See my reply to your earlier thread, which reply included this map:
https://ridewithgps.com/routes/29469149?beta=falseI did a good deal of research while planning my three trips that included passing through Wise River and nights in Butte. As far as I have been able to figure out, you have two choices: What's shown on the map or frontage roads from the junction of MT 43 and I-15 (town of Divide) and a relatively short stretch on I-15 and the I-15/I-90 (only 6.2 miles total) to Exit 122, where you can pick up paved Grizzly Trail Rd. then the BA&P Trail, which takes you gently up the Old Town section of Butte.
The unpaved sections of the route mapped out are doable on 32c tires. Just keep an eye out for mud in one or two spots if it's been wet.
BTW...If you ride MT 43 use caution. There is little shoulder and, depending on the time of year, you can encounter a good number of vehicles towing float boats. Also keep an eye out for cattle.
https://www.flickr.com/photos/105349603@N05/27402606314/in/album-72157667672266654/Divide Bridge Campground, on the right just before you cross the bridge over the river, is a nice, cheap BLM campground.
In the end, the route I mapped out between Wise River and the BA&P Trail is 50 miles. Going
via MT 43, frontage roads and the Interstates is 33.3 miles. That's not much of a difference if you plan to make that a day of your trip. Plus, the longer route has services in the Anaconda area. I believe the other way is devoid of services except for a roadhouse or two on MT43 before ZDivide. Ultimately, I think you have to decide if you can stomach Interstate riding. It's not always ideal, but in your case we're talking about 6 miles, much of which (before you get to I-90) could be very traffic light from what I have observed while in Melrose three times. Back in 2011 I rode maybe 3 miles on I-90 heading west from Butte because I chose not to explore the unpaved alternatives. Not ideal, but I never felt it was dangerous.
