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PostPosted: Wed May 23, 2012 3:06 pm 
retrobike rider
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Location: A wretched hive of scum and villainy...
Quote:
so it remains a mystery, at least to me, why they are not fitted that way round.

Isn't it so that, under braking forces, the torque between the outer rim of the rotor and the hub compresses the leg and causes them to jack out?
This holds the braking surface in tension, keeping it out and straight; working against it's tendency to collapse in and buckle under braking.

Look at all the current one piece rotor structures and directions. Tangential arms facing forward is definitely the consensus after years of bitter experience, lawsuits and testing.

The Hope rotors are pretty overbuilt, so a failure is unlikely (and AFAIK nobody has had trouble), but personally, I'd turn them around just to be on the safe side.
Hope authenticity pedants might point and stare, but it's only 12 screws, a few minutes. The braking's not going to get any worse, and it just might save your life.

All the best,


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PostPosted: Wed May 23, 2012 4:25 pm 
retrobike rider
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I have no idea.
But if, as mentioned, HOPE made them then they do I should hope.
So pop to the site and you can find something like this
http://www.hopetech.com/webtop/modules/ ... _small.PDF
another randomly picked one shows the same direction.

from http://www.hopetech.com/page.aspx?itemID=SPG131


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 Post subject:
PostPosted: Wed May 23, 2012 5:03 pm 
Gold Trader / rb Rider / Special
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What danson says makes sense (to me at least), the spokes/metal will act like a spring while staying within its elastic limit.


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PostPosted: Wed May 23, 2012 6:57 pm 
retrobike rider / Gold Trader
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Joined: Tue Apr 20, 2010 11:29 pm
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i got a note from Hope after emailing them..

Quote:
Hello Rick, when we manufactured this model we did indeed run them the
way you have shown us in the photo.

Many thanks
Nick

Service & Warranty
Hope Technology (IPCO) LTD
Hope Mill
Calf Hall Road


so i'm goint to trust their advice.. for now. Cheers for the opinions tho.


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PostPosted: Wed May 23, 2012 8:20 pm 
retrobike rider
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Quote:
Hope: when we manufactured this model we did indeed run them the
way you have shown us in the photo.

Quote:
TrickyLad: i'm goint to trust their advice.. for now

Unless there was more, I don't think Nick's statement constitutes advice...
Their old rotors may have been run that way, but were they designed that way? No statement of which is the right or safest direction to use their old rotors. :roll: A fairly disappointing non-committal reply from Hope.

Honestly, IMHO you should seriously consider the chances that Hope (and only Hope) were right for a few years, then they and every other manufacturer (and their lawyers) perversely decided to design and fit their rotors the other (wrong/less safe) way around ever since? This isn't a 50:50 matter.

Fit them facing back for the 'concourse d'elegance' so Mr. Picky doesn't dock you authenticity points, then turn them the better/safer/correct way around to ride. :wink:

All the best,


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PostPosted: Thu May 24, 2012 9:04 am 
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Joined: Sun Apr 22, 2012 1:22 am
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Location: north nott's
danson67 wrote:
Quote:


Honestly, IMHO you should seriously consider the chances that Hope (and only Hope) were right for a few years, then they and every other manufacturer (and their lawyers) perversely decided to design and fit their rotors the other (wrong/less safe) way around ever since? This isn't a 50:50 matter.




have there been lots of reported incidents of rotors failing and causing injury to people?
and this due to them being fitted the wrong way round?
i can imagine there have been cases of rotors failing due to excessive wear and poor maintainance leading to stress fractures etc.
the hope floating rotors have direction on the braking surface, but the spider is symetrical. kind of questions the whole torque/ elasticity thing in relation to stresses being transmitted through the hub/ spokes.


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PostPosted: Thu May 24, 2012 2:29 pm 
Retro Guru

Joined: Mon Jun 02, 2008 2:52 pm
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Sadly in the MTB world, especially a place like Hope, there is probably a pitifully small amount of testing ever carried out. It is not a mass market car, it's just a bicycle :D
Point being, there has probably been no good test as to which is best/safest in relation to the forces encountered in actual use.
Run them which way is prettiest as if you (not the OP) people worry about something like this failing and killing you, you should probably leave the bike at home :lol:


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PostPosted: Thu May 24, 2012 4:00 pm 
retrobike rider
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Magsy wrote:
Sadly in the MTB world, especially a place like Hope, there is probably a pitifully small amount of testing ever carried out. It is not a mass market car, it's just a bicycle :D
Point being, there has probably been no good test as to which is best/safest in relation to the forces encountered in actual use.
Run them which way is prettiest as if you (not the OP) people worry about something like this failing and killing you, you should probably leave the bike at home :lol:


Surly in the Motorbike world it's quite tried and tested and other than power and weight, whatever works there should work in the MTB


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PostPosted: Thu May 24, 2012 4:16 pm 
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Joined: Sun Apr 22, 2012 1:22 am
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Location: north nott's
FluffyChicken wrote:
Magsy wrote:
Sadly in the MTB world, especially a place like Hope, there is probably a pitifully small amount of testing ever carried out. It is not a mass market car, it's just a bicycle :D
Point being, there has probably been no good test as to which is best/safest in relation to the forces encountered in actual use.
Run them which way is prettiest as if you (not the OP) people worry about something like this failing and killing you, you should probably leave the bike at home :lol:


Surly in the Motorbike world it's quite tried and tested and other than power and weight, whatever works there should work in the MTB


i was thinking the same. having two big heavy fast motorbikes.
ive also been thinking about the whole torsion thing.
the braking of a bike, rim or disc, comes down to two points of contact. the tyre and the braking surface. so the sresses placed on the system as a whole should be the same. all stresses regardless of system are transfered through rim, spoke and hub. the biggest elastic effect is the tyre. not the metal of the rotor.


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 Post subject:
PostPosted: Thu May 24, 2012 4:54 pm 
retrobike rider
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Quote:
Crossland: the hope ... spider is symetrical. kind of questions the whole torque/ elasticity thing in relation to stresses being transmitted through the hub/ spokes.
Floating rotors, including motorbike rotors and the newer Hope ones are brilliant, but they are an entirely different structural arrangement to the one-piece rotors.
The aluminium centre is well triangulated and, as it's made of alu, can be 3x as thick for the same mass, this hugely reduces the chances of buckling.
Braking loads are taken by the massive steel rivets in shear.
The interface around the rivet on Hope Floaters is angled forward, so that the braking surface leg and rivet are still kept in compression under braking.
The braking surface is completely free to expand without distorting as it heats up, but the braking forces stop any play developing as the rotor warms up.

Quote:
Crossland: the hope floating rotors have direction on the braking surface
The directional arrows on Hope floating rotors are to make sure the jagged outside edge sweeps across the pad towards the outside. And also that the countersinks for the bolts and hub machined into the thick aluminium spider are positioned correctly, otherwise the rotor will sit 1.5mm outboard.

Few serious motorbike rotors are one-piece, but those I've seen tend to have their tangential legs facing forwards:
Image

Quote:
Magsy: if you (not the OP) people worry about something like this failing and killing you, you should probably leave the bike at home
I agree, there's a whole lot of other things out there in the world and on our old bikes that's far more likely to kill us, but the OP did ask...:D

All the best,


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