Tyre pressures - advice sought

[MSTRS:Me]

My bike handles like a piece of crap with the sort of pressures you would think "normal". Wobbles all over the show, wallows even Personally I would not have believed that a couple of psi in a tyre could make such a dynamic difference to my ride, but it does.

I dont have fancy pants tyres, but my bike is old and heavy and needs a bit more pressure in the tyres than you would normally think to use. If your handbook is saying run 42, then run 42. If she still handles like a dog then maybe you will have to review your suspension set up

All true. But the Radian runs 90 profile tyres. That would mean that low pressures in yours would lead to huge sidewall flex...something that is less likely in a 55/70 profile.

[Mom]

All true. But doesn't the Radian run high/er profile tyres than a sprotbike? That would mean that low pressures in yours would lead to huge sidewall flex...something that is less likely in a 55/70 profile.

Well now, you are perhaps right, all I know is, run my tyres soft and I may as well pick the bike up and run around the corners, the bike will be as graceful as I am attempting to get round the corner

My point in case it was missed is tyre pressures make a huge difference in the handling of your bike, you can never assume what you always have used in the past will suit the tyres and bike you are riding now.

[MSTRS:Me]

Well now, you are perhaps right, all I know is, run my tyres soft and I may as well pick the bike up and run around the corners, the bike will be as graceful as I am attempting to get round the corner

My point in case it was missed is tyre pressures make a huge difference in the handling of your bike, you can never assume what you always have used in the past will suit the tyres and bike you are riding now.

As usual, you speak with the voice of womanly wisdom.
I went and checked the Radian specs and changed my post, but you'd already quoted me.
Too soft is probably worse than too hard. Back when I had the 1100, I found a dodgy servo airpump gauge was delivering over 50psi when it was reading 40. The ride was harsh and a bit skittish.

[DMNTD:Me]

IMO 36/38 is the magic set of numbers for most tyres for road riding.
In saying that when I've owned upright bikes I've run them within 1 PSI of each other and found them bang on.
IE: on both of my Superdukes plus also my Brutale I ran the tyres at 35/36 and got good stickablity© and at least 2000kms

[Mumbles]

89 ZXR 750 Running 36F 42R have always run this ...

[StoneY]

Great stuff everyone, and thanks MoM!
My old 1100 way back with higher profiles...memories, and answers
Sweet as everyone I now am happy to just tweak the tyre pressures, check em cold, and find MY zone

Awesome, question thoroughly answered, KB rox

[ynot slow]

Bandit states 36/42 f/rsame two up.

[SPP]

IMO 36/38 is the magic set of numbers for most tyres for road riding.

Yep.

I changed to Pilot Power 2CT not too long ago (8000km on them now). I've played around a little with different pressures. 36/38 seems to be bang on for these (for me).

I tried lower 34/32-34 but the rear squirmed around a little too much for me and higher pressure didn't seem to be any less grip.

I commute a lot so raise to 36/42 weekdays to preserve them. The feel fine and are wearing quite well.

42/46 seems pretty high.

[p.dath]

Found this interesting article on the Continental Tyres web site.

Basically they recommend running at the highest pressure level recommend by the motorbike manufacturer - even though some comfort will be lost doing this. They say to do this because the tyre pressures are chosen based on safety, not comfort.

They also talk about under-inflated tyres heating much more, and if you've read all the threads about racers, you'll know tyres have a limited number of heat cycles.

So my impression is that running the tyres below the manufacturers recommendations, while more potentially more comfortable, is likely to reduce the life of the tyres, potentially reduce safety, and reduce fuel economy.

[Ocean1]

on both of my Superdukes plus also my Brutale I ran the tyres at 35/36 and got good stickablity© and at least 2000kms

I changed to Pilot Power 2CT not too long ago (8000km on them now). I've played around a little with different pressures. 36/38 seems to be bang on for these (for me).

Yes, on the Buell it got pretty obvious when the PP's were out by more than a psi or so, the front in particular. I ran them at 36, front and rear, less than that and it felty like the front was folding, much more and it'd feel washy. The rear was less critical.

[crash harry]

Have a look here at teh michelin reccomendations for an ST4s (I assume from your profile that's what we're talking about here?)

Seems they recommend Pilot Road with 2.2 bar front and 2.4 bar rear (that's 32 psi front and 35 psi rear in old money...). From my experience, pressures for powers and roads are similar for best handling, they're a similar carcass as far as I know.

I suspect that the pressures recommended in your manual are for tyres with soft-as-all-hell sidewalls or they're trying to get a million miles out of them or something... I've had a set of Dunlops on the R1 that performed best at 36/42 psi (front/rear) - the Michelins it's got on now run 37psi front and rear and feel brilliant at that.

[crash harry]

Found this interesting article on the Continental Tyres web site.

Basically they recommend running at the highest pressure level recommend by the motorbike manufacturer - even though some comfort will be lost doing this. They say to do this because the tyre pressures are chosen based on safety, not comfort.

They also talk about under-inflated tyres heating much more, and if you've read all the threads about racers, you'll know tyres have a limited number of heat cycles.

So my impression is that running the tyres below the manufacturers recommendations, while more potentially more comfortable, is likely to reduce the life of the tyres, potentially reduce safety, and reduce fuel economy.

Basically true, though I would go with the recommended pressures from the Tyre manufacturer, not the Bike manufacturer. Too many variables in different tyre constructions. Interesting also that after stating that, Continental list tyre recommendations for different models, complete with inflation pressures. For the ST4s in question they recommend all sorts of tyres, all with 2.2bar front and 2.5bar rear (32psi / 36psi). They do make you accept an agreement that they take no responsibility for the recommendations and you're on your own if you follow them though..

[p.dath]

I wonder how much the "weight" of the rider has an impact on the recommend tyre pressure.

I assume when a motorbike manufacturer recommends a tyre pressue it must in part be in part based on the weight of the bike.

[Hiflyer]

I really dont know what difference the pressure makes to my bike, Ive only ridden my bike for long periods of time, (I rode my flatmate's bike for a wee bit but was too worried about adjusting to the riding position) Maybe I'll let it run down to below thirty then pump it up and c what hapens hahahaha

[MSTRS:Me]

So my impression is that running the tyres below the manufacturers recommendations, while more potentially more comfortable, is likely to reduce the life of the tyres, potentially reduce safety, and reduce fuel economy.

Not necessarily. There are so many factors at work. It is finding the ideal combination for you that is most important.
For interest's sake - I have seen 'official' recommendations for my 750 at anywhere from 36/36 to 38/38 to 36/42. They can't all be right! I run mine at 33/37, and the last set of PR2s gripped and lasted pretty well. 18,000kms.