tire growth at speed

I have been rehabilitating an '83 XJJ750MK acquired from Tim O the last couple of months and got it out for a nice ride this last week. As is my habit when replacing tires I went 1 size larger on the front. This generally helps make the speedometer more accurate in the legal range I generally ride at and up to 75 or so. That means I installed a 110/90-19 Shinko 712F and it really filled the fender, fitting with maybe 1/4 inch clearance at the top/front of the fender. Getting out on the local interstate for a short blast after 40 miles of local roads that produced no problems or issues I could smell tire smoke. At 70-ish mph the tire grows in diameter enough to just kiss the rear/bottom fender lip. That must have been quite the picture going up the road with smoke coming off the front tire!
If any watch pro drag racing you have seen how the rear slicks on the cars grow in diameter greatly as the do their burnouts and at the top end. That our bias ply tires would grow at speed makes sense but I had not considered it an issue, or even given it any thought. I would think that radial tires do not do this, or at least not nearly as much.
I shall be adjusting said fender and smoothing the inner lip of the fender before anymore interstate efforts.
Just something to think about.
John

 

I looked at Dunlop's website and an Elite 4 in 110/90-19 requires a rim from 2.15-3.00 with 2.50 nominal.
Since you're running a 110 on a rim only 1.85 wide you are changing the profile of the inflated tire.
I would expect you will see more growth than a properly specified tire/rim combo.

 

how much clearance is/was there ?

 

I am not near the bike at the moment but I would say there is about 3/16" at rest, at the rear and 1/4" at the front so the is "a bit" of wiggle room. I will loosen the mounting bolts and see if there is any room in the holes to move the whole fender away. Or I could just not ride interstate speeds...... yeah, right!
I had just never considered the tire growth previously. I imagine radials do not do this, or at least minimally.
John

 

shinko 712 is not a radial amazon calls it a radial



Part # Size Speed Rating Load Index Permitted Rim Size Outside Diameter Width Max Load @ Tube Type
87-4142 110/90-19 H 62 2.15~3.00 26.81 in. 4.29 in. 40 psi Tubeless

87-4141 100/90-19 H 57 2.15~2.75 26.1 in. 3.98 in. 40 psi Tubeless

 

i think as a general rule, when the tires start smoking, your going too fast

 

Good point! I slowed down and it stopped smoking.

 

or just drinking too much!

 

reminds me of the Roadrunner/ Wiley coyote cartoons

 

The new tire is about 2.5% larger in circumference. tire expansion at speed is enough to make contact as you mentioned. But once friction starts now it really will grow because of the heat, plenty of that if it's smoking.