Ive been offered a set of mavic xm119 wheels laced to slx hubs with dt swiss spokes and im tempted to buy them for my second bike I currently have alex rims from standard can anyone tell me are they any good? Will they be a big upgrade over the alex? Ive had three uckles pulled out so far and just need somthing stronger.thanks for any replies.

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Depends….
It’s a narrow rim but you can fit a wideish tyre to them – maybe 2.4″ max. If the wheels have been put together by an experienced wheel builder then they will pretty strong. But then exactly the same can be said for an Alex rim. (I’m guessing you’ve got a low end Alex rim?) Also depends on whether the person truing your current wheel knows what they are doing. Truing a wheel is easy. Truing a wheel, and tensioning the spokes evenly so it stays true is a much harder skill.

SLX hubs are OK, so long as they are regularly serviced. But a hub with cartridge bearings like Hope are preferable in my opinion. Shimano hubs don’t last long in my experience without regular servicing.

The biggest factor by far is the skill of the wheel builder. But if you ride hard/badly/are heavy, then you may be better off looking at a mavic 521 or 721 rim.