Tire inflation pressure

[redpoint5]

Obviously higher inflation pressure will reduce rolling resistance and increase MPGs, but how does pressure effect the longevity of the tire itself? On a car, increasing pressure tends to increase tread life. I have a theory that decreasing motorcycle tire pressure increases the contact patch, and therefore increases the area that wear is spread over.

What pressure technique is best for getting the most life out of a tire, considering the centers wear out before the edges? What is best for getting the most grip and fast cornering?

My rear tires only last between 3-4k miles, and if I could extend the change interval that could potentially save me some money and keep some petrol products out of the fills.

My ride: 2001 Honda CBR600 F4i
Mods: LED marker turn and brake lights. HID headlights

[alvaro84]

I have some experience with only 2 kinds of tires so far:

- I learned that I could inflate my Metzeler Z6 set to 2.9 bar cold without any problem
- Lately I switched to a Heidenau K73 set and they feel to distort at such pressure. 2.5 bar cold feels fine so far, though.

I think the latter really means that their contact patches decrease. At least they feel like balancing on blades or balls or dunno.

The first Z6 set (got them used with Teresa) took 21k km (13k miles) and the second pair (bought them new) 28k km (17.5k miles).

These Heidenaus are new now with 1500km (<1000mi) in them, so I don't really know anything about their longevity. The only thing I know that I got the rear one punctured within the first 1000km... the repair spray has been holding it together since then, though.

[euromodder]

Originally Posted by redpoint5

My rear tires only last between 3-4k miles, and if I could extend the change interval that could potentially save me some money and keep some petrol products out of the fills.

What tyres are you running ?

[redpoint5]

Michelin Pilot Power 120/70/17 front and a 180/55/17 rear. When I first got my bike, I would go through rears at about 3000 miles, and fronts every 9000.

I do about 1 track day every other year, and ride spirited whenever I head out on the back-country roads.

I wonder if a dual-compound would be good for my situation? I haven't looked into buying tires in a couple years now.

[piers.singer]

I once inflated my Pirelli City Demons from 28psi (recommended) to 36psi. They were striped within 500 miles. They were cross-ply though, so, as a general point, if you're going to mess about with tyre pressures, it's safer to use radials.

Specifically, redpoint, your tyres are radial and so shouldn't distort if inflated higher than recommended. As for under-inflation, this will cause uneven wear and increased drag on the drive-train components (thus a loss of drive-train efficiency and therefore a drop in MPG). It may also increase the bike's propensity to slide in the corners. I once rode my old Honda 125 with a rear puncture and it handled like it was on ice. The only reason that I didn't realise that I had a puncture was because it was so wintry that I thought that it WAS ice!

Clearly, that's an extreme example of under-inflation, but I shouldn't risk spirited riding with under-inflated tyres. If in doubt, stick to the manufacturer's recommended pressures.

I believe that the chap who rides the 100mpg Ninja 250 inflates to 60psi, so clearly, like cars, motorcycles also benefit from greater inflation.

[euromodder]

Originally Posted by redpoint5

Michelin Pilot Power 120/70/17 front and a 180/55/17 rear. When I first got my bike, I would go through rears at about 3000 miles, and fronts every 9000.

I do about 1 track day every other year, and ride spirited whenever I head out on the back-country roads.

Those are as good a compromise as it gets for street riding.
If you really want more miles from the rear one, I'd say you'll have to compromise a bit more on the rear tyre - and start looking at the best sports-touring rubber.

I wonder if a dual-compound would be good for my situation?

A comparable dual compound, like the Pilot Power 2CT would have softer edges, the middle compound would be similar to the straight Power.
So, they'll only give comparable mileage, but better grip at extreme angles.


Some of that sports touring rubber is pretty good when properly warmed up.
I graphically recall seeing the ground down footpegs on a friend's 2001 Bandit 1200 on the stock sports-touring tyres (BT020, IIRC).
And yes, I mean the pegs themselves, not the hero blobs - about 1/3rd of them gone, right up to the rubber

I've seen him go through Pilot Power 2CT and a score of comparable tyres (MeZ, Dunlop, Conti) in about 2500-3000 miles.
I doubt there's any miracle tyre out there.

[kawboyCAFE]

adding too much extra pressure in a tire actually causes it to wear out quicker. more weight in a smaller contact spot. never inflate motorcycle tires more than 10 psi above recommendation. if you do, your asking for trouble. and plus, with the type of riding you said you do, you just need to keep the proper pressure in them. add more pressure, and you wont enjoy the "spirited" riding as much.

[alvaro84]

I did the math now to see what my pressure looks like in PSI.
Well, BMW recommends 2.2bar=32.3PSI front and 2.5bar=36.75PSI rear.
With the Metzeler Z6s I used 2.9bar=42.6PSI and it was OK like that.
The new ones (Heidenau K73) start to feel slightly wrong at 2.6bar=38.2PSI, at that 42.6PSI they felt like balancing on blades or so. I may try different pressure front/rear, for now I surely can't go above 38 PSI with the front without compromising handling (I don't know how much it's different because it's now one size larger (120/70) than normal). That's not even 10 PSI above factory recommended.

Ciliegia is a bit differemt because Hyosung recommendations are lower. 1.75bar = 25.7 PSI front and 2-2.25bar = 29.4-33.1 PSI rear. There's no big difference in their weight (167kg/368lbs vs 187kg/412lbs), but the sizes are quite different (110/70-17 + 160/60-17 on Teresa and 110/90-16 + 150/80-15 on Ciliegia). But no way that I could inflate anything under 2 bar.

[Varn]

Ah, I think motorcycles require a different mind set than a 4 wheeler.

Efforts to reduce friction in the tire/road interface can cause a crash. Efforts to decrease aero drag can lead to instability in side winds and on some road surfaces.

Be very careful with running higher than recommended air pressures in your tires.

[euromodder]

Originally Posted by alvaro84

for now I surely can't go above 38 PSI with the front without compromising handling (I don't know how much it's different because it's now one size larger (120/70) than normal). That's not even 10 PSI above factory recommended.

If you mount a 120 instead of 110 on the same wheel, it'll be pinched a bit more, so the profile becomes more curved/pointed at the contact patch.

If you then also increase pressure, making the contact area even more pointed on a semi-circular tyre, handling will be negatively affected - it'll become very twitchy .