Is this crankset free enough?

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boxrick
Posts: 5
Joined: 2 Aug 2020, 7:23pm

Is this crankset free enough?

Postby boxrick » 24 Aug 2020, 8:29pm

I have just fitted a brand new GRX Crankset and Hollowtech Bottom Bracket making use of this guide, both are brand new

https://www.youtube.com/watch?v=QqBtB8Kyl2U&t=328s

Now when I spin it, it doesn't feel like its spinning freely enough. I did however try this without any pre-load applied at all and it feels basically the same. I was also extremely cautious with the amount of tightness I was applying.

Any advice or thoughts?




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andrewwillans49
Posts: 96
Joined: 11 Aug 2018, 7:38am

Re: Is this crankset free enough?

Postby andrewwillans49 » 24 Aug 2020, 10:03pm

Something not right there. I've never seen a crankset binding like that, ever.
Coincidentally, I was recently watching some YouTube videos of Hambini. His subject matter was bottom brackets. Well worth a look especially for the OP.

Brucey
Posts: 42931
Joined: 4 Jan 2012, 6:25pm

Re: Is this crankset free enough?

Postby Brucey » 24 Aug 2020, 10:07pm

IME if a HTII BB binds, the cause is often that the BB shell needs the threads chasing and the ends facing. If this hasn't yet been done, and there is no other cause apparent, I'd get the frame prepped properly and try again.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

boxrick
Posts: 5
Joined: 2 Aug 2020, 7:23pm

Re: Is this crankset free enough?

Postby boxrick » 24 Aug 2020, 11:10pm

I refit it all and the same sort of affect even with 0 tension on the preload ie it wasn't even inserted. From what I read, this is caused by fresh grease inside the bearings before it has been ridden properly and potentially quite normal? Especially once its under load.

This is a picture *before* I cleaned it, there was basically no dirt and the threads were perfect. I then applied grease to the threads and a little to the outer silver rim.

IMG_3759.jpg

tim-b
Posts: 1675
Joined: 10 Oct 2009, 8:20am

Re: Is this crankset free enough?

Postby tim-b » 25 Aug 2020, 5:59am

Hi
That looks normal to me, albeit I can't say that I've ever counted the number of revolutions on one of mine, and it doesn't help that it catches the inner cable. The pre-load needs to be as little as possible to remove play only. Does it feel smooth when you turn it?
Regards
tim-b
~~~~¯\(ツ)/¯~~~~

pwa
Posts: 13883
Joined: 2 Oct 2011, 8:55pm

Re: Is this crankset free enough?

Postby pwa » 25 Aug 2020, 7:44am

It is difficult to decide whether a BB is completely right sometimes because the new grease does sometimes make bearings a bit stiffer than they will be after some use.

Des49
Posts: 754
Joined: 2 Dec 2014, 11:45am

Re: Is this crankset free enough?

Postby Des49 » 25 Aug 2020, 7:51am

Looks fine to me and in line with what I have experienced. I fitted a couple of bikes with more expensive Hope stainless steel bearing bottom brackets and these were the same as the Shimano versions.

Fit the pedals and the cranks will spin a bit longer.

It is really difficult to tell if a BB is stiffer than it should be, no way to tell what it is like when under load during actual use.

I do find the Shimano UN square taper BBs spin a bit longer, a Chorus square taper sealed BB I ride spins much freer, then a loose ball cup and cone Dura-Ace BB spins most of all though this does vary depending on what grease I use.

bgnukem
Posts: 605
Joined: 20 Dec 2010, 5:21pm

Re: Is this crankset free enough?

Postby bgnukem » 25 Aug 2020, 12:28pm

When new, there is bearing seal drag to consider as well as drag created by the new grease to consider. Over time the seals will wear (unless kept lubricated by oil/grease - most people don't bother) while the grease thickener will break down and the grease become more fluid. I'd be more concerned if there is a 'tight spot' in the rotation somewhere than just a general slight drag that doesn't vary with the BB fitted to or removed from the frame.

NickJP
Posts: 338
Joined: 24 Sep 2018, 7:11pm

Re: Is this crankset free enough?

Postby NickJP » 25 Aug 2020, 12:48pm

Just because it looks good doesn't mean that the left and right threads are co-axial and the left and right faces co-planar. Welding distorts things. I always chase and face threaded bottom bracket shells to ensure proper alignment, regardless of how nice they look beforehand. External bearing BBs are much more reliant on everything being correctly aligned than square taper cartridge BBs.
boxrick wrote:I refit it all and the same sort of affect even with 0 tension on the preload ie it wasn't even inserted. From what I read, this is caused by fresh grease inside the bearings before it has been ridden properly and potentially quite normal? Especially once its under load.

This is a picture *before* I cleaned it, there was basically no dirt and the threads were perfect. I then applied grease to the threads and a little to the outer silver rim. IMG_3759.jpg

boxrick
Posts: 5
Joined: 2 Aug 2020, 7:23pm

Re: Is this crankset free enough?

Postby boxrick » 25 Aug 2020, 2:44pm

A few videos and articles talk about spacers.. in my case I took the HT ii bottom bracket and inserted it with whatever came on it. Does that mean that there could be spacers potentially causing an issue. Or will this not be the case?

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Redvee
Posts: 2346
Joined: 8 Mar 2010, 8:58pm

Re: Is this crankset free enough?

Postby Redvee » 26 Aug 2020, 1:18am

My understanding is the biggest cause of drag on BBs are the seals on the axle. My HT II bottom bracket is several 000 miles old and spins a little more freely but IIRC it was that tight when new too.

tim-b
Posts: 1675
Joined: 10 Oct 2009, 8:20am

Re: Is this crankset free enough?

Postby tim-b » 26 Aug 2020, 7:10am

Hi
boxrick wrote:A few videos and articles talk about spacers.. in my case I took the HT ii bottom bracket and inserted it with whatever came on it. Does that mean that there could be spacers potentially causing an issue. Or will this not be the case?

The GRX chainsets are road chainsets which use a 68mm wide bottom bracket (BB) shell. They can use either Ultegra or Tiagra BB which don't need spacers, however you will need a GRX front derailleur because of the wider chainline
I can't see an issue with what you show in the video (and photo), but it's clearly not the same as being there. I'd be surprised if anyone can do more than speculate on what your video shows, and of course you'll get positive and negative speculation
Regards
tim-b
~~~~¯\(ツ)/¯~~~~

Jamesh
Posts: 1800
Joined: 2 Jan 2017, 5:56pm

Re: Is this crankset free enough?

Postby Jamesh » 26 Aug 2020, 8:52am

Has it had a free running BB in it before?

If so then it's highly unlikely to be a BB shell issue.

More likely a seal / grease stiffness.

Cheers James