Both my road and MTB shoes are Sidi 43.5.

I'd disagree with Tom D about that sizing philosophy. It really depends on your foot. Sizing is not really about length, but more about supporting your foot and providing the best power to the pedals.

So, the best thing for your foot is a custom/semi-custom insole.

Since I have a high arch/high instep, my shoes actually have a tiny bit of room in the length, but that's b/c my arch/instep fits the 43.5 the best. My feet don't move even with the straps undone.....

In general...you certainly want them more snug than loose, yes.

Good luck.

I don't have my mtn bike shoes nearly as tight as my road shoes because you end up walking/running/climbing/hiking more on the mtn bike.

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Don't hold back

One problem I have with some mountain bike shoes that I never have with road bike shoes is the foot coming out at the heel while running. Something to check for. I also found latches to be a nuisance if you get them a bit muddy. Velcro all the way for me.

just bought new mtn shoes. I didn't get them as tight for reasons already listed, i.e. hike-a-bike. also look for something with big nobs on the bottom, that way you won't be walking on your cleat. I went with carbon soles too, as I liked the upgrade in road shoes, so figured is was worth in in mtn shoes.

When I was trying on shoes, the mtn shoes seem to have a higher heel, and more wiggle room in the toes then the equivalent road sized shoes. Could just be perception though

-bcreager