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Old 21-Dec-2006, 08:14 PM
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Tyre/Wheel - Can I fit a bigger tyre?

Will a 180 tyre fit on a 6.25" rim,or do you have to go to 190?
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Old 21-Dec-2006, 08:22 PM
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It depends ...

Some tyre profiles are more sensitive to rim width than others. Dunlop, for example, says that their 180 slick works fine with up to a 6.25 inch wide rim. In the past, both Michelin and Dunlop have stated that a 5.5 inch wheel is suitable for 160 through 180 tyre widths. Different tyre manufacturers specify different rim widths for their tyres.

In general, you'll expect to use a 190 on a 6.25-in rim.
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Old 21-Dec-2006, 08:56 PM
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Whats the best combination for a 190/50 then?Keep the 120/70 or go to a 120/65?
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Old 21-Dec-2006, 09:08 PM
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Have you thought of using 190/55's?
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Old 21-Dec-2006, 09:10 PM
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Yes mate,i am open to suggestions.I have posted the quandry in the 851/888 section!!

I read somehwere that the new 190/55 gives the same speed of turn in as the 180/55 which would be perfect.

But what front?
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Old 21-Dec-2006, 10:16 PM
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I'd stick with the 120/70 front and pair it up with a 190/55 rear.

Had a 120/65 front on my ZX6R, and I didn't like it, just felt like it was going to tip in a little sooner. Couldn't imagine what a 120/60 would be like!

Dunlop also do a 190/60 which I've heard good things about...
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Old 22-Dec-2006, 02:29 PM
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The 190/55 Diablo Corsa is not available until the 2nd quarter of next year.So it looks like 190/50!
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Old 22-Dec-2006, 02:53 PM
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Tire Sizes

by Kevin Cameron

Because tires become bigger every year, many riders assume that (a) this is progress and (b) bigger must be better in every way. This leads to the temptation to overwhelm motorcycles with the biggest tires the owner can find. Little 250 racers from the 1960s - initially so nimble and quick-responding on their original narrow-section 2.75 x 18F/3.00 x 18R tires - become ponderous when their vintage-racing owners re-equip them with the biggest tires that will physically fit into their fork legs or swingarms.

Look at a cross-section of a tire on a rim and you will see that, as a bigger tire is mounted on the same-sized rim, its sidewalls become more cantilevered, and therefore more flexible, which increases heat. Any tire is what it was designed to be, only when mounted on the intended rim width. If you must put bigger tires on your bike, and they call for wider rims, use them. Otherwise, either be happy with tires that are right for the bike, or trade up to a later model machine that already has the size tires you want.

In tires, everything is compromise, so you must consider the whole picture, not just a single variable like size. The bigger the tire, the greater its rolling resistance and the lower the top speed. But a larger section tire may increase cornering grip. Balance against that the fact that a narrow, sharp tire profile handles quicker than does a fatter, round-profile tire. On the other hand, braking can be more powerful and more stable on the round tire.

In the end, it comes down to crazy, unanswerable questions like is it hotter in the city than it is in the summer? Would you rather have in-corner grip with slow, heavy turn-in and two miles per hour less top speed? Or quick turn-in, less speed at the apex but a bit more on the straight?

History shows a never-ending cycle of tire and chassis develpment. As Dick O'Brien, for years head of Harley's race team, said back in 1969, “About the time we get the chassis handling really good, the damned tire people come up with more grip, the chassis starts to flex again, and we have to start over.''

Although great big tires may look bitchin' on that 20-year-old Kawasaki Z, go carefully. At the time, those chassis had to be braced to make them even marginally stable with the grip of race-sized tires. Just levering on bigger tires is not enough of an up-date. If you want a vintage Superbike, build the whole bike - rims, tires, braced chassis, updated suspension.

Sportbike Performance Handbook, 1998, p127
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