Tire Question(s) Revisited

[Altritter]

References: Earlier thread (Crossrodes 07/11/08 at 13:53:43)
Thread on tire pressures (tire mfg's or BMW-recommended pressures under the seat) recently on MOA Forum's Airhead board

After reading these threads, I checked out my '81 R65 that I bought Oct. 2007 w/23K miles. Tires: Metzeler ME33 Laser 100/90/18 (front); Metzeler ME88 Marathon 120/90/B18 (rear). Snowflake wheels, tires are labeled tubeless. I know snowflakes aren't rated for tubeless, and I haven't had tires off rims, so I don't know if tubes are in them. Tires are not worn and are not cracked. Don't know how old they are. Rubber is hard, but I don't know whether they are excessively hard for a touring tire.

Question 1: Whose recommended pressures?

     Metzeler's Load Ratings (cold) are: Front - 495 lb. load at 42 psi; Rear - 760 lb. load at 49 psi. I'm pretty sure these are max pressures. No "recommended" pressures are given.

     BMW's under-seat specs are (for solo rider):      Front                 Rear
                                Up to 80 mph                                27                   26
                                80 - 100 mph                               29                   28
                                > 100 (good luck on R65!)            30                   32

Quite a disparity! Now, realizing that Metzeler's ratings are likely maximums, I also have seen postings on the MOA Airhead forum counseling owners to ignore the BMW data because of changes in tire technology in the intervening 25 years, and stating that with modern tires, BMW's pressures might cause excessive flexing and consequent heat buildup.

My riding style is neither aggressive nor particularly fast. Are there some intermediate tire pressures that that members prefer?

Question 2: Tire date codes (this is an extension of the Crossrodes posting)

Crossrodes mentioned 1318 as the potential date code on his ME77, and crazy_dan said his ME77 showed 1318. My tires don't show anything even close. Here are all the numbers I can find on them:

     Front (ME33 Laser):  E375R  0051608          DOT  EB6A   BPH458     0507 (just above "Manufactured in Germany")
     Rear (ME88 Mara-)    E375R  0055599          DOT  EB6L   CKP3700      138    "      "             "               "      "

None of this looks like any date code I can imagine, except for the numbers above country of manufacture, and those don't have an equivalent  number of character fields.

Since we all ride bikes of similar design and age, can anyone share knowledge on this?

TIA, JT

[Crossrodes]

Here's one item on air pressure from Metzler.

http://www.us.metzelermoto.com/web/products/tire_pressures/default.page

[Crossrodes]

Here's some info on date codes:

http://www.amadirectlink.com/roadride/Riderresc/tires.asp

[montmil]

... I haven't had tires off rims, so I don't know if tubes are in them.

Usually, a tubed tire will have a threaded valve stem that most often points straight up at the axle. Should have a thin nut securing the stem to the rim's exterior surface.  

A tubeless tire would require a tubeless-style valve stem. It will be beefier-looking, usually chrome plated and will likely have a rubber grommet partially visible on the exterior of the rim.

Hope this helps you to determine if you are tubeless or not.

Monte

[nhmaf]

I don't carry much of a load on my R65LS, though I guess that my 210 pounds is certainly equivalent to some
other riders with a load.    Depending on tires, etc. and the use of the bike, I use different pressures, but my
R65 seems to handle quite nicely with about 32 PSI in the front and 35 PSI in the rear tire.   Running BT45s
on it now, but with Metzlers I Was running pretty much the same thing, or maybe +2 PSI more in the front tire.

Tire technology has dramatically improved in the past 25-30 years.

[Altritter]

Vielen dank! That just about covers it. I really appreciate the help.

I checked all the links supplied. Those, plus the practical info supplied by everyone, helps tremendously. The one gap remaining is the date code on the M88. I'm going to hit Metzeler's site again and try to learn whether Metz. uses a nonstandard date code. Also, I'll take another look at the tire. (My eyes aren't what they used to be.)

Montmil wrote: <<a tubed tire will have a threaded valve stem that most often points straight up at the axle. Should have a thin nut securing the stem to the rim's exterior surface. >>

Yep. Thanks for reminding me. I haven't seen a tube in anything other than a bicycle tire in so long (about 40 years, I guess) that I'd forgotten what a tube-type valve stem looks like. I noticed the threaded collars & made a SWAG that the tires were tubed, but I really had forgotten.

Nhmaf wrote:  < R65 seems to handle quite nicely with about 32 PSI in the front and 35 PSI in the rear tire. >

Thanks for the information. I've been running just slightly more than that. (Sure didn't trust the 26-30 that the old stick-on suggests. I'll try yours & see. (FWIW, there was a thread on MOA Airhead Forum regarding a supposed formula (that no one could remember) for calculating heat expansion from cold pressures. I *certainly* wasn't about to trust that one.)

Thanks again to all! Guess that about wraps this one up.

Cheers, JT