Front tire size changes?

[Baldini]

...I just think it helps one predict how it will handle if you visualize going both smaller and larger rather than just visualizing going smaller....atleast it became clearer me....

 

Yeah - I get it. Still can't see re the smaller profile/higher pressure=less overheating tho....

 

KB

[Guest trispeed]

go ahead and try the 120/60. If you ride well, you will immediately have your definitive answer. Don't let anyone try to help, it's best to find out for yourself. FYI, if you want to fit 170/60 on a 5.5" rim, make sure the tire is intended for that size rim. Many 170/60 tires have an optimal fitment on a 5" rim, a la VFR 750 when they switched from a 5.5".

ALL 180/55 tires are intended for 5.5 " rims, check the manufacturers fitment guides for yourself. 190/50-17 was made for 6" and had little success for the street.

120/70-17 is the standard front tire for all sportbikes from 600-1400cc. There are a couple commuter bikes like the SV650 etc., that use 120/60 but that's the first thing to go when a skilled rider wants to ride half-way fast. The 120/60 steers quicker and tucks alarmingly when you least expect it. It's nothing at all like sliding the fork tubes up a bit; you have a different rolling radius, different side wall and tread profile, etc.....

Try for yourself and let us know what you find.

[dlaing]

Yeah - I get it. Still can't see re the smaller profile/higher pressure=less overheating tho....

 

KB

81061[/snapback]

The smaller profile has less area, and air volume to displace the heat, so it will run warmer and heat up faster.

By increasing the air pressure you are putting in more air, which may have an effect on heat, but I am not sure.

But higher air pressure makes the tire more rigid and it flexes less.

Less flexing equals less heat.

An underinflated tire is more likely to explode while riding across the desert at high speeds.

The smaller profile tire will require a higher air pressure than the normal profile tire....if only one or two PSI.

Likewise if you put larger tires on, you would need less air pressure.

In general the larger the tire, the heavier the load rating.

Also, the higher the air pressure, the heavier the load rating.

In any case the rear tire will almost always be running hotter, so I would not be overly concerned about one size profile difference, unless you are a very heavy braker.

[Guest trispeed]

C'mon guys, this is really simple. If you have a 5.5" rear rim, use a 180/55-17. If you have a 4.5", your best fitment is a 160/60-17. You could even go to a 160/70-17, like what is prescribed for an ST1100 ( Pan European) . It's made for a 4.5 and has a sport touring compound. Should be great for a heavy bike like ours.