I found a couple journal entries at CGOAB regarding the Mt. Evans climb, and it seems like a great thing to do if you're passing by. Good way to spend a rest day ! Anyway, I was wondering if anyone tried to summit Pikes Peak on a bike. I'm not even sure if they allow bikes on the road up to the top, but it sure seems like it'd be a heck of a ride!

I just has a week in Colorado Springs and enquired about riding up there:
I wouldn't recommend pedaling up Pikes Peak. Bikes are not allowed on the dirt road up the mountain, and the singletrack leading to the top is unrideable for at least the last two miles heading up

There is a place that drives you up there and you can cruise down.
https://www.bikithikit.com/pikes-peak-biking.htm

I don't quite get it. If bikes are not allowed on the dirt road, then how come you can bike down the dirt road.

From what I have read I don't think you can ride up the road. If you Google it, there is a fair amount of info about folks mountain biking up the trail, but it sounds like they all walk some of it.

The Pikes Peak road is a controlled toll road (private road owned by the City of Colo Springs), heavily patrolled and bikes are not permitted. I wouldn't want to ride it anyway, too many cars, mostly gravel and dusty. The trail to the summit is not a good ride on a mountain bike, too steep and rocky to ride it above tree line, and very popular with hikers and trail runners (you'd be stopping all the time to let them walk by) .
There are lots of nice mountain biking trails on the west side of the mountain, enough to keep you happy for a long time, no need to bother with the summit, IMHO

It's a concession just like the donut shop on the summit. Rides are fully controlled paid for. Pikes Peak is a tourist attraction first, a mountain second.