tire pressure

[dave01]

I run 20/28 to 20/30, depending on where I am riding and the road conditions. I found the 30 in the rear was great in the mountains but a little too stiff here in Fl with the potholes/road construction/sandy roads. 90 percent of my time is riding one-up too.

 

[NancysToy]

. . . . according to Kenda, 30 psi is the max you should have in the tire - either front or rear, and hot or cold.

see this thread; http://www.spyderlovers.com/forums/showpost.php?p=133603&postcount=4

Tom

This one remains a puzzle to me. All other manufacturers follow the philosophy that the sidewall pressure is the maximum normal operating pressure when cold. The tires are expected to gain 4-8 pounds or more as they heat up. Kenda is the only one that has ever mentioned "never" to exceed this pressure. No tire I know of, nor any other product, lists an operating pressure or temperature that is close to the point of failure. There is always a large safety margin. Kenda's approach baffles me. Perhaps something was lost in the translation.

 

[Director]

This one remains a puzzle to me. All other manufacturers follow the philosophy that the sidewall pressure is the maximum normal operating pressure when cold. The tires are expected to gain 4-8 pounds or more as they heat up. Kenda is the only one that has ever mentioned "never" to exceed this pressure. No tire I know of, nor any other product, lists an operating pressure or temperature that is close to the point of failure. There is always a large safety margin. Kenda's approach baffles me. Perhaps something was lost in the translation.

It's a head scratcher, all right, Scotty. I have never heard of such an approach either. I can't see checking the pressure every time I stop on a trip to make sure the pressure hasn't gone over the limit. :dontknow:

Bruce

 

[Tom in NM]

another Mystery of Life . . .

This one remains a puzzle to me. All other manufacturers follow the philosophy that the sidewall pressure is the maximum normal operating pressure when cold. The tires are expected to gain 4-8 pounds or more as they heat up. Kenda is the only one that has ever mentioned "never" to exceed this pressure. No tire I know of, nor any other product, lists an operating pressure or temperature that is close to the point of failure. There is always a large safety margin. Kenda's approach baffles me. Perhaps something was lost in the translation.

It's a head scratcher, all right, Scotty.
Bruce

I share your confusion, but I am used to being confused.

It is obvious that if the tire pressure exceeds 30 psi by 4 to 8 pounds, it will most likely not experience catastrophic failure - too many people are running at 30psi cold and I have not seen one post about exploding tires.

My totally uneducated and fact-less based guess is that the tire does have that margin of safety Scotty mentions and will not fail catastrophically if its PSI hovers above 30. But, above 30 PSI the tire (given its structure and class of materials) may deform and wear at a higher rate. In its design/engineering/manufacture/marketing this was probably a trade-off decision - not an unusual type of business decision for any product.

I really don't know if this is right, and if true, if it is a good or bad thing - and will probably never know. But, I will operate on this assumption and inflate my tires so they seldom go over 30 psi and hope I get more life out of them. That has called for some monitoring of tire pressures and riding conditions, events, style and preferences. My riding probably has a larger swing in temps and altitude than most. For the Summer, I got to 25psi (rear) 17psi (front) being my target. ( I like a firm ride ). With Fall and Winter coming, I will probably change that.

Like most mass consumer products, I am guessing as long as you stay in the specified range, you will be OK. Like I said, maybe by watching this, it will optimize my tire's life. Maybe not. The only things I know are;

• I hate the idea of replacing tires - especially the rear.
• I do not like riding on worn tires.
• I hate getting flats.

So, I will watch it, maybe it will help. I also have a spare set of front wheels and tires. (yes, I hate those 3 points above enough to have spent the money on having spares ready-to-go)

Tom

 

[NancysToy]

My question, purely conjectural, is that if the 30 psi max is to keep the center from wearing faster at higher pressures, what keeps the outside from wearing faster if the pressure is lower than optimum? And what about loading...a heavy rider vs. a skinny one, or carrying a passenger? Not yanking your chain, just playing the devil's advocate with a little food for thought.

 

[Director]

I share your confusion, but I am used to being confused.

It is obvious that if the tire pressure exceeds 30 psi by 4 to 8 pounds, it will most likely not experience catastrophic failure - too many people are running at 30psi cold and I have not seen one post about exploding tires.

My totally uneducated and fact-less based guess is that the tire does have that margin of safety Scotty mentions and will not fail catastrophically if its PSI hovers above 30. But, above 30 PSI the tire (given its structure and class of materials) may deform and wear at a higher rate. In its design/engineering/manufacture/marketing this was probably a trade-off decision - not an unusual type of business decision for any product.

I really don't know if this is right, and if true, if it is a good or bad thing - and will probably never know. But, I will operate on this assumption and inflate my tires so they seldom go over 30 psi and hope I get more life out of them. That has called for some monitoring of tire pressures and riding conditions, events, style and preferences. My riding probably has a larger swing in temps and altitude than most. For the Summer, I got to 25psi (rear) 17psi (front) being my target. ( I like a firm ride ). With Fall and Winter coming, I will probably change that.





Like most mass consumer products, I am guessing as long as you stay in the specified range, you will be OK. Like I said, maybe by watching this, it will optimize my tire's life. Maybe not. The only things I know are;

• I hate the idea of replacing tires - especially the rear.
• I do not like riding on worn tires.
• I hate getting flats.

So, I will watch it, maybe it will help. I also have a spare set of front wheels and tires. (yes, I hate those 3 points above enough to have spent the money on having spares ready-to-go)

Tom

Sounds like a reasonable hypothesis, Tom. So far, I am pretty happy with the Spyder's tire life, especially after years of changing motorcycle tires every 9,000 or 10,000 miles or so.

Bruce

 

[Bersquack]

I also do 20 front / 30 rear and it has been working great for me.

 

[FANG]

I have 11,000 on my tires and have run 18 in the front and 28 in the rear - in Fla in the summer. I have very even wear and am still a good ways off of encountering my first wear bar on the rear tire.

I run at 70-80 on the Interstates. Ambient air temp yesterday was 90 degrees.

I don't do burnouts but I ryde hard.

 

[NancysToy]

Sounds like a reasonable hypothesis, Tom. So far, I am pretty happy with the Spyder's tire life, especially after years of changing motorcycle tires every 9,000 or 10,000 miles or so.

Bruce

I'd kill for that on my Beemer. Usually only 5,000 to 6,000 on my RT, front and rear.

 

[Tom in NM]

Scotty, my chain has been yanked so hard and so many times . . .

My question, purely conjectural, is that if the 30 psi max is to keep the center from wearing faster at higher pressures, what keeps the outside from wearing faster if the pressure is lower than optimum? And what about loading...a heavy rider vs. a skinny one, or carrying a passenger? Not yanking your chain, just playing the devil's advocate with a little food for thought.

. . . . it broke off years ago.

My guess-imate is that the answer lies in the engineering and construction of the tire - and what the "optimum" is for the conditions you list. If the tire has "steel belt" reinforcements, how they were organized to distribute stresses would have a lot to do with how well the tire retains its shape or deforms. These "belts" composition, weave, tensile strength, flexibility, and plastic memory under different temperatures, pressures and kinetic forces and their frequency are probably the main factor in tire shape under usage - much like how the construction (weave and embedded kinetic shield plates) allow them to perform their function (protect the wearer) better.

For an everyday kind of item, tires are very complex - at least to my simple mind. I would also guess that the road surface would have a lot to do with the wear of the tire. Chemicals, like Chlorine, oil, gas, tars and other solvents, pavement texture (like different grits in sandpaper), and road debris that cuts, but does not puncture the whole tire probably also degrade the tires "rubber" and can cause them to wear [tread] out faster. I would also guess that that would effect their structural integrity and 'shape' performance.

Given all the variations in how tires can be engineered, the components used, the surfaces they are used on, what they are exposed to, and all the other factors mentioned and all the ones we have not considered (tire size and manufacturing anomalies for example), it would be unlikely we would come up with " The Answer " or "The Best Tire" for everyone.

The simple answer for my simple mind is, "keep it under 30 psi as best you can", as far as the stock tires on the Spyder go.

Tom

 

[Dudley]

I'd kill for that on my Beemer. Usually only 5,000 to 6,000 on my RT, front and rear.

Best mileage I ever got on a rear tire was 28,000...2000 Yamaha RoyalStar Venture.

 

[NancysToy]

The simple answer for my simple mind is, "keep it under 30 psi as best you can".

Tom

The answer for me comes to us via Mad Magazine's Alfred E. Newman..."What, me worry?"

 

[jnt]

18 Front; 28 rear. One-up only - she 100lbs, me 165.