Index Categories:
Hub Engineering – Hub noise and bearing play
From:
matti58 Jul 17, 2006, 8:01 AM
Question:
Tightening hub on Zipp wheels?I've got an 808 rear wheel that has some lateral play when secured in the dropouts. I imagine I would need some special tool to tighten the hub?? Thanks.
Josh:
Proper torque on that hub is 88 in lbs for the rear using 2x5mm allen keys. At that torque, the hub should have a small amount of play (0.002", which extrapolates out to 0.010-0.015" at the rim), it is a sign that the balls are perfectly aligned as what you are feeling is the ability of the balls to rock laterally in the races as there is no lateral preload in the system.
Index Categories:
Hub Engineering – Bearing importance
Hub Engineering – Machining tollerances and real-world effects
From:
Bucky Sep 21, 2005, 7:59 AM
Question:
Hub quality on discs?
How does the quality of the hub/cassette body affect the speed of a rear disc? Does it make any difference at all? Does anyone put smoother/fancier hubs on their discs?
Josh:
I think in general there are a lot of misconceptions out there about hubs. We started making our own hubs 4 years ago now when we had supplier issues that warranted it. The first lesson you learn is that a hub is possibly the most difficult part on the bike to really make well. The first 18 months of our hub project saw over 400 design revisions, and in the years since then we have essentially redeveloped the thing every year.
From a machinability and tolerance perspective I don't think I'm going out on a limb to say that our 2006 stuff is the tightest toleranced hub product ever released into the bike industry. We've put new machines on the floor which can repeatably deliver +/-0.0002" tolerances in 3 axes...something almost no CNC machine on earth could maintain in production even 5 years ago. The internals are produced on a special lathe developed for manufacturing chronograph internals for companies like Chopard and TagHeur, so we're talking numbers that are almost unfathomable, but critical in an assembly that needs to run this smoothly.
From our testing the biggest issue with disc wheel hubs is stiffness and control of geometry from left to right as most all disc hubs are made from two halves bonded into the disc. This means that lengths, concentricities, etc, can only be controlled as well as you can bond the two parts together. This is why a lot of companies use loose balls on one side and cup/cone type arrangements. A cup/cone system just uses preload adjustment to compensate for tolerance issues in any of the mating components, if the outer race is too small the cone just doesn't screw in as much, if the hubshell is too short is just screws in further...these systems also allow for angular misalignment which is why an axle doesn't necessarily have to be straight in a cup/cone hub but has to be absolutely perfect in a cartridge bearing hub.
The stiffness is simply a result of design and geometry, but poor stiffness in the hubshell will result in higher rolling friction as the deformation of the hubshell ruins bearing alignment, we use a 15mm oversized axle and the 2006 product has been totally redesigned in such a way that the bearings are spaced further apart and the shell is slightly oversized relative to last year, which actually stiffens the assembly by about 8% while we also cut about 40 grams of weight out.
All in all with a perfectly toleranced and aligned hub with the highest precision bearings (we use 10 millionths toleranced Swiss balls/cartridges, these are more than 2.5x rounder than any other ball available and our cartridges have race diameters controlled to tighter than ABEC9 standards) can save 1-2 watts over cup and cone or adjustable cartridge bearing type hubs made by traditional CNC methodologies. Our 1 millionth toleranced ceramic bearings save an additional watt or so. To give you an idea of how critical these millionths of an inch are, we tested our hubs with some aftermarket 25millionths toleranced ceramic bearings and the wattage to spin increased over the stock steel balls, so the roundness and control is of paramount importance. We have a white paper on this that explains it slightly more in depth: http://www.zipp.com/...ents/Anoteonhubs.pdf
In terms of overall disc performance I would say that the hub is in the top three of importance, but the reality is that the construction and design of the disc itself is certainly primary as a poor shape, or aluminum rim lip or other surface discontinuity can cost you 3, 4, 5 watts of aerodynamic efficiency whereas the finest hubset in the world can only save you 2-3 watts over an average hub. The other issue would be weight, not for the sake of weight itself, but because so many people seem to not ride their disc when they really should due to the event having a climb or something in it, so if buying the lightest disc possible is what is necessary for you to want to ride it whenever and wherever, then weight would be the third factor on my list. (although technically stiffness trumps weight for most course profiles and with most modern tt/tri frames, but I rarely meet anybody who isn't riding their disc in an event due to stiffness concerns).
For more information on this see the papers in our Hub Technologies section:
A Note on Hubs A Note on Bearing Technology
SHIFT (Spoke Hole Impact Forming Technology)
http://www.zipp.com/Technology/HubTechnologies/SHIFTSpokeHoleImpactFormingTechnology/tabid/105/Default.aspx
Index Categories:
Hub Engineering – Bearing importance
Hub Engineering – Ceramic bearings upgrades
Hub Engineering – Machining tollerences and real-world effects
From:
bigd Feb 9, 2006, 10:30 AM
Question:
Zipp Z series – worth it?So lookin at the Z series wheels from Zipp... are they really that much better for all that money?
Josh:
The answer of whether the Z series is worth the price really depends on the individual. I've heard comments about who should buy the Z series wheels ranging from 'anybody to whom 3-4 seconds per 40k is important' to 'anybody with $3000 to spend on wheels' and the answer is really all of the above. The entire point of the Z series wheels is just to do a cost-no-object wheelset that is exactly equal to what the top pro's are riding.
Although most companies are selling product that is very visually similar to what you can buy in the store, these parts are not the same, for instance most 'aluminum wheels' used in the TdF are actually limited run magnesium rims that the pro's get for key mountain stages and the like, but you can't actually buy. Most teams also now upgrade their hub and component bearings to ceramics through third party sources (in some cases that's us), or at least to higher grade steel bearings, and 90% of the pro teams out there will rebuild their pre-built sponsor wheels using spokes and building techniques that the mechanics trust. Of course, not everybody is doing this, but many, many of the parts that the top level pros are really riding have been 'tuned' relative to what you will find in the store.
Now we've never believed in that, so we wanted to integrate all of this into our wheelsets from the outset. So in 2000 we developed the original 280 rims around a wheel to be built for Jan Ullrich at the olympics, and ended up with 280 gram rims (future 303 tubular rim), Sapim spokes and Tune hubs with ceramic bearings that we helped spec (we didn't make our own hubs then) and Jan bought 3 sets of the wheels and loved them. So we just started trying to integrate all of these technologies into a stock wheelset.
When we started with CSC, we wanted to just be albe to ship them product off of the shelf so that they weren't getting custom everything, and in the first year we make like 200 changes to rims, hubs, bearing seals, wheelbuilding, etc. to hit the criteria that was demanded, and likewise the Z series underwent the same development, so that now any random customer will receive wheels built right alongside and no different than what CSC, Phonak or Peter Reid would get, and there is no 'cherry picking' of products for these guys, but of course the top level guys still need 'tuned' parts for ultra high level events, so the Z series fits that bill, and again is a product that we can have on the shelf that may be shipped to you or to Ivan Basso without hesitation.
As for ceramic bearings, just like steel bearings, they are all not created equally. Many affordable ceramic bearings are no better than low grade steel bearings and use the same low grade races. These are primarily used in high temperature industrial applications like on carts used to roll lots of aluminum in and out of ovens for heat treating, but have absolutely no benefit to performance. Our ceramic balls are made in the US to a grade 1 tolerance (round and diameter matched to 1 millionth of an inch) making them about 1000 times rounder than a Campy Record grade 25 ball and are assembled in Switzerland into ABEC 9 races which are cryogenically heat treated to refine grain structure and even use a super groovy ceramic specific grease which costs over $250 per kilogram.
Most of the ceramic bearings hitting the cycling industry right now use either grade 25 or even grade 40 balls (making them significantly less round than the bearings used in the standard Zipp hub (grade 10)) and use traditional ABEC1 or ABEC3 steel races and traditional greases, which leads to premature wear or damage to the races as they were not designed to handle the higher hardness of the ceramic balls. Like many things, you get what you pay for, matched grade 25 balls sell for about $1 per 100, while grade 10 balls sell for about $12 per 100 and grade 1 ceramic balls sell for about $7 per ball...with 15 balls per cartridge these get expensive very quickly.
Our ceramics are very expensive, but we actually sell these bearings to 3 non-Zipp affiliated ProTour teams as well as providing them to CSC and Phonak in Z series products. Shockingly enough, the ceramic bearings are one of our lowest profit margin components as applying standard profit margins would make them almost unaffordable.
Are they worth it? Well to a guy like Dave Z, their benefit was nearly equal to his winning margin over Lance in the Tour Prologue last year...he probably would have beaten him without the bearings, but they made for a reasonable cushion. We also have age group TT's world wide where the top 2 or 3 guys in a 40k are separated by less than the 3-4 second margin afforded by the 1 watt savings of our ceramic bearings. Don't get me wrong, I can no longer break an hour in the 40k so they aren't doing anything for me, but to anybody who's ever been beaten by a razor thin margin, they are probably worth it...if you have the money of course :-)
The Z-series wheels have now been replaced by our Zed-Tech custome weels line. You can find more information here:
http://www.zipp.com/Zedtech/tabid/163/Default.aspx