WTF tire pressures???

On a BB site and there was a topic about the new Dunlop Sportmax Q3 tires. Someone pointed to an article about the tires here: http://www.motorcycle-usa.com/545/1...unlop-Sportmax-Q3-Motorcycle-Tire-Review.aspx

In the article was this statement:

The tire in the article and on the VFR800 and BB are the same size. So I responded below.

Whoaaa that is a huge difference in air pressure! What is the deal with that between the OE of the bike vs the tire mfg. Our bikes are supposed to have 42# front and rear. What are you going to set your tires at?? A 12# difference in the rear seems almost like a flat tire compared to the 42# the OE calls for.

So what is the optimum tire pressure for the XX? The 4# difference for the front is a lot in my book, but 12# difference in the rear to make the TIRE perform optimum has my head spinning. Don't you want optimum on the street? How do you know what the optimum is for the XX on the street then? That much lower than what the OE specs out is a little, no, a lot of confusion for me. It just doesn't ring true with what I have known for years about air pressure for tires. The GSX-R is not that much different from the XX. So splain it to me and make me more edumacated, please!


So what's the skinny here on tire pressures? Or is it just these tires and Dunlop should be contacted about each particular tire pressure/bike? Or should we just disregard the mfg tire pressures and run what the tire mfg suggests, if they even suggest anything? I'm assuming that all bikes that use these tires may have the wrong pressure in them if the owners are adjusting by what the bike mfg wants. A couple of #'s either way is one thing but 12#'s is a real lot!

 

I see this all the time on cars/trucks (as passenger vehicles, not racing), and it leaves me wondering as well.

I put a set of Continentals on the wife's Accord. Honda OEM specs call for 32. But the tire has a max inflation of 44. So technically, running it at 32 is more than a 25% decrease/variance from the tire manufacturer. I've been running them at 35, and it seems to be a good compormise. Not a harsh ride, mileage is unchanged, wear on the tires is even (inner and outer, as well as front to back).

My Ram is the same thing - I put a set of Cooper Zeon LTZ on there with a max inflation of 50+ (can't recall specifically at the moment), but if I ran max inflation, I'd either snap my spine or suspension. I've found that 37# is a good setting.

Then you can look at guys running street tires at the track, and I've seen them drop pressure to 12-15# to help hook up on the hole shot.

A lot depends on not only the compound of the tire, but I guess their "ply rating". Maybe this Dunlop is just constructed where its "OK" to run it on the soft side.

Everything needs to work in conjunction - tires, rider weight, suspension settings, terrain, etc.

That's my long way of saying I don't know, but for my personal vehicles, its a combination of trial and error.

 

I am no expert but I have talk to many on the Track including my little Bro.
They like to lower the air pressure for better grip :noidea: I am sure other expert will chimp in with their thought.

 

I think there are two things at play here, on the street there are more "obstacles" that you need to worry about, pot holes, rocks, square edge bumps from uneven pavement, even mileage, having a lower PSI could definitely be detrimental to your rim if you were to hit some of these obstacles, especially with a heavier bike like the VFR. Mileage comes into play as the lower PSI definitely affects not only MPG but tire wear as well. On the track you typically do not have to consider most of these things (as much), as most tracks are pretty clean and smooth and mileage typically isn't an issue but traction is. The lower the PSI is the bigger the contact patch of the tire will be, and thus providing more tire area for traction. Some tires take a while to "warm up", especially at higher PSI settings, where a low PSI the tire will typically warm up faster. There is also side flex, a lower PSI setting allows the tire to flex more and thus keeping as much contact with the ground as possible. The new Q3 is supposed to have a much better and stronger side wall and thus can be run at a lower PSI without compromising the sidewall integrity. A great example of tire PSI and contact patch is when you get stuck in the snow or sand, letting out as much air as possible helps your vehicle's tires get as much contact with the ground as possible.

When I took the Lee Parks Total Control class last year, the first thing they made us do was set the tire pressure to 30 PSI, this was for everyone, Harley's included (Yes there were Harley's there too), by coincidence, the standard air pressure for my Ducati 900SS is 30 PSI (F/R). Being that the Duc is so light and it is a super sport Ducati probably figured 30PSI was sufficient to run daily. I can say though, the mileage I got out of my Q2s was very low in comparison to the mileage some guys said they got out of them with their VFR, but they were running the standard 36/42 called for by Honda.

 

As a racer, I can tell you it is routine to lower your tire pressure on the track. This gives a bigger contact patch AND counteracts the increased pressure caused by extreme high speeds and extreme braking. Generally, each tire manufacturer posts a recommended pressure on club race/practice mornings. The AMA only allows Dunlops, which suck IMHO. I find them prone to sudden wear (no warning), less sticky and less predictable than Pirelli. Plus boy racers fight to get the "European" Dunlops which are said to grip better than the brand's American-made tires.
Running low or under-inflated tires reduces mileage and can impact handling. This is not a concern on the race track due to heat (see above) and the fact racer's routinely trash their tires after a couple of sessions.
On the street, I keep all my bike's inflated to 2 psi UNDER the max recommended pressure. I check my tires every day before a ride. Even if I rode the bike the day before.
I highly recommend the Pirelli Angel GTs. Recently switched to them on my CBR1000RR (now a street bike) away from Dunlops. Better performance in the wet, softer ride and gripper, too.

 

OOTV and Boscoe pretty much have said it all in there posts. I think most tires pressure for OE is for 2 up riding too. When I doubled dutied my CBR street/track with DOT race tires the pressure differences where similar to above. I run my VFR tires a little under the max tire pressure unless I'm riding 2 up.
Bosco I have run the European and US Dunlops GPA 211's at various tracks. The older US were not as good as the ntec European ones and the cost reflected this but now the US ones are close on grip. I like them and get a lot of laps out of them. Running the slicks only. I have heard good things about the Angel's.