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TOUR 09/2017
Reading time 1:50 minutes

Press-fit bearings: a reasonable thing?

Reader’s question

While looking for a new road racer, I keep coming across press-fit bearings used on both less expensive as well as high-value carbon frames. The manufacturers save costs as they no longer have to cut threads for bearing shells. But what is actually the advantage for me as user? In addition, I came over videos during my inquiries, in which the bearing was removed by hitting it. In the case of a steel frame this is acceptable, but in the case of an aluminium or carbon frame? In the forums there were discussions about a faster wearing down, because the bearings could not be built in like threaded bearing cups. What do you think?

Reply by Dirk Zedler, TOUR technology expert and bicycle expert

It is correct that more and more press-fit bearing cups are used, as this reduces the number of work steps. In the past, when carbon frames were fitted with screwed in aluminium bottom bracket shells the cutting of threads into the bottom bracket shells had often led to damage to the carbon frame. In the long run, this was not only annoying for the manufacturers, but also for the customers. This means, press-fit bearings not only save time and money for the manufacturers during the first assembly, but are also a sound solution for the customers in the long run. To date, we have knowledge of clearly less failures with this procedure than of notched cups in the past. Nevertheless, the manufacturer must take care that the fit is round and even, thus ensuring a precise pressing in and fitting. Of course, there are differences between the manufacturers. But the bearing shells of carbon frames also wear down when mounting and dismounting the bearings quite often.
On the basis of our experiences, however, we cannot generalize broadly that the system is poor. As a matter of fact, the press-fit bearings must be hit out when they are worn down, but only in this case. If carried out appropriately, this does neither result in damage to a carbon frame, nor in damage to an aluminium frame. In this case as well the disadvantage compared to for example corroded cups in aluminium shells or to aluminium frames in the case of threaded bearings are not clearly more important. This means that if appropriately done, the press-fit bearings, regardless of diameter and type, are not a poor solution.

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