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RADBMX.CO.UK  |  Technical & Reference Section  |  Tech and Restoration  |  Chainring Top Hats
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Author Topic: Chainring Top Hats  (Read 1134 times)

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Offline oldtired

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Chainring Top Hats
« 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? 

Offline Dannywhac

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Re: Chainring Top Hats
« Reply #1 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.
"Listen. I don't care what you say. Chlamydia is a soup." (Phelps, L. 2000)

Offline oldtired

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Re: Chainring Top Hats
« Reply #2 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:

motomagII

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Re: Chainring Top Hats
« Reply #3 on: February 28, 2012, 12:45 PM »
fsa chainrings are 19mm onkly so not top hat

Offline Dannywhac

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Re: Chainring Top Hats
« Reply #4 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 :)
"Listen. I don't care what you say. Chlamydia is a soup." (Phelps, L. 2000)

Offline pickle

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Re: Chainring Top Hats
« Reply #5 on: February 28, 2012, 01:48 PM »
Ti softer?  i thought it was one of the hardest metals about?  ???

Offline Dannywhac

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Re: Chainring Top Hats
« Reply #6 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
"Listen. I don't care what you say. Chlamydia is a soup." (Phelps, L. 2000)

Offline oldtired

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Re: Chainring Top Hats
« Reply #7 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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