We've had these 185/60/13s on the Ka for around 20,000 miles. The fronts are down to just over 4mm, the rears somewhere around 6mm.
When I first put 'em on I had some concern about sidewall deflection. Diddy ickly rims, lots of sidewall - but had no problems whatsoever.
Now I'm getting sidewall deflection at cornering speeds and loads where before it was _never_ an issue.
My first suspicion was that the pressures are low, but they're just fine. I can't believe that slightly warmer temperatures will make a difference, 'cos lets face it, tyres are not cold after the first few miles anyway. So I guess the tyres could be wearing a little?
Charlie's advice is, "yeah well we need at least 16" rims then, oh look, the Streetka uses 16" wheels, they'll go on just nicely."
Next she'll be wanting chrome 22s and a big V8 pickup. :-)