Tire rating and speed expansion

Tire rating and speed expansion ponder. We've a Honda Reflex scooter that I run up on its stand to see rear expand like a inch or more in the 60-70 mph range unloaded. Peel's best all around tire was a dual purpose tractor like tire with a H speed rating. Its the tire that gave me multiple road orgasms on Ms Peel and my hobby to piss off squids before the game started and sneers turned to frowns. Anyway a strange thing happened a couple times I tried to hang on till Peel topped out only pulling to 6000 steady rpm speedo would suddenly increase a few mph but the tach didn't. I had my face planted on clocks to make sure, which is the scary part of not having a data logger. Peel clocks were fresh and fine back then with one to one immediate steady reaction to speed and rpm changes. So always wondered if I exceeded the tire rating somehow? These speed runs were only done after some good tire heating twisties, as that's whats on either side of the 1/2 mile straights here and there. Will attach some type of witness material if I ever go that fast again. Has anyone else noticed tire expansion? Just because tire expands though don't mean its over heated and about to blow right away but at some threshold ... what happens? I had just put on Supervemons when Peel blew her stack so never had power to pull off her power steering so never got to taste actual street tire traction limits, but could feel the better grip teasing me to test it.

Yeah, just like John Force.. only with 50 horsepower :roll: :mrgreen: :lol:

When you run it up on the stand, be sure to have the video rolling. Ever see a snowmobile come off the stand with the throttle taped WFO? They launch very strong :lol:

I learned about tire speed expansion when I put a larger diameter front tire on my new Bonnieville. I did that to help raise the front end back up from the ill effect on handling (too easy to start tank slapping) of a even larger rear tire I had previously put on. There is lots of extra room for the rear tire so I had no clearance problem with it. However the front did not have nearly as much clearance between it and the fender stay bolts. About half the clearance was lost with the larger tire but it looked like there was enough left to work ok. I went for a test ride and all was well around town going under 45 mph. When I got on a highway at about 50 mph or so I started to hear a noise from the front of the bike so I pulled over and could not see any problem with the tire or the fender bolts. This happened again with the same result. So the third time I stayed at speed a while longer and the noise got louder and I saw smoke and smelt burning rubber. When I stopped and inspected this time the bolts were real shiny and there were hot grooves in the tire matching the bolt locations. It then dawned on my pea brain that centreficial force must be expanding the tire diamater enough at speed to contact the bolts. So I rode home slowely so I would not cause any more damage to the tire. Luckely for me the cut groove was only about 1/3 of the way through the tread block so it did not get too deep to cause a blowout. I got shorter fender bolts that did not project past the stay nuts and there was just enough clearance for the tire. I don't remember the exact amount for sure, but I think my tire expands about 1/2 inch or 5/8th something like that at speed. I had never even thought about tire expansion before this lession.

Alrighty Mighty! This is exactly the feed back I wanted and not find out the hard way my self. i'll definitely have to plan around tire expansion in Peel then. I was thinking Peel's tractor tire deep grooves allowed more thread flexablity so might not be such an issue on pure 149 mph rated street tires but your report makes me think its an innate tire issue no matter the speed rating. You also impressed me how slow it can happen enough to matter. Thanks again for resolving this mystery to me.