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What's the problem with tire pressure?

WalterK75

Member
I see repeated tire pressure threads and I'm not sure why. Since the manufacturer gives the recommended pressures in the owner's manual I don't understand why there should be any need to discuss it.
 
I see repeated tire pressure threads and I'm not sure why. Since the manufacturer gives the recommended pressures in the owner's manual I don't understand why there should be any need to discuss it.

different brands of tires prefer different pressures.

different styles of riding prefer different pressures

It is all about learning the bike, and your preferences.

Sharing your preferences helps other people learn.

Simple

Rod
 
Because some BMW riders seem to be OCD when it comes to proper inflation. There was a post asking if they needed to adjust pressures when they rode up and down mountain passes!
 
Simple answer is, BMW publishes their recommended pressure averages for their bikes - not their customers, the loads they carry, the differences in one tire manufacturers optimal pressure for the design of their tire - again with an average load.

I ride an R12RT. The total permitted weight of this bike is 1091 lbs.

With me on it, and ready to ride long distance or in a rally, that bike weights 940 lbs. That's the actual weight taken by the NM MTV on August 18th. Before Aerostitch, helmet and boots, I weigh 160 lbs.

Here's some food for thought. How much do you weigh? How much does your passenger weigh? - both ready to ride? What about gear in your bags you travel with normally?

How does BMW know whether it's me on my bike - at 940 lbs. actual weight - or my buddy that weighs over 320 lbs. before Aerostitch, helmet, boots - with a passenger?

I recently had a discussion with the service manager at my local shop while I was changing front tires. I gave him my tire pressure gauge and told him to have the tech set the front tire pressure at 40 psi, using my gauge. Knowing me pretty well, he related a recent tire seminar he attended in Las Vegas with a few tire manufacturers [forget who he said sponsored it]. He told me that every tire manufacture rep told the group the same thing. For highway riding, the best performance and mileage is almost always going to come from tires inflated to the maximum pressure on the sidewall. Every rep also agreed the difference of one lb. can make a significant difference in how long the tire lasts - again, under highway conditions.

I have a calibrated gauge. I've been running 40/40 and 40/42. I've now bumped that to 42/42 and even in the mountains [just came home for a rally in MT that was mostly mountains] the only thing I "think" I notice is the front attacks frost heaves and the like more aggressively - less of a "thud" - more of a "Bump!" I think much harsher.

I'm watching wear pretty close - not because I much care about how fast I can scrub tread off, but rather if the extra couple lbs. of air are going to make a difference. In regards to the ride, I don't notice much yet. However, my new Ohlins shocks go on the bike Saturday. That's going to be a whole new story.:thumb
 
Since the manufacturer gives the recommended pressures in the owner's manual I don't understand why there should be any need to discuss it.

The manufacturer recommends oil changes at certain intervals
The manufacturer recommends brake fluid changes at certain intervals
The manufacturer recommends a certain octane rating for the fuel
The manufacturer recommends a specific oil weight
The manufacturer recommends a certain total maximum weight for the bike incl passengers and all luggage

...and we all do what we think is the best choice and what works for us.
 
The manufacturer recommends oil changes at certain intervals
The manufacturer recommends brake fluid changes at certain intervals
The manufacturer recommends a certain octane rating for the fuel
The manufacturer recommends a specific oil weight
The manufacturer recommends a certain total maximum weight for the bike incl passengers and all luggage

...and we all do what we think is the best choice and what works for us.
Not sure about that "and we all do what we think is the best choice and what works for us." That is IMO what we should do. We "should be" smart enough to adjust settings for the conditions. I'll swear a whole bunch of BMW riders tend to need info from Bavaria to light their bike up in the morning. :)
 
BMW generally gets it about right at the time they publish the recommendations. This is true of the latest models too. But tire technology has changed substantially over the past 25 years. What BMW got right for a specific Airhead in 1972 or 1995, and what BMW got right for a classic K bike in 1985 or 1995 may well no longer be right today. That depends on what tires are fitted today.

As noted by several posts above, what works for me with 150 pounds of luggage in the desert southwest in August may well not be the best pressures for somebody else in Minnesota or New England in October. Tire temperature (along with pavement temperature) are key determinants of traction, and tire operating temperature is directly related to both ambient temperature and tire pressure.

So the one size fits all recommendations by BMW are a good place to start. If published in the past few years they won't be way-off but also may well not be optimal for a specific rider, bike, and environment.

So, as David Hough would explain it in his new book "The Good Rider", the good rider would actually think about this stuff, and would learn how to know if the tire pressure is optimal, good enough, or not.

As an added note to the OP, BMW makes recommendations for a bike with no regard whether the rider is in Ontario or Arizona. In those two cases I suspect the compromise recommended pressure is not quite right.
 
I agree. I just wish I didn't have to spend so damn much of it....:banghead

You only rent good suspension, as it will:

A. will increase the resale value of the bike
B. before you sell/trade you refit the OEM and sell the shocks to the next enlightened rider.

Eeither was you should recoup 2/3 - 3/4 of the investment.
 
To go just a bit further with Paul's analysis, consider what your owner's manual specifies, with the OEM tires. Is that tire still the tire you put on, and under what conditions do you ride it? I remember when car tires would routinely be set to 30-32psi, now with the newer ones, 40+psi is not uncommon, per the sidewall info. My shop has had to deal with tire warranty issues because people put newer higher-pressure tires on their heavyweight bikes, but the owners ran them at the old pressures and destroyed the tires. Your bike is pretty much a constant, its technology doesn't change much, but tires are constantly changing. Become better informed.
 
Running a little over what the tire sidewall says on my LT's gives me at least 1/3 extra tire miles. I get far less cupping & get over 20,000 miles between tire changes. My Metz 880 front is always at 42 psi & my Bridgestone Battle Axe 020 rear is at 48 psi one up & 50 psi loaded for a trip.
 
Pic

The manufacturer recommends oil changes at certain intervals
The manufacturer recommends brake fluid changes at certain intervals
The manufacturer recommends a certain octane rating for the fuel
The manufacturer recommends a specific oil weight
The manufacturer recommends a certain total maximum weight for the bike incl passengers and all luggage

...and we all do what we think is the best choice and what works for us.

In aviation we have an acronym, PIC, Pilot in Command, emphasis on the word Command. It is implied that command means you will comply with the operators manual implicitly, however, with caveat, adedum, the regulation states that we can deviate from "normal" procedures in the event of an emergency. Now, what relevance does this have with the current conversation; like flying, riding is implicitly dangerous. Will the manufacure be on the bike when something goes wrong? No, you will. This gives you full authority to deviate from recommendations as the PIC sees fit. I take into consideration as a PIC of my motorcycle, all credible information, owners manuals, BMW master technicians, maintenance manuals, and experienced riders with a history of credible information, like Paul Glaves and others. The purist who follow the operators manuals and maintenance manuals implicitly will do well, but deviations are necessary, especially with tires and oil due largely to the changing technology on expendable items. Even some OEM parts change over time but are recommended as replacement parts for bikes that didn't include them as original stock; recalls come to mind. Like I tell my students, if ATC makes a mistake, your dead, if you make a mistake, your dead, this fact puts you the PIC in charge.
 
A wise old tire Guru once told me that the proper tire pressure is always changing with weight, temp, driving style ect. His recommendation is to start with the recommended tire pressure checked cold. Ride and when you stop immediately check the tire pressure. The optimal pressure change will be 1-2lbs. If more you are under inflated, less you are over inflated.

Having the tire pressure monitor on the bike makes this very simple. I have michelin PR 2 on my 08 RT and I have found that my optimal pressure using this technique is 38 front and 42 rear.
 
A wise old tire Guru once told me that the proper tire pressure is always changing with weight, temp, driving style ect. His recommendation is to start with the recommended tire pressure checked cold. Ride and when you stop immediately check the tire pressure. The optimal pressure change will be 1-2lbs. If more you are under inflated, less you are over inflated.

Having the tire pressure monitor on the bike makes this very simple. I have michelin PR 2 on my 08 RT and I have found that my optimal pressure using this technique is 38 front and 42 rear.
I just changed a set of PR2 tires on a 2012 RT that had just over 15,000 miles on them with 37 psi on the front & 42 psi on the rear & they could have gone another 1000 miles before they were at the wear bars.
 
Sidewall tire pressure is the maximum per the tire mfg.

It is not always the recommended or optimum tire pressure.

Paul and others have it right. It pays to listen to the voices of experience.

Your mileage WILL vary.
 
It's always interesting to see reference to "newer, higher pressure tires."

Correct me if I'm wrong, but in most cases this is the difference between radial and bias-ply tires.

In most cases, the tire specified for your bike is one or the other but never both. If that's the case, there simply aren't "newer, higher pressure tires" applicable to your bike.

(One exception may be Conti's new radials directed towards Airheads and maybe old Ks, but haven't studied that. They have just been introduced this summer.)

And, the numbers on the sidewall are completely meaningless except that they indicate the maximum pressure safe to use in this tire. This has NOTHING to do with BMW's or the tire manufacturer's recommended pressure for your particular bike and load conditions.

Except for the following, that is ... A recent presentation at our dealer by a Metzeler tire rep featured the notion that if your goal is to maximize tire mileage, i.e. tread life, then you should indeed run your tires at the maximum pressure indicated on the sidewall. It's printed a little less strongly in Metzeler brochures, too. This of course, is NEVER the basis for BMW's pressure recommendations for your bike and most obviously may involve some handling and/or comfort and/or performance compromises. I'm not doing it, as my goal is fun associated with riding and for sure not carefully saving every penny and diminishing the fun. I mean, if it's about only tread life, just never ride.

If you've a current model BMW, recommended tires by brand are listed at BMW's website. These charts don't go very far back as regards discontinued models IIRC. There is, not completely coincidentally, sometimes not sizes for older bikes in the latest/greatest tire models, and the older bike guys then use the older models anyway. The notion that perhaps tires (brands) not on the recommended list somehow require completely different pressures is a bit of stretch in logic, too, I think. Look for that brand to publish something instead.

Bottom line, I think, is that BMW's recommendations are simply fine and are good for a long time. If a tire manufacturer will publish in writing or on its web page that they indeed have different recommendations for you, then pay attention. There's not a lot of data provided by various internet contributors to back up their claims when it comes to varying from BMW specifications, and they should direct you to data rather than their opinions and unscientific observations. I know for sure that I've never seen specifically published by a tire manufacturer that pressures recommended by BMW in, say, the 1990s or 80s or 70s have been superceded by "new technology." I'd love to be directed to it.

You can also rationalize that somehow BMW's specifications don't apply specifically to you because you must weigh something different than their average rider or something like that, but I'd instead conclude their figures can be recognized as covering normal variations. BMW's figures are quite fine and it's not really about demonstrating that you know more than they do, is it? When it comes to "voice of experience," nobody tops BMW.
 
To go just a bit further with Paul's analysis, consider what your owner's manual specifies, with the OEM tires. Is that tire still the tire you put on, and under what conditions do you ride it? I remember when car tires would routinely be set to 30-32psi, now with the newer ones, 40+psi is not uncommon, per the sidewall info. My shop has had to deal with tire warranty issues because people put newer higher-pressure tires on their heavyweight bikes, but the owners ran them at the old pressures and destroyed the tires. Your bike is pretty much a constant, its technology doesn't change much, but tires are constantly changing. Become better informed.


Per your comment on warranties-which matters (the most?) the door jamb sticker or the sidewall number? FWIW. do vehicle mfg's(dealers do not) these days change that sticker when various tires are placed on vehicle as brands change some. Now back to MC tires...I'm not sure I "get" that info from tire mfg's saying max performance comes @ max pressure on sidewall? Somethings missing here...
 
Remember nothing is free, yes higher pressure lowers rolling resistance and heat, and makes tires wear longer, BUT also reduce traction due to less heat in the tire and smaller footprint on the pavement.

Pick your poison!
 
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