Any issues with shimano 8000 motors throwing cranks !

Simon

New Member
May 23, 2019
11
2
Sydney Australia
G’day all anyone’s shimano 8000 motors having issues with cranks not staying on ! After getting my warranty replacement motor it’s throwing the crank arms of ! I’ve been through 3 lefties & one right now ... it’s becoming a serious issue as I can not commit to anything as I feel as though my crank is going to wrigle loose ! I’ve spoken with shimano Australia ?? & they are investigating the matter! All I want to do is ride & get sendy with my trail slaying machine ? any help would be greatly appreciated.
Cheers simmo.
 

Jonnymac

Member
Feb 21, 2019
40
54
Inverclyde
Yes. I've experienced it with both the original XT cranks and my 155mm Miranda cranks as have 3 of my mates who have E8000 equipped bikes. Even with thread lock it still happens. Checking crank bolt tightness is now part of my pre-ride check before every ride unfortunately.
 

Gary

Old Tartan Bollocks
Author
Subscriber
Mar 29, 2018
10,496
10,685
the internet
Should have said. I had the LH crank come loose and fall off on my first E8000 motor. the above solved the issue and I've done the same on every motor since and had no issues with cranks loosening at all.
The plastic threads on the OEM preload caps just don't hold a loose crank on the splines.
(that's not their job. They're made of plastic to avoid owners overtightening them on standard HTII cranks but unlike standard HTII cranks E8000 cranks don't need to be adjusted for correct bearing preload. So you can do up the Alu caps a little tighter.
it's a PITA most Alu caps use a 10mm allen key though.
I carry a short 10mm adapter bit rather than a big allen key in my tools on the bike (just incase).
 

Jonnymac

Member
Feb 21, 2019
40
54
Inverclyde
Just noticed another thread on the site regarding the same subject and they suggest using longer (35mm) crank bolts. Might give that a go too.
 

smokey_jo

Active member
Patreon
Jun 28, 2018
123
75
Uk
Had the same with mine - managed to get just enough purchase on the plastic ones for them to have stayed on for a while now but they will be replaced by alu ones next time they fall off.
 

Simon

New Member
May 23, 2019
11
2
Sydney Australia
Yes. I've experienced it with both the original XT cranks and my 155mm Miranda cranks as have 3 of my mates who have E8000 equipped bikes. Even with thread lock it still happens. Checking crank bolt tightness is now part of my pre-ride check before every ride unfortunately.
Yes. I've experienced it with both the original XT cranks and my 155mm Miranda cranks as have 3 of my mates who have E8000 equipped bikes. Even with thread lock it still happens. Checking crank bolt tightness is now part of my pre-ride check before every ride unfortunately.
Yeah that’s what I’m doing but it’s driving me insane ! & I also got little metal end cap bolts today instead of the plastic! It held up today fingers crossed ?
 

Simon

New Member
May 23, 2019
11
2
Sydney Australia
Should have said. I had the LH crank come loose and fall off on my first E8000 motor. the above solved the issue and I've done the same on every motor since and had no issues with cranks loosening at all.
The plastic threads on the OEM preload caps just don't hold a loose crank on the splines.
(that's not their job. They're made of plastic to avoid owners overtightening them on standard HTII cranks but unlike standard HTII cranks E8000 cranks don't need to be adjusted for correct bearing preload. So you can do up the Alu caps a little tighter.
it's a PITA most Alu caps use a 10mm allen key though.
I carry a short 10mm adapter bit rather than a big allen key in my tools on the bike (just incase).
Carrying this at all times now

C57836A2-C6D1-40C3-A175-D32B509DEDF0.jpeg
 

Gary

Old Tartan Bollocks
Author
Subscriber
Mar 29, 2018
10,496
10,685
the internet
Ah.. you got shimano Alu caps.

Using most multitools and a little ingenuity you can also tighten/undo those. Eg. using the flat blade screwdriver/bottle opener/spoke key or even an allen key jammed into the spline at an angle ;)

I just have super cheap 10mm allen key ones from ebay
 

Eckythump

Well-known member
Founding Member
Jan 16, 2018
832
680
North Yorkshire
Are the preload caps even neccesary at all on M8000 motors?

If so, why?
The caps needing to be installed seems daft. Having said that the only times my cranks have worked their way off is when I have previously taken the cap out to use a crank stand and forgotten to put it back in.
Cue crank dropping off yesterday ?
 

tonyker

Member
Jan 28, 2019
48
28
Surrey
I had this issue and thought it was just me. after torquing the cranks to the required amount they still kept coming off then went higher and higher still coming off.

Then got the ali caps and now all good!
 

Gary

Old Tartan Bollocks
Author
Subscriber
Mar 29, 2018
10,496
10,685
the internet
Don’t the original cranks come with a little lock clip to stop them falling off if loose? Did you remove that?

Gordon
That little clip is only a thin plastic spacer with a tab. It's not secure enough stop a loaded crank falling off.
E8000 cranks that do fall off often aren't actually even particualrly loose. (pinchbolts still tight enough they need loosening to replace the crank arm on the spline)
what is actually happening is the crank arm is "walking" on the splined axle under load/flex.
The STUPID plastic shimano HTII pre-load bolt/cap with it's weak plastic threads then deforms as the crank walks and flexes, gradually walking the crank arm right off the axle. As the pre-load bolt lossens it will occasionally fail completely at the threads and the little clip also being plastic deforms/fails/pops out when the crank ejects itself from the axle.
The reason an Alu HTII pre-load bolt/cap fixes the issue is because it does not deform so easily and the threads are stronger so can be nipped up tight enough it's holding the crank arm tight(er) to the axle (less flex). Also when the crank pinchbolts nip down on the alu cap they actually hold it in place. unlike the STUPID plastic ones which deform.

The reason shimano make those caps/bolts from plastic is to deter home mechanics from over tightening/pre-loading their HTII BB bearings.
when an E8000 crank is pushed on to the BB/Motor axle with the HTII pre-load bolt/cap the crank doesn't add pre-load to the BB/motor bearings so there's no need for it to be plastic. infact it being plastic is the entire reason multiple cranks are falling off.

Sort it out SHIMANO, eh?

@Eckythump also see above
 

Simon

New Member
May 23, 2019
11
2
Sydney Australia
That little clip is only a thin plastic spacer with a tab. It's not secure enough stop a loaded crank falling off.
E8000 cranks that do fall off often aren't actually even particualrly loose. (pinchbolts still tight enough they need loosening to replace the crank arm on the spline)
what is actually happening is the crank arm is "walking" on the splined axle under load/flex.
The STUPID plastic shimano HTII pre-load bolt/cap with it's weak plastic threads then deforms as the crank walks and flexes, gradually walking the crank arm right off the axle. As the pre-load bolt lossens it will occasionally fail completely at the threads and the little clip also being plastic deforms/fails/pops out when the crank ejects itself from the axle.
The reason an Alu HTII pre-load bolt/cap fixes the issue is because it does not deform so easily and the threads are stronger so can be nipped up tight enough it's holding the crank arm tight(er) to the axle (less flex). Also when the crank pinchbolts nip down on the alu cap they actually hold it in place. unlike the STUPID plastic ones which deform.

The reason shimano make those caps/bolts from plastic is to deter home mechanics from over tightening/pre-loading their HTII BB bearings.
when an E8000 crank is pushed on to the BB/Motor axle with the HTII pre-load bolt/cap the crank doesn't add pre-load to the BB/motor bearings so there's no need for it to be plastic. infact it being plastic is the entire reason multiple cranks are falling off.

Sort it out SHIMANO, eh?

@Eckythump also see above
Couldn’t agree more ?
 

Spiff

Active member
Feb 27, 2019
409
232
Earth
The eBay descriptions state left hand because in analog bikes with Hollowtech2, right crank arm is attached to center axis and does not require the cap, it is only required in left side.

According Shimano doc, HT2 left and right bolt use the same standard thread so I purchased 2 "left side" caps, but I have not installed them yet ( if it ain't broke, don't fix it)
 

HORSPWR

E*POWAH Master
May 23, 2019
847
674
Alice Springs, Australia
The eBay descriptions state left hand because in analog bikes with Hollowtech2, right crank arm is attached to center axis and does not require the cap, it is only required in left side.

According Shimano doc, HT2 left and right bolt use the same standard thread so I purchased 2 "left side" caps, but I have not installed them yet ( if it ain't broke, don't fix it)

Cheers, I’ve got 155 Miranda crank arms on the way so I’ll fit a pair of these at the same time.
 

HORSPWR

E*POWAH Master
May 23, 2019
847
674
Alice Springs, Australia
Fitted the Alu caps with Miranda cranks a couple of months ago and had no further problems with cranks since doing so.

Has anyone else noticed that the machined step on the ebay aluminium caps is larger than whats on the Miranda crank and doesn't actually sit in properly flush, looks like that step needs to be about a mil smaller in diameter.
 

KenX

E*POWAH Master
Jul 21, 2019
287
245
Briançon, France
Has anyone else noticed that the machined step on the ebay aluminium caps is larger than whats on the Miranda crank and doesn't actually sit in properly flush, looks like that step needs to be about a mil smaller in diameter.

Yes, same for me! Just worked the cap in by rotating back and forth until it was seated, can't get a better fit than that :sneaky:
 

Miguel.975

Member
May 14, 2020
26
3
ES
Hi everyone. I've just had the same problem with the left crank that you describe. It has happened a couple of times so that the internal thread of the crank has worn out. I lost the plastic bolt twice and I have bought an aluminium one from Amazon. By the way, the warranty covered new cranks but they haven't arribes yeti.
Did you manage to solve the problem completely by installing the aluminium bolt?

Thanks a lot
 

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