# Broken Bosch motor mount bolts!



## Internal14 (Jan 21, 2004)

So....customer brought his Scott Strike in which has the Bosch Perf. CX Gen4 motor. 
complained that the chain was being 'thrown' under acceleration. I took it for a spin and could tell the whole unit was shifting around. 
Pulled the cover off
Loosened the large six bolts which thread into thin brackets that themselves are bolted to the CX motor by some slightly smaller than 6mm hardened bolts 
Three out of the four bolts were broken damnit Leaving behind hardened steel shafts in the alloy body of the motor.
Anyone seen anything like this before?? Any magic remedies for getting these broken bolts out?

joy


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## blueglide (Apr 23, 2020)

Drill appropriate size hole for EZ Out...before using extractor drop of liquid wrench in each hole and let sit for couple hours. Use heat around each motor mount boss followed by EZOut. Good luck


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## RickBullottaPA (Mar 4, 2015)

blueglide said:


> Drill appropriate size hole for EZ Out...before using extractor drop of liquid wrench in each hole and let sit for couple hours. Use heat around each motor mount boss followed by EZOut. Good luck


I would make certain that you are SUPER careful to not get drill tailings/metal bits from drilling for the EZ Outs into the motor/drive system. That could be a real mess. Drill in a position that minimizes bits falling into the motor, and use a combo of a magnet and vacuum to get out any junk or do whatever you need to do to ensure no metal fragments are left behind.


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## Salespunk (Sep 15, 2005)

Personally would not touch that project. Let the manufacturer take on the risk of the fix, there is simply too much that could go wrong.


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## wschruba (Apr 13, 2012)

Center punch the stubs carefully, and start a hole with a small bit (1-1.5mm). Enlarge the hole until you reach the size for the easy out (smaller size is typically 2-3mm). You'll need carbide or cobalt-steel (not coated, cobalt steel alloy) drill bits, lots of lubricant, low rpms, and some good feed pressure to cut into the screws without problems.

Before using the easy out, get a soldering iron hot, and touch to the screw you're removing for 10 seconds or so. This will break the loctite remnants free, and you should be able to remove the last bits without issues.

Unless something has changed, all of the mounting points on the Bosch motors are blind, aka, don't go into the motor compartment.


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## Taroroot (Nov 6, 2013)

wschruba said:


> Center punch the stubs carefully, and start a hole with a small bit (1-1.5mm). Enlarge the hole until you reach the size for the easy out (smaller size is typically 2-3mm). You'll need carbide or cobalt-steel (not coated, cobalt steel alloy) drill bits, lots of lubricant, low rpms, and some good feed pressure to cut into the screws without problems.
> 
> Before using the easy out, get a soldering iron hot, and touch to the screw you're removing for 10 seconds or so. This will break the loctite remnants free, and you should be able to remove the last bits without issues.
> 
> Unless something has changed, all of the mounting points on the Bosch motors are blind, aka, don't go into the motor compartment.


Also look for left handed drill bits, some screw extractor kits come with one.


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## jona-Strive (Jun 15, 2018)

I have the same issue on my bike (Cube stereo Hybrid 2020 model)
was this also on a Cube? EDITTED i just saw that you wrote it was a Scott Strike (meaning that the brackets are part of Bosch motor,and most likely used on all bikes)
Were you able to fix it?
First I had right side bracket and now it's the left. last time the screw was sticking out long enough i could remove it with pliers.
now not so lucky
I ordered EZ out left tapping and a TS (torx with 5 points and hole) bits for te screw that wasn't broken.


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## Lopaka (Sep 7, 2006)

Should have used a pedal assisted ratchet.


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## jona-Strive (Jun 15, 2018)

Lopaka said:


> Should have used a pedal assisted ratchet.


Sorry don't understand what you mean


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## PierreR (May 17, 2012)

Use cobalt drills only. Not High Speed Steel. Preferably a left hand drill. High Speed Steel can be used but you have to go really slow with the drill speed and plenty of cutting oil. DOT 3 brake fluid doe not work bad for cutting oil but takes off paint.


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## jona-Strive (Jun 15, 2018)

Hi 
I ordered the special torx bits and the EZ out dings. in the meantime i tried to drill a hole (after Center punching it) and the screw is remarkable soft. drilling wasn't that hard i guess could explain why the screws broke in the first place. 








I'll keep you postend on progress


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## jona-Strive (Jun 15, 2018)

i replace the screws with stronger ones ( tensile strength 10.9) also it is important to NOT use stainless steel as this can cause contact erosion of the magnesium housing. I use zinc plated steel screws:


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## jona-Strive (Jun 15, 2018)

i i bought such left taps (ez out). Used drill 2,5 mm. Success


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## GrandpaMark (Dec 14, 2021)

jona-Strive said:


> i replace the screws with stronger ones ( tensile strength 10.9) also it is important to NOT use stainless steel as this can cause contact erosion of the magnesium housing. I use zinc plated steel screws:
> View attachment 1912267


Do you have the specs on those bolts you replaced the broken ones with?


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## jona-Strive (Jun 15, 2018)

GrandpaMark said:


> Do you have the specs on those bolts you replaced the broken ones with?


ISO number 7380-2


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## GrandpaMark (Dec 14, 2021)

Thanks. Do you know the length, thread pitch, etc.?


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## jona-Strive (Jun 15, 2018)

1


GrandpaMark said:


> Thanks. Do you know the length, thread pitch, etc.?
> [/QUOTE
> i used 10 mm M5 (normal pitch)


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## GrandpaMark (Dec 14, 2021)

jona-Strive said:


> 1


They're actually M5x16x0.8mm


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## Trijiconzero (12 mo ago)

Hello,

I also own ebike with Bosch Performance Line CX Gen4 and experienced through trouble you guys did.

My case,mounting plate has been broken to two pieces and after I checked how parts looks like,I think it is too thin to hold motor and weight road of rider's.
If design allow to add more thickness it would be better but there are very limited space to add.To reinforce it,using harder and stiff material such as tool steel(S45c) with heat treated.

Original one seem to use stainless steel,tensile strength is like 500n/mm.S45C with heat treated is like 700n/mm which is 40% stronger than usual S304 stainless steel.

I am thinking about producing reinforced mounting plate using heat treated S45C,but making just one qty cost a lot.Is there someone else has interest in parts like this?


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## GrandpaMark (Dec 14, 2021)

It turns out the Bosch warrantied my motor and amazingly the replacement arrived in 1 week! I had already repaired the old one but never got a chance to install it. Every now and then things work out the way they should...


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## mhj.notenboom (11 mo ago)

Trijiconzero said:


> Hello,
> 
> I also own ebike with Bosch Performance Line CX Gen4 and experienced through trouble you guys did.
> 
> ...





Trijiconzero said:


> Hello,
> 
> I also own ebike with Bosch Performance Line CX Gen4 and experienced through trouble you guys did.
> 
> ...


I am interested. LMK


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## dyounggolfmaster (6 mo ago)

jona-Strive said:


> I have the same issue on my bike (Cube stereo Hybrid 2020 model)
> was this also on a Cube? EDITTED i just saw that you wrote it was a Scott Strike (meaning that the brackets are part of Bosch motor,and most likely used on all bikes)
> Were you able to fix it?
> First I had right side bracket and now it's the left. last time the screw was sticking out long enough i could remove it with pliers.
> ...


Jona,

Thanks for all the great detail about the extraction process. What specific torx bit did you use? The security T25 torx bit I had and the one's I bought the hole was too small. 

Thanks,

Daniel


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## jona-Strive (Jun 15, 2018)

it's not a 'normal' torx(6point star). it's a TS-variant with 5 points
like this








Which size it actually was, i can't recall. i bought a set


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## elder_mtber (Jan 13, 2004)

Torx Plus is the name. Odd, seems it should be Torx Minus.


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## jona-Strive (Jun 15, 2018)

elder_mtber said:


> Torx Plus is the name. Odd, seems it should be Torx Minus.


sorry that is not correct, torx plus has 6 point-star. on the bosch motor (at least on mine) has screws with 5 point-star. see photo and link in previous post.
those are called TS


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## elder_mtber (Jan 13, 2004)

Ahhh - I stand corrected.

But it appears I am not the only one who has misunderstood the characteristics of Torx Plus. The screen grab is from Insight Security.

Seems my humor attempt was a failure. 6 lobes vs 5 lobes = minus one lobe, hence Torx Minus. Ha, ha. Gotta laugh at my own dumb-ass joke.




*Tamper Resistant Torx Plus Drive*
The tamper resistant Torx Plus Drive variant (security Torx) uses a pentalobular (five point) design with a solid security pin at the centre of the recess. All of the Torx Plus benefits are included in the tamper resistant version along with additional security provided by the 5 lobe design with a central security pin.


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## leogonzalezc (5 mo ago)

Hi, i need to know how torque (Nm) is necessary to thight this torx plus 25


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## Galenbo (Aug 3, 2020)

Highly controversial, and widely unknown.
When steel bolts break into an aluminium housing, we weld them out.

On racecar aluminium cylinder heads, M8 even when the bolt broke off 5mm inside. With great success.
But there are several prerequisites: The person who does it has to be a good welder, open for discovery, and preparation is crucial !

Possible when a steel bolt broke off in a steel housing too, but a bit more difficult and risky.


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