Can I use mountain biking cleats on a road shoe...? I have an older pair of road shoes that appear to support both two-hole and three-hole cleat systems.
I've attached a two-hole Shimano mountain bike cleat to them and gone for a very short ride to find the bottom of the shoe is taking a fair bit of damage (perhaps I didn't fasten the cleats firm enough?).
Are these shoes simply not designed for these cleats? Or, should I just tighten them right up and expect a little bit of damage to the shoe?
The shoe is a Specializer Sport.
Yes, this shoe also accepts the MTB-style two bolt cleats.

Three-bolt and two-bolt cleat pattern fits all major road and mountain
pedals.

(from https://www.specialized.com/jp/en/sport-road-shoes/p/117510?color=&amp;searchText=61217-3238)
They will accept Shimano SPD, Crankbrothers and other MTB cleats. However, the sole will get deformed or damaged. With some cleats this is expected and even true MTB soles will get signs of use of these cleats. I am not completely sure about SPD, but for Crankbrothers the sole is in a direct contact with the pedal so the pedal directly pushes into the sole and it will certainly make some imprints during the use.
There are sole protectors available by Crankbrothers. I have no idea whether they also work for SPD or whether Shimano also sells some, but some vendors (like Ryder) make SPD-compatible cleats that include sole protectors in the package.