Tyre pressure - higher on the rear or higher on the front?

[kiwifruit]

Do you run higher pressure in the rear or the front tyre?
Why?

[mynameis]

Because my rear tyre is bigger than the front one :laugh:

[BASS-TREBLE]

The pressures that you should run are higher in the rear as you generaly sit closer to the rear axle, ie. cruisers have a lot of weight while sport bikes will have a little more weight on the front (crouching position.)

I would think that due to the amount of weight on the rear wheel when under acceleration more is needed in the rear.

Can anyone clarify?

[crash harry]

cos the owners manual says to...
and it seems to handle well that way, so who am I to question it?

[Pussy]

cos the owners manual says to...
and it seems to handle well that way, so who am I to question it?

That's what I reckon, as well

[kiwifruit]

cos the owners manual says to...
and it seems to handle well that way, so who am I to question it?

Thats what i thought as well, until i was told by a rider who knows his shit i was wrong.
Hopefully he or someone as clued up will come along and post the science behind it all :D

[Crasherfromwayback]

Because my rear tyre is bigger than the front one :laugh:

That's probably on the button! Because of the size, the rear tyre probably distorts under load more than the smaller front, so needs a slightly higher pressure to stay in shape as compared to the front.

[Motig]

Manual says same for both so I stick to it.

[Crasherfromwayback]

Manual says same for both so I stick to it.

Obviously the maker knows best, but as far as road bikes go, I think they go on the high side with pressures. Maybe for resistance to flats or distortion for continued high speed runs. Most (road) race bikes will be running around 29-32 psi.

[The Stranger]

The pressures that you should run are higher in the rear as you generaly sit closer to the rear axle, ie. cruisers have a lot of weight while sport bikes will have a little more weight on the front (crouching position.)

I would think that due to the amount of weight on the rear wheel when under acceleration more is needed in the rear.

Can anyone clarify?

Perhaps, but surely the larger air quantity would mean that for the same pressure it is able to support a greater weight.
For example a typical car tyre which is supporting a lot more weight per wheel than a bicycle uses way less pressure than a bicycle tyre due to the greater air volume.

Weight distribution is often quoted by the manufacturer. In the case of the Fazer they quote 51% front 49% rear. I assume (though I realise assumption is the mother of all fuck ups) that is with a rider on board, if not, why quote it as it would be useless information as a bike can't be ridden without a rider. Therefore you have roughly equal weight distribution. The forces under decelleration are greater than accelleration, so were a variance in presure required for accelleration, surely they would be required for decelleration and require greater pressure in the front.

One reason however for the manufacurer suggesting more in the rear could be to ensure it handles max load acceptably.

[The Stranger]

Thats what i thought as well, until i was told by a rider who knows his shit i was wrong.
Hopefully he or someone as clued up will come along and post the science behind it all :D

Perhaps the greater air volume would mean greater increase in pressure when it is heated?
Have you noticed the big tyres on rail cars or funny cars they run those things real flat. Bet they aren't at the end of the strip.

[Tony.OK]

Depends what you are doing really.On road it'd be higher in the rear whereas on track lower on the rear cause its working harder and getting hotter.

[cowpoos]

Do you run higher pressure in the rear or the front tyre?
Why?

While this subject is very dependant on riding style,bike type,set-up and use.

From your point of view as a very rapid road rider and also being fucking handy on a bike around a track...your after out right grip...and probally not as concerned about getting every last KM of life from your tyres.

They truely acurate way to get your tyre pressures right for you and your bike is using a pyrometer..these devices if your not familar with them measure temprature..and will measure the temp of your tyre hot..and with this info you can see if in the conditions you have been riding in, you have reached or are near the tyre manifactuers temp range for the tyre/compound etc..
and using that info you can adjust your tyre presures accordingly.. but it also comes down to feel and out right grip...running softer pressures will increase the contact patch of a radial tyre..but the trade off is loss of feel..and in the front can slow turn in..another side of the tyre presurre debate is carcuss temprature...the lower the pressure the more the carcuss can flex..but you don't want the pressures so low that the carcuss is able to deform..as this will cause a bike to be unstable and unpredictable in corners..but alowing this flex creates a bigger contact patch..and any fool can understand the benifits of that!!!

on a track day you could easily expect a front tyre to increase 2-4 psi from cold and 6-8 psi from cold on the rear depending on your starting pressure/temp but it is a marked increase regaurdless and can relate a heap to your feel and grip..and tyre life... manifacture's recommended pressures come from a balance of getting extended life from tyres..and are aimed almost directly at the typical I can't be bothered thining about this sort of shit sportsbike rider..which is obvious if your talking to riders and the tyre brand.type convosation comes up...no one ever talks pressures!!

another part of this debate is tyre side grip at high lean angles...at high lean angles your suspension is trying to put a vertical force through a semi horizontal plain..with huge resistance from the swingarm link ratio's and spring,damping curve..so the tyres do alot of work on tiny bumps while cranked right over..and you cant just run your suspension super soft to counter this.

between tyres,suspension,geometry,riding style,etc there is a good comprimse for everyone in there somewhere!...main thing is...different things will work better or worse for different people!! eg: slow person on a gsx1400 will benifit from a complely different set up from a fairly rapid dude on a R1 etc ;)

your on supacorsa pros?? [I think u said] 32 rear , 34 front would be what I reckon you should start at and go from there.

[kiwifruit]

Thank you Mr Poos :love:

(yes, on super corsas and yes, they seem to work alot better with the rear lower)

[The Stranger]

manifacture's recommended pressures come from a balance of getting extended life from tyres..

So, just to be sure, are you saying that increased pressures will generally extend tyre life?

[xwhatsit]

So, just to be sure, are you saying that increased pressures will generally extend tyre life?
Well they don't seem to square off so quickly.

I think rear-weight bias has a lot to do with it -- you'll notice most bikes tell you to bump up the rear tyre pressure when carrying a pillion, for instance.

[YellowDog]

Do you run higher pressure in the rear or the front tyre?
Why?
Twisties = Lower Pressure
Straightline Drag = Higher Pressure

[Crasherfromwayback]

Twisties = Lower Pressure
Straightline Drag = Higher Pressure

High speed runs in a straight line = high pressure, but straight line drag = VERY low rear pressure!

[jrandom]

slow person on a gsx1400 will benifit from a complely different set up from a fairly rapid dude on a R1 etc

Quite true, actually. We were discussing this via MSN when the thread went up.

I run Betty at 36 front 40 rear, because I'm a total nana on the throttle and I don't tend to warm up the rear tyre much on the road. I also get the shits if the rear tyre flexes in corners, so I prefer to have it as rigid as possible without actually forcing it to skitter around.

There are tyre life benefits to riding the way I do - I've had 13,500km out of my current set of Pilot Road 2s.

:shit:

[madandy]

I put 'depends' because well...it depends.
If I had rear wheel traction issues I'd lower my rear tyre pressure and if that meant it was running a lower pressure than what was working for me on the front tyre then so be it. Same applies for the front.

Assuming you have the suspnsion set up well for starters of course :yes:

[Marknz]

If you go to a ride day in Aussie, particularly the Eastern Creek and Phillip Island Ride Days, they tell you in no uncertain terms at the beginning of the day to go 30 front and 30 rear. But that is for ride days, and generally your ambient and track temperatures will be warmer there than here.

My GSX-R600 tyre sticker tells me to run 36/36 for solo riding, and 36/42 when two-up.

[trumpy]

The Continental website lists my S4 as 35F/39R for the Sport Attacks so I have used this as a starting point. I have found that if I lower the rear pressure too much the handling starts to suffer. Some of this may be due to tired suspension and/or less than ideal setup. Once Robert Taylor has rebuilt my suspension then it will be interesting to see what what differences changing the front/rear pressure balance does.

[The Stranger]

Well they don't seem to square of so quickly.


Hmm I find the opposite.
I run 32 front and 27 rear on the road for normal riding and commuting. Any higher and the rear disappears before my eyes (figuratively).

Point is, I think it really does depend on the tyre, the bike and the rider and there is no hard fast rules. One should keep an open mind.

[saltydog]

On the R1, 32 in the front, 34 in the rear. My last tyre, Dunlop D208? lasted 3500ks on the road, I thought that went a big quick. The pressure is so dependant on all these other variables. Thats why biking is so bloody good, every ride is a new one. I'd definiatley put higher pressure in the rear if I was doubing. But my new seat cowl and exhaust hanger got rid of the possibilty of ever being passenger any more.
And down to 30 in the front if I was fangin requiring a bit of extra rubber on the road.
First set of these 2CT's, seem quite good. Cant complain, seem to perform and with it appears more wear in them.

[Forest]

Perhaps, but surely the larger air quantity
Weight distribution is often quoted by the manufacturer. In the case of the Fazer they quote 51% front 49% rear. I assume (though I realise assumption is the mother of all fuck ups) that is with a rider on board, if not, why quote it as it would be useless information as a bike can't be ridden without a rider. Therefore you have roughly equal weight distribution. The forces under decelleration are greater than accelleration, so were a variance in presure required for accelleration, surely they would be required for decelleration and require greater pressure in the front.

Weight distribution figures are quoted without a rider on board.

It is basically marketing wankery ... along the same lines as quoting dry weights.

[Grub]

The geometry of each bike is different and calculated my super-computers, the best money can buy. So ....

- Use the tyres specified for that bike
- Use the pressures specified for that bike.

On both CBR's I've owned the pressures are 36F, 42R and I can immediately feel a drop of 2psi. On Nasty's GSXF750 its 36/36 so the poll could mislead the unwary into dangerous territory.

[cowpoos]

Weight distribution figures are quoted without a rider on board.

It is basically marketing wankery ... along the same lines as quoting dry weights.

not really...its of alot of interest to racers and people who understand its relivence.

[homer]

more psi less heat
less psi mpre heat

in other words more heat ......less tire life and less heat .....more tyre life

i dont have the dollars to try it all
so 39 psi front and 40 psi rear
r6 roadtecs
near 6000 km now and just showing a slight flat on the rear
the front well its a crappy pilot road , its got some shoulders now , done about 8000km since ive had the bike , on the bike when i got it .
I think itll be good as for another 10000km piss easy .
Heaps tread left on the front , theres a new road tec sitting waiting to go on the front.

[Ocean1]

I'll ad some more numbers, Pilot Sports on a 179Kg Buell (and bike weight's definitely a major factor) really don't like less than 30psi on the front, you can feel them start to get unstable and distort. They feel fine at anything between 34 and 38psi. I've found 36psi both ends is a good compromise.

I wondered, (belatedly) if this was all about sportsbikes, general road bikes, or bikes in general... 'Cause all the numbers quoted so far are wayyy over the top off road.

Oh, and the drag slicks are run that soft because, firstly the silly-putty compounds grip much better with the larger contact patch, (and little or no lateral load means they can get away with it) and secondly one of the characteristics they're looking for is a huge increase in diameter over the run, to provide progressive gearing.

[The Stranger]

Weight distribution figures are quoted without a rider on board.

It is basically marketing wankery ... along the same lines as quoting dry weights.

Hmm, after xerxesdaphat's post my interest was piqued so I measured the Fazer.
I guess it was dumb luck that Yamaha got it pretty spot on with me on board. Sure I could sit up and shift it back or lean forward and move the weight forward, but for my normal riding position the claimed 51% front 49% rear is remarkably accurate.

On the face of it one would wonder how it helps marketing, which is better? more of a front or rear bias?
Is there a magical number?

However the fact remains, we were discussing wieght difference on the tyres and in that regard it is pertinent.

[Ryan432]

I went from 32/32 (what was in the tyres when a bought the bike) to 36/38 and I noticed the bike felt more grounded from the very start of the ride but almost the same after "warming up". I always roll on a harder rear tyre, I like me front wheel to feel firmly planted to the road (laterally that is, not so much vertically :whistle:)

[mister.koz]

34F - 36R - why? because the guys at speedtech reakon that its a good amount :) and they race kawaz so, i ask, they tell, i listen.

Was running 30 - 32, although it didn't feel bad, there was a more than noticeable improvement on the ride when i put the pressures up. I am not overly light (105kg)

Tempted to follow these instructions, look like the ticket:
http://www.kiwibiker.co.nz/forums/showthread.php?p=1503903#post1503903

[skidMark]

So, just to be sure, are you saying that increased pressures will generally extend tyre life?


Duh...........

[skidMark]

34F - 36R - why? because the guys at speedtech reakon that its a good amount :) and they race kawaz so, i ask, they tell, i listen.

Was running 30 - 32, although it didn't feel bad, there was a more than noticeable improvement on the ride when i put the pressures up. I am not overly light (105kg)

Tempted to follow these instructions, look like the ticket:
http://www.kiwibiker.co.nz/forums/showthread.php?p=1503903#post1503903


For road i ran 32 front 36 rear in my zxr ...

for track i ran 29psi front 31 psi rear.

seems to be about right, but yes with your weight i would say more i'm a lightweight, between 60-65 kg's is what i range between.

[DUCATI*HARD]

:girlfight:32/32

[pritch]

Do you run higher pressure in the rear or the front tyre? Why?

Insufficient information. It depends to an extent on what you are doing.

For road use I run the recommended pressures which happen to be higher in the back (where most of my not inconsiderable weight is located?).

[kiwifruit]

I left the question open to interpretation on purpose, honest.... :pinch:

If it was a me specific question it would have gone like this:
Should i run higher pressures in the front or the rear in my super corsas on my 1000cc road / track bike considering; I ride fast(ish) i'm not worried about tyre life, all i want is grip.

[jrandom]

I left the question open to interpretation on purpose, honest.... :pinch:

If it was a me specific question it would have gone like this:
Should i run higher pressures in the front or the rear in my super corsas on my 1000cc road / track bike considering; I ride fast(ish) i'm not worried about tyre life, all i want is grip.

Interestingly, a quick googling session led me to this page on suspension setup (http://www.gostar-racing.com/information/motorcycle_suspension_set-up.htm), which recommends 32psi front, 30psi rear as a starting point for track riding.

Which, of course, makes intuitive sense vis-a-vis wanting to maximise the contact patch on the rear.

Also, I wonder whether the rear tyre typically heats up more than the front when riding at track pace? You'd kinda think it would, wouldn't you?

It'd be interesting to use, say, a cooking thermometer to test the surface temperature on a bike's tyres as it came off the track. I'd love to see whether there was a difference between front and rear.

[The Stranger]

It'd be interesting to use, say, a cooking thermometer to test the surface temperature on a bike's tyres as it came off the track. I'd love to see whether there was a difference between front and rear.

Well, we didn't use a cooking thermometer, however in measuring Two Somker's tyres when he comes off of the track, the rear was always clearly a higher temp than the front.

[Ocean1]

It'd be interesting to use, say, a cooking thermometer to test the surface temperature on a bike's tyres as it came off the track. I'd love to see whether there was a difference between front and rear.

You can feel the difference with your hand dude. Interesting, also, to compare tyre temp's across a group, there can be quite a difference in spite of having just completed essentially the same "workout".

[jonbuoy]

I thought you dropped the air pressure on track days because your tires will be running hotter than on the road, air expands when its hot. Unless you got nitrogen filled tires.

[lankyman]

Do you run higher pressure in the rear or the front tyre?
Why?

Had a play around with different pressures over my favorite local twisties, found my NC30 a lot lest twitchy under hard accel exiting corners with a bit more pressure in the rear. Matter of personal preference i suppose. Trust your instincts.

[Brett]

I too run higher pressures in the rear than on the front. Normally at track days I run about 31 on the front and 33 or so on the rear. My theory too is that prominantly it is the front doing most of the work under heavy braking etc. Also when cornering it is the front that is handling two vector force changes whereas the rear is generally just along for the ride. Granted, the rear is handling a lot of power under full throttle...

Still, I am much happier with my rear wheel swinging aorund than with my front wheel slipping out.

[jrandom]

You can feel the difference with your hand dude.

Yeah; oddly enough, I've only ever bothered to feel one at a time, rather than compare them.

[pritch]

I haven't seen many references to checking tyre temperatures at the track. It isn't uncommon though to see advice re checking pressures when the tyres are hot.

If the warm pressure is more than 10% higher than the cold pressure the tyre is underinflated.

There are variations on this theme but that's representative...

Then there's this: http://www.feelthetrack.com/tire-wear.html