This issue it’s tyre time! Yes they're black and generally round, sometimes flat at the bottom.
A few pointers first.
- Rear tyres will wear out before front, rear tyres, are more likely to get a puncture.
- Worn tyres, in wet weather, are more likely to puncture.
- When replacing a tyre fit a new tube, from a reputable manufacturer, keep the old one as a spare.
- Use a good lubricant to fit a tyre, try not to use levers! It’s possible with some stout boots and fancy foot work. I’ve done this at the side of the road.
If you're lucky to have 16” wheel rims on your later Indian tyre choice is easy as an Avon SM is available in 5.00 x 16”, relatively cheap and easily purchased in the UK, about £75. Looks the part, and a quality tyre.
If you have 18” rims things get a lot more difficult if you want a 4.50 x 18” tyre as originally fitted, the only source in the UK is Northants tyres who sell a Coker diamond pattern tyre, looks very nice but……….£127.50 plus 20% VAT.
or a Beck tyre at 230.00 plus vat with a 2” white wall! Alternatively I tried a Dunlop K180 130/80/18” tyre as fitted to the front of a Suzuki Van Van 125
Not too modern looking but the rear tyre only lasted about 2,000 miles, now currently retailing at over £90. However they grip really well, one time when I was uncharacteristically pressing on a bit, I felt quite confident even though both front and rear wheels were drifting on bends.
There is a large selection of this size tyre on the market, but many of a modern tread pattern quite out of place on a vintage motorcycle.
However, you could try a 4.00 x 18” tyre and again an Avon SM is available at around £70 A good classic tyre which wears well
Earlier Indians used this size. Look a little skinny on later machines, also Dunlop make a K70 tyre which looks the part in this size retailing around £95.
Pre 1929 Indians used a (Beaded Edge) clincher type rim where the tyre bead is like a dove tail. I cannot make any recommendations here, other than on my 1928 Scout, came with these rims, which I immediately replaced with well based -wired on modern tyres.
The dove tail like profile relies on higher pressures (60 psi! ignore this at your peril) to keep the tyre on the rim. If you intend to ride a lot this type of tyre needs constant pressure checks or it will come off the rim with disastrous results. Many people have had this happen and usually have the wheel rebuilt to take a wired on modern tyre. One time in Ireland a friend on a Big Port AJS had his tyre come off the rim, from behind it looked like he had ridden over a black cat!
Finally please read this blog by Paul d'Orléans for the sobering story of a fatal accident using Clincher tyres. http://thevintagent.blogspot.co.uk/search?q=James%27+fatal
Remember:
You always win with Indian Tim 
