Cassette, Lockring & Freehub issues

[Johan Bornman]

Question - Why were the old screw on style "clusters" replaced with cassettes? The screw on ones could not come loose, as they were tightened by your pedalling... This did make them fairly difficult to remove. Would be interested to know why the change occurred.

 

For a whole bunch of reasons we can collectively call progress.

 

The first issue was that of the overhang. Here I refer to the right hand side. The last bearing that supported the rider's load was the right hand side one in the wheel itelf, with none in the cluster. (A screw-on cluster of sprockets is called a cluster, the things we have today are cassettes). This caused a large unsupported section between the right drop-out and where the wheel begins. That flexed the axle and made it break. It got so bad with 8-speed that these setups were considered totally unreliable. As you go up in number of sprockets, the larger the unsupported overhang became and the quicker the axle broke.

 

The advent of the freehub solved this. A freehub accepts a cassette and has two widely-spaced outboard bearigns as well as two inboard bearings. A freewheel accepts a cluster and only has two bearings, one on the left and one almost in the middle of the wheel.

 

The freehub now offered us bearings where they were needed. It also offered a better way of fixing the cassette. A cassette made up of loose or riveted sprockets could be made much lighter and more reliable. Screw-on sprockets cannot be hardened since one cannot harden fine threads. Therefore they were realitively soft and prone to damage from chain skip.

 

Freehub sprockets had no threads and could be case-hardened for extra durability.

 

The freehub also solved the problem of supporting a torque load on a fine thread in aluminium. This is an engineering no-no and anyone who has had to struggle with removing a freewheel will tell you tnat it is a crappy idea.

 

In summary, the freehub solved the overhang, the soft sprockets, the weight and durability problems. All-in all, it is progress. Unfortunately Shimano made a mistake in its design and you're still paying for it. The flutes on the freehub body are not deep enough so that you can make the body from a lighter material. It has to be steel so that you don't have the bite-in you get with aluminium freehub bodies.SRAM copied Shimano's design, for reasons of compatibility, I hope. Campag went clever and designed a deep-groove freehub body that can be made lighter and strong enough to not have sprockets eat into it.

[Stretched@Birth]

And again we must thank Mr Bornman for his insight and knowledge, and giving us a lesson in the evolution of bicycles. Thank you Johan for always taking the time out to answer these questions, I for one really appreciate it!

[RodTi]

And again we must thank Mr Bornman for his insight and knowledge, and giving us a lesson in the evolution of bicycles. Thank you Johan for always taking the time out to answer these questions, I for one really appreciate it!

 

Hear hear!

[Johan Bornman]

Thanks guys. Feedback really appreciated.

 

JB

[Shebeen]

I'm going to come back on monday and reread this one rather. bit heavy for this part of the week!

[RodTi]

Happy to report that said bullet was dodged...

 

did some proper cranking up hills yesterday afternoon, and not a squeek of slippage...

 

joy, joy and joy again!

 

Thanks peeps!

[SURFER]

Maybe I have the same problem. LBS replaced freehub 3 weeks ago. When cycling Contermanskloof I broke the change, Luckily I had all the right stuff to fix the chain.

 

Seeing that I am doing Seweweekspoort this weekend, I decided to replace repaired chain with new chain (plan is to use “old” chain again after seweweekspoort) . On my first ride with the new chain it slipped on some of the chain rings. The cluster had only 1500 km and with still the first chain ( I checked chain and no wear over limit).

 

Decided to be safe for this weekend and got new cluster. When removing “old” cluster I did noticed that lock ring was very loose.

 

It seems that that could be the problem. Will try “old” cluster and “old” chain after seweweekspoort.