Report by David Wilde
I have Hope tandem hubs fitted to the front and rear of my tandem. The main reason for choosing the Hope hubs is to enable the Hope disk brakes to be fitted.
Both hubs are 36 hole (we are both lightweights).
The Hope hubs shells are machined from a solid piece of aluminium alloy. The bearings are standard 6001 series, which are widely available from any bearing dealer. The rear axle is hollow steel, with a large diameter centre section. The ends of the hole are threaded and the hub is supplied with allen key bolts and load spreaders. Quick release spindles can be fitted, and would probably increase the strength of the rear axle.
No problems so far
We have experienced cracks in the cassette body. This was reported to Hope who replaced it promptly free of charge.
Other teams with Hope hubs have also experienced the same problem, sometimes more than once. The titanium body has also been tried with no better experience. Swallows advised that Hope are to change the heat treatment process to solve the problem.
The basic design of the hub puts significant bending moments on the axle, and excessive load in the inner drive side hub bearing. There are actually four bearings, two on the cassette body and two on the hub body. If tolerances were perfect, and drive was taken equally by each pawl, most of the drive loads would be taken by the cassette bearings, and most of the weight by the hub bearings. Rotating our freewheel slowly shows that this is not the case, most of the load being taken by one pawl. The effect is to add considerably to the loads experienced by the inner drive side hub bearing, which now has to handle the reaction force to that applied by the pawl. These forces are several times greater in magnitude than those generated by the weight of the tandem and riders, and probably exceed the design rating of the bearing at slow speeds.
The uneven sharing of the load will also contribute to the failures of the cassette body.
The latest Shimano Tandem hubs offer a
One other team has also experienced a failure on a 48 hole hub where the flange failed and the spokes pulled out. With so many holes the effect is simlar to the perforations on stamps to make tearing them apart easy.