Odd Questions - Tire Mounting

[sloowpoke]

If all you look at is the speed rating, you are fine until you use the brakes. Most people never think about how heavily they are loading the front tire, during hard braking. On my K12GT I'm looking at loading the front tire up to about 900 pounds peak weight during hard braking, when riding one up. Since the front tire is only rated for 520 pounds max load, I try to avoid situations where I might have to brake hard. When you buy a new front tire, do you make sure you are buying a tire that can handle the full weight of bike, passengers and cargo during braking? If not, you are probably exceeding the tire's rating. Likewise if you run less than the tire manufacturer's recommended max load psi in the tire, it is likely being overloaded even during mild braking.

Doing a 'stoppie' puts more weight on the front tire than the total combined weight of bike, riders & cargo. If I recall correctly, it's possible to reach a peak load of double that combined weight, just before losing control and tumbling over the front end, but I no longer recall the math necessary to calculate various loads at different angles of stoppie. I think that double weight peak would occur when a straight line originating at the contact patch and passing through the combined center of mass, is at an elevation of 45 degrees. Depending on rider/cargo weight distribution, that may happen as early as when the rear tire is only elevated 10 degrees.

The same factors apply to the rear tire weight load, during acceleration and wheelies. Do you still think you are not exceeding your tire ratings?

regards,
Joe

[racingiron]

Originally Posted by sloowpoke

Doing a 'stoppie' puts more weight on the front tire than the total combined weight of bike, riders & cargo.

I don't think that's possible. Where does the extra weight come from? Now, I understand what you're saying. Heavy braking and acceleration cause additional forces to be applied to the tires, but the vertical component won't ever be above the total weight of the motorcycle+rider+gear unless you're landing from a jump or otherwise accelerating upwards.

The extra forces will still apply horizontal stresses to the tire, increasing heat, strain, etc. I'm sure a good motorcycle can decelerate in a straight line at a rate approaching the acceleration of gravity (32 ft/s/s which would be about 2.75 seconds from 60 mph to 0), so that might be where your "double" figure comes from, but the horizontal deceleration and weight (vertical) on the tire act in separate planes.

Do you still think you are not exceeding your tire ratings?

AFAIK, the load ratings are for "continuous operation", meaning the manufacturers take dynamic loads that may briefly exceed the rating into account. For instance, the standard P-metric load ratings for tires mounted on cars is lowered by 9% when the exact same tires are mounted on light trucks/SUVs. The tire hasn't changed, but the tire manufacturers understand that the dynamic load on the tire might be greater due to the higher center of gravity of trucks (resulting in greater weight transfer under braking, cornering, etc). The end user doesn't have to calculate the weight transfer when the truck is fully loaded and braking heavily if they follow the P-metric guidlines. Same goes for motorcycle tires. Now, I'm not saying it's a good idea to take a fully loaded beemer out for some stoppie fun, but there's no need to break out the slide rule when looking for tires.

I'm not disagreeing with you, just letting my inner nerd out for some exercise. I'm open to correction from any physics types out there.

[George_in_KG]

I'll bite. Why do you ignore a manufacturer's recommendations and intentionally mount your tires backward? What problem are you trying to solve by reversing the tire?

Originally Posted by sloowpoke

.......
I and thousands of other riders have routinely ridden on tires mounted backwards. ..........

regards,
Joe

[reppans]

Originally Posted by George_in_KG

I'll bite. Why do you ignore a manufacturer's recommendations and intentionally mount your tires backward? What problem are you trying to solve by reversing the tire?

Now that is an interesting idea.....

How about to even out left side tire wear? I still have a decent amount of rubber down the center of my rear tire. I think I could get another 20-25% mileage out of my tires that way .

[mudman]

The manufacturers say, "There is more probability of tire ply separation" if the tires are run to the reverse of the recommended direction. Personally I don't see any possible advantage to doing this. Why tempt fate? Does anyone know of any CONFIRMED logical or sane reason for doing this? Show me.*************************MdMn********

[Brokerecord]

I have deliberately reversed my front tire on my Honda Hornet several times. From hard braking I assume, the front starts trying to cup, with the tread blocks getting sharp on one side and rounded on the other. When I notice this I flip the wheel and leave the correct spacer with the fork legs it mates too. Cold, heat, rain, and dirt roads, I can not tell any difference except, I pick up 3K extra miles before I'm to the bars. I never go past the wear bars. I think the arrow is more for liability protection then actual harm, on a street tire. I ride my bikes like I paid for them and riding over my head is taboo on the streets.