So I have decided to get a SON28 front hub for a new bike build.

The rear hubs is going to have Shimano Center Lock disc brake rotor mount.

When looking into the front SON28 hubs, I noticed that all variants of the SON28 have strain-hardened stainless steel axles, except the Center Lock variant which has a aluminium 7075 T6 axle.

I have great concern of the durability and impact strength of the alloy axle, since I every so often hit pot holes so hard and fast it sends shocks up my arms that actually causes pain.

Will the alloy axlebe just as strong and long lasting as the steel one?

I put a set of wheels built with Shimano XT, aluminum axle hubs on my touring bike for a 3,000 miles tour. Four hundred miles of that route was over dirt and unsurfaced roads, and over 500 miles was on cobble or sett stone roads and trails. That was 7 years ago, and several thousand more miles ago, and they are still running as smooth as the day I put them on the bike.

I believe the concern for using aluminum axles in a touring environment is overblown. The main criticism of the XT hubs was the freehub, not the aluminum axle. I'd ask the question: How many people have actually had a problem with aluminum axles?

+1 to Doug's comments.

I have XT hubs with aluminum axles on both my touring bike (7 years old, 10,000+ miles) and my mountain bike and have not had any problems with them yet. The only axle failures I've seen (either personally or as a mechanic) have been been older rear hubs with freewheels, and those are almost always steel. The material of the axle is far less important than the overall design of the hub - placing the bearings as close to the dropouts as possible (as in modern freehub designs) minimizes the stresses placed on the axle. Also, all of the axle failures I've seen have been bends rather than breaks. If the axle bends, the bike will still be ride-able, though handling will suffer and you might have to open the rear brakes.

Another thought - riding technique is important for avoiding damage to wheels from potholes. Supporting as much of your weight as possible on your legs (as opposed to your arms and butt) will reduce forces applied to your wheels by a large factor. It will also reduce wear and tear on your wrists. And this will be true even on a loaded touring bike, since a loaded bike still weighs less than the rider.

There were a number of reports of early problems with Aluminum axle hubs on long haul truckers with XT m770 rear hubs. The smaller diameter ball bearings were cited as an issue. But, nobody seems to have a problem anymore with them, so maybe it was a temporary glitch?

Front, I did not have any concern with putting a M770 XT Aluminum axle hub on my folding bike. Front wheels get much less stress than rear.

I was not aware that the SP Dynamo PV-8 used an Aluminum axle when I bought it in Spring 2013, that concerned me when I learned about it later. But, people use that hub on mountain bike races, so I stopped getting too worried about it. Go all the way down to the bottom of this page to see the citation for people racing with this hub.
SP 8X dynamo hub

Since then I have used my SP for mountain biking.

But I have no clue if it is an issue on a Son hub. Send them an e-mail?

I had a road bike wheelset with aluminum axles. The front was problem free, but there were issues with the rear - the hub design did not have the freehub body fastened to the hub shell (like Shimano has) but instead the edge of the hub shell and the edge of the freehub body made up the freewheel mechanism, and the whole thing was held in alignment by an aluminum axle passing through four sealed cartridge bearings. It groaned and creaked and skipped when I put any power down. I never swapped it for the (available) steel axle, but I suspect that would have allowed the thing to function properly under my 270 lb weight and reckless riding habits. If the hub had been a SHimano-style freehub like gorshkov's XT then I am positive it wouldn't have been a problem, just as it wasn't a problem on the front wheel.

FWIW 7075 T6 aluminum is comparable to 304 stainless steel (most common kind) in strength.

Since the axle on those is apparently oversized, I wouldn't be concerned. I've never saw or heard of a Phil hub axle failure in many years of wrenching. If it is a standard threaded 9x1 type front axle out of aluminum, that would likely fail eventually. (IIRC there were some in the weight weenie era, OMAS? ) I'm pretty sure that's not what they did.

If you're concerned, perhaps you could contact Schmidt or a knowledgeable Schmidt dealer and ask them for recommendations?

Pre worry . a forum regular outlet.

Sure If they're Oversize .. My Bullseye hubs have 5 pieces around the axle

2 are the 6001 sealed bearings and 3 are thick sleeves between the bearings and on the ends around the axle

where the QR skewer campresses the frame dropouts against all 5 ..



the Axle is reduced in diameter just on the ends its much larger between those ends ,

and the steel skewer supports those ends being within the axle.



these are German trained Engineers at Schmidt,

... not some itinerant Swagman in the Outback ..

Pre-Worry is the driving force behind most bicycle industry sales. They need a constant feed of Pre-Worry so that they may devise extravagant, expensive, lucrative solutions to problem that exist only at the 2nd or 3rd Standard Deviation...the 5% who may actually need thru axles, hydraulic brakes, 4" tires, 44mm headtubes, DI2 shifting, etc etc.

Yes, bearing life was the issue. Shimano changed their rear hub std 10mm steel to a 12mm Al axle and downsized the 1/4" balls/cups/cones to 3/16" (front hub parts). You get a lighter, stiffer axle, but smaller bearings do roll with more friction, usually resulting in shorter bearing/cup/cone/hub/wheel life. This is unlikely to help the average tourist, more likely to hurt.

I've never bent an axle AFAIK. I have worn out the cups in rear XT hubs due to my weight and >15,000 miles (fronts usually still good, as they get perhaps 1/3 of the load). Since the cups can't be replaced you have to replace the hub, or perhaps the whole wheel if you can't order hub cheap and rebuild yourself.

Buying a new rear wheel often turns into a whole new wheelset, then maybe even a whole new bike...

My 6001 bearing cartridges are Enduro , an all ball 90% fill radial contact sealed bearing

Do 13, 3/16" balls have less surface against the bearing race than 9, 1/4" balls? I don't know the answer to this, but I suspect the difference is not significant.

I have the Surly LHT 52cm 2008 in 11-2013 I sold the Stocked Wheelset with Shimano XT m770
with Aluminum Axles and I had a Custom Wheelset made with Shimano XT M756A and M756
disc hub with Steel Axles to get Ready for Disc Brakes!

Shimano Stopped making XT Rim Brake Hubs
and Shimano Rim Brake Hubs in Deore, LX Only

It's not surface area or the number of balls that matter, rather the size of the balls is most important. Larger balls have a lower approach angle and lose less momentum rolling over surface imperfections (less friction), which also results in slower erosion of bearing and races.

Big balls are what matters - just ask ole One Ball.

I just got an email back from Schmidt and this is what they said

>I have noticed that all the SON28 hubs have strain-hardened
> stainless steel axles, except the center lock hubs they have
> aluminium 7075 T6 axles.
>
> Which of the two hubs have a stronger axle?

The stainless steel axle definitely has the better corrosion resistance.
If you will use the wheel also in winter on salted roads or near the sea
with sea salt in the air (and the rain), we would recommend our hubs with
the full stainless steel axle.

Our hubs with the stainless steel axles have also a wider distance of the
bearings, which results in a little stiffer wheel - which is relevant for
heavy riders, cargo bikes, tandems or harder offroad use.

> Do you use the same size bearings in both axles?

Yes.

> And why doesnt the center lock hub have the same steel axle as the rest of the SON28 hubs?

It gives you the choice between a lighter more compact design hub and a
heavier, wider, more robust variant.

Thanks for posting.

I'm not disagreeing with you, because I don't know the answer. I'm just curious where you found the information you stated.

I would like t see some publication that explains the differences ball size makes, and quantifies the differences in load etc. I've been laid up with a bad cold and spent more time than I really wanted this afternoon looking for something that clarified this question. I could not find anything.

Do you know of any papers or publication that cover this topic?

The late Jobst Brandt might have had something to read. I know he was right into dissertations about ball bearing headsets.

So ? you get 6 bolt disc hub & have a small Torx wrench in your tool bag..