Tire pressures

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MichaelB

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I believe the manuel says 22 & 26. I always thought this to be a bit soft.
I was just curious as to what others are running with what type and size of tire.
I am currently setting up a bike with 90/90 X 19 & 110/90 X 18 Avon Super Venoms. I will start with 26 & 30. Anyone else with this combo??
 
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MichaelB,

I also have Super Venoms installed on my Norton. I run about 36psi in the front and 40psi in the rear tire (the label on the sidewall says 42psi max).

The tire pressures published in the manual are for the old style Dunlop tires that were original equipment on our Nortons. However, I feel these pressures are too low for the more modern Avon tires.

Jason
 
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Jason
Don't know what the others think about your tire pressures....but that sounds a bit scary to me. That's in the red area on any tire pressure gauge and those tires must be stone hard which must make your ride awful hard and provide almost no absorbtion of road bumps etc. The tires are supposed to provide a bit of help for the shocks and the front end, you know. At that pressure, the amount of tire on the road must indeed be rather small, my guess is that it is so small, that you might have the bike go out fron under you some time in a curve. the amount of tire tread on the road is rather small to start out with on a motorbike and if you have that much pressure in the tires....you must have reduced that already small amount by about half. Half as much rubber on the road might get you into problems, the first time you have to push it towards the limits in some curve, or if you encounter some slight amount of oil or sand. Another point is where you live. The pressure in a tire is measured when the tire is cold. This is because when the tire is hot...from friction and normal riding..not to mention high speed highway trips....the tire pressure increases a couple of pounds...to what the manufacturer has decided is the area where the tire is sitting on the road flat and providing the best/safest amount of traction. If you start out at some incredable amount of pressure and then go for a nice long ride on the texas roads on a nice hot texas day...what kind of pressure have you got then? Lots. And you must be mighty close to the highest allowed pressure as stamped on the tire sidewall...which is only what the tire can handle, and not a recommended tire pressure. That high amout of tire pressure would only apply if you weighed 500 lbs and you needed that much pressure to make sure you didn't smash the rims on the first bump in the road. My quess is that you don't weigh that much....or?

Haven't you ever noticed that the car will handle sort of skitterich in the corners if the tire pressure is only about 5 lbs too high...sort of like driving on ice. The steering just too light and too quick? Same goes for a bike. Light , unsure steering and handling.
I use Dunlops and have, since I bought the bike, and true, I have no experience with the venoms,.......but I can tell when the Dunlops are just ONE pound too low on pressure. It just doesn't feel right. Bet the venoms are just as sensitive. 22 and 26 might be incorrect for the venoms....but the pressures you are using are surely risky.....get someone elses opinion...before you dump the bike.
 

ntst8

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I've been running around 32 to 34 front and back on supervenoms, but read somewhere recently (another forum perhaps) 28 front 32 rear was recommended.

Cheers
 
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Hewho,

Thanks for your concern about my safety. However, my 36psiF and40psiR tire pressures aren’t as unsafe as you think. You’re correct in saying that there is a relationship between pressure and temperature; that’s called Charles’s Law. The tire pressure increases when riding the bike, owing to heat from friction and other factors. The resultant pressure may be greater than the sidewall pressure, especially if the initial pressure before riding is the same as the sidewall pressure.

However, all tire manufacturers have taken the effects of Charles’s Law into account when they designed the tire and posted the sidewall pressure. All tire manufacturers recommend checking the tires when cold. It is perfectly safe – from a tire design standpoint – for the cold pressure to be the same as the sidewall pressure, even if the resultant running-pressure exceeds the sidewall recommendation.

I weight nearly to 200 pounds and have found that 32psi in the front tire is too low. After some 5,000 miles at this pressure, I noticed that the sides of the front tire were worn more than the center, a classic indication of under inflation. So, I ratcheted the front pressure up to 36 psi and increased the rear proportionally. I don't have enough miles accumulated to get a tire wear indication; so at some point, further adjustments may be necessary.

Keep in mind Hewho that under inflation is more dangerous than over inflation. Also keep in mind any passenger weight when checking and adjusting tire pressures.

Now, I may end up with the wrong side of my Norton on the pavement one day, but I can assure you it won’t be due to over inflated tires.

Jason
 
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Jason
I wasn't really too concerned about the amount of pressure simply because it was very close to the manufacturers recommended maximum allowed pressure as noted on the sidewall. I know that due to the "Mac Donalds" law of physics...they would never say it would handle x amount of pressure, unless it would in reality handle a heck of a lot more....too much risk of law suits.......and even I run near to the label amount on my old 1941 "Wanderer", because I couldn't stand to dent the rims on some pothole...but I don't "Hang ten" with that old lady anyway.

My concern was that if the pressure is plain too high...it will definately decrease the area of contact with the road, and maybe to a point that it will bite you in the butt just when you need it the most. Bet the machine will turn on a dime with that much pressure in the tires...but think about why. Because it has no friction/resistance...and that....will cost you a new set of teeth...faster than you can say "hope my Blue Cross is paid up".
I can't tell you how much is correct for the tires you have, you will have to be the judge of that...but one thing is for sure....you don't run much risk of underinflatement as it now stands.

I evidently won't get you to change your mind...but think about it......uneven tread wear, or not..... ten new tires will be cheaper than ten new teeth.

Wish someone else would step in on this.....please. :?
 
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My opinion after running Avon Venoms from early 80's, (when they were actually a race tire (tyre)) I always ran 26 front 28 rear measured cold. These tires are really sticky runners, and I think the pressure is more of a comfort thing as opposed to a sticktion idea. Although hewho has some good points, I myself would be reluctant to go over about 36 lbs in the rear and 32 front.
The lighter the air pressure (to a degree) the more the tire will roll (side to side) through corners. also the tire does have more contact patch at lighter pressures. I find it hard to believe that at 32 psi the front tire is showing signs of outside wear with no contact wear in the centre?
If you run it hard I would lurk on the websites of the vintage race forums and ask there for ideas. The Avon supervenoms are used by a lot of racers, and are quite common.
My 2 cents
Steve Jowett
 

L.A.B.

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The reccomended Avon tyre (tire) pressure information for Nortons (and others) is available on their website, this gives the reccomended pressures for Commandos as = 29 front/32 rear for solo/unladen use.
These figures are for Universal Roadrunner or AM18 fitments although I would believe that other suitable tyres would also run at similar pressures.

The max-pressure figure given would be for when running the tyre at maximum loading, this loading figure (as far as I am aware) is 'per wheel' and not the total loaded weight of the motorcycle?

But ultimately it's the riders choice as to what suits him/her (and the motorcycle) best I suppose?

http://www.avonmotorcycle.com/us/en/Fitments.asp +Norton+750/850+(model)
 
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Ok you win Hewho!

I'm going to adjust my rear tire pressure to 36 psi and the front to 34 psi. I'm still bothered by the edges on my front tire being worn more than the center, however. Very strange.

If anyone is interested, the averages of all the tire pressures posted in this thread are: 28.1 psi front and 31.6 psi rear.

L.A.B. - yes, the load rating on the sidewall is per wheel.

Jason
 
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I find it hard to believe that at 32 psi the front tire is showing signs of outside wear with no contact wear in the centre?

Can happen though....I do use the Dunlops...and I do run about 22 in the front, but when I changed the front tire a couple of weeks ago, mine was also worn like this. Strange, as logic would say it would wear just the opposite way......but as the tire pressure is good for my weight, and the tire had lasted way too many years without needing to be replaced...I won't ponder on it too long.

Jason
I didn't need to "win" this discussion...that's not the point. The point of this forum is to pass ideas and info back and forth. I have maybe a "thing" about some subjects and after a couple of good dumps myself, and having two children also end up in wrecks...I'm quick to go off on a crusade....forgive me. Anyway......I learned some things I didn't know....and maybe you did too......so we both got something out of it. Enjoy your ride and put a picture of your baby in the forum..... :D
 

MichaelB

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Good posts guys.
Correction, my tires are Roadrunners, AM20 & AM21. The Super V's were on another bike.
I ran about 50mi. Saturday of moderate riding. No real issues. I'll bump it to 29 / 32, dial in the supsension a little better and see.

Back in the 70's on my original 850, it came with Avon GP's. 22 / 26 was too soft for those too. I can't remember exactly, but I either ran 24 / 28 or 26 /28. I think it was the latter. Which leads me to believe the 22 / 26 is for Dunlops. Which also explains why I never really cared for them, I probably ran them too hard.

Anybody else?
 

Ron Hulton

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My 2002 Triumph Trophy came with Bridgestone's and lasted for 17 km
before needing replacement. I replaced them with Metzlers and there was an incredible improvement in handling and with 22 km now on these tires they still handle as well as the day they were put on new. I would guess that i will see 25 km + before they will need to be changed. I will definately be putting the same tire back on.
 
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