Bridgestone tire running hot

[xswheels]

Is anybody riding on Bridgestone Spitfires and finding they run hot? I recently mounted a rear and it gains 6psi at operating temp. I subscribe to the theory that a properly pressurized tire should gain 10% when hot compared to cold pressure. With a cold pressure of 32psi my result was an increase of 20%. I further tested at 40psi cold, and expected the tire to heat and expand less due to a harder tire experiencing less flexing, but instead resulted in the same increase of 6psi. Now when you do the math at 40psi the resulting expansion is only 15% but why won't the tire respond predictably to various pressures? The sidewall max cold limit is 41psi and I am not comfortable going beyond that limit. Who knows what the maximum hot temp is for this tire, but I suspect there is very little buffer left at 47psi. There are no associated problems with my wheel. The previous tire delivered a 10% increase at 38 psi cold; my gauge is guaranteed accurate, my brakes are not sticking,  the tire is the recommend size and fresh, and the balance weights haven't left home. One odd thing is when the tire was brand new, I experimented with different pressures and settled on 38psi cold resulting in a operating pressure of 41.5 (10%) which was perfect for me. I now have 1,000 kilometers and it is running hot and unpredictable.

[fret not]

Try dry air to fill the tire.  Moisture in the air in the tire can expand a significant amount.  This is why some folks use nitrogen to fill tires.  It isn't the gas so much as lack of moisture in the nitrogen.

[Walt_M.]

I always subscribed to a 1 psi change per 10 deg F temperature change. Can you measure the tire temperature after running? I have a thermocouple attachment for my VOM and may do some checking myself.

[xswheels]

Try dry air to fill the tire.  Moisture in the air in the tire can expand a significant amount.  This is why some folks use nitrogen to fill tires.  It isn't the gas so much as lack of moisture in the nitrogen.

Good point, the repair shop that mounted the tire could have had a compressor tank with a lot of  water in it. I will remove the air and fill it with my hand pump. BTW I removed the schrader valve and stuck a wood  probe into the stem, but it didn't locate standing water in the tire.

[xswheels]

I always subscribed to a 1 psi change per 10 deg F temperature change. Can you measure the tire temperature after running? I have a thermocouple attachment for my VOM and may do some checking myself.

I have no way of accurately determining tire temp other than the hand test. The rear is considerable hotter than the front.
I realize increased higher outside temp account for an increase in pressure, but for my test the outside temp remained relatively equal during my test.

[YellowJacket!]

Try dry air to fill the tire.  Moisture in the air in the tire can expand a significant amount.  This is why some folks use nitrogen to fill tires.  It isn't the gas so much as lack of moisture in the nitrogen.

I would tend to think that most good shops would have a dessicator on their compressor tanks to trap/absorb any water.

David

Good point, the repair shop that mounted the tire could have had a compressor tank with a lot of  water in it. I will remove the air and fill it with my hand pump. BTW I removed the schrader valve and stuck a wood  probe into the stem, but it didn't locate standing water in the tire.

[Rikugun]

It seems like we're dealing with unknowns here, unless someone works in the tire industry? Do we know what the max allowable temp or pressure is on that tire to compare to what you are experiencing?  Also, you got exactly what you thought you would. When you started with more pressure (41) you experienced less gain (15 vs. 20%). That tells me your assumption that a more rigid tire rolls with less resistance and therefore less heat buildup is correct. The 10% rule of thumb is just that, not an absolute. Make sure to check your gage against others to see if they agree. What's the condition of your rear shock? I've heard a weak shock can increase tire temp esp during aggressive riding.

I wouldn't worry that 46 or 47 is too high. What do you think that tire would realize driving across Death Valley? Yikes! I don't recommend anyone try the following but for reference only. My dad pulls a utility trailer with his truck. The trailer has 14" auto rims with "B" rated, bias belted, significantly dry rotted tires. He routinely airs them to 60 psi (cold). This is over the max pressure as stated on the sidewall buy a goodly amount. When asked why he'll respond: "cause they run cool as a cucumber overinflated" He goes on to explain you're in much greater danger of a blowout from running an underinflated tire. Sounds crazy and it is. He gets away with things most wouldn't dare to try. Or, the max pressure listed on the tire sidewall is grossly understated for liability reasons. Tire manufactures certainly want to cover their ass.

[YellowJacket!]

I guess if you look at the side profile of a tire as it rolls, a tire that is underinflated or at normal pressure has a bit of compression in the lower part of the tire (its not round).  As it turns and is compressed, that rubber will heat up due to friction.  An over inflated tire would tend to keep its shape better and thus have less friction in the side wall.  Just a thought that is not rooted in any fact that I'm aware of.
And as for your dads tires, maybe they are not dry rotted, just stretched.  8)

David

Hey, what is the recommended pressure anyway?  I run my Avon Super Venoms at about 32 PSI and they seem to run best there.

[Lucky]

When asked why he'll respond: "cause they run cool as a cucumber overinflated" He goes on to explain you're in much greater danger of a blowout from running an underinflated tire. Sounds crazy and it is.

no it's not, makes perfect sense:

if the tire is under inflated the sidewall bulges at the bottom where all the weight is.

over inflated it'll remain more square to the road.  

that bulge stays at the bottom  so the tire is allways changing shape, increasing wear & creating friction (more contact area, more heat)

--Lucky

[h2olawyer]

I'm with Lucky on this one.  I worked in the tire industry about 30 years ago.  Definitely a greater chance of a tire failure when underinflated.  There is a rather large safety margin built into the markings on tires.  You can fill most tubeless motorcycle tires well over 60PSI to get the beads to seat (but with proper lube & a clean rim, it should never take that much).  I saw an occasional car come into the shop with tires well overinflated and all they showed was lots of wear in the center of the tread.

Recommended tire pressure for the V depends on load weight &  typical speeds / riding style.  It is in the manual - same info in the Haynes, Yamaha shop & owner's manuals.  I don't recall exactly what I run mine at because I haven't ridden it since last fall.  I'm pretty sure I run 32 in my RoadRiders and ran that in the Super Venoms as well.  but, I am not small and have the full fairing as well.  I have it written in my owner's manual, but that's in the tail of the bike at the moment.

H₂O   

[Lucky]

Hi H2O!, is it cloudy out or sumtin?   ;D ;D

The only time i ever experienced a true "blow out" was on a worn tire i knew had to be replaced on a Van, i hadn't gotten around to it..

the tire was a little low so filled it up & went on my way.  when the tire blew I was doing about 35 thru town, & I think the jogger on the sidewalk had a "code brown" lol

[Rikugun]

And as for your dads tires, maybe they are not dry rotted, just stretched

Now that's funny!

[h2olawyer]

Hi H2O!, is it cloudy out or sumtin?   ;D ;D

We've had clouds & even snow over the last week.  Not quite a 'damp' as you folks in TN, though!  Also just started building my new telescope and need to take occasional breaks.

It is easy to see when a tire has been run severely underinflated.  There is normally a nice, rough ring in the sidewall on the inside of the tire.  There are lots of little rubber balls rolling around in the tire as well.  If run long enough, the exterior of the sidewall will show a darl stripe as well.  The tire need not be totally flat to cause the symptom.  when I was doing tires & would see this situation, I would strongly stress the importance of replacing the tire.  I was not working on commission and did not make any extra $$ for selling tires - I was just concerned for the customer's safety.  Often, the customer would hesitate until they got a look at the damage inside the tire.

H₂O

[xswheels]

I thought I would update my hot tire issue. Actually there is no change. I did exchange the air with a hand pump, but it made no difference. I tried to get nitrogen locally, but the two dealers I went to didn't sell it. In fact Goodyear called nitrogen filled tires a scam. I picked their brains at Goodyear but they had no answers for my high pressures when hot.

[lexx790]

Compressing air carries the moisture in the surrounding air so it doesn't matter if you use a hand pump or compressor.
I think most nitrogen is produced through semi permeable tubes which need dried air, so this may be another reason why nitrogen is used in tyres.

[Rikugun]

I tend to agree with the scam comment - it seems to be an unnecessary expense for the casual motorist.  I'm also not surprised that changing out the air to that provided by a hand pump yielded no improvement.

Is there any cupping or other signs of unusual wear? This goes back to my earlier queston of the rear shock's ability to properly dampen movement. I'm assuming you still have the original shock and damper. I'm also assuming it's been balanced properly and if directional, installed correctly.

I suppose it's possible you could have a defective tire  - delaminating plies (not outwardly apparent) causing friction and heat?

[Brian Moffet]

Is anybody riding on Bridgestone Spitfires and finding they run hot? I recently mounted a rear and it gains 6psi at operating temp. I subscribe to the theory that a properly pressurized tire should gain 10% when hot compared to cold pressure.

I'm not sure where this figure came from, but is it for motorcycle tires?  Car tires?  Low-profile car tires?   Having a 6 psi increase when my tires are hot doesn't seem like a big deal to me.  What is the actual temperature of the tire? 

My 1 cent, but I'm not a tire engineer, and I've never measured my pressure after riding.  I have had my tires warm enough to be "hot" to the touch.

Brian

[Rikugun]

The tires on my Kawi are "hot" to the touch after riding as well and seems to be nearly the same front and rear. To me it's normal and I know the history of them.  The increase described doesn't seem extreme to me either .

However, XS claims that this tire did not heat up like this when new so I guess that is where the concerm lies. I would think it would act similarly at 600+ miles as when new so it does seem a bit strange.

Getting back to the highly subjective "feel" criteria....I didn't see if you (xswheels)mentioned a difference in the feel of the front vs. the back.

[xswheels]

My tire appears to be wearing normally with no evidence of cupping, or any unusual wear so far. The front tire is warm at operating temp, but the rear  feels considerably warmer. The previous tire would heat about the same as the front. I realize some styles of tires are predisposed to running hot, but I doubt gaining 20% in air pressure is desirable.
There are no associated problems such as wrong direction; unbalanced, sticking brake causing the rim to heat,  bad wheel bearings, rubbing. The shock is an upgraded low miles '83 that responds to changes. Like I said when the tire was originally mounted I experimented with different pressures and settled on its sweet spot at 38psi cold/41.5 hot. Now, 1,000 kilometers later, no matter what pressure I use(between 30 and 42) it gains 6psi and just feels too hot.
I tried finding a link for questions on the Bridgestone site, but didn't find one.

[Night Vision]

is your tire mounted backwards? just a thought

I check my tires cold... but never during or later after a ride... so I don't know how much they heat up.

they DO heat up, I just don't know how much....  I'll check on Friday if I remember

I do know that a BS Spitfire I had was huge for it's size and not very sticky (read "hard rubber") maybe that's just the way they are