What About Tyre Pressures?

[magnum]

between 34/36 front and back,track days ill drop 2psi/tyre so 30/32,diablocorsas.

[scumdog]

According to the Metzeler online fitment guide, your Honda VTR1000F should be running Rennsports, at 2.5 BAR front and 2.9 BAR rear.

What the hell a Browning Automatic Rifle got to do with tyre pressure - except maybe letting the pressure down sort of real quick?
Seriously, I'm a dinosaur and it's always psi to me - and h.p. and mpg
The mental gymnastics I go through to convert litres per 100 km to m.p.g. just about gives me cranial meltdown why is it not km per litre?

[RiderInBlack]

Bike model: Honda CBR1000FL (:spudwhat: fu*ken heavy, 2 to pick up if it's on it's side )

Type of riding (commuting, touring, etc.): Mainly Touring and Commuting (open road 40Km+). The odd hoon, specially if I am chasing/try to keep up with other riders Some track time to improve skills and to help set the bike up better (no real racing). No off-road if I can help it, but do have a Km strip of metal road to get to my home.

Laden weight:
Rider - 85Kg
Passenger - at times. Around 75-85Kg
Luggage - Touring: kitchen sink if I can get away with it
Commuting: 20Kg:spudwhat:
Track: None

Type of tyres: Pirelli Diablo
Front - 120/70 ZR17 M/C (58W)
Rear - 180/55 ZR17 M/C (73W)

Riding style: Varies. Am trying to get my knee down on the track but have only touch the tip of my boot and the underside of my foot pegs (just, once going around the "Hill" corner leading to the home straight @ Puke).
Tyre pressures:
Trailing various pressures at the moment for different rides/conditions
Normal commuting on dry open-road - Front 36psi, Rear 42psi (cold).
Track Open Days - Front 36psi, Rear 40psi (hot)
Am trying to find best hot pressures for my tyres.

Feel WKO is right that hot pressures are more accurate as this is the temp that the tyres are working at.

If the Volume is constant then Pressure increases/decreases proportionately to Temperature (somebody's law:spudwhat: ).

[Big Dog]

My understanding of why more air in the rear is the back wheel tips over further (front tyre stays almost vertical on the road) so it needs more pressure to prevent sidewall deformation (less true in modern low profile tyres, especially those with virtually no sidewall).

Front tyres also need to absorb more direct impact so need to be softer so as not to affect steering as much when hitting potholes tramlines etc.

Eg lower tyre pressure = smoother cruising and better straight line grip due to larger contact patch, making stoppies easier.
But slower tip in and less adequate cornering grip (should you need those brakes after all, or want to get the knee down) as your sidewalls will deform less, so direction or inertia changes will be more stable.

A soft rear tyre may squirm without actualy breaking traction under heavy acceleration due to trye deformation, meaning you can't go as hard.

A too hard rear tyre will have little or no grip in the wet while the tyre is cold.

[riffer]

Bike model = 87 FZR750R 2LM with FZR1000 forks and rear suspension (stiffer suspension) preload set about halfway on front and rear. No idea about fork oil age (never done it) but forks are pretty stiff.
Type of riding = commuting & weekend play
Weight = bike 228kg (wet) + rider 90-95kg + bag 2-5kg
Type of tyres = IRC SP11 120/70-17 front, Dunlop Sportmax 205 160/60-18 rear
Riding style = mainly keeping to the speed limit commuting, lanesplitting as much as possible, try to find corners as much as possible in the weekends but tend to ride smooth rather than ridiculously fast.
Tyre pressures = 36 F, 42R measured cold for the road. Haven't been to a track day so no experience.

[TonyB]

I'm a dinosaur and it's always psi to me - and h.p. and mpg
The mental gymnastics I go through to convert litres per 100 km to m.p.g. just about gives me cranial meltdown why is it not km per litre?

Never fear, go here: http://www.metroyamaha.com.au/tools.htm#torque

[TwoSeven]

This is the rather bizarre way I work out tire pressures.

I ride my bike around a lot and write down the tire pressures that I feel comfortable with when the tires are hot. My notebook would contain the air-temp and tire pressue (since I use the same brand of tires, most of its in my head now).

General method is to take a pressure that is slightly hard, ride the bike till the tires are warm and every now and again let a psi out (using an accurate guage). When I like the feel, thats the one I keep.

When the bike cools down again, you need to re-measure your tire pressure to find out what the cold value should be (so when you initially inflate the tires what to put in).

Also try and make a note of how long the tires took to get warm for that air-temp). I dont have a thermometer for this, so I just guess.

For racing, its just a matter of working out what the current air-temp is, then finding the appropriate warm setting in your log book. If the tires are cold, set it to the cold setting (and remember how long it will take to warm up - this is how many slower laps you need to do). If using tire warmers, then the warm up laps will be reduced).

Writing down the cold setting after the tires have cooled saves you from having to calculate tire pressure expansion as the tires warm up. When I did track days and the like, I measure the tire temp as soon as I come in, then 15 mins later and how I thought the bike felt. Next day I can sit down and work out the ideal settings. It means next time you get similar conditions you can be more accurate.

Also remember that tires cool down real quick (different brands at different rates), so if you are scratchin and slow down for a while, or stop at some lights, the tires will cool. Helps prevent the slide due to suddenly code tire syndrome.

I know this method sounds a bit like hard work, but at the end of the day, you can ask someone else for some settings, but that means the info they will give back will be their preference for their riding style, bike, type of tires and may not be suitable for you (it does give you a good ballpark tho). Since you will be out riding your bike - why not write down the settings every now and again.

For road use I often run way harder than track pressures. I can be anywhere from 33/33psi (D207s) to 36/38 on the road - depending on the mood I am in and the feedback I am getting (I hate dunlops out of interest).

[wildfire1]

Start with what the hand manual says.

Then look at what the Tyre Manufacturer recommends

split the difference and you will always have the perfect cold tyre pressure

Or Not.....

It's just a matter of experimenting in differenct conditions

Some people are heavier, some are lighter, some sit more forward, some carry luggage....get my point.

[Hoon]

For racing the way I calculate my tyre pressures is measuring the difference between hot and cold. I measure my pressures before I go out and then again as soon as I get back to the pits.

I forget where I read it but you should be aiming for a 6-8 psi increase between cold and hot pressures.

- If you are getting less then you are running too much pressure and the tyre is not flexing enough to generate the heat required to reach optimum grip.

- If you are getting more then not enough tyre pressure as the tyre is squirming around too much.

I find this method more accurate than "what my mate bob uses" or "what manufacturer x recommends without even knowing what type of bike, track conditions, my weight or riding style I use" but it doesn't take into account whether you're in Antartica or Bahrain.

On my RGV I use to have more pressure in the rear however with the ZXR 29-30psi is spot on but I'm struggling to get enough warmth into the front tyre (even at 28psi I was only seeing +2psi when hot and I sure aint going any lower!!!). So I suspect I'm not getting enough weight onto my front end. The fact that I still have another 10cm from bottom of fork travel and steering which I'm sure could be quicker kind of confirms this.

[FROSTY:Me]

Hoon--I definitely noticed Im not working my front tyre as hard at Pukie as at Taupo.
I'm wondering if it's the nature of the track with only one real braking point but a lot of flat out riding.
I was definitely noticing a similar temp change
Another thought was that I noticed im sitting back furthur at pukie not loading up the front as much into corners.

[Sensei]

36 F / 38R as they will go up around 4 PSI when hot
Sensei

[DEATH_INC.]

'99 Gixx 7fiddy,90something kg rider,no one game enough to pillion,no luggage,various sport tyres......
32psi front 35psi rear generally for road use,no track riding.