Running tires at the sidewall max PSI

[perterra]

Originally Posted by randyo

so you really think I only tried it once at one low pressure, experimenting means trying all pressures and for more than a few miles at each setting

If it felt like you were riding on a flat tire, yes. I have ridden on flat tires, you spend your time at 20 mph. If you were running 65 mph then it was nothing like running on a flat tire.

[dillon]

Originally Posted by randyo

on a car, not on a bike, a single track vehicle leans in corners, if yer scrapin pegs over inflated or under inflated you'll wear the edgesm, if yer dronin in a highway, over inflated or unde rinflated, you'll still wear the center.

tire pressure in a bike regulates the amount of flex, or how hot the tire will get, not the contact patch

Yes I know this, the relation to automotive tires was put in there as there was talk of automotive tires. Also it does help illistrate that underinflation can be worse than over inflation, thats what I was going for anyway.

[Thanantos]

Well, I can tell you my KLR is like a completely different bike in this MI sand when running the rear at about 14psi compared to the recommended 28 (with corresponding decrease in the front).

So, is the concensus on proper air pressure the 10% method?

[DAKEZ]

I use it (10% method) because it has served me well.

I am however of the belief that there are no hard and fast rules. For instance: When it is 95 degrees and above and I am on a trip, I will run slightly higher pressure to help reduce heat.

Mainly because when it is hot you can almost watch a tire disappear on a trip. I hate it when a rear is done in under 2000 miles.

[Mambo Dave]

Of the things and big-highway-miles travelers I've read, I run max or just above on my street bikes now - especially after having tried under max pressure for load and having seen its effects.

I'm not saying anything for dirt - although low pressures on mountain bike tires sure do help when the terrain gets tough... the balance being how low can you run vs. risking a punctured tube (or a snake-bite) or a sidewall problem.

But for the street, for guys who do big miles in a year and can go through a set of tires, or more, yearly - 2 or 4 psi above max pressure (for max load) works on heavier street bikes.

[Thanantos]

Originally Posted by DAKEZ

I use it (10% method) because it has served me well.

I am however of the belief that there are no hard and fast rules. For instance: When it is 95 degrees and above and I am on a trip, I will run slightly higher pressure to help reduce heat.

Mainly because when it is hot you can almost watch a tire disappear on a trip. I hate it when a rear is done in under 2000 miles.

Thanks Dakez and whomever recommended this, I've always wondered if I should use the tire recommended or bike recommended pressure, but this makes more sense than either as it is tire/bike independent.

[duck]

Originally Posted by perterra

Why does too hard make it wander? Tire profile?

Never had that issue, I have run at over the max load for days on end. And can tell you from trailer tires, heat build up here can kill a tire quick and I dont mean wear out the tread, I mean letting go all at once.

My guess is that it makes the tire profile too hard/round. I suppose it all depends upon the particulars of the bike/tire combination.

[perterra]

Originally Posted by duck

My guess is that it makes the tire profile too hard/round. I suppose it all depends upon the particulars of the bike/tire combination.

I get that feeling with new knobbies, was told thats lively and responsive not squirmy. I agree it can be a little disconcerting but after a hundred miles I dont notice it.

Texas has gone to some sort of chicken shit highway asphalt that makes the bike feel as if it's moving around underneath you. Gets old sometimes but it is what it is.

[JSharp]

The 10% cold-hot change is an old rule of thumb that's probably still pretty useful. I was checking the Bridgestone site today for some info since I changed to a different Bridgestone tire on my Ninja and found this -


Checking Tire Inflation

• Check your tire air pressure at least once a week and before long trips. Be sure to use an accurate pressure gauge.
• Check your air pressure when the tires are "cold." The tires are "cold" when your motorcycle has been ridden less than a mile at moderate speed or after being stopped for three or more hours.
• If you must add air when your tires are hot, add four pounds per square inch (4 psi)(28 kPa) above the recommended cold inflation pressure. Recheck the inflation pressure when the tire is cold.
• Never release air from a hot tire in order to reach the recommended cold tire pressure. Normal riding causes tires to run hotter and inflation pressure to increase. If you release air when your tires are hot, you may dangerously under inflate your tires.
• If your tires lose more than two pounds per square inch (2 psi)(14 kPa) per month, the tire, the valve, or wheel may be damaged. Consult your local dealer for an inspection.
• Use valve caps to keep valve cores clean, clear of debris and to help guard against air leakage.

That dovetails with the 10% rule nicely since most of our street bike tires are running around 40PSI +- 5PSI...

[Mambo Dave]

Just found my front 33 psi max psi was 20, and my rear max 41 psi was 21, and it's been getting that way over 2000 miles of commuting the last two months.

I'm kinda lazy about checking pressures... thanks to this thread I checked 'em this morning before the 40 mile commute home.

34 front, 42 rear now.

.............

Edit: Alright, made it home. Wow did that make a difference

More stable at speed, even for the one-handed ride I do 90% of the commute, and obviously quicker to handle.

Anyway, I felt I should explain my laziness - I ride over 400 miles a week now, so I treat the bike like it's a car. I don't check it as much for a given mileage as many recreational riders would, or like I used to before getting into serious commuting. Yeah, that's a short-coming and risk on my part, but it is what it is. Also, this was a new set of tires on a newer bike to me, so I had no clue they'd lose this much air in this amount of time. The front is a tube, the rear tubeless, so I found it also surprising that the front, which started out with a lower p.s.i. when full and new, lost less of a percentage than the rear tubeless.

[bemiiten]

I always run maximum in the rear and the front about 5lbs under at 37. If the front is just a few lbs softer, I notice a negative effect on handling. I've ridden thousands of off road miles and never felt i needed to air down. Same as when I use to road race. Tire guys were recommending around 25lbs. I always had very good results in the 29-32 range.

[markk53]

Originally Posted by bemiiten

I always run maximum in the rear and the front about 5lbs under at 37. If the front is just a few lbs softer, I notice a negative effect on handling. I've ridden thousands of off road miles and never felt i needed to air down. Same as when I use to road race. Tire guys were recommending around 25lbs. I always had very good results in the 29-32 range.

Try running max pressure on a trials bike riding trials!

I've harescrambled before and ran about 18 psi most all the time. In off road riding on the KLX when it gets serious I drop to about 20 or so. The tires were too hard for the terrain, slipping off of the rocks roots, and ruts far too easily. I fell off 3 times, then dropped pressure... no more crashing. I do run 32 on the road because that is what has worked for me in almost every type of tire I've run. I arrived at that by riding at sidewall psi and having some patter when cornering on slightly rough pavement (which most is). A friend had the same issue with the same brand model of tire and had the same results when dropped down arond 32. Allowed the tire to stop bouncing.

[randyo]

Originally Posted by markk53

Try running max pressure on a trials bike riding trials!

trials and rock crawling with a 4x4 is a totally different LOW SPEED animal

[DAKEZ]

Just admit you are wrong about airing tires down and move on.

[markk53]

Originally Posted by randyo

trials and rock crawling with a 4x4 is a totally different LOW SPEED animal

As is running a 125 through the woods on muddy slimey trails with roots and rocks. seldom getting over 30 mph and a whole lot of 2nd & 3rd gear. Until you really know what it's about and been there you really won't understand. We ran 12-18 psi in the knobbies. The flex helps clean the tread as well as conform to the terrain better than an aired up tire running over 20 psi or more. But, don't believe me...

Here is a blurb from Motocross Hideout:

Tires can help you win a race. If it’s cracked or worn out then it’s time for a new tire! Tire pressure is also very important for racing. Although you’ll probably have to check/change it throughout the day, it’s good to pump them up to 15 psi the night before. A good pressure for soft terrain is about 10-12 psi, and hard-pack about 13-15 lbs.

Here's Dirt Rider's blurb on Endurocross prep:

3. Dial in your tire pressure. Obviously, 'full' doesn't cut it as a tire pressure setting for EnduroCross. Since trials tires are banned from competition, you need every advantage possible when it comes to finding traction aboard your machine. You can chop up your knobbies to make them hook up better, but that's not always practical for the racer on a budget. One of the best things that you can do is to pay close attention to your tire pressure, which will drastically affect handling and hook-up while out on the track. For EnduroCross, you typically need enough air in both tires to maintain traction without inviting a pinch flat when slamming into obstacles. Because of this, we've found that 11 - 13 pounds of pressure works great in the front tire, while you can typically get away with as low as eight PSI in the rear. Keep a close eye on changes to this setting that result from external air pressure and temperature, and be sure to set the pressure right before you go out so that it is as close to accurate as possible

And last, but not least, again from the great source, Dirt Rider there is this:

12. Finish off the bike prep by setting tire pressures. This can wait until you arrive at your riding area, since air pressure changes with temperature and altitude. The average is 12 to 14 psi, with a few pounds more recommended for severe rock conditions.

So it really isnt a figment of my imagination. I'm letting the authorities back what I, and others, have said repeatedly. But hey, believe what you want. Just don't blame me when you're on your head on some slimey root covered trail!