Tyre Pressures.

You also need to consider the tyre size (diameter, profile and width) - are they all the same?

 

this a great watch if you haven't seen it before

 

I’m not surprised. The tyre pressures for bikes rely on an estimated rider weight and load carried and both bike manufacturer and tyre manufacturer recommended pressures will not show any variation in recommendation for solo or two up riding, whereas your car manufacturer will, a total nonsense.

To illustrate this by example my Ducati dry weight is 185 kg and my Triumph is 168 kg. Both bikes have exactly the same rim width and wheel diameter for both the front and back wheels. The bike manufacturer recommendations, which are non brand specific are within a couple of psi at 33 front for both bikes but 36 psi rear for the Ducati and the usual 42 psi for the Triumph which is the lighter bike. In the twenty or so years I have owned the Ducati I have always added another 3 psi to the rear tyre for carrying a pillion and have never experienced any problems.

I took this up with the tyre tech guy at Dunlop as their recommendations replicated those of the two bike manufacturers. He could not give me a valid explanation of this apparent discrepancy. In normal clothing I go 66 kg and since owning the Striple have set my tyre pressures to those recommended for my Duke without any problems either solo or carrying a load of luggage.

So don’t be ruled by what it says in the handbook and be prepared to experiment. Do please watch Dave’s video shown above and you may notice in the comments that I made this same observation a year ago.

 

Thinking back to bikes I've owned in years past, many of them did have alternative tyre pressures in the owners's manual for both solo riding and high speed or fully loaded riding. My current ZZR and Triumph list only one standard pressure as most modern machines seem to do. I put this down to the advance in tyre design, construction and materials. Modern tyres are in a different league to those available 30-40 years ago, especially the premium sports rubber, not only offering more grip but more able to handle a wider range of loads and speeds without adjusting pressures to avoid distortion.

 

I hear what you say about the advancements made, particularly this century, in the compounds now used in both car and bike tyres, but every car I have ever owned has advised increased pressures for carrying more than two people or an increased load. Even my current car which has run flat tyres with their stiffer sidewalls shows higher pressures for carrying more people/load. My Ducati does in fact recommend a higher pressure for one circumstance, see photo

 

There will always be occasions where tyre pressures require adjustment for optimum performance. Those who drive/ride off road will be familiar with the necessity to drop the pressures to increase the footprint. I run the dirt bike knobblies at 12-15psi which certainly makes them squirm around on tarmac but increases grip substantially in the soft wet stuff while still giving some resilience to pinch punctures. 4 x 4 drivers will probably do the same. As for the " one pressure suits all" given in owner's manuals it will suit 99% of riders 99% of the time. In fact I've always run the ZZR tyres at the stated 42/42 psi through different tyre makes and types, solo high speed riding and loaded up with luggage and never had any issues, wet or dry or felt the need to try different pressures..

 

Is that 42 front and 42 rear, wow. I’m not disagreeing with anything you’ve said. What I do urge other riders to do is not treat the handbook pressures as cast in stone, be prepared to experiment, like you do with your dirt bike.

 

Yes that's front and rear up to a max load of 175Kg. I can't remember what my previous 1198 or R1 pressures were, 36F 42R springs to mind but I remember thinking when I bought the Z that 42 is quite high for a front. 200+bhp isn't unusual now on litre plus machinery but at 260kg the Z is no lightweight. Big power & torque, high weight and semi sporting pretentions puts huge demands on tyres.

Edit........it would be interesting to know what tyre pressures are run on production bikes at the TT and if they differ from standard.

 

Considering the average lap speeds I would guess somewhat lower than those in the handbook before they put the tyre warmers on.

 

Nitrogen is often used to fill race tyres as it offers more pressure stability/less variation with temperature than normal air as it contains no water vapour. It is more expensive though so wether the privateer teams use it is anybody's guess.

 

You will find that the tyre bays in the CostCo outlets use nitrogen, not compressed air. So, as you say, it’s an inert gas I would not be surprised at all if they did. Yes it would be more expensive but given that the air we breathe already contains nearly 80% of the stuff I guess it’s not going to be prohibitive.

Out of idle curiosity I looked at the BOC website and find that I can buy their smallest cylinder of the stuff containing over 2 m3 for £36 inc VAT, so if it has distinct advantages over compressed air I would expect all teams to use it.

 

Absolutely, managing tire pressures for a bike like the Z with its significant power, weight, and semi-sporting characteristics is crucial. I recall similar pressures for my previous bikes, but the Z's weight does make you reconsider optimal settings. The demands on tires are indeed substantial. It would be fascinating to learn about the tire pressures used on production bikes during the TT and if there are variations from standard settings. The extreme conditions of the TT must necessitate some unique considerations in terms of tire management.

 

Before you start on this slippery slope & mind boggling variations remember this,
Moisture is NOT just in the air you use..it`s in the tyre carcass so you need to know where that tyre`s been. Racing guy`s from what i`ve seen use a dry air system by Pneu-air or similar. This system takes air in & it goes through 3 dryers which take the moisture out. In tests it`s proven better that Nitrogen by a couple of points.

 

Interesting, I guess it’s similar to dewatering the compressed air that you would use for paint spraying.

 

Might be worth pointing out that not all pressure guages are the same so it's best to stick with the same one which should always carry the same error (if it has one).