I don't know went out and checked the fatboy (sidewalls) both say forty this fatman always run both at 40psi BUT if you read the manual the front is usually 2 psi less than the rear on most models hummm maybe I should let some out,

 

chit the manual says 41 front 40 rear on the fatty dam now I gots to add
have you tried goggling or binging it

 

the owners manual i think is 20 bucks, or you can get what you'll end up using a lot more, for 60, the service manual.

 

WRONG< WRONG< WRONG

Any professional riding school as well as motor cops will tell you to run the max pr listed on the side wall. No, it won't blow up. The max pr is to keep the sidewall from flexing, these are not car tires.

The manual for the bike was printed for the oem tires that year. What if yu go to Metz, Mich, Cont, Avon? There pr are all 40 -42 psi and you have a 5 yr old manual that states 36. Most cupping is a result of underinfaaation of the front tire.

One of my bikes is an 08 Nightster. The manual says 30 and 36, but the oem tires say 41 and 40. I will always run the higher.

check 6

Bwana

 

I was mystified by those numbers, so wrote to Avon Tyres (I use Venoms). That is not strictly correct! They explained those numbers on the side wall give the max load at a given standard pressure. The recommended pressure for my Venom rear tyre is higher than the value on the sidewall. The maximum permissible pressure for Avon Venoms is 50psi.

Avon recommended pressures for your model of Harley are available from their website. Other brands may do the same. It is worth checking, if you use non-standard tyres. They may recommend higher pressures than the factory handbook. Harley recommend using 2-4 psi above solo when two-up or heavily loaded.

For my 1990 FLHS I use 38F and 44R solo with my Venoms, 44F and 50R when fully loaded for touring. Our all-up rolling weight is around 1200 pounds. We've just got back from a 2,500 mile trip to Slovakia with those settings, riding every sort of road you can imagine!

 

Check the clutch side around the steering neck in front of the gas tank. Should be a label there for the correct tire pressures.

 

Not "all" riding schools! On a race track most will tell you quite the opposite, *lower" your tire pressure from what the motorcycle manufacturer suggests in the manual. The last motorcycle I took spec'd 33F and 36R. (The side walls gave 36 and 42 as the maximum) The instructors advised running no more than 30F 32R. Their own bikes were set up at 30 F&R. By the way the side wall is *supposed* to have flex. For anyone that's running high pressure, like 4 or more PSI than your owners manual call for, try riding briskly around on a curvy road. Then set your pressure to the manual and ride that same road. You may be quite surprised how much better the bike feels.

As others have stated the sidewall gives the maximum load the tire is rated for and the pressure needed to achieve that load. Has nothing to do with your motorcycle. In fact that same tire may be spec'd for many different motorcycles and each manufacturer will work out the best compromise pressure based on the weight, and handling characteristic. Recognizing the potential for pot hole caused wheel damage, customers who complain of tire wear and whine when their tire cups, owner's manuals err on the high side. Which is fine for the street.

 

+1 on the max pressure on the tire and Bwana.

Ridewva - racing is a different venue and usually is geared toward max grip at very high angles of attack (read lean) for very short durations using racing tires. Running your road tires soft will change the handling characteristics, generally badly and shorten tire life. Even with that said - I have never head of significantly underinflating road tires. Now off road tires yes.

grbrown - Your answer from Avon is interesting. The pressure printed on the sidewall, by government mandate is the pressure that accomodates the highest load when cold. While this (http://www.tirerack.com/tires/tiretech/tirespecskey.jsp) is focused at cars, the standard and rules are the same. And this (http://www.officer.com/article/artic...on=19&id=27281) explains it from a more performance under stress point of view.

This article (http://www.sportrider.com/tech/tires...ure/index.html) makes sense and follows the guide to ask the vendor.

For my ME880s (http://www.us.metzelermoto.com/web/p...s/default.page) recomends minimum pressures, that by golly are pretty close the the pressure on the sidewall. Dumlap (http://www.dunlopmotorcycle.com/info...tips.asp?id=31) also has these instructions.

If you want more math (http://ezinearticles.com/?Motorcycle...sics&id=530176). Again, a general approach but for those into physics.

I could not find a inflation recomendataion on the Avon site.

I found no place that recomended an inflation number higher than that for cold max load - the number on the side of the tire.

...gene

 

I wasn't referring to racing but rather street motorcycles riding around a track where one can experience and practice good handling. And not at triple digit speeds. I wouldn't advise running tires (too) soft. It's not too difficult to check by the 10% warm increase method.
What I was commenting on was Bawana1 saying "Any professional riding school will tell you to run the max pr listed on the side wall" This is just wrong. No motorcycle manufacturer and no tire manufacturer would advise this. And the few riding schools I've attended advised if anything to lower tire pressure for better handling.

For street riding what I do is use the motorcycle manufacturers pressure when using their spec'd tires. As new tires fitments come out that are recommended for your bike, but aren't listed in the owners manual, naturally go with the pressure the tire manufacturer gives. This is on their website under fitment. (Not the max tire load pressure on the tire)

For those that over-inflate their tires attempting to get the maximum milage at the expense of ride, handling, and wearing out the center of their rear tires, each to their own.

 

Gene,

Interesting stuff! 40psi may be an industry or government standard, but has nothing to do with the most appropriate pressure for any particular vehicle. If 40psi is right for your ride, that is coincidence, not design. Or in other words the moulding on the sidewall seems to have no benefit for the consumer, except to cause confusion and misunderstandings, as we have already seen above!

Recommended solo pressures for the original Dunlops on my bike are 36F/36R, 36F/40R two up, which in practice were never satisfactory (nor were the original tyres!). Avon's pressures tend to be a little higher than Harley's factory handbook and for my bike are 38F/44R and they recommend adding 2-4 psi fully loaded which gives 42F/48R. I find my bike handles better with just a little extra.

On Avon's website, r/h side of their home page, there is a feature "Find an Avon tyre for your Motorcycle" where you can select your brand, model and year. It will give you their recommended tyres and pressures. Just done it (once again!) to prove it still works (see attached image).

For your bike (as it happens, same as for mine):

"FLHR / I / CI Road King / Classic (1994 - 2003)
Front tyre
Venom
Pressure front:
2.6bar(38psi)
Front size:
MT90B16 74H (also NW,WW)
Rear tyre
Venom
Pressure rear:
3.0bar(44psi)
Rear size:
MT90B16 74H (also NW,WW) 140/90 B16 77H"

Considering the healthy disregard Harley owners in the US and elsewhere have for such legislated things as quiet mufflers and restricted exhaust emissions, I don't think tyre pressures should be looked on any differently. Ride safe!

Added later:

Metzeler recommend tyre pressures similar to those I use for my Avons (taken from Gene's link):

ME880, Solo, 2 Up Light, 2 Up Heavy
Front, 38-40, 40-42, 40-42
Rear, 44-46, 46-48, 48-50