Tire pressures

Hi,

Just replaced both sets of tires with the new Dunlop Roadstar Sportmax (here in AUS)

My last set of tires suffered bad cuping even after looking after the pressures on a regular basis.

When I arrived at the store I was direcred straight to the changing bays and the tire pressures were

checked hot. Both were about 7 PSI above the recommendations that I normally run and it occured to

me the reason for the cupping, the tires normal hot running pressure of about 49PSI.

I was told to drop the cold pressure 5-7 PSI, ie front 34 rear 36.

What would be the general consensus ???

Regards

Ken

If you were running Bridgestones, they are known for severe cupping.

What is normal for "HOT" temperatures? We are always told to check the tire pressure "COLD" then ride our bikes. You might check your tires, then go ride 20 miles or more and check them again. All tires are going to increase in pressure after being ridden.

I normally rum my tires @ 40 lbs cold and have never suffered cupping....except on Bridgestone 020s.

Well,

I think most run higher COLD PSI than that... I run 40 COLD up front and 42 COLD to the rear. If you were told that the higher tire pressures cause cupping.. I suspect that you were given bad info.

WW

40 and 42 here with no problems.

34 is too low on the front.

FJRMGM said:

40 and 42 here with no problems.

Click to expand...

Ditto, though I'm also happy if it's a pound or two higher.

Doesn't altitude also effect tire air pressures?

Ken

A low cold tyre pressure makes it flex more which generates heat raising the running pressure. Higher cold pressure reduces the flexing and will run cooler. Check the pressure on a cold tyre. I run my Storms at 42 front and 44 rear - 230 lb solo rider, 25 lbs luggage. When I used the pressure stated in the manual the front tyre cupped and I had a wobble around 45 mph. With the higher pressure and proper balancing (dynamic with no center weights, not static) the wobble went away.

Just my observation, your mileage may vary.

Brodie

Queensland Ken said:

Hi,
Just replaced both sets of tires with the new Dunlop Roadstar Sportmax (here in AUS)

My last set of tires suffered bad cuping even after looking after the pressures on a regular basis.

When I arrived at the store I was direcred straight to the changing bays and the tire pressures were

checked hot. Both were about 7 PSI above the recommendations that I normally run and it occured to

me the reason for the cupping, the tires normal hot running pressure of about 49PSI.

I was told to drop the cold pressure 5-7 PSI, ie front 34 rear 36.

What would be the general consensus ???

Regards

Ken

Click to expand...

I run 40 rear and 38 front. Higher with luggage and/or two up.

You could get really fancy and run nitrogen............set it and forget it

It's the Bridgestones...mine came stock and had significant cupping early.

Always check pressure cold...

I run 40 front, 42 rear.

Ken is in QLD

Over summer you can expect consistent day time temps in the 30-40 degC (86-105deg F)

Being in Sydney we also have similar summer temps. I run my Z6's at 36 Front and 38 Rear (cold pressure). In the Winter I may up that my 2 PSI.

Last ride I checked my tire pressures at home, rode to our meeting spot (about 20km) wher we all checked fuel, tire pressure. etc. My pressures were 38 and 40 so that's a 2 PSI increase in just a few quiet km.

The Sports bike boys were saying OHHH too much pressure.. But my bike doesn't weigh 200kg..

My last set of Z6's did cup slightly (although only on the right side) but nothing of any real significants. This would I guess indicate I ride harder in Right turns??

Brodie is right.

Check Your Cold Pressure, ride the Bike as you normally would until the tires are warmed up, check the "hot" pressures.

You should be between 5% to 8% higher than the cold pressure.

If the difference is greater than 8% Add more air. ( As Brodie said, higher pressure reduces tire flexing, less heat build up)

This will set the correct pressures for your weight, riding style etc.

Holy physics 101 class.

39/41 for the road, and I'll drop them down to 22/22 for the dirt.

Oh, wait... wrong forum. Sorry.

LDRydr said:

Doesn't altitude also effect tire air pressures?

Click to expand...

No. The pressure is the same inside the tire, it changes on the outside.

Dr. Science of Blues and tire pressure presents; FJR Forum online physics class. :goatee:

Your bag of chips you bought at sea level has X pressure in it. The sea level atmospheric pressure keeps the bag deflated (so to speak) by the outside pressure pushing against the bag-O-chips. At say 7K feet, the outside pressure is less so the bag inside pressure is able to push out and inflate...so to speak. No inside pressure change, just the outside.

Test next Tuesday on, Why women think we're all crazy. This is a pass or fail exam. Please make sure Bust and odot get the proper tutoring before the test. :graduated:

Me n odot in the same class? Why would anyone want to abuse them selfs that badly :blink:

:jester:

I found that if tires pressures are low (especially the front tire) the FJR handles like a truck. Keeping it at 40/42 cold makes the handling feel light and nimble.

:blink: '05 manual had it broken down in different catagories of weight/high speed riding and the front and rear inflation ranged from 36 psi front and 36 psi rear to 36 psi front and 42 psi rear.

The '06 manual just has flat 39 psi front and 42 psi rear for all situations.

I run 40 psi front and 42 psi rear.

I check it before everyride and everyday before getting started on my extended day rides around the U.S. and Canada...yeah I know, type "A".

40 PSI Front.....42 PSI Rear. Running Metzler Z4 Front and Z6 Rear. Just changed the rear and will see if this pressure helps with a longer tread life.

FJRBluesman said:

Your bag of chips you bought at sea level has X pressure in it. The sea level atmospheric pressure keeps the bag deflated (so to speak) by the outside pressure pushing against the bag-O-chips. At say 7K feet, the outside pressure is less so the bag inside pressure is able to push out and inflate...so to speak. No inside pressure change, just the outside.

Click to expand...

Hmmmm...........dusting off physics cobwebs from the little rock between my ears............................

The pressure in your bag of chips did not change from one altitude from the other because the VOLUME inside of the bag changed, keeping it the same.

PV=nRT - The Ideal Gas Law

Not true in a motorcyle tire where the change in volume of the interior of the tire would be minor. So an altitude change, and the corresponding change in exterior pressure would have an impact on the interior pressure of the tire (making it greater) IMHO. However it would be a very small one, and nothing needing any consideration.