The guts of a mountain bike, or, that budget bike is hiding something


One area where ALL suppliers / manufacturers hide a cut corner is in the rear hub.  It's a place where you really have to know what you are looking for to see what you are getting which brings me back to the story:

       I was walking thru the warehouse last summer and saw this little piece of rear axle on the floor.  Head-rush of memories from the '70's when!  Some things don't change- and one of those things is that you get what you pay for!  And I have learned from my perspective here in the bicycle shop that you have to suspect everything you get at the discount stores.  Their bicycles for example have chronic problems- always have.

      One Constant is that Discount Store Bikes have rear wheel problems.  More specifically bent or broken REAR axles.  Cheaper Bike Shop bikes and much older bike shop bikes did too, but technology has changed- in the Bike Shop at least.


The old-style hub:

This is what an old style REAR Hub looks like without the gears.  The Gears thread onto it on the right side.  Notice the offsets:  On the Right, it is to accommodate the gears.  On the Left, it is to help make up for the offset on the right.  The Bearings are under the threaded portion of the hub.  Notice the distance from where it attaches to the frame and where the bearings are.  It's over an inch.  This style system has been around since 10 speeds first came out.  We had problems with it then, but now we have 8 gears instead of 5 back there, so the extension is longer.  

      On new bicycles we have 21 and 24 speeds instead of 10.  The pedal arms are longer, the gear ratios are lower, the tires are wider and theoretically, the bicycles are more capable.  But the old style system, that wasn't very good back then, is really out of date now!  

 If you have a newer bicycle and you ride it off road, odds are you will damage it just by pedaling it.  This is because of all the leverage you can put on a drive train that was originally designed to be used with 5 gears, not 7 or 8 and was designed to be ridden on the road, with skinny tires, not in the grass or dirt  with a high traction fat tire.  

      The above picture is of that part, which I spotted on the warehouse floor and the hub it belonged to.  This was off of a 6 month old bike, a MONGOOSE from a discount store.  It apparently bent and then broke from the stress of use, and the owner of the bike said he hadn't gone off-road.  He was put out and lamented, "I guess ya get what ya pay for..."

      Yes.  You "save" up front, but pay and pay in the end.


So what does the new design look like?


     This is what a CASSETTE rear hub looks like without the gears.  The gears actually slide onto that huge, bronze colored, splined piece on the right.  The bearings are under the hi-lighted area.  Notice how short the distance is from the hi-lighted area to where the axle attaches to the frame- it's about 3/8 of an inch.  

      It is physically impossible to bend the axle on this style hub just by riding the bicycle-- even off road!