Aspect ratio on motorbike Tyre's?

The aspect ratio is the height of the tyres' sidewall, given as a percentage of the width of the tyre. So, for example, a 120/80-16 rear and a 100/80-16 front means the rear tyre is 96mm high and the front is 80mm high? But if you had a slightly wider rear wheel like a 130/80-16, then the rear would be 104mm high. In this example, how would the handling dynamics of the bike change.



Also, what if the front tyre had a different (i.e. higher or lower) aspect ratio to the rear wheel, regardless of the tyre widths - how would that affect handling characteristics?Aspect ratio on motorbike Tyre's?As long as the rim width is correct for that particular tire, extra width doesn't make a lot of dfference. That's why some of the 240 tires use a 5.5 inch rim, that's wider than a lot of cars.



If you use a tire that's too wide for the rim, the tire will take on a pyramid shape with a very narrow contact patch when upright. Tire wear will increase in the middle of the tire. When leaned over, you'll suddenly get a lot more tire contact, which might or might not be to your advantage.



If the rim is too wide, the tire will take on a shape like the top of a bread loaf, being rather flat in the middle. Like a worn rear tire, initiating a turn requires more effort to get the tire up onto the square shouder of the tire. You also have very little contact patch when leaned over and makes for squiggly handling.



The tire manufactuers have recommended widths or width ranges for each tire. That's what to go by because they know what shape the tire carcass is designed to have when inflated. The old Dunlop 71's (I think that's the right number) in the late 60's and early 70's had a very triangular shape. This gave very quick handling when upright and when leaned over, excellent contact. The British bikes used them and with the combination of their good frames, the higher horsepower Jap bikes couldn't keep up with the Brit bikes when they got into the curves.



As far as using different aspect ratios on either end of the bike, that probably isn't enough to make any difference in handling as long as the rim width is ok. A shorter tire up front is going to decrease the rake and trail slightly, which in theory would quicken handling but possibaly reduce straight line stability. In actuality, putting on the brakes and compressing the front springs is probably going to decrease rake and trail more than the extra 6 mm of height between a 120-80 and 120-90 for example. (The actual tire height difference is 12 mm, but the axle is only going to be 6 mm higher off the ground. A heavily loaded bike with the rear springs highly compressed will going to do the opposite, in theory.



A taller tire in theory is going to do the opposite by increasing the rake and trail. Now if you were going from a 16%26quot; to a 18%26quot;, 19%26quot; to 21%26quot; or vise versa, then that is certainly going to make some difference in handling. A taller rear tire is going to do the same thing as a shorter front tire and vise versa...but again, if you're just changing aspect ratios up or down one notch, it's so little that it probably won't make any difference.



If your bike's handling is too twitchy for your likes, a taller front and shorter rear tire might make enough difference to suit you. Too lazy and do the reverse. Just remember that just because tires from two different manufacturers have the same size stamped on the sidewall, that doesn't mean their actual size is equal. Again, check the manufacturers info, Dunlop is tops when it comes to providing actual tire width, actual tire height, recommended rim widths and usage. You'll find that there's a slight size difference between their own tire lines.Aspect ratio on motorbike Tyre's?In older times, tyre width was a dificulty, as occasionally still is. Vis: if the tyre is wide,and you are leaning over, the contact patch of the tyre with the road is a little off center towards the inside of the corner. If a significant bump occurs further inside the radius of the corner, and it becomes the new contact patch point, the alignment of the bike with the road is affected, such that the rate of turn changes tighter, lean, %26amp; increasing tyre adhesion stress and perhaps, on a shorter wheelbase %26amp; fat wheels, dislodging the rider with the jerk. Modern tyre compounds have eased the troubles a bit with better grip, but the physics remain true, and I sometimes worry when I see huge modern tyres. The Suzuki RV series were particularly bad, but even today's large bike riders need to be careful.Aspect ratio on motorbike Tyre's?the centre digits are % of the width measured rim to rim, not the tyre, this gives the height of the tyre from the base of the rim to the apex of the crown, unlike a car tyre where it is the wall depth. Thus by fitting a wider tyre you will increase the height of the tyre but without the reinforcment of the side wall. Therefore if the tyre is wider the tyre rides higher and the handling suffers.

If you kept the same size tyre but increased the rim width the trye would ride lower on the wheel and the sidewalls would be more stablized, thus there would be a mild increase in handling, but if you go to wide you will make the bike unhandleable in anything but a straight line.

It is better not to alter the width fitting of a tyre but only the aspect ratio of the tyre.Aspect ratio on motorbike Tyre's?I believe this may help, These are the three most common ways of sizing tyres, but keep in mind that there have been other ways of sizing tyres. (early tyres had both rim size and overall size, I believe that Coker still uses this on some Antique replacement tyres) EX 28X4.75X19