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Tyre Pressures?

Discussion in 'Bling and Appearance' started by RobE, Apr 7, 2008.

  1. (I did a search but did not find anything that seemed to match.)

    I like to run my wagon with higher tyre pressures (at 40 psi) than whatever is recommended by Ford. I think I get better road feel, braking and cornering.

    How do Forum members feel about recommended bike tyre pressures?
  2. My ex did an advance driving course and they recommended higher pressures. I think the manufacturer recommends 32psi and they said 40psi.

    Softer tyre pressures mean a more comfy ride but not as much grip on the road - or something like that.

    For the beast, I stick to the tyre manufacturer's recommendation. 42psi for the BT021. I check them when I fill up which is about once a week.

    My experience is that the tyres will naturally reduce pressure logrythmically (sp?) as in lose a lot of pressure in a short period and then stabilise.


  3. Cars can frequently use more pressure to promote even tyre wear. Even tyre wear (in general) is a sign that your car tyres have "correct" pressures. A vehicle driven harder around corners will frequently need even higher pressures.

    Bikes, on the other hand, need pressures accurately checked when cold. A hand pencil gauge is frequently the most accurate method.

    A tyre will heat up in just a few hundred metres (car or bike) and so checking when you get to the servo, unless it is just around the cornewr, will frequently see under-inflated tyres unless you compensate for the higher expected pressures.

    Bike tyres work better when warm and heat up more quickly when at the rated pressure. Higher pressures are usually no advantage in controlling wear on a bike, and will help to increase warmup time and reduce grip.

    With such a lot at stake, i just wouldn't bother. I know of no advantage in having higher pressures except when running off-road with really low pressures initially. Warm-up is not so important on an off-road tyre - tread pattern is more likely to help you stay upright.


    Trevor G
  4. Interesting, always wondered about this.

    My SV is recommended 33/36. I put in 36/39 the other day just to try it, and it was too solid for my liking. But I find in between (say 34/48ish) is nice.

    Just try a few different pressures and see what you feel comfortable with, theres no right pressure for everyone given different bikes/tyre profiles/load/etc.
  5. I'm not sure I can agree with that.

    There is a right pressure if you are using the tyre size and type that the manufacturer recommends - it's usually very close (within a psi or two) to what they say. I believe it is not unusual for modern bikes to have the same pressures recommended for one and two up riding.

    Once you have a hand gauge, test at home when cold, then ride a few hundred metres. It doesn't seem to matter whether it's 40C or 10C, the same effect seems to occur - the pressures will increase by around 2 psi.

    Be careful that there is no extended hiss from the valve as you fumble to connect the gauge head correctly.


  6. The wrong tyre pressure could cost you your life. At the end of the day what keeps you on the road and in the direction you want is your tyres.

    Running high pressures make for less predictable traction. I drove an under powered car while on my P's and I use to run 42psi because it allowed for my wheels to ?spin? easier. unfortunatly doing 70 around a sweeping turn that was posted 75 in slight drizzle was my undoing. It slipped round 180 unexpectedly (it didn't even feel like it was at any limit of traction, it just let go) and I later found out that tyres harden and change composition over age and temp.

    My father runs slightly under pressure and he goes through his wheels twice as quick as me because of the increase in wear.

    Engineers have tested and designed your tyres, simply put 'we dont know better then them so use the pressure they recommend'
  7. You're probably right Trevor, but from my experience at least on my 250 - the recommended pressure (28/32) was fine, but 30/34 made it handle huuggely better in twisties, so sometimes its worth having a play.

    Engineers have tested and designed our suspension too, doesn't mean its set up right for the rider when it comes out of the factory does it? I'd have to say the recommended pressure is the best starting point obviously, its designed to be a fairly moderate figure so that it can hope with a bit more/bit less, in all conditions, etc. Doesn't necessary mean it'll be the best, especially once you change the tyres to non oem ones.
  8. Interesting comments on the higher pressures. I've heard racers recommend lower pressures for race track ..about the 25psi front and rear. I believe it's to get some heat into them. (note that are on about traction, not mileage.) Anyone care to comment?
  9. The idea is that you'll be going faster around corners so more cornering pressure, hence more heat will build up, and the idea is also less air = more flex = more contact patch = more traction. BUT I've heard counterarguments saying that for the track you should be using the same pressure as on the road, for various other reasons.
  10. My bike is recommended to have 29 front, 33 rear by the manufacturer. My dad suggested to me to try approx 33, 36 for sharper handling. Which is what i now run and i believe it does a better job.
  11. Racers do not run the same tyres as you. Even a nominally legal tyre like the BT002 comes in two flavours, 'Race' and 'Street'. The construction of the tyre is more or less the same, but the compound is different. It has a narrow operating temperature range and a limited amount of heat cycles it will reliably tolerate before it loses grip and feel. Lower tyre pressures are used by racers for a number of reasons. A lower pressure will cause the sidewalls to flex more, generating more heat, more rapidly. Given the general overall higher temperature range, the difference from cold to hot pressures and therefore the tyre profile and performance is greater.

    Slick tyres run a much stiffer sidewall construction. The stiffer sidewall permits the use of lower overall pressures whilst still retaining sidewall stability. The slick tyre compound also runs at a narrow operating temperature and the lower pressures can be used to generate that heat.

    This is what I've learned over the last 12 months doing the club racing from various sources. It's very broad brush view. Pro's and more experienced racers will feel the difference of 1 or 2 psi. Me, I'm lucky to tell the difference between flat and 60 psi!
  12. 33/36 is a good point to start at on most road bikes. If your suspension is not very adjustable or you don't get the responce you want out of your suspension then it's worth playing with tyre pressure to get the bike better.

    I wouldn't be going into the 20s on a road bike unless it was a particully light bike with overly large tyres. Also I wouldn't be going over 40 unless it was a heavy bike with thin tyres.
  13. The reason for lower staring pressure is that the higher heat build up when "racing" eventually produces the correct pressure in the tyre. More "flex doesnt produce more grip ( in fact the opposite which is why you take it easy until the tyres have warmed up) and if you start with street pressures the tyres will be over pressure and loose traction.
    Same applies to cars or anything else using pneumatic tyres.
  14. Depends? If the tyre flexes (talking about when the bike is upright) you will have more contact patch, hence more traction?

    Different when you've got it laid over of course? What with cornering forces and what not.
  15. Yes you definetely need to lower the pressures when on track. They heat up more on track, resulting in a higher pressures which makes the tyres more 'round' and reduces the contact patch. But nothing like 25 psi ... usually around 30 to 35 (cold), depending on the bike and the tyres.

    Of interest is a recommendation that has come from a tyre importer of late; that you must NOT lower tyre pressure on track (unless you're running slicks). It's amazing, as the track guys say you MUST lower pressures.

    So I tried running with standard road pressures ... and left black lines coming out of the corners, almost fell. You definetely need to lower the pressures! I have no idea why the importers would be giving such advice.
  16. I would suggest you run your pressures pretty close to the manufacturers reccomendation. They have tested their products for wear and performance. All you need to take in consideration is the weight of the rider on the bike as to whether you should add or deduct a couple of psi. Simple trial and error will help you solve this.

    Everyone will run slightly different pressures in their tyres. Personally on my Gixxer with BT002's I run 32/34 front rear respectively. I find it offers the best handling characteristics for my riding style. On my Motard (Michelin pilots) I run slightly higher pressures on the rear as I like to slide it into corners a little.

    There is no real right or wrong answer as different tyres/profiles/bikes etc will require slightly different pressures. The only real wrong is running overly high or low pressures IMO.
  17. Well, that's different! ;-)

    I thought you meant something other than a couple of psi. I often do the same.


  18. The BMW R1100s weighing in at 220 kg wet needs firm tyre pressure.
    Usually 37 front and 40 rear.
    37 front because of the telelever suspension preventing scalloping.
    120/17 front 170/17 rear wheels Metzeler z4B front z6 rear.
    If tyre pressures are lower the handling gets very sluggish but at these pressures it is a very sweet handling bike despite its size.