Tire Pressurr

[badgertom]

What Tire Pressure should I use on my 2008 R1200R. The Manual indicates that the front tire should be 32 (or 36) psi and the rear 36 ( or 42) psi. My BMW mechanic and the print on the tires indicate a pressure of 40, or 42 PSI for both tires, respectively. What should I use?

[BoxerSteve]

I think it depends on the tires you are running and the load. You might be able to find recommended tire pressures on the web site of your tire manufacturer. When I bought the Michelin PR2's I am currently running on my '08 R1200R, the dealer recommended 36 PSI front and 42 rear for one up riding.

[ammolab]

The pressures printed on a tire are the MAXIMUM safe pressure to run in that tire. It is NOT the 'vehicle specific' tire pressure and almost always TOO HIGH of a pressure for optimum ride/handling.

Correct tire pressure should come from the vehicle mfg or from the tire mfg.. if they even bother to post vehicle specific tire pressures.

You may get good recommendations from experienced riders here but note that they may have different year bikes, different tires and different overall vehicle loads than what you have.

For my 2011 R1200R BMW only posts F36/R42. This covers "all loads".. I run F32/R36 solo and go to the BMW specs only when loaded/2up.

[TinkerToy]

It would be great if a tire savy individual, tire rep, or a manufacture rep would educate us as how to determine the proper tire pressures for the tire your running. This past summer at the MOA rally I had a conversation with different tire reps...one company suggested the recomendation of the bike mfg. the other took me to a pile of discarded tires and showed me the outcome of a known under inflated tire and the resulting wear pattern.

The under inflated tire also showed interior discoloration in various areas... quqrter to half dollar size dark spots resulting from the heat build up under inflation causes..he suggested to run the tire at the max. tire pressure [ on the sidewall ] rear and two pounds less in the front tire. The wear pattern I'm referring to is the stepping of the tread near the groves...Don E corrects this by belt sanding the tire back to smooth ... I've done this also, reshaping the rear tire removing the flat center and removing the 'cupping' resulting in a quit and smoother ride Comments... suggestions welcome... correct me if I'm out in left field... Thanks... Tinkertoy said that...

[MTBeemer]

Maybe, just maybe, we should assume that the people who designed and built the R1200R, and selected a specific size and type of tire for the bike, know what they are doing and we should follow their recommendations for tire pressure.....Just an idea. Never heard of anyone having a problem caused by following BMW's recommendations instead of some guy on the internet or even a tire company's rep who is first, last and always a salesman.

[ammolab]

Maybe, just maybe, we should assume that the people who designed and built the R1200R, and selected a specific size and type of tire for the bike, know what they are doing and we should follow their recommendations for tire pressure.....Just an idea. Never heard of anyone having a problem caused by following BMW's recommendations instead of some guy on the internet or even a tire company's rep who is first, last and always a salesman.

Do you not think that a mfgs Liability is now a factor in BMWs USA tire pressure specs? When they used to give us pressures for one up AND fully loaded but now only list one spec (the former "full load"? Same thing on my 2002 BMW M Coupe as they list pressures for "driver only" and "Fully loaded" on the door panel but these pressures are labeled "Out side the USA only". Below these usefull pressures are another listing: "For USA" and these pressures are the "MAX LOAD" pressures.

I think the "one spec" pressure listed now is fine and best for BMW when someone overloads a bike and sues BMW after the accident but not at all optimum for any and all driving/load conditions.

But don't ever follow my advice or any other internet advice without first doing your own research!

[deilenberger]

I think BMW decided that the US customers are all fat slobs carrying a lotta-crap(tm) around and with a fat pillion. That's the only reason I can think of for eliminating the solo tire pressure recommendations (32F/36R).

One point I like to try to stress - the recommended pressure is at 20C (~68F). Tire pressure on the R1200R varies by 1.5-2PSI for every 10 degrees of temperature change. That means if I left the house in the AM at 40F, with my tires filled to the recommended pressure - by the time the tires (and they day) warms up - they could well be overinflated. Sometime I'll start making notes on what the exact change is in pressure (assuming NJ air - no synthetic air in these tires..) is.. but I try to set my tire pressure at 68-72F. Oh - on a day where the temps start out at 40F - the tire temperature can easily reach 90F by the time I get home (depends on how fast and hard I'm riding.) You can do the math for a 50F change in tire temperature.

If you're wondering how I know this - I have a tire-pressure-monitoring-system (TPMS) that gives real time pressure and temperature readings, without being temperature compensated like BMW's is (if you fill a tire using BMWs system - it automatically corrects for the temperature/pressure variation. In some ways a good thing - makes it simple for people - in other ways not so good since you never know the actual pressure except at 20C, and the BMW system doesn't tell you what the temperature is... It knows it, but it won't tell you.)

And the marking on the side of the tire is a warning to NOT inflate the tire above ## PSI. It is not a "recommended pressure" to run the tire at. It's the tire company covering their butts from people who might overinflate a tire (which can also cause tire failures, plus slows the warmup which lessens the grip available.)

[MTBeemer]

Do you not think that a mfgs Liability is now a factor in BMWs USA tire pressure specs? When they used to give us pressures for one up AND fully loaded but now only list one spec (the former "full load"? Same thing on my 2002 BMW M Coupe as they list pressures for "driver only" and "Fully loaded" on the door panel but these pressures are labeled "Out side the USA only". Below these usefull pressures are another listing: "For USA" and these pressures are the "MAX LOAD" pressures.

I think the "one spec" pressure listed now is fine and best for BMW when someone overloads a bike and sues BMW after the accident but not at all optimum for any and all driving/load conditions.

But don't ever follow my advice or any other internet advice without first doing your own research!

I think liability considerations have everything to do with their recommendations; all the more reason for BMW to provide the best info possible. Your last line is the bottomline.

[red baron]

In the winter when temperatures here in Texas are mostly in the thirties and low forties my tire pressure are 36.5 F 42 R. In the summer I use 35 F and 40 R since temperatures rise in the 90 to 100 degrees. I am using presently Dunlop Roadsmart 2 tires which are one of the very best if not the best tires I ever used on a bike.
Peter

[deilenberger]

In the winter when temperatures here in Texas are mostly in the thirties and low forties my tire pressure are 36.5 F 42 R. In the summer I use 35 F and 40 R since temperatures rise in the 90 to 100 degrees. I am using presently Dunlop Roadsmart 2 tires which are one of the very best if not the best tires I ever used on a bike.
Peter

Peter - problem with your winter temp pressure - the tires DO warm up. And as they warm up the pressure increases by 1.5-2PSI/10F.. (that's measured - not theoretical..) Are you measuring the tire pressure at ambient temps, or at 68F?

I'm not an aggressive rider - but it doesn't take too long (20 minutes maybe) of riding for the 40F tire temperature to raise > 70F, and after 30-40 minutes up to around the mid 80F's.. Your 36F/42R set at 40F pressures are going to increase as the tire warms up (40F(temperature differential) * 1.5 PSI/10F = +6 PSI) so you'll end up with 42F/48R when the tires are warmed up. The 48R is likely to exceed the manufacturer's MAX allowable pressure rating for the tire.

Your bike, your choice. I can only provide the info..

[Shakey]

@BadgerTom Please have a read of this item (clicky)

36/42 is indeed the answer to life, the Universe and Everything

I've run all my bikes at this regardless of number of passengers / luggage. I used to increase the rear to 44 for 2 up with luggage but I forgot once and it made no perceivable difference.

[red baron]

Don: Thanks for your reply. My garage is neither heated or airconditioned. The winter temps in the garage are around 40 degrees in the morning and in the summer about 80 degrees when I check the tire pressure. So I keep the cold tire pressure to 40 R in the summer and 42 R in the winter. I have never checked tire pressure after I have returned from a ride but I have heard tire pressure increases by about 2 PSI after tire is warmed up. May be this assumption is wrong?

[Tybus]

I run 34/40 psi in mine.

The book say's 36/42 is the max pressure for the Metzler Z6, which the bike came with.
I find I get good mileage from them at 34/40 psi (16000 kms).

Ride it like you stole it, Cheers Ty.

[waynemathews]

Don: Thanks for your reply. My garage is neither heated or airconditioned. The winter temps in the garage are around 40 degrees in the morning and in the summer about 80 degrees when I check the tire pressure. So I keep the cold tire pressure to 40 R in the summer and 42 R in the winter. I have never checked tire pressure after I have returned from a ride but I have heard tire pressure increases by about 2 PSI after tire is warmed up. May be this assumption is wrong?

At the track, the optimum cold inflation pressure is one that results in the tire's tread warming to its designed operating temperature for maximum grip. Not having a tire pyrometer or the tire manufacturer's recommended operating temperature makes this approach unfeasible. On the street, comfort is also factored into the equation. One rule of thumb is that pressure should rise about 10% when a tire is warmed. My understanding has been that the rear tire pressure should increase more than the front. Larry Kelly suggests 10% for the front and 20% for the rear http://www.mad-ducati.com/Articles/TirePressure.html. Sportrider had an article on tire pressure in their June 2010 issue http://www.sportrider.com/tech/tires/14 ... index.html which suggests increases of 2-4 psi for the front and 6-8 for the rear at the track.

Tire Rack reports that automobile tire temperature increases 1 psi every 5 minutes for 20 minutes. They suggest that air pressure is increased by 4 psi after driving up to 45 mph and 6 psi over 45 mph.

[hankth]

I run 37/42 on my '07. I check it often, and have 9100 miles now. Both tires still look ok to me. I'd guess there is about 2000 miles left on both. My riding style is average to on the slow side, ( I'm old ) lol.

[deilenberger]

Don: Thanks for your reply. My garage is neither heated or airconditioned. The winter temps in the garage are around 40 degrees in the morning and in the summer about 80 degrees when I check the tire pressure. So I keep the cold tire pressure to 40 R in the summer and 42 R in the winter. I have never checked tire pressure after I have returned from a ride but I have heard tire pressure increases by about 2 PSI after tire is warmed up. May be this assumption is wrong?

That assumption is wrong. I'll repeat - about 1.5-2PSI change in pressure with 10F temperature change. Your tired can easily reach 120F temps in the summer. Think about that.. if you filled your tire at 80F in the summer to 40 PSI - by the time the tire is warmed up, the pressure could be up to 48PSI. Look at what the max pressure marked on the side of your tire is.

And I'm a bit confused about your pressure settings. You set the pressure HIGHER in the winter (measuring it at a lower temperature?) That's the opposite of what I'd do.

You hear lots of things hanging around motorcyclists and the forums they frequent. Most of it has to be really looked at with a critical eye. I still hear people with the 10% rule for tire pressure (you look for an increase of 10% in tire pressure between a cold and warm tire..) Which wasn't too far off with bias-ply tires, but is completely wrong for radial tires. Bias-ply don't flex like radials, and the flexing causes heat, so the temperature changes are much greater.

Set pressure to the bike manufacturer's recommended pressure with the tire at 68F (or as close as you can get to it) and you'll be just fine.

[deilenberger]

At the track, the optimum cold inflation pressure is one that results in the tire's tread warming to its designed operating temperature for maximum grip. Not having a tire pyrometer

The $20 Harbor Freight IR remote temp sensor - with laser - actually works quite well for measuring tread temperature..Note that there can be a difference between interior tire air temperature, and the tread surface temperature. The interior temperature is more important for pressure. The tread temperature for traction/grip.

or the tire manufacturer's recommended operating temperature makes this approach unfeasible.

Real race tires - the manufacturer will give you numbers on.. but generally - the warmer the better (which is why all the racers use tire warmers..) Racers I know claim the tire is snakey until the tread temperature starts to reach 110-130F.. and one I know has measured >150F on a tire coming in off the track.

On the street, comfort is also factored into the equation. One rule of thumb is that pressure should rise about 10% when a tire is warmed. My understanding has been that the rear tire pressure should increase more than the front. Larry Kelly suggests 10% for the front and 20% for the rear http://www.mad-ducati.com/Articles/TirePressure.html. Sportrider had an article on tire pressure in their June 2010 issue http://www.sportrider.com/tech/tires/14 ... index.html which suggests increases of 2-4 psi for the front and 6-8 for the rear at the track.

As I pointed out above - the 10% rule dates back to bias-ply tires, and wasn't bad for them.. but it should be really put out of mind with modern motorcycle radials. The increase in pressure will be much more then 10% when properly inflated, and the radials also run warmer then the bias ply tires did. The sport rider recommendation is much more in line with what I've observed.. and if it's good enough for the track, it's likely good enough for the street (I can't think of any reason for wanting LESS grip..)

Tire Rack reports that automobile tire temperature increases 1 psi every 5 minutes for 20 minutes. They suggest that air pressure is increased by 4 psi after driving up to 45 mph and 6 psi over 45 mph.

Auto tires have an air volume many times that of a motorcycle tire. Boyles law of gases (and the laws of thermodynamics) explain how this effects the PSI/Temperature relationship.. basically the more volume, the less change in PSI for a given temperature rise. There is a difference in pressure increase on the front to rear tires on a motorcycle (why I've quoted it as 1.5-2 PSI - measured in real time..) just due to their volume difference. The larger volume rear tire won't increase in pressure as much as the smaller volume front tire - IF both increase in temperature by the same amount. Fact is - they don't. The rear tire tends to get hotter faster due to it providing both cornering, braking and power traction. The front tire only provides cornering and braking traction.

Again - manufacturer's recommended pressure at "room temperature" 20C/68F and you'll have the same sort of pressure rise that SportRider is recommending. I go for GRIP not longevity in tires. Lack of longevity will only cost me money, lack of grip can cause PAIN. I dislike pain.

[red baron]

Hello Don:
I checked this evening the manufacturers instructions on my tires Dunlop Roadsmart 2 with R1200R sizes. At cool tire conditions at max load factors max PSI: rear 42 and front 36. Nothing is mentioned about ambient temps etc. only cool tires. Obviously if you park your vehicle over night the tires will be cool. So in my opinion it makes sense to start off in the summer at a lower tire pressure than in the winter. In the winter warm up will be a lot less than in the summer when ambient temps reach 100 degrees and much higher temps on the surface. While ambient temps in the winter maybe in the 50 to 70 degrees range. Again it all has gotten too technical for most riders/drivers of motorcyles respectively cars.
Peter

[waynemathews]

At the track, the optimum cold inflation pressure is one that results in the tire's tread warming to its designed operating temperature for maximum grip. Not having a tire pyrometer

The $20 Harbor Freight IR remote temp sensor - with laser - actually works quite well for measuring tread temperature..Note that there can be a difference between interior tire air temperature, and the tread surface temperature. The interior temperature is more important for pressure. The tread temperature for traction/grip.

or the tire manufacturer's recommended operating temperature makes this approach unfeasible.

Real race tires - the manufacturer will give you numbers on.. but generally - the warmer the better (which is why all the racers use tire warmers..) Racers I know claim the tire is snakey until the tread temperature starts to reach 110-130F.. and one I know has measured >150F on a tire coming in off the track.

On the street, comfort is also factored into the equation. One rule of thumb is that pressure should rise about 10% when a tire is warmed. My understanding has been that the rear tire pressure should increase more than the front. Larry Kelly suggests 10% for the front and 20% for the rear http://www.mad-ducati.com/Articles/TirePressure.html. Sportrider had an article on tire pressure in their June 2010 issue http://www.sportrider.com/tech/tires/14 ... index.html which suggests increases of 2-4 psi for the front and 6-8 for the rear at the track.

As I pointed out above - the 10% rule dates back to bias-ply tires, and wasn't bad for them.. but it should be really put out of mind with modern motorcycle radials. The increase in pressure will be much more then 10% when properly inflated, and the radials also run warmer then the bias ply tires did. The sport rider recommendation is much more in line with what I've observed.. and if it's good enough for the track, it's likely good enough for the street (I can't think of any reason for wanting LESS grip..)

Tire Rack reports that automobile tire temperature increases 1 psi every 5 minutes for 20 minutes. They suggest that air pressure is increased by 4 psi after driving up to 45 mph and 6 psi over 45 mph.

Auto tires have an air volume many times that of a motorcycle tire. Boyles law of gases (and the laws of thermodynamics) explain how this effects the PSI/Temperature relationship.. basically the more volume, the less change in PSI for a given temperature rise. There is a difference in pressure increase on the front to rear tires on a motorcycle (why I've quoted it as 1.5-2 PSI - measured in real time..) just due to their volume difference. The larger volume rear tire won't increase in pressure as much as the smaller volume front tire - IF both increase in temperature by the same amount. Fact is - they don't. The rear tire tends to get hotter faster due to it providing both cornering, braking and power traction. The front tire only provides cornering and braking traction.

Again - manufacturer's recommended pressure at "room temperature" 20C/68F and you'll have the same sort of pressure rise that SportRider is recommending. I go for GRIP not longevity in tires. Lack of longevity will only cost me money, lack of grip can cause PAIN. I dislike pain.

I'd add the caution to use your surface scan thermometer as soon as possible after stopping as the tread surface cools more rapidly than the rubber deeper in the tire. Do you have any data that correlates inner air temperature to rubber temperature? I'm sure that if you ride long enough they equilibrate, but how long does it take?

I think that it is interesting that 10-20 rule and the SportRider recommendation actually correlate pretty well for tires in the 30 - 40 lb inflation range.

[mogu83]

After reading all this air pressure info I'm afraid to ride my bike.

Actually I would imagine the capabilities of the tires most of us use far exceeds the capabilities of most of the riders, and as long as the tire pressure is within a few pounds of where it should be most would never notice it or experience any problems. But I could be wrong.