I've got a 1998 Evo carb FLHR Road King done 63,000klms with a DJP sidecar mounted and I'm in heaven! I bought the bike a few months ago, I'm the 3rd owner, then got the sidecar and mounted it myself with the help of  a local engineer. The bike has near new Dunlop D402 tyres and the sidecar has a 10" Mini wheel with a near new tyre. The outfit tracks properly, is easy to steer and handles quite well for a heavy hack - 550kgs total with me on it.

Has anyone with a sidecar put car tyres on their bike? Better traction?

Looks good, do you have a reverse gear fitted ? Cant help you on the tyres.

I can understand wanting to put whatever decent tyre that fits the sidecar on, but just to clarify your post, are you asking if anyone has done what you have with the addition of a car tyre on the sidecar....not on the bike? I would imagine traction is still going to be a major factor with the front and rear, but under the sidecar, I can't see this as being a critical point. What people with tiny wheels and tyres neglect (especially on tiny trailers), is the fact they have tiny wheel bearings spinning at super speeds, and quite often tyres that are not rated for anything over a wheel barrow speed.

I'm asking if anyone with a sidecar attached has put car tyres on the bike rims and was it successful? i.e.: more traction?
No reverse gear at this stage.
cheers

this may help. set up looks a little different & tyre/wheel is probably bigger. As previous poster said, traction on the side car is not really an issue. It just follows the bike.