You can stay off the free way and leave Spearfish by heading up to Belle Fourche and grabbing 212 all the way to Billings and down to Red lodge.

 

Here is a suggestion for a more scenic ride. Go up 95 from Spearfish to Bella Fourche and visit the Park and museum for the geographic center of the US. Very interesting. Then fuel up and take 212 west (called the Warrior Trail) Refuel at Broadus Mont. Possibly get a frig magnet there with the 212 emblem and wings. The end of 212 is right at the battlegrounds where Custer got what he deserved. Good museum and gift shop there also. From there if my memory is right it is 89 and it intersects with 1-90 again and drop down to your destination. After you filled at Broadus fill at the next station as they are far and few between Broadus and I-90. Very scenic along the two routes and some Indian villages with abject poverty evident.

I have done that route several times over the years and it is always worth the ride. Montana State roads are 70 mph limits so you don't loose much time. However note that there are no guard rails and only 4 feet on sloped shoulders with huge drop offs.

 

Just a thought, if you take Hwy 85 N from Spearfish to SD 34, just south of Belle Fourche (turns into WY 24) you get the Black Hills in WY - along with Aladdin and Hulett. Then Devils Tower is on Hwy 24 which you can follow to Moorcroft, WY and back to I90. From there you can pick and choose from the many suggestions above - all great roads!

 

I can vouch for 212 being a pretty ride. Places out there that you can see forever and not see a manmade object except for the road. Just be VERY aware of speed limits in the towns.

 

Thanks everyone for all the great suggestions, time to do some planning.

 

A good idea to plan your fuel stops and pay very close attention to the weather. You won't need to stop for fuel often, but when you need it . . . Use of Google Maps and Gas Buddy can be very helpful. Over the years I've also had the "pleasure" of encountering wonderful weather as well as snow storms, hail and I spent an afternoon in a small town while a series of tornados (visible) came and went around us. Spectacular but not something I'd care to experience again. Luckilly a woman came running out of a shop and flagged us down as we were riding through, so that we'd take shelter a few minutes before the "show" started.

 

I agree with the suggestion to go to Belle Fourche. I admit that the biggest reason I like going to that town is because that's where "The Cowboys" took John Wayne's herd in what may be my favorite movie ever.

Are you planning to see Devil's tower while you're out there? If you don't have it in your itinerary already, you should see it either on the way out or back.

I don't think you'll find a bad way to get to Red Lodge from Spearfish. Every road I've been on out there is gorgeous, even the freeways. So if you find yourself pressed for time and you have to take a freeway, it's not the end of the world.

 

I'm going to give my .02 worth, I just came off of the bear tooth 2 days ago.
So I left Cody about 9:30 in the morning and got into Red Lodge about 2:30 -3:00pm. If you are going up there just to do it that's fine too but there is so much up there to see I wouldn't rush it. We headed up Chief Joseph's to 212 then headed east over the Bear Tooth . There is lots to see just on Chief Joseph's alone! I'm not going to go into details but all I'm going to say is plan on a hole day to do it, it will be time well spent! We spent the better part of the day going up to Red Lodge and about 1.5 hours (at most) coming back to Cody via 308 to Belfry then 72 south to Cody.
Jmo

Sorry I didn't answer your main question!