I would just like to say that I am shocked at the wear or shall I say worn out tire on my 13 GSA. Max pressure front and rear Luggage and my 180 lbs on recent trip, end result was down to wear bars and flat as pancake in middle. I am really amazed at how fast it wore at only 3505 miles upon trip end. I rode Vstrom usually 7-8000 miles to a rear so I expected at least 6-7000 on GSA. Not burning much oil though D.
It is not reasonable to compare tires for motorcycles to those for cars. A car tire runs flat on the ground and the pressure must ensure that it stays flat. That is, that the weight on the tire is compensated by an "equal" amount of pressure within. A tire for a bike is round. It is slightly more comfortable to run with less pressure. The tire is softer and tiny uneven-nesses are absorbed. Thus the designer of the bike, BMW in this case, would want you to obtain a ride as comfortable as possible. BMW thus has a clear motive to make you run your tires softer than you could. On my 1150 I can't feel how much pressure I have in the tires. Maybe my butt is insensitive, but the difference is so small that in a "blind test" I would not be able to reliable feel the difference between, say, 2,5 bar and 3.0 bar. My experience is that if you run with more pressure than BMW recommends, the tires lasts much longer. For safety: Never run with more pressure than the manufacturer of the tire has designed it hold. And never with more load. [TaSK]
I'm the OP and when I asked the question originally, I had 36f/38R. After reading replies to this thread, I changed pressure to 38F/40R - riding solo. For me, it made a pretty noticeable seat of the pants difference in handling, for the better. Couple of lbs. really did change the ride....for me. Seemed to handle quicker-a little easier. Didn't notice any abrupt changes in feel on the road. May try 40F/40-42R just to see how that feels in comparison.
At 36/42, I just pulled my rear tire off @ 9k miles and it's approximately 1/8 inch away from the tire wear indicators. I check my tire pressure every Sunday as part of a weekly gloss over. The front is wearing well and still has plenty of life.
For decades the standard has been from cold tire pressure to hot tire pressure should be a 10% increase.Metz Marathons do exactly that on my 04 GSA when I use 35 front and 39 rear.Last set went 21,000 miles and the front could have gone another 4-5 thousand.Ride 2 up and loaded all the time.That is a great tire for the street on a GS.
The problem that I have with that is that the tire manufacturer doesn't know what type of bike the tire is going on and most importantly the weight of the bike/rider/luggage/pillion, etc.
How, precisely, do any of those variables make it acceptable to exceed the design specifications of the tire? That's kind of like saying, "Yeah, that vehicle lift is only rated for 10,000 lbs., but they didn't know I want to use it for a D10 dozer, so I'm fine." Just because you want to use it on the D10, doesn't change the load rating of the lift from 10,000 lbs. to 180,000 lbs, in the same way that just because the bike manual says the tires should be at 42 psi, doesn't change the specs of the tire that should be kept below 37psi.
I'm not sure I see anyone saying that you should exceed the max inflation number on the tire. Rather I see argument over wether you should actually inflate the tires to the tire max, or should you leave them lower as the manufacturer recommends. I will also say that if the manufacturer (BMW) recommendation is higher than the tire's max inflation, than the tire is probably under-specced for the bike (to low of a load rating?) On the question of going BMW recommendation or tire max, here are my thoughts.... a) never exceed max b) the bike manufacturer recommendation is a compromise number based on an estimation of how the bike will be used. Not knowing, the manufacturer gives you a number that will work, though not ideally, for everyone. BMW is actually better than many manufacturers in that they provide different number for different situations (solo, two up, luggage, etc.) Some manufacturers only give you one pair of numbers. c) it is still possible that different numbers will be better for one individual than another. I would start at the recommendation, then adjust accordingly. I wouldn't go straight to max (and definitely don't exceed max) as it might not work well for you. For instance, I live in an area where some paved roads are barely better than dirt roads. A little less pressure will help the tire deform and provide a little better grip. Whereas if you live in an area where the blacktop is smooth, that is less of a concern. Geof
I haven't see a BMW recommendation that exceeded the max rating on the tire, but I could be wrong. Max is just that, not optimal for lighter loads, in my opinion.
Not true. Again, going back to the K60, it has a 715 lbs. load rating (for a 150/70-17 anyway), and a max pressure of 36 psi. I do agree with your points a through c. The point that I'm trying to make (and maybe not doing it well) is that no one source is the be all end all. The values listed in the manual are suggestions, but the values listed on the tire need to be taken into account and NEVER exceeded. We see a bunch of people come into our shop that only reference the bikes manual/data plate, resulting in over inflated tires. Then they wonder why their tire is nearly bald at 2000 miles, and blame the tire for poor longevity and handling rather than planting the blame on the error.
Their recommendations (at least in the pre-08 R1200GS/GSA manuals) exceed the max pressure on a Heidenau K60 front for all riding configurations except "One-up, no load", and the recommendations on the rear exceed the tires max pressure in all riding configurations. We're in agreement on max not being optimal.
When you optimize, you choose to give priority to some factors, while some are not deemed important. Thus, there will be many optimal situations - depending on what you want to achieve. Now, what is BMWs optimal situation: Most comfortable ride, or to make the tires last as long as possible? On the other hand: What is the tire makes optimal situation? And, again, do not confuse the need for correct pressure in wheels that run flat on the ground (as on cars) with round tires (as on a motorcycle). [TaSK]
Max is optimal for best tire life, regardless of load. Beyond that, it's easy enough for you to reduce pressure by a few PSI at a time and prove to yourself that lower than max offers no benefit in traction. So this will then beg the question of why you would run lower than max in any situation if it reduces tire life and does not improve traction (I'm referring to on-pavement traction for the purposes of this discussion)