Trek Procaliber 18' Headset Bearings

Hey guys and gals,

I own a Trek Procaliber 18’ and want to change the headset bearings. I contacted the local Trek dealer and he would not give me the dimensions, he just told me that they have the set for sale.

Does anyone know the dimensions?

On a website someone wrote ZS41/28.6 upper and ZS52/30 lower by FSA. Can anyone confirm that?


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No experience with that bike, but there is a good chance the bearings are labeled.

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Find another bike shop that is more helpful.

MR122 (1 1/8) top and MR127 (1.5) bottom according to Trek Tech (I work in a Trek store in UK)


Thank you Burt, I really appreciate it! :slight_smile:

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The shop in question had the correct headset in stock.
Employees in badly understaffed bike shops don’t really have time to operate a hotline for several random people a day fishing for free tech information without any intention of purchasing the products. They are already busy enough with actual paying customers.

Bingo. Sounds like you work in that shop. :wink:


Fair enough, your argument is very reasonable, thus, my question in this forum in order to find the correct bearings. I am not accusing the local Trek dealer of anything, just to be clear.
To be more exact, I contacted a shop employee who I personally know outside his work hours and asked for the information, therefore, I did not waste anyone’s 15 seconds during work time. His reply was very professional towards the bike shop and told me I can buy the kit if I want to but he cannot give me the bearing details.