Originally Posted by
RVD72
I have a mountain bike (Trek 6500) and a road bike (Cervelo RS)... 16 miles... along a beach path... no traffic... only have to stop moving once or twice... weather in Southern California is great... warm all year... rarely rains
I think you just made A LOT of enemies here with your post. Count me as one! I'm coming to get ya, 'cause no one deserves this kind of paradise! Muahahahahaha!!!
But it is a bit uncomfortable. Would most of you in my position just ride cycling shorts and jersey to work and then change when you get there? It is a 16 mile ride so it's not like it's only a couple of miles.
If it's uncomfortable, by all means wear bike-specific clothes. Riding a bike should be fun!
Should I get a new commuter bike?
You can never have too many bikes...

But really, unless you really want another bike and have spare cash, you really do not need another bike at all.
Should I just swap out the tires to more commuter friendly tires (i.e. 26x1.25 tires)? Should I just ride my road bike and be happier?
Whatever rocks your boat! Switching to narrower higher-pressure tires will certainly make a lot of difference on your MTB. Locking the forks might help a bit too. Riding a road bike will be fun, no doubt. Your choice. BTW, do you have a secure place to store your bikes at work? If not, then maybe you do need another bike - just a really simple reliable beater, so that your world is not shattered if it gets stolen.
It takes me about 1:15 each way so my average is roughly 13 MPH. I know it's not fast (especially BF standards) but I'm also not hammering and I wear a backpack with my laptop, etc. I am hoping to bring this time down a bit to slightly over 1 hour. The ride is mostly flat but there are a few small hills here and there.
It's nothing to be ashamed about. Most people inflate their average speeds anyway (and almost everyone means "rolling average" when saying "average"), so don't try to compare yourself with internet speed daemons.

Your goal is fine, if it's there for fitness and fun, but it wouldn't actually save you all that much time to shave 5-10 minutes off a one-way commute.
And in the end it actually takes LESS time than a car commute, because you're combining commuting and exercise... don't need to spend time at the gym on a stationary bike.