How often do you
check the air pressure in your tires? Do you check them
once a month or when you change your oil? If you are like
me, the tire pressure gets checked two or three times a year at best.
What is the result of running tires at other than
Do you really know
the optimal inflation pressure? Does the ambient
temperature have any effect on the pressure? Do you
need to recheck or even change the pressure when you are two up
or loaded with luggage?
I see posts all the
time asking "What is the correct pressure?" We all
have an idea from our personal experience or from what we
have read. But again, if you are like me you dont have
the specific answer.
Tires are probably
the single most important item on our bike. The
condition of our tires, how they grip the road and
handle the load, is paramount to our safety. Yet we
seem to neglect them and take them for granted.
If it is possible to
put safety aside for a moment and focus on the cost of
our tires, they are the single most expensive cost to
the operation of your bike, excluding fuel.
So, the real
question is with the safety factor and the cost
involved with tires, why do we guess at or ignore
the pressure? Why are they so neglected?
things have happened within the last month to put me on
this quest for answers. First, Carol hit the 10,000
mile mark on her 1300 Retro. And like
other 1300 VTX, the front
end has encountered the elusive wobble.
information on the Wobble Demon is all speculation.
It's the tires, its the head bearings, its this or
that. But actually, nobody is sure what is causing
this problem. Tires are replaced
and the problem is solved. Head bearings are tightened
or replaced and the problem is solved. The problem IS
solved, temporarily. A few hundred miles later and
the Wobble Demons come back. Many have even contacted
Honda and of course Honda says there is no problem.
Looking at Carols
bike I found nothing loose nor did I find any obvious cause for the
wobble. The stock Dunlops look almost new, 12/32nds or
more of tread. Next, I pull the front tire and check the balance.
Could I be that lucky to find it out of balance? Nope, a
perfect bubble. Damn.
Before I reinstall
the front tire, I run my hands across the tread from
both directions, with and against the rotation. I
feel it. Not even visible to the eye yet, but its there,
a slight cupping of the tire.
opinion and I have said this all along, I believe the
"Wobble Demon" is being awakened by the tires. In every
case of wobble there has been cupping on the front tire. The
cupping is found even on tire brands other than the
of us riding the VTX with the OEM Dunlop tires have
determined the main cause for the cupping to be low air
pressure. Currently I am running 40 psi in the front and
42 psi in the rear. That doesnt seem low to me, but how
do I know? No matter, Im done with the Dunlops and I
have purchased the new Metzeler 880s front and rear.
a wear pattern develops on a tire, that pattern will
continue throughout the life of the tire. No matter what
you do, there is no way to stop or correct the wear pattern.
So before I install the new tires, I would like to know the
proper inflation to eliminate any cupping.
So, I head back to the
board to read some more. Hopefully I can
find something about tire pressure. I find every
combination of pressures ranging from 35 to 45 and every
one is subjective. The Metz 880 for the front of the 1300 is new this
year so there is no real information available to draw on for this
In reading to solve
this problem, I find the single most important reason
for my quest of answers. Considering the years our VTX
has been in service and the importance of our tires, no
one really knows what the correct tire pressure should be for any
tire brand. We all have very different ideas.
The correct tire pressure
the optimum tire wear and fuel economy not to mention
the best handling tendencies, yet
everywhere I looked for information on tires I saw the same question, What
is the correct tire pressure?
What happens if the pressure
is too low? The
maintain shape, it becomes flatter than intended, it
could weaken the tire's internal structure and
eventually lead to tire failure. Lower inflation
pressures allow more deflection as the tire rolls. This
will build up internal heat, increase rolling resistance
(causing a reduction in fuel economy of up to 5%) and
reduce the tire's tread life by as much as
25% while increasing irregular tread wear. You will also
find a loss of steering precision and cornering
stability. (Under inflation information source Tire
Rack Online performance source.)
What happens if the pressure is a few pounds too
The tire is stiff
and the size of its footprint in contact with the road
is reduced. If tires are over inflated they could be
damaged more easily when encountering potholes or debris
in the road, as well as experience irregular tread wear.
Higher inflated tires cannot isolate road irregularities
as well causing the vehicle to ride harsher. However,
higher inflation pressures reduce rolling resistance
slightly and typically provide a slight improvement in
steering response and cornering stability. (Over
inflation information source Tire Rack Online
talk about different tire brands, the handling
characteristics of each, how they perform in adverse
conditions, high speed and various loads, yet we all
tend to use the OEM (Dunlop / Honda) recommended
owners manual provides a pressure range but what
happens to that range when you are not running the OEM
tire? A motorcycle is affected much more than a car when
add or remove a passenger. How about the added weight
from luggage? A passenger or loaded bags can change your
load weight as much as 80% and GVW as much as 20%, so
how does 150 lbs or more of added weight affect your
change in ambient temperature of only 10 to 15 degrees affect
your tire pressure? Can sitting idle in the garage for a
couple of weeks affect your tire pressure? If the pressure
is only checked while doing an oil change,
how many times is the bike ridden with under inflated tires?
Just how important are
our tires? These two
tires play a crucial role in our safety. As the only
part of the bike that physically touches the ground,
tires are one of the key factors affecting a vehicles
handling, performance and overall safety. I would say
they are VERY important.
Have you ever
calculated the cost per mile on your tires?
These numbers are mine of course and they are determined
by my riding style and tire choice. If you want to check
out your cost per mile, use the equation and input your
Operating Cost Per Mile (CPM)
Front Tires - $.015 CPM (tire cost + mount) divided by
average frt tire mileage
Rear Tires - $.022 CPM (tire cost + mount) divided by
average rr tire mileage
Combined Tire Cost $.037 or rounding up $.04 cents per mile
comparison AAA shows the average tire CPM on medium and
large sedans to be $.008 cents per mile. Think about
that for a second. Our cars average .03 cents LESS per
mile than the motorcycle and they have four tires! If
you ride 10K miles this year on your bike at a cost of
.03 per mile that is an additional $300.00 over what your
car tires cost for the same mileage.
compared with other operating
Fuel - $.047 CPM
Insurance - $.024 CPM
Oil and Filter - $.006 CPM
Better care of our
tires and we will ride safer and cheaper.
Is there a hard and fast formula that we can use for all
Sometime back I had
a conversation with Nick at RMCG - Cycle Parts and
He said their tire vendor gave him a formula to use and
this, according to the vendor, was the most accurate way to
determine the correct tire pressure in Avon tires.
According to Nick, this is what the vendor told him.
Air your tires cold. Ride the bike at highway speed for
20 minutes or so to get them to operating temp,
pull over and recheck the pressure. If the hot pressure
is more than 5 pounds above the cold pressure the tire
is under inflated, building heat and
adding pressure. If the hot pressure is 5 pounds or
pressure the tire is properly inflated. If the hot
pressure is close to or the same as the cold pressure,
the tire is over inflated.
Yes, this is hard
work and I understand we can't perform this before or
during every ride. But if you can rely on a formula and
you check it a few times in varying conditions of
ambient temperature, loaded / unloaded, two up or
whatever scenario you find yourself riding, you should
be able to get an average cold pressure that you can use
for your varying riding conditions.
To prove or
disprove this formula I do a search, here is what I
found at "Dans Motorcycle Tires and Tubes."
the tire cold, take the tire pressure. Now ride for 15
minutes or so at freeway speed. Stop and take the
pressure again. If the pressure has gone up more than
three PSI the tire pressure is too low. This allows the
tire to heat up too much, raising its pressure. If it's
the same, the tire pressure is too high. It's not
allowing the tire to warm up right. If it's hot pressure
is three PSI higher than its cold pressure, the cold
pressure is correct. The tire is the correct temperature
and all is right with the
To again prove or
disprove I went a step further and contacted Avon Tyres.
They make it so easy, under contact us it says if you
have a technical question contact our engineers. Well
now were talking.
There were 3 emails
back and forth with Avon. To make it easier to follow
the process here, I did a cut and paste to remove the
needless chatter and allow you to see my
question with their answer.
I have a few Motorcycle Tire Pressure Questions for you.
had many conversations and opinions vary on correct
motorcycle tire pressure. I was curious if Avon would
have a formula or calculation that keeps in mind the
factors affecting a motorcycle like rider weight,
occasional passenger, luggage etc.
formulas for working out pressures for certain loads.
These are kept confidential due to competition between
tyre companies however. It can be quite complex with
each bike weighing differently, different loads but also
different ambient temperature.
Currently I am riding a 2002 Honda 1800 VTX R, the wife
rides a 2005 Honda 1300 R with cast wheels. When looking at your
fitment guide I see your recommended pressures but they
seem to be a bit low from what I have found.
Pressures stated are normally the best compromise
between mileage, grip and comfort.
OEM with Dunlop, these bikes have had major wear and
cupping issues. Bumping the pressure up to 40 - 42 psi
seems to slow this down but not eliminate it.
Its normally better to be slightly over inflated
(reduces cupping and wear) on heavier bikes.
Currently I am on my fifth set of Avon's. I would be
considered an aggressive rider with varying GVW and
average 12K miles on the rear and 17K on the front running 38 -
40 psi front and 40 - 42 psi rear. Most people tell me I
am over inflated.
info on the 1300 with Avon as you don't have a tire to
fit that application.
Any help on a PSI suggestion / formula would
With regard to the 1300, we haven't tested one as we
don't make the tyres so I can't help there, sorry.
Pressures we normally quote are for solo use (170lbs
average rider). For heavier loads i.e. over 240 lb
rider, 2 up or 2 up with luggage, we suggest an extra
1-2 psi in the front and 2-3 psi in the rear.
Peter, Thanks so much for the speedy response and the
limited info, I appreciate it.
difficult for the end user to find a good pressure and I
would expect the OEM Dunlop information that
Honda offers with the bike will not transfer to an Avon
after market very well.
is such a wide range of suggested pressures and with the
1300 and 1800 both having major wear issues I was hoping
for a bone.
You are correct that OE pressures may be different to
other manufacturers tyres. We test all our tyres at OE
pressures and ensure they work at that. This is because
many people will set them to that anyway. If we find
its better at another pressure, we state it in our
Online where all info can be found, I saw a rule of
thumb where you check pressure cold, ride at highway
speed for 30 minutes and recheck the pressure. If no
increase in pressure, you're over inflated, 8 to 10%
increase in pressure you are fine, over 10% you are
under inflated. I'm not asking you to give away any of
Avon's secrets but hypothetically speaking, is this
something a person could live with? I really am just
curious and trying to solve the cupping on Carol's and
No direct Response this time on the formula.
Another quick question if I might, sorry, I have seen
several people running the Avon's on the 1300. Venom R
on the rear and bias on front. How much of an issue is
it to run a radial with a bias ply? A few years back
this was considered a BIG NO, has this changed?
It is ok to run a bias ply with a radial, but only with
the radial on the rear. It is illegal to run them the
other way round.
above emails with Avon were with Peter J McNally M/C
Technical Product Manager. Thanks so much Peter for
taking the time to respond.
isnt much information we can glean from Peter, but what
stands out to me is there are formulas used to calculate
accurate tire pressure. Peter isnt fessing up as to
what they are so we need to do some experimentation.
most significant tid bit to me was this, and I quote
Pressures we normally quote are for solo use (170lbs
average rider). For heavier loads i.e. over 240 lb
rider, 2 up or 2 up with luggage, we suggest an extra
1-2 psi in the front and 2-3 in the rear. I would
venture to say, most of us are over the 170 range and
certainly over that range with any luggage or passenger.
Whatever psi is suggested on their fitment guide, we
should increase 2 PSI for the front and 3 PSI for the
believe what Nick heard from his Avon tire vendor to be
fairly accurate and that would be a good place for me to
start. I would definitely start with the PSI on the top
end of the spectrum. The reason for
starting so high, I will quote Peter again to refresh
your memory. Its normally better to be slightly
over inflated (reduces cupping and wear) on heavier
going to install the Metzeler ME880's on Carols bike
and to be sure they agree with my assessments, my next step is to contact
Metzeler. This was not an easy task compared to Avon.
After several phone calls and getting past the
condescending attitude, this is what I receive from
Metzeler Technical Support.
Explaining the situation I tell him, OEM with Dunlop,
these bikes have had major wear and cupping issues. Im
replacing them with Metzeler and to insure no cupping
and proper wear, what is the correct tire pressure?
The OEM Dunlop is
produced to Honda's specifications. They are
intentionally soft and run at a low pressure to enhance
the ride and handling of the VTX. The VTX is a cruiser
and Honda would not want you to feel every bump in the
road or handle poorly.
We live in the
States and as such we don't run high speeds or hit many
corners. Most of our riding is on the Super Slab,
cruising in a straight line and there is no need to use
the entire tire. The center of the tire is the main
contact patch and the side or curved area of a
motorcycle tire is seldom used on a cruiser in the
States. As such, we (Metzeler and other tire
manufactures) purposely suggest a lower PSI for the
cruiser tire and that type of ride. Lower pressure gives
you better handling and a better ride on a cruiser.
him if he was familiar with the VTX, Colorado and how
the bike was actually
ridden. This is not Kansas or Chicago, we have twisties, run two
lane back roads most of the time and seldom ride a Super Slab. I have no
chicken strips on my tires!
His response, "Good for you!" I continue with,
what about the serious cupping issues we experience with
the VTX and if your fitment guide gives us a low PSI
what do we do to find the correct pressures? Would the
above mentioned formula help us to determine the correct
old wives tale and a waste of time. Just air it up to
what you want and ride.
which I responded, we don't mind replacing a tire that
is worn out but were tired of pissing money down the drain every time we pull
a tire at 4,000 miles that should have much more life.
The Metzeler fitment guide suggests 36 PSI for the front and 38
PSI for the rear, your printed brochure suggests 36 to 42 PSI
front and 40 to 42 PSI on the rear. I asked him if these
pressures were for a solo rider of 170 pounds with no
and with the information you are giving me, I would
suggest you start with 40 PSI front and 42 PSI rear. If
you notice your front tire cupping go to 42 PSI in the
front. If you are loading a passenger or luggage add 2
PSI to the rear.
A bit of
clarification here, this was a phone call and even
though I took notes, I don't have an exact quote
from him. The bolded areas are a fair representation of
his comments and I use the bolded areas to better
separate his part of the conversation from mine.
He did give me his phone number and asked me to follow
up with the results after 3,000 miles or so.
most significant information in my mind, from both Avon
and Metzeler is that the suggested
pressures are for solo use (170lbs average rider) and
pressures are purposely set low for the cruiser riding
style and a better ride.
use the above information or not. Personally I think the
formula is the most accurate way to determine and
maintain proper inflation and worth
the extra effort to formulate it.
going to start with 40 psi in the front and 42 psi in
the rear. If I notice any start to the cupping I am
going to bump the front tire up to 42 psi. Two up or
loaded with luggage, I will bump up the rear tire to 45
will also test the cold and hot pressure and from those
results make whatever adjustments seem appropriate.
After my research,
I found that tires are indeed affected by sitting idle
in the garage. In fact, they will loose approximately 1
psi per month on average, idle or not.
This means that if
air isn't added for two to three months, the tire's
inflation pressures will probably be 2 to 3 psi low.
changes in ambient temperatures,
I found the
rule of thumb is for every 10° Fahrenheit change in air
temperature, your tire's inflation pressure will change
by about 1 psi (up with higher temperatures and down
My source for
this information was "The Tire Rack" and you can read
more about it from this direct link.
believe tires are the most neglected item on
bike and they should be checked before every trip,
especially if you have a significant change in ambient
temperatures or a change in load weight.
you found this information interesting and that you were
able to gain some insight into your tires. If you have
anything you would like to add, ideas or comments please
post them on the Colorado Range Riders Message Board
under the topic of "Tires - Tires - Tires." We can
discuss the topic further there. To find the post "Tires - Tires -
Tires" all you need to do is...
findings and overall results, along with any comments
you add will make a good follow up and part 2 to this
As if you don't
have enough to think about now, I thought I would
mention one more topic. Some
of you may have noticed a trend that has been dubbed
going over to The Dark
The topic has drawn much national interest and it's gaining
riders, for various reasons have installed a car tire on
the rear of their bikes. In Colorado we have BigVTXMan
Saul and Dennis who are currently trying it.
questions have been raised, is it really safe, how will
it corner, and what type of mileage are they getting? I
have put in a few links for those of you that would like
to check it out.
Follow this link
for a view of the car tire in action -
Dark Side The Video
This link will take you to the VTX OA post -
Discussions on the Dark Side Video
This link is called -
Life is a Road - The Dark Side
This link will take you to the VTX OA post -
How many have come over to The
Dark Side? If you are looking for
several hours of light reading just do a search on the
VTX OA for Dark Side.
this something that you're interested in? If so, let me
know, this would be a good topic for another day, maybe
you were able to find something of interest and pick up
a few ideas. I'm looking forward to hearing your
I have included some links that I ran across during this quest. Some
were used as reference material and some are here
because I found other interesting information in them. I
hope you have the opportunity to check them out.
The Tire Rack - Online Performance Source
Dan's Motorcycle Tires and Tubes
Sport Rider - Tire Pressure Not a
Lot of Hot Air
Pace - How much does it cost to
Common Motorcycle Tire Wear
Until we ride again