The above posts have just answered a couple of questions about tyres that were bothering me. Firstly, the low pressures on Vintage bikes. Members will see a feature in the forthcoming edition of The Star about a 1927/28 BSA Combination and the rear tyre looks decidedly low in pressure to me. I now know the reason why- Comfort!
Next was the Roadrider on the front as per my Thunderbolt and the 'ponderous' steering. This doesnt happen when the rear tyre (Roadrider aswell) is new but as the crown wears flat, the problem becomes more apparent until it gets to the stage when the ride becomes, lets say, less enjoyable. As Julian says this starts about 2500 miles and at 4500-5000, although legal treadwise, its time to renew. At £80 a pop this may be considered by some as uneconomic, but when the new one is fitted, the bike handles brilliantly. TT100's give the same effect.
Also, be aware, if considering to fitting a Road rider or TT100 to the front of an OIF B25SS or B50SS as its likely to rub against the wire mudguard stays.
Chris