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So as some of you may remember I was asking around about a dual disc hub, for... reasons. Because I can't find one, I've decided to design and make one myself.
The thing that I am struggling with is the clearance required between the disc and spoke flange, I dont have a hub to measure and based on the lack of information online does any one have any suggestions? It is going to be a 36" wheel so the spokes are going to be pretty steep in angle and with any luck it will be two 160 rotors and my worries are that the callipers will will clip the spokes until either the spokes or the callipers are worn.
Quick measure of a Hope Pro2 comes in at 19mm from ouside edge of flange to outside of rotor, so allowing 2mm as rotor thickness (it was cold, and i'm in a t-shirt, so didn't measure that too), 17mm sounds about right.I daresay careful caliper selection could allow you a little more leeway, my other bike with original Minis and 165mm rotors still has a few mm between spokes and caliper.
Why don't you buy two Deore hubs, cut them in half & get a machine shop to sleeve them together internally & externally...you could even have it welded afterwards.
Taki - I am doing all the work myself so that wouldn't be a huge issue to do as you describe (although I wouldn't like to weld heat treated ally) but I can only get deore in QR and I am intending to custom make a 15mm axle as a QR is unlikely to be stiff enough. SLX is double the price and its cheaper to do the work myself from billet than it would be to chop up two SLX hubs.
Coatesy - Cheers man, caliper selection is limited, using a splitter from a mechanical lever means BB7s or nothing really.
Magura do a hydro 2:1 splitter.
Max - you are a lunatic!
On a more helpful note, my hubs sat here (front dt240s) have 16.5mm flange to inner side of rotor, there is also 4mm of clearance between the spokes and the caliper with a 160mm rotor (XT m765)
as for 2 calipers - why not use a splitter like [url= http://www.tartybikes.co.uk/rim_brake_spares/trialtech_sport_hose_splitter/c5p11623.html?tab=questions ]this[/url] , and run one of the new style shimano levers with servowave, so you don't get any pad dragging on the rotors?
also http://www.pedicabshop.com/shop/spare-parts/brakes/big-magura-twin-hydraulic-disc-brakes.html - especialy as you are spending £160 on tyres 😉
Considering costs for a singlespeed version are edging towards 1k without [url= http://waltworks.blogspot.co.uk/2012/10/the-new-36er-tire-preorder-now.html ]these tyres[/url] then I don't think buying an extra front hydro brake is really what I need, although could be interesting, bb7's would be much simpler and have no lack of stopping power (based on jeds campus bike). Its going to be an absolute pig whichever way I do it.
1.625kg per tyre, 1.1kg rims - with a 36 inch diameter - the rotational inertia on this beast will be about 7 times more than your current bike (assuming 26er ralphs on crests)- bb7s may manage but I don't want you following me down anything 😉
There's also a Tektro Auriga Twin disc set which isn't as chunky as the Magura Big.
OP I thought you'd agreed on your last thread that there was no need?
Cynic - After doing calculations I would need a ~240 rotor and I am less keen to design my own rotor than I am my own hubs, they also do (with the given weights) have more energy to get rid of (~5% more) and the equivalent of a 360 rotor would help me to stop on a ten pence piece (and dissipate heat much better). Also as ben noted in the previous thread, "just because" is more than enough reason, its going to be ridiculous, why not take it a step up?
Ben - The appear to be OEM only (according to tektros website)
Oli - Yep, 3 bb7's will manage fine, like 1 bb7 on a 360mm rotor then 1 on a 180mm rotor, atleast I would be saving a lot of weight by going tubeless 😉
So you'll have the 2nd caliper on the front RHS of the fork?
That's the plan, one cable running through to the two calipers, then a canti-equivilent set up to pull both equally.
Ben - The appear to be OEM only (according to tektros website)
I have my sources 😀
Let me know if you want a set and I'll work out a price - I think it's around £180ish.
Thanks ben, you may be getting an e-mail at the end of the summer from me 🙂