Tyre pressures & handling sensitivity?

[sootie]

Since I started riding litre plus bikes, I have been somewhat surprised at their sensitivity to tyre pressure (handling wise).

Most of the small bikes I have ridden don't seem to care that much. My 150cc scooter for example would be very rideable (though not ideal!) with tyre pressures of 20 or 40 psi. (And this is with small wheels!)

The manufacturer's (single rider) recommendation for my ZZR1100 is 42psi front & rear. I have always considered this high, but a bit of experimentation has confirmed that it is in fact pretty close to the optimum. 10% high in the front & bike becomes hard & bouncy, 10% low & the low speed handling deteriorates enough to notice. (A surprisingly small range to me.)

A well known NZ racing rider gave a talk a year or two ago about how he had been reducing the rear tyre pressure to around 30psi because he reckoned it improved road grip during hard cornering. I tried this and agreed with him, but the lower pressure unfortunately reduced the tyre life.

I currently use cold adjust pressures of 42psi front, and 39psi rear. I think these are very close to my optimum. I am aware that from a cold morning start to middle of the day after a long fast run, the tyre pressures will rise about 10%.

Anyway, I would be interested in hearing a range of other opinions on this topic. :scratch: :scratch:

[GrayWolf]

Since I started riding litre plus bikes, I have been somewhat surprised at their sensitivity to tyre pressure (handling wise).

Most of the small bikes I have ridden don't seem to care that much. My 150cc scooter for example would be very rideable (though not ideal!) with tyre pressures of 20 or 40 psi. (And this is with small wheels!)

The manufacturer's (single rider) recommendation for my ZZR1100 is 42psi front & rear. I have always considered this high, but a bit of experimentation has confirmed that it is in fact pretty close to the optimum. 10% high in the front & bike becomes hard & bouncy, 10% low & the low speed handling deteriorates enough to notice. (A surprisingly small range to me.)

A well known NZ racing rider gave a talk a year or two ago about how he had been reducing the rear tyre pressure to around 30psi because he reckoned it improved road grip during hard cornering. I tried this and agreed with him, but the lower pressure unfortunately reduced the tyre life.

I currently use cold adjust pressures of 42psi front, and 39psi rear. I think these are very close to my optimum. I am aware that from a cold morning start to middle of the day after a long fast run, the tyre pressures will rise about 10%.

Anyway, I would be interested in hearing a range of other opinions on this topic. :scratch: :scratch:

I actually used the opposite with my ZZR, 40-42 rear and 38 front. ( am 107kg though). HOWEVER what I use and would recommend, is the dual compound sport touring tyres (I currently use BT023gt, they are the ones with the heavier carcass for high loads) The ZZR is considered a heavy beast 240kg for a modern bike, whereas the sprot litre plus are around 190kg these days. Almost the weight of a rider difference. I think you'd find a noticable difference in how stable the bike will feel in the tight stuff.
With the MT as its a big twin its hard on rear lids, and the Wainuiomata hilll (which is notorious for destroying tyres) I got 9,000km out of my last rear on the MT (BT023gt).. previous on a Pirelli Rosso (touring)was 6k.

[Rhys]

Maybe I should check my tyre pressure.

If they are black and round, I thought they were good to go.

[sootie]

I actually used the opposite with my ZZR, 40-42 rear and 38 front. ( am 107kg though). HOWEVER what I use and would recommend, is the dual compound sport touring tyres (I currently use BT023gt, they are the ones with the heavier carcass for high loads) The ZZR is considered a heavy beast 240kg for a modern bike, whereas the sprot litre plus are around 190kg these days. Almost the weight of a rider difference. I think you'd find a noticable difference in how stable the bike will feel in the tight stuff.
With the MT as its a big twin its hard on rear lids, and the Wainuiomata hilll (which is notorious for destroying tyres) I got 9,000km out of my last rear on the MT (BT023gt).. previous on a Pirelli Rosso (touring)was 6k.
Have read this with interest, and will store a copy of your posting in my ZZR folder. Actually, I have recently replaced the front & rear tyres on the ZZR (again) with Metzler Z6s which I like. The previous rear Z6 did 15,000kms, and front did 18,000. (As mentioned, I think I slightly shortened the life of the previous rear.)

It may not be a fair comparison with your mileages. I don't regard myself as a racing rider these days, but I am not a Sunday afternoon man either! I do ride enough twisties to keep the flat off the back tyre. This bike also has an Ohlins rear damper fitted by a previous owner - an improvement I think. (I weigh 93kgs plus clothing & I do not pillion much.)

The bike had previously had Pirelli and Bridgestone tyres on it (sorry I can not remember which models). I much prefer the Metzler Z6 handling to anything I have used previously. As I say though, I have been surprised at sensitivity of the handling to tyre pressures. Currently, I would describe the bike handling as very good, but not excellent. It is not on a par with the modern 180kg naked machines but I would not expect this. :) :)

[sootie]

Maybe I should check my tyre pressure.

If they are black and round, I thought they were good to go.

Hi Hobbyhorse!

Actually with all my smaller bikes that is how I have felt! I am trying to rationalise why it seems to be so much more noticeable to me now than it used to be.

I bought present ZZR1100 in Whangarei one morning, & rode it home in the afternoon. It really worried me for the first few kms. Bike was unstable at low speeds. It had been stored some time, & I did pick tyre pressure problems. Both tyres were showing 25psi. I raised them to 40psi for that ride, and was fairly happy after that although I did not particularly like the Pirelli tyres which were fitted. It was a wet day on a big strange bike, so I guess that did not help! :) :)

[insomnia01]

Have used all available tyres & settled on Avon storms for the past +3yrs constantly get 15-16k out of the FR & 14k out of the RR, ride twisty back roads most weekends with a GC or C1KC planned ride or tour 2up where ever @ once or twice a year... run 40 - 42psi @ both ends getting down to 37 or 38 makes it feel like I'm riding on wet tar :eek: manageable but not ideal. Ohlins rear with Std front but looking at Racetech internals, no chicken strips to be seen at either end, very ( in my opinion ) well balanced Blackbird that keeps sporties honest, just my 2c worth :msn-wink:

[Akzle]

I currently use cold adjust pressures of 42psi front, and 39psi rear. I think these are very close to my optimum. I am aware that from a cold morning start to middle of the day after a long fast run, the tyre pressures will rise about 10%.

Anyway, I would be interested in hearing a range of other opinions on this topic. :scratch: :scratch:

derp derp.

as air expnds when hot, so too does rubber. just not as much and it takes longer to cool down. warm tyres are nice.

[G4L4XY]

Whats a tyre pressure :scratch: :clap:

[vifferman]

While the VFR's not a litre bike, it probably weighs the same as one. I've found that tyre pressure makes a very notable difference, but this varies with tyre type/brand. For years I ran Avons and could notice if the pressure was higher or lower than 36F/42R, but it was still OK at say, 34/38. However, since I've been on Michelins (Pilot Road rear and Pilot Power front), I can tell straight away if the pressure's not spot on.Although it still rides OK, it's more 'wandery' if it's low, and the steering's slower. Even the suspension setting makes a difference; I added some preload to the rear shock because there's some large, long bumps in a corner on my daily commute and the VFR felt a bit wallowy. As soon as I went out after adjusting it, I went WTF?!?! because the very slight adjustment in attitude made me think the front tyre was flat. As it turned out, it was down a couple of PSI, but felt like much more. I guess the PP has soft sidewalls?

[Hitcher]

Too much air in a tyre and they explode. No air at all, and you'll grind the rims, especially when cornering. Like most things in life, the truth of air pressures for motorcycle tyres lies somewhere in the middle.

Tyre manufacturers invest a lot of time, effort and resources figuring out recommended tyre pressures for different models of motorcycles. This information is actively promoted, particularly through online fitment guides.

Sadly that investment is all wasted, given the propensity of many motorcyclists to ignore those and fanny around with pressures that vary considerably from manufacturer recommendations.

[sootie]

I am getting the feeling that the heavier a bike is, the more important it becomes to optimise the tyre pressures so that bike handling is not degraded. It seems that other riders are finding that this is a general rule too. I don't think I have actually read this anywhere. :confused:

[sootie]

Tyre manufacturers invest a lot of time, effort and resources figuring out recommended tyre pressures for different models of motorcycles. This information is actively promoted, particularly through online fitment guides.
.
Totally agree, but it is always helpful to understand any unlying principles about anything.
As I say, with light bikes a given % variation does not seem to make as much difference.

[Gremlin]

You're ignoring the tyre itself. Some tyres will be extremely sensitive to the pressure, others won't, which is largely down to the construction of the tyre. Some tyres, like the Pilot Road 3 are very soft and flex a lot. Not only does it give different handling characteristics (that some love and some hate) but also responds differently to altering pressures.

On the other hand, a set of tyres I've been using recently, Heidenau K60, have very stiff sidewalls, to the point that many have commented they cannot DYI fit. The front has a reputation for losing air, and according to my monitoring system (BMW) the front was down 7psi morning to evening during one day. In some ways I think it might have handled even better, but mostly I didn't notice.

[sootie]

You're ignoring the tyre itself. Some tyres will be extremely sensitive to the pressure, others won't, which is largely down to the construction of the tyre. Some tyres, like the Pilot Road 3 are very soft and flex a lot. Not only does it give different handling characteristics (that some love and some hate) but also responds differently to altering pressures.

On the other hand, a set of tyres I've been using recently, Heidenau K60, have very stiff sidewalls, to the point that many have commented they cannot DYI fit. The front has a reputation for losing air, and according to my monitoring system (BMW) the front was down 7psi morning to evening during one day. In some ways I think it might have handled even better, but mostly I didn't notice.

Are you saying that light bikes (say under 150kgs) are just as sensitive to tyre pressures, handling wise as heavy bikes (say over 250kgs)? I don't believe so. I am happy to accept that other factors are at work here, am just proposing a very broad wash brush against which it is wise to consider other factors.

Putting it another way, I am proposing that in general, the the tyre types & pressures used on smaller bikes are a lot less important than they are with heavy biikes. :scratch:

[Subike]

Are you saying that light bikes (say under 150kgs) are just as sensitive to tyre pressures, handling wise as heavy bikes (say over 250kgs)? I don't believe so. I am happy to accept that other factors are at work here, am just proposing a very broad wash brush against which it is wise to consider other factors.

Putting it another way, I am proposing that the the tyres & pressues used on smaller bikes are a lot less important than they are with heavy biikes. :scratch:


I think that it depends upon how you ride the bike, A smaller bike ridden by an aggressive rider would be sensitive to pressures, but the same bike ridden as a daily commuter would barley have any difference. On my little cruiser, 5lb fin the front lower than 28lb, and it handles like crap, front feels like it wants to roll across the road. Not nice on wet roads. My XS11 on the other hand, being a heavy bike, is very sensitive to pressures, too hard and its fucking awfull, wants to follow every grove in the road, too soft, and it fels like it wants to lie down in corners. eeek!. I check the pressures every time I fill her up, or if she has been sitting in the shed for more than 2 weeks between rides.
Tire pressures are important no matter what size bike you ride, big, small, sports or cruiser. Its what keeps you upright on the road. Find that sweet spot for your riding style, starting from the manufactures recommended pressure, and adjust up or down to find your zone.

[sootie]

I think that it depends upon how you ride the bike, A smaller bike ridden by an aggressive rider would be sensitive to pressures, but the same bike ridden as a daily commuter would barley have any difference. On my little cruiser, 5lb fin the front lower than 28lb, and it handles like crap, front feels like it wants to roll across the road. Not nice on wet roads. My XS11 on the other hand, being a heavy bike, is very sensitive to pressures, too hard and its fucking awfull, wants to follow every grove in the road, too soft, and it fels like it wants to lie down in corners. eeek!. I check the pressures every time I fill her up, or if she has been sitting in the shed for more than 2 weeks between rides.
Tire pressures are important no matter what size bike you ride, big, small, sports or cruiser. Its what keeps you upright on the road. Find that sweet spot for your riding style, starting from the manufactures recommended pressure, and adjust up or down to find your zone.
I am basing my statement on my own experiences, but I have only recently started to think about it from a general point of view. My little 150cc scooter (as mentioned) does not seem to care much 20 to 40psi what the tyre pressure is. Sure you can feel that difference, but the handling difference is small.

If I halve the tyre pressures on my ZZR1100 the bloody thing is horrible to ride, particularly at low speed (I would say unsafe actually). You can notice quite an improvement after 30 minutes or so of riding with low tyre pressures. This is entirely predictable. If the tyres go from say 10 to 40 degC then assuming the usual gas laws the pressure would increase about 10% & an improvement should be noticeable - & it is.

I am afraid I do not see how the way you ride affects the basic stability of the bike itself in any way??
(It would affect safety issues though!!)
Actually, I don't quite follow where you are at here, as you also say:
"My XS11 on the other hand, being a heavy bike, is very sensitive to pressures" :confused:
(This seems to be supporting my basic premise here?)

[nodrog]

what sort of air are you using?

[sootie]

what sort of air are you using?

What sort of air would you like me to use?
This is based on the pretty normal Ak suburbs stuff around our way! :killingme

[nodrog]

What sort of air would you like me to use?
This is based on the pretty normal Ak suburbs stuff around our way! :killingme

Make sure there is no residual whangarei air in there, air from two different climate zones will play havac with your tyres internal barometric atmosphere.

Its actually safer to drain all the air out and refill before every ride. That way you have the correct humidity percentage inside and out, and the tyre will function to its full potential.

[sootie]

Make sure there is no residual whangarei air in there, air from two different climate zones will play havac with your tyres internal barometric atmosphere.

Its actually safer to drain all the air out and refill before every ride. That way you have the correct humidity percentage inside and out, and the tyre will function to its full potential.

Actually, I hear that air from the Chrischurch region is very good too. Same idea as James Bond's Martinis; ie something to do with the air from down that way being shaken rather than stirred.

[bsasuper]

Just put 42 rear 36 front for road use, as recommended by mfr, done:facepalm:

[Maha]

Just put 42 rear 36 front for road use, as recommended by mfr, done:facepalm:

Yes...its not as scientific as some are suggesting, cept nodrog, he knows a thing or two.
My (cold) tyre pressures are on the swingarm, up to 90kg 42 rear and 36 front...done.
May add a few psi if I use a really well packed pack, but other than that....all is good.

[sootie]

Yes...its not as scientific as some are suggesting, cept nodrog, he knows a thing or two.
My (cold) tyre pressures are on the swingarm, up to 90kg 42 rear and 36 front...done.
May add a few psi if I use a really well packed pack, but other than that....all is good.

Yeah; it is handling sensitivity to tyre pressure change that I am banging on about here; not too bothered about the actual pressures used.
(The point about sidewall stiffness is well made though. I would imagine this affects the final sensitivity considerably too.)

I guess high (40+psi) tyre pressues are a function of tyre loading, so maybe the use of high normal operating pressures
is likely to be associated with tyre pressure handling sensitivity.

The point about this being that if a bike uses tyre pressures of more than say 40psi, the tyre pressures should probably be checked more frequently
than those of a bike whose normal recommended tyre pressures are around 33psi (say). This would tie up with my own experience on different bikes,
but others will have a more varied experience here than I have. (Please note use of "probably" in the same sense that more HP = more speed!)