I currently have an Orbea Aneto which is basically a flat bar road bike. It does have 135mm spacing in the rear, but for the most part, the components are road.

I am contemplating getting a new set of wheels, something a little more sturdy, and at the same time I am thinking of getting more of a mountain cassette like a Shimano Deore 9 speed 11-32. I currently have a Shimano Tiagra 9 speed and am wondering if the spacing is the same between the two.

Do you foresee any problems that I might have? I really like the idea of just swapping out the wheels when my trips go from road to trails.

Thanks.

The spacing is the same between shimano mountain and road cassettes. However, the Tiagra derailleur may not be able to handle a 32.

It is unlikely that the Tiagra will clear the 32 tooth cog on the cassette. Officially it has a 27 tooth limit. It will often clear a 30 tooth, but going to a 32 tooth is unlikely.

Good point. Is there a way to know ahead of time or something you just have to try. I do have a long cage rear derailleur and there is a triple up front. Don't know if this impacts it or not.

I see. Thanks for the info.

So would you think that something like this Shimano 9 speed 11-28 would work?

Mine clears a 30T. No problem
I have a 11-34, I just don't shift to the 34T.
Getting a XL RD will allow me to use the 34T

Spacing is the same, switch the rear derailer to a MTB unit to make the big cog. I can get a long cage Ultegra or Tiagra to go to 30T, but it won't make 32, I've tried.