Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > Tyres > Tyre Pressures

[John W]

having read the recent thread on the Michelin power !s, and the pressures being quoted, this got me thinking.

I pretty much always run 38/42 on all my bikes, regardless of tyre brand or model, and also regardless of solo, with luggage, or fully loaded and 2 up. I can tell the difference in handling when either tyre is down by more than a couple of degrees (slower steering, tracking in bends, rear rolling under power).
It therefore seemed somewhat odd to hear some of you guys saying to run pressures as low as 22.5 (cold).

I'm not questioning your decisions, or indeed the advice given by experts to do this, just wondering if I'm missing a trick, or am I just too stupid to notice (don't answer that last bit )

So. In simple terms, what do you notice by running such lower pressures ?
e.g.
better more stable braking ?
less tyre wear ?
less rubber migration across the tread pattern ?
tyre lasts longer (doesn't get too hot and go off) in a session ?

I doubt I could ride any faster / better at different pressures, and I'm not asking for that reason. I'm asking as much as anything to learn, because I don't see the benefit. I always seem to wear tyres out quickly too, and the fitters reckon they look to be under inflated, not over inflated.

Eagerly awaiting your collective wisdom

Cheers,
John.

[John W]

So, given that I got no replies, should I assume everyone else already knows the answer to this and I'm just too stupid to be told

Or is it that your all too busy playing in the snow and writing letters to santa

[Chris Wood]

Modern race tyres i think John - Dunlop NTechs are designed to have very low PSI when cold.

Yours above seem high to me - I always run 32/32 cold on my 916, drop to 30/30 on track.

On the DD bikes - running Diablos - always ran 29/29.

Check the manual and the tyre recommendation maybe?

What psi do your fitters recommend?

[Cobbett]

John, where did the figs of 38/42 come from? I too would have thought that was very high, unless 2-up and fully laden. I tend to think of my defaults as 32/34, though as you say sportier/trackday riders often go for less, the calculation simply being that with the pressure lower (eg dropping a Diablo from 32/34 to 29 both) you'll get heat into them quicker, and that grip rather than durability is the issue. I always think that the tyre manufacturers' psi recommendations need to be consulted: many people stick with what's quoted in the bike manual, but it seems to me that that's only good for the tyres it actually came with, and that what Ducati thought was good for the Dunlop-Whatevers my SS came with in 1997 might not be right for Pirelli Diablo Rossis over a decade later. It's easy enough to check tyre manufacturers' recommendations these days too - some have that facility online (I know Pirelli do).

[John W]

Thanks for the replies.

The following is taken from the pirelli web site:
"Tyre Pressure
It is important to always inflate the tyre to the correct pressure. Be sure to check cold inflation pressure frequently (i.e. once a week). Although most motorcyclists love to work on their bikes, they seldom remember to check tyre pressures. Correct tyre pressure, however, is critical for safe handling. Over-inflation or extreme tyre pressure will impair your riding comfort and decrease the contact of the tyre with the road. Under-inflation or too little air pressure will result in poor handling and the bike will be inclined to "wander." Improper and insufficient tyre pressure will also cause rapid tyre wear, an increase in fuel consumption, lower top speed, and provide less control. Remember to check the inflation pressure of your tyres weekly.

You will find the correct pressure in the operating manual of the motorcycle. The manufacturer's information is the minimum values only. With luggage or with a second rider the rear tyre needs an extra 0.2 bar, and for high speed riding the pressure of the front tyre should also be increased by 0.2 bar.
Attention: When the recommended pressure has been changed for use off-road (race track, off-road), it must be reset to the correct value before riding on the street."

The tyre fitment chart for the ST4S recommends 2.2 bar front, 2.5 bar rear for each type of tyre in the list presented.
I run with 2.5 & 2.9 due to the 2 up with luggage loading, rather thsn the 32/36 above, and that matchs the pressures in the bike manual.

Its interesting to see the same Pirelli tyres fitted to an 08 R1 (my other bike) are quoted as 2.5 & 2.9 for normal use. In fact Ducatis are the only bike I can see that gets quoted with a lower pressure...

Thanks again for the comments, I'll drop the pressures for at least the start of our next trip and see how we get on.

Cheers,
John.

[Cobbett]

Certainly the case that specified pressures seem to be notably higher for Jap bikes, never really understood that either.

[PS meant to say 'Diablo Rossos' rather than 'Diablo Rossis' - wishful thinking!...]