Tire Pressure

[Guest dkgross]

Yeah, my Pilot Roads have 2000 miles on them and look great.

docc...did you not like the Pilots? I was thinking of trying them when the OEM 02's wear out.

[docc]

The OEM tire on the 2000 Sport was Pirelli Dragon Corsa. For me, too soft ( 2500 mile rear) and very nervous at speed ( 90 on Interstate). I then ran a series of Dunlop 205 and Bridgestone BT 020 finally downsizing the rear to 160/60-17. Usually I'll get 4500 miles from a rear as I like to accelerate through the gears and engine brake aggressively.

 

At 2000 miles the Pilot Roads let go in a line change in a corner. There were lots of other factors ( rear weight bias, high tire pressure, off-camber, up hill, decreasing radius, rider error) But, upon inspecting the tires I expected them to show some substantial wear. But, no, they look really good. This impressed me as their being much too hard for my liking.

 

I'll go with the Dunlop 220 ( the follow on of the 205). They appear to be good compromise on traction and tire wear. I found the 020 Bridgestone to be predictable as well. Probably a little less sticky than the Dunlop and more stable at highway speeds.

[Guest captain nemo]

I run with Dunlop 220s, but haven't had them long enough to comment on wear. I am impressed with them in every other way. They are perfectly stable well over 100 mph and I have never felt anything bur rails in corners. But I have a 170/50 on the back.

[Guest IanJ]

Something that hasn't actually been said yet in this thread:

 

Higher pressure in a tire tends to:

 

* Extend tread life

* Decrease traction (in terms of cornerning and braking traction)

* Decrease "flex" heating/wear

* Decrease rolling friction (in the sense of resistance to forward movement)

 

Lower pressure in a tire tends to:

 

* Decrease tread life

* Increase traction (up to a point)

* Increase "flex" heating

* Increase rolling friction

 

This is important stuff to understand, because how you inflate your tires has a definite impact on traction and tread life.

 

When a tire has high pressure in it, that pressure prevents the tire carcass from deforming as much at the roadway contact point. So, the contact patch is smaller. That means the tire rolls easier, and has less traction/friction in general. With lower pressure, the contact patch gets bigger. Obviously, deforming the carcass of the tire around this bigger contact patch will cause more flex, and more tire to be in contact with the ground. The more the tire flexes, the more heat it generates -- heat increases traction by softening the tread compound, and reduces tire life by causing heat-related breakdown of the rubber.

 

What all this means is that you should tailor your tire pressure to your riding style and environment. Me, I ride around in the city at relatively low speeds and with low traction requirements (in terms of cornering and braking). I'm not blasting around sweeping curves at maximum lean; I hardly lean the bike at all most of the time. I'm also a cheap bastard, so I run high tire pressure (around 40 front and rear) to extend tread life and increase gas mileage. But, when I take a bike out for some country-road riding, I take the pressure down to around 35 PSI front and rear, to take advantage of the greater grip afforded. Note that some people will take exception to my statement about needing low braking traction in-city; however, I've never found an occasion on which I hit the brakes and the tire lost traction before I lost my nerve to brake. I don't think I'm putting myself in any danger by riding with taut tires.

 

If you're riding where grip is essential, lower the tire pressure. If you're doing some high-speed freeway runs, increase the pressure to avoid excessive tread wear. Don't lower the pressure too far, or your tire can fail, losing pressure very suddenly -- this is a cause of numerous bike accidents, as people let their front tires drop into the low 20's. Check your tire pressure at least once a month, preferrably more like once every week or two.

 

Note that when I say "lower" and "higher" in terms of tire pressure, it's entirely dependent upon the tire to define those terms. For some tires, 36 PSI is really high pressure. For others, it's only moderate pressure. Adjust your numbers for these terms according to your tire.

 

Finally, be careful! Your tires are the one and only link between your motorcycle and staying upright. Aviators check the wings on the plane before every flight -- your bike's tires are its wings, don't neglect them.

[Guest IanJ]

Also, my BT020 front was cupped all to heck and back at 5000 miles on my 02 Le Mans. I was seriously unimpressed, because my rear tire looks perfect, with many mm of tread left. I've replaced the 020 with a PIlot Road on front, and left the 020 on back. The bike likes to fall into corners now, which I dislike, but not enough to spend another $150+ on a new rear tire yet. I'm hoping the Pilot Road lasts a bit longer than the 020 did. Because I'm a relatively conservative rider, I'm not too worried about the front running out of grip, and I value tread life over ultimate grip. I'll probably throw a Pilot Road on the rear when the 020 wears out.

[roberto]

Tyres provide the suspension (spring rate, damping, etc) for the unsprung weight. Changing the tyre pressure affects this "suspension" and possibly the way the tyre copes with some bumps. Thus incorrect pressures can require the fitted suspension to do more work. I don't recommend running pressures more than a couple of psi outside the manufacturers recommendation. e.g. I experienced a repeatable low-frequency weave at around 110mph once and found it was due to 34psi in the front tyre, as an increase to 36psi cured it. The tyre was part-worn at the time.

[Guest captain nemo]

I hear the Motorcycle Safety Course recommends you run the pressure that is stamped on the tire. They say sidewall collapse and deformation is possible if you run low pressure. This is what I heard; I take the course myself next week so I will find out.

 

Also, I bought those valve stem covers that supposedly tell you what your tire pressure is. You can get them at any auto parts store. FORGET ABOUT IT - they don't work. Waste of money.

[Guest Brian Robson]

As with everything, out comes the myths and suppositions. Its no wonder motorcyclists everywhere have something to talk about, its because no one agrees with anybody over anything.

Tyre pressures up in the city, down when riding fast, high pressure for fast corners, low pressure for slow corners, inflate to the sidewall pressure blah, blah blah....like women in a fabric store

They are tyres...put air in at what the manufacturer recommends (do you think that they pick this number out of thin air?), check there are no holes in the rubber (good advice both on your bike and in the bedroom) and that there is legal tread and ride the bollocks off the bike.

[Guest captain nemo]

There is nothing I like better than talking about my Guzzi with the Guzzisti over espresso - like we are women at the fabric store. Most of us here like nothing better.

[Guest IanJ]

Brian, a reason to care about things like the differences in handling and traction and wear with tire pressure is if you're worried about getting the last bit of traction out of your tire (say, on a racetrack). You might also care if you want to be as safe as possible. Or as frugal. Of course you can just fill it up and ride, and that's basically what I do -- but if I can get more miles out of my tire by running it at higher pressure, I will -- air's cheap, tires aren't. Likewise, if I can reasonably increase my ability to go around that corner by making a practically free modification to the bike, why not do it?

 

Definintely, anyone who goes around checking their tire pressure every day and adjusting it in half-psi increments needs a life. In that case, definitely stop fussing over your bike and ride.

 

I guess I'm just saying that there's always something to learn about motorcycles. And really, if we didn't talk about motorcycles, why would we be wasting our time on a web board?

[docc]

$air

 

Trying to get a little more life out of your tires, especially the front, will be false economy if the thing ever lets go.