Thanks to finding a buyer for my ill-fitting Yokohamas so quickly I was able to buy another set of tyres this week without having too feel too guilty about how much I've spent on stance this last fortnight. Stance is what this car is all about though, so money should be the last thing causing me to compromise. You can't fight progress after all...I got back to mulling over sizes and decided not to take any chances on buying tyres too big again and went a couple of sizes smaller on width as well as a lower profile. The 8-inch wide front wheels have now got 195/40 tyres, as opposed to 205/45. That 5% decrease in the tyre-wall is more pronounced than I figured, but they still just about went on with a couple of assistants pressing the sides in. Still no need for the butane / lighter trick or a 'bead-blaster', but boy are they stretched! I think we're pushing the boundaries of legality here [Offence Code 112].
To my amazement there was - the 'bicycle inner-tube' gambit. This involves stretching a bicycle inner-tube round the wheel-rim and inflating it to create an airtight seal in the gap between the rim and tyre, deflating it as the tyre expands and finally sliding it out as the bead is reached. It sounds almost simple and to be honest it is. Unlike the butane / lighter method, which is very hit-and-miss when you don't know what you're doing, the inner-tube trick has a much steadier learning curve. You can see what's going on, gauge the pressure, find leaks easily and if the tube is going to pop out and break the seal it does so gently and with fair warning. With a bit of common sense anyone can handle a tyre popping off the rim at 40-odd psi, so this is by far the safest way to stretch tyres at home - I even managed it with a foot-pump, though I wouldn't like to do that again. It only took two proper attempts to get my first tyre on this way and, of course, there's zero chance of damaging a rim or melting rubber. Here's a great vid on Youtube of how easy it is - https://www.youtube.com/watch?v=lzxHYEdA8Qo, and it really wouldn't take many tries to get it down that good. I got 3 inner-tubes from Halfords for £10, so even if you need a dozen practise goes it still costs less than paying someone.
It's best to keep the tube size close to wheel size, but a bit smaller to get a tight fit. For my 16" wheels I bought 14" tubes, but a guy on the forum that convinced me was using 12" tubes on 15" wheels, so a few inches smaller is fine it seems. Getting an airtight seal was the most difficult part, but once you get a few PSI in and the tyre begins to press onto the tube you're away - make sure the valve on the tube is well proud of the seal as it inflates. Deflating and sliding the tube clear without breaking the seal can be troublesome, but it is just trial-and-error needed to get this right and it doesn't take much. Even though my first try was a fail and popped the seal it still managed to fully seat the opposite-bead, which is something two of us couldn't do using the old suspending the tyre on axle-stands and jumping on the wheel trick, so this is a good, safe method to do that. On my successful attempt, I still got a bit of tube caught in the bead, which is still stuck in there and caused the tyre to need quite a bit of pressure to pop onto the rim over it - about 65psi in fact, thankfully as with the foot-pump my legs just couldn't make any more! Still, the skinny 215 is on and I would recommend this technique to anyone stretching tyres at home.
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