So the RGU sidecar rig has gone dark. Now time to figure out the Street 750 sidecar rig . factory tire is a bit odd shaped a 140/75R15.
looking at 3 options now that should work. Looks like plenty of room . With a Street tugging a sidecar IMO a tire that lower ration would be better than one that raises it. However 1/2 MPH at 65 would make no real difference.
165/65r15 would be an inch wider than stock and it you be very close on gearing 65.49 vs 65 MPH
165/60R15 would be almost prefect 63.68 vs 65 Mph.
155/60R/15 would work 62.36 vs 65 mph

 

Big issue. It seems that once you get down to a 15 inch motorcycle rim things change. A 15 inch Car tire will not fit right on a 15 inch motorcycle rim different size. To expand my efforts .Is there a 16 inch rim that will direct fit a 2015 Street 750? I Know the 2018 Street Rod has a 17 inch rear wheel. No giving up on this yet.

 

Mounted a 15 inch tire on the 15 inch Street rim today. As of now it not working as it should Tire is not centering on the rim will filled with air Hard to explain I will have to post pictures. Sure seemed like it was going to work when I put the tire n the wheel.

 

Never give up until you are sure it won't work. keep in mind I am doing this at home with some old spoons. Broke the tire down again. lubed it some more at filled it with air at110 pound pop the breads popped into place all around. Let air out to 35 pound no leaks.
I did this on a use rim so did not care about scratches it was from a wreck.
Next step pick the size I want to use buy a new tire and mount it on the bike. This is going on a Street 750 sidecar rig.

 

I ran 15 inch car tires on motorcycle rim for years on my Shovel with no problem. They did fit extremely tight and were very hard to dismount due to tight bead.

 

I kept finding a lot of reasons why it would not work, Some claiming a motorcycle 15 inch was a different size. I talked with Hd dealer today he said that bead on the wheel they have can be a bit of a pain for the tire to pop over . Now time to pick a size to try Looks like a 165/65r15 will work.

 

As I said a 15" CT on a motorcycle rim is extremely tight. but if you do it the other way around a 15" MC tire on a car rim is too loose to hold a bead if you lose air. And before someone comments about "why" would you do that I had (and still have it) a VW rim that has been dimpled for spokes. Ran it on a shovel also but found out when I mounted a MC tire on it that it was too loose.

 

The new tire will get mounted when we get back from our trip. The bike it is going on is a sidecar rig. The factory tire still looks new on thew sides but is wore out down the center. Normal for a sidecar rig.

 

Research is done. Decided on a 155/60r15 for the Street.. it is very close in width and just slightly lower. .

20 mph (32.19 km/h)19.19 mph (30.88 km/h)

25 mph (40.23 km/h)23.98 mph (38.6 km/h)

30 mph (48.28 km/h)28.78 mph (46.32 km/h)

35 mph (56.33 km/h)33.58 mph (54.04 km/h)

40 mph (64.37 km/h)38.38 mph (61.76 km/h)

45 mph (72.42 km/h)43.17 mph (69.48 km/h)

50 mph (80.47 km/h)47.97 mph (77.2 km/h)

55 mph (88.51 km/h)52.77 mph (84.92 km/h)

60 mph (96.56 km/h)57.56 mph (92.64 km/h)

65 mph (104.61 km/h)62.36 mph (100.36 km/h)

 

Glad you’re so persistent on making things work. Definitely let us know how it acts. Any chance the Street may get unhitched from the hack and ran on 2 wheels while dark? I’d be interested to hear your opinions of it.