteran
Location
East Devon
I think you blame others too much for your bad 'luck', maybe some of it self generated.
But I appreciate that you probably get therapeutic benefit by sharing your interpretations of your interactions with all the inadequate suppliers/dealers/mechanics with whom you've chosen to deal.
Your tales of woe are outliers (ie I haven't read similar stories from others) but maybe others suffer without sharing. I'd like to learn from your experiences but I'm not sure what the lessons identified are.
 
OP
silva

silva

Well-Known Member
Location
Belgium
I think you blame others too much for your bad 'luck', maybe some of it self generated.
But I appreciate that you probably get therapeutic benefit by sharing your interpretations of your interactions with all the inadequate suppliers/dealers/mechanics with whom you've chosen to deal.
Your tales of woe are outliers (ie I haven't read similar stories from others) but maybe others suffer without sharing. I'd like to learn from your experiences but I'm not sure what the lessons identified are.
I think you're defending ppl doing bad jobs trying to hide it, too much.

Lessons, haha, well I've one, make sure they do the job well or bike and money back. How: by a written down and both signed list of your demands, and the price agreed. That's how companies deal with eachother.
Based on all previous experience, I wanted to do that, but the dealer maneuvered out by saying that the engineers (that were gonna determine the needed bike components) at the bikes producer needed something to work with.
Seen afterwards, a comedian case, since the bike was delivered with a 5 mm wrong chainline, a drivetrain that wore out in a month usage, a rear tyre that ran 5 mm out of the fronts trail, a drive side crank mount that worked itself lose and needed to be loctited, a hydraulic brake line that had a mount in a turn so tight that it broke there, crank thread damage, a 3/32" instead of 1/8" chainring, my heel hitting the bikes stand, a too narrow rim tape causing a flat, and the storyline didn't change afterwards (even the socalled bombfree wheel whose rim cracked entirely 'round).

Luck?
Self-generated?
Lol?

The dealer (and whom he's dealing for) sold me a mockup bike priced 4300 euro.
Be sure I warn other people, and next time you dare to blame me, the customer, for this crap I'm gonna end my line of tolerance and start sticking names as to raise a warning flag for potential further victims. Something that I actually should already have done from the first problem. A bike price-tagged delivered like that, it's a shame.
 
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