I have discovered, after lengthy correspondence, that manufacturers consider their sizing e.g.190/55 as nominal only and widths in particular can differ considerably from these sizes. On most bikes, this isn't a big problem but some Ducati's tend to run their chains VERY close to the tyre so any INCREASE can be a problem. As an example, I fitted Dunlop Qualifier 2s to my Multistrada 1200. They were recommended in the on-line Dunlop fitting guide. They performed well but after a track day I was checking the bike and noticed that the edge of the rear tyre had been well thrashed by the chain plus the tyre had cut into the rear dirt guard. To cut a long story short, I sent photos and a complaint to Dunlop who, though they insisted the Qualifier was OK for the Multistrada, couldn't bring themselves to state that the contact was safe (of course it wasn't) and reluctantly ended up giving me a set of Sportsmarts in replacement. I measured the "190" qualifier at just over 210 wide! The point is, whenever you fit a rear tyre that you haven't used before to a Ducati (especially a 1098 which has no more than 5mm chain/tyre clearance) measure the width fitted and, if it seems a bit wider than nominal, check that the chain clears adequately. Don't rely on manufacturers, especially Dunlop.
Always an interesting issue this. On handling rather than chain clearance grounds, many if not most 99* owners switch from handbook 190/50 to 180/55.
Its not a case of not trusting the sizing. there is a tolerance level ( I think +/- 5% but will have to check.) I work for a tyre company on the car side but on checking the 190/55Z17 Sport on our brand it is indeed 190mm. The sport touring version is 192mm The 180/55 sport is 181mm and the sport touring is 188!. It is all down to the testing and getting the best out of the tyre in safety and performance / grip for each application The industry cannot have sizes of 192/50Z17 and 182/55 so numbers are standardised. You are correct that in switching brands the dealer should be asked the width of the tyre to ensure it is safe to fit.
Avon, by any chance? I recently fitted a 180/55 Storm to my 900SS and then had to un-fit it, sell the tyre to my mate and fit a 170. Everyone else's 180 clears OK, including Avon's old Viper Extreme.
Stickywicket - I reckon that 188 for a 180 nominal width may be within 5% but is absurdly over-width. It is so much nearer to a 190, why don't they call it that and be done with it. My main complaint was that Dunlop had just blindly recommended their tyre for my bike without ever checking that it's severe overwidth allowed it to be fitted safely. That is a dangerous practice that the industry ought to be ashamed of. Surely the manufacturers have an obligation to keep the actual width near to nominal and not wider than the next nominal size up as was the case with my Dunlop Qualifier (a 190 measured at 205). At 188 for your sports touring you are inviting all sorts of interference issues with chain, swinging arm and other components. This is not simply a customer bitching, it is a real safety issue manufacturers need to address. I do NOT believe that tyre manufacturers cannot control the manufactured width of a tyre more closely. They just choose not to for their own reasons thus putting their customers at potential risk. Ask the width of the tyre? You think that you can easily find that out from the retailer, distributor or even the manufacturer? And why should you? It just should not be necessary.
I cant answer your questions as I am not in tyre design. I will however ask the question. Believe me, when designing a tyre the number one priority is safety. They certainly would not add 8mm to a tyre for the sake of it. Think about it. The cost x the number of tyres produced would be ludicrous waste. As for asking the width of the tyre, my point was that the dealer should be aware of the sizes ( although I dint word it that way). Anyway we can second guess the issues until we get some facts. I will ask the motorcycle tyre designers next week
