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Technical & Reference Section => Tech and Restoration => Topic started by: oldtired on February 28, 2012, 12:00 PM

Title: Chainring Top Hats
Post by: oldtired on February 28, 2012, 12:00 PM
so the majority of bb are either 19mm or 22mm so why do chain rings still come with the one piece size hole   so that you kneed a top hat , which you can never fookin find in the tool box   :tickedoff: :tickedoff:   :2funny: :2funny: are the spline drive ones reliable? 
Title: Re: Chainring Top Hats
Post by: Dannywhac on February 28, 2012, 12:31 PM
I use a Tree spline drive and it's fookin lovely  :daumenhoch:

Just don't use them on Ti axles.
Title: Re: Chainring Top Hats
Post by: oldtired on February 28, 2012, 12:34 PM
I use a Tree spline drive and it's fookin lovely  :daumenhoch:

Just don't use them on Ti axles.

interesting ,  why not ?  been looking at the Tree cro mo one  :smitten:
Title: Re: Chainring Top Hats
Post by: motomagII on February 28, 2012, 12:45 PM
fsa chainrings are 19mm onkly so not top hat
Title: Re: Chainring Top Hats
Post by: Dannywhac on February 28, 2012, 12:46 PM
More of a manufacturers recommendation - the Ti's way softer than the treated splined part of the sprocket and with the larger forces placed on the axles in a smaller point (as the crank arms have a larger contact area so force spread less) makes the axle more prone to failure.

Saying that, I've only ever seen one 'smooshed' Ti axle from a spine drive sprocket, and that was on a bike that it's owner didn't maintain it (loose crank arms anyone?) Sprocket was still fine though  :daumenhoch:

If you get a Tree Sprocket (and they are very nice) give the splines on the axle a little bit of a clean up with a wire brush (not too much though) as they're a snug fit :)
Title: Re: Chainring Top Hats
Post by: pickle on February 28, 2012, 01:48 PM
Ti softer?  i thought it was one of the hardest metals about?  ???
Title: Re: Chainring Top Hats
Post by: Dannywhac on February 28, 2012, 02:08 PM
Yep - didn't really explain meself very well there....

The chromolly arms/spline are heat treated so hard as fook, Ti although it has really good strength and fatigue/elongation properties (better than steel) has a lower specific elasticity (it's more bendy than chromo/steel for a given weight of material) = bad combo mix on your gearing if your using a steel splined sprocket on a Ti axle cos all the force on the splined sprocket is concentrated in a thinner area than the large splined area of the crank arms.

Is that making more sense? Not explaining very well......  :D
Title: Re: Chainring Top Hats
Post by: oldtired on February 28, 2012, 04:17 PM
  :daumenhoch: makes sense to me ,  was thinking the same thing ,  will stick to a bolted one i think
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