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Tyres : Tips, Myths & Recommendations

Discussion in 'Bling and Appearance' started by VCM, May 18, 2008.

  1. After searching the forums, I was unable to find a thread on this.
    Could be a very interesting and informative topic. I'd like to hear your experiences with tyres.. not just your reviews on brands, but also the type of tyre used for different styles of riding. ( ie commuting, wet weather, twisties etc .. )
    Also love to hear anyone willing to dispel or confirm 'Tyre Myths' especially things like tyre pressures for different riding conditions etc.

    One Myth is one of lowering your tyre pressures in order to increase traction in the wet. I was in the opinion that lowering pressures would increase the 'contact patch' therefore improving traction on wet roads. I am now thinking that lowering pressures just may have decreased the tyres ability to dispel water, and raised the probability of hydro-planning. On top of that it also may have contributed to poor trailing at low speed ( walking pace ), making it difficult to keep the bike on a constant line.


    EDIT: I'm specifically talking "road use only "
  2. I find the knobbies better for the dirt/mud and the slicks better for the tarmac.

  3. How about sticking to the manufactures recommendations?
  4. Yeah; for wet weather the tyre pressures should be normal or slightly raised if anything, to increase the pressure on the (reduced) contact patch to help cut through the surface water.

    It's the same reason mud tyres have chunky, sparse blocks - to cut through the slurry and reach the hard surface beneath.

    Hardpack tyres have smaller, more plentiful blocks because they only have to cut through a thin dust layer.

    To push the analogy all the way, for a dry tarmac racetrack slicks are used because there's no water or dust or mud to 'cut through'.
  5. But spots, slightly less pressurised road tyres will warm up better and stick better... when its bitterly cold, I go a few PSI down SO LONG as my tyre tread is in good shape.
  6. I suppose it depends whether you're more afraid of aquaplaning in surface water or sliding around on a relatively dry road due to cold tyres, really? :)

    Edit: for wet weather driving/riding I don't bother adjusting my pressures up or down from normal; but as rob said, tread depth is critical.
  7. Yes good advice there....cant really go wrong can you. Pretty simple, after all you would think the manufactures should know best. :wink:
  8. I dont adjust my tyre pressure for rain, but I do bump my tyres up by a couple of pounds at the front and about 10 at the rear if I am doing any serious highway work. The higher pressure helps the tyre deform less, run cooler and last longer.
  9. PP : I did initially, but then thought that the recommended pressures may not take into account all riding conditions. Been playing with pressures and you may be correct, recommended pressure seems to be a good all round level.

    Spots, Rob .. this what I'm talking about, different people have different opinions, come say slightly higher in wet, others slightly lower.

    Daz, prob right, but surely there ar factors such as rider weight that has to be taken into account. ie same bike, two riders.. one 65kg, the other 100kg ???
  10. You would, wouldn't you? Yet manufacturers (or rather, distributors) have been running a campaign lately advising track riders NOT to lower their tyre pressures when they go on track. All the track guys think this is crap, including the few "professionals" I have access to, but nevertheless I though I'd try it at Easter Creek. It was a nice warm day, perfect track conditions; I started slowly, got the tyres nice and warm for a few laps and eventually built up to my normal speeds. I was sliding all over the place almost lost it exiting turn 5. I went back into the pits, lowered the tyre pressures and all of a sudden perfect grip.
    Yep, the distributors' advice is crap.

    So here's a little bit of advice for this thread; lower your tyre pressures when you go to the track.
  11. Well, we're having different opinions because Rob and I are talking about different situations. Rob will have to clarify this just to be sure, but he and I aren't talking exactly about the same thing.

    I'm talking specifically about aquaplaning without consideration of temperature - for the sake of argument, let's say summer weather. Rob is talking specifically about cold weather riding that might happen to be wet.

    But the NRMA advises people to not reduce tyre pressures for the wet (Edit: or used to. Can't find discussion of hydroplaning on their site anymore), Dr Karl advises people that reducing pressure for wet roads is a mythconception, mud tyre and wet-oriented tyre design is designed specifically to reduce contact patch (increasing the pressure exerted on the road). If the question is specifically about aquaplaning, reducing the pressure exerted on the contact patch (by making it bigger) is a great way to encourage aquaplaning.
  12. I don't remember mentioning the track nor did pro pilot and I was talking manufacturers not distributors (makers of tyres not distributors)have had no trouble with mine when sticking to manufacturers specs for( Road use )of course.
  13. If you do the sums, you'll find that a psi or two either way will make very little difference to the area of the contact patch (maybe 5-6%) but can alter its shape significantly, which is where most of the differences in handling will come from.

    Whilst I'll agree that lower pressures will allow your tyres to warm up quicker, how much difference will this really make on the road? On a 0 degree morning my old K100 with its cast-irom Michelin Macadams felt a little squirrely on the first couple of T junctions but was fine after the first 500 m or so. On its much more modern radials, the R doesn't even require that before it feels normal.

    Personally, I keep the pressures at the tyre placard recommendation for high speed, heavy load conditions. All the grip I can use and tyre life so long that I can't be arsed with the fiddling around that would be necessary to (maybe) gain an improvement.

    Track use is another teapot full of eels entirely and I can't really comment there.
  14. Nope, I was talking about cold and wet.

    If my tread is good, I'll happily use lower tyre pressures to help heat up the tyre a bit in both cold and cold/wet conditions.

    FWIW, the theory of using lower pressures on track is that with the extra stress and heat generated at the high speeds and cornering loads, heats up the air/gas which increases tyre pressure back up to about the manufacturer recommendations. If you START at the manufacturers recommendations, you're tyres will be way too stiff on the track when they heat up.
  15. Tyre pressures are a compromise for the wide variety of conditions found when riding on the road, from commuting through traffic in the cold/wet to high speed riding on the open road in the middle of summer. Unless you know what riding conditions to expect every time you leave home, the best pressures to use are what the manufacturer recommends, as believe it or not, they don't want you crashing on their tyres.

    Track conditions are more predictable - constant high speed use - so the tyre pressures can be "fined tuned" for maximum grip and quicker warm up. By starting with lower pressures the tyres heat up more quickly and when they reach operating temperature, the pressure is "correct". (Road based tyre pressures don't work as well on the track. When the tyre gets very hot, the pressures are too high for maximum grip.)

    This needs a bit of educated guesswork to work out so the distributors are reluctant to deviate from manufacturers recommendations - not because it doesn't work, they just can't know the effect of every combination of pressure/rider/bike/track/weather etc. If they recommend a setting and someone crashes on it, they would be liable, so they play safe.
  16. Just about all road tyres have an operating temperature range that allows them to work well, from the get go in just about all temperatures. Highly strung sports tyres will be slightly narrower, but they should work straight away. Lowering pressures a few PSI will probably have little to no effect in the cut and thrust of the daily grind. Lowering them too much will close the tread up and reduce their ability to disperse water.

    Track riding is so different and I agree with Rob here totally. I have no idea why tyre companies and their reps are saying to leave the tyres at their recommended pressures, unless they are trying to accommodate the lowest common denominator in their estimations of riders speeds. it also occurs to me that if they recommend a lower pressure and the rider then squirms off the track, they might then be held responsible. I'd imagine that some track punters might salivate at the thought of blaming their accident on a multi national tyre company...
  17. I know that the threat of litigation and liability is being used for all kind of crazy stuff, but i don't really see the correlation between this and the advice the distributors have been giving of late. The general advice given to new track riders is to lower tyre pressures to 30psi cold - in fact, this is what the track school instructors will do to your bike, period. This is pretty good for most sport bikes, and certainly safer than the recommended road tyre pressures. On the blackbird it's usually around 35psi cold, but that's a little unusual, as even the 'road' pressures are a high 42psig.

    Suggested pressures don't come from tyre manufacturers, they come from bike manufacturers. I have no idea why they should now be advising NOT to lower tyre pressures. If anything, it is this advice that is against expert opinion, and more likely to leave themselves open for litigation.
  18. I have 2 recent Hondas (one 99 and one 03) and neither recommend any more air when carrying a passenger.

    We can assume that tyre technology has changed and once the design pressure has been reached the tyre will perform correctly under wide-ranging conditions.

    Cars still recommend different pressures for different loads.


    Trevor G
  19. There are so many variables at play, there is not one single answer to all situations.

    It's a cold day. You turn up at the track and the track day expert advises you to drop to 30psi. So off you tootle, pottering around the track. You run a street tyre that works across a huge range of temperatures and is designed to provide optimum grip in this range and with the tyre at a certain profile. But as you ride PI around 15s a lap slower than your mate, your tyre never gets warm enough to generate the extra pressure to maintain the tyre profile. You don't get any of the benefits from running a low pressure. You slip and slide around the circuit.

    It's a hot day. You run your pressures nice and low. As road tyres have relatively soft sidewall construction, your tyre carcass flexes during your lap. It gets extremely hot and goes beyond it's ideal operating temperature. Result. Cooked tyre.

    So, when someone who's job it is to sell me tyres tells 130 people on varying bikes, with massive speed and performance disparities to all drop our pressures to 30psi without asking a single question of any one of us, then I call into question that persons motive and therefore their advice.

    I am categorically not saying that different pressures are not required for the track. But you cannot simply say that xx psi is good and yy psi is bad.

    The effects of too much pressure are as bad as too little. Run 5 or 6 laps at a quick pace and the tyre pressure will increase markedly. The tyre profile will change and the contact patch will alter. The performance of the tyre will fall off.

    Also bear in mind that slick pressures are much lower due to the increased sidewall stiffness. Slicks can run stiff sidewalls as comfort is not a concern. Slicks have a narrow and high operating temperature range and only work well at these temperatures. Wets do not need temperature to work and heat is their enemy. Higher pressures are used to open the tread blocks.

    There is so much more to tyre pressures than you would initially think.

    The quick guys at the track will pick differences of a 1 or 2 psi. I can only notice 3 or 4, but that does make a huge difference to feel.
  20. See next post .... :oops: