Rode my winter bike with studded tires for the first time this morning. Added at least 10 minutes to my 8 mile commute. Also added at least 40 bpm to my average heart rate just to maintain that slower pace. My winter bike is an old heavy mountain bike, and I usually commute on a hybrid or a road bike so some of the loss of speed is due to a slower bike in general. But the studs definitely add resistance.

I have a love/hate relationship with my studs. I love the increased security of riding on ice. I hate the increased rolling resistance, especially on those days when 90% of the pavement is clear and you're only riding the studs because of the 10%.