An old Cycleops magnetic trainer. Friend gave it to me last year after I was hit by a car and couldn't ride outdoors for a couple of months. Really helped maintain most of my hard-earned conditioning. Mostly I use it with the Ironman, but I also use it to test all my bikes for shifting accuracy, etc. Just needs the right skewer and end cap that securely fits the adjustable holder doodad on the trainer.

I still use it occasionally especially on cold rainy days, mostly for short interval sessions using a timer; or longer very easy recovery rides while watching TV. I tend to push myself too hard anytime I'm outdoors on the road bike, so when my legs are sore or dead I do better on the trainer, just moving my legs around with little effort for an hour or so. Helped last week. I road pretty hard four consecutive days and my legs were still sore a couple of days later. A couple hours on the trainer at a very easy effort helped.

And I find it difficult to do regimented high intensity interval training outdoors. Not enough flat terrain. So I'll do three to five sets of intervals, usually 5 minutes on, 5 minutes easy effort, lather-rinse-repeat. I usually do 10 seconds max effort, 20 seconds easy, for 10 reps per 5 minutes; or 15 seconds max effort, 45 seconds easy effort, for 5 reps per 5 minutes. Mostly good for cardio/respiratory conditioning.

Some folks recommend special trainer tires but I just use the same Continental Ultra Sport II tires that I ride outdoors with. No problems. Very tough tires, durable, grippy and a bargain at $15-$20 each. I got one wire bead 700x25 Ultra Sport II for around $7 closeout from Nashbar last year, but the folding bead versions hold up just as well on the trainer.

But I wouldn't use expensive road tires on a trainer. There are some reports of tread separation, etc., mostly from overheating due to friction. Resistance trainers with metal rollers do get pretty hot, especially at high rpms. I max out at 160 rpm but only for 10-15 seconds. So far, so good.