Tyre Pressures, clever clogs required.

[Suntan Sid]

I need some advice regarding tyre pressures.
Last weekend I was out with a couple of mates, it was very hot, 34 degrees to be precise, ( I live in Cyprus by the way), our ride out took us round some very nice twisties. However we all noticed that our tyres were slipping across the white line road markings.
Obviously it wasn't wet, (we're not going to see any rain here till November), I can only assume that with the road temperature being pretty high our tyre pressures were going up as we were riding.
So my question is this, given that road temperatures are always high here, should we be reducing our initial tyre pressures and if so by how much?

I should say I'm on a CBR600f, the other bikes were a Benelli 900, (don't know the model), and a bandit 600, all on standard size tyres.

[G]

I'm not sure specifically, but for racing you generally do try and work to hot pressures - so for supercorsas will do 35 front and rear when hot.
This generally equates to around 31 front 29 rear when cold.

[Suntan Sid]

[Ben.]

[G]

<shrugs> - the first time I got a 4th place in club racing (best result I managed) I realised half way through the race my tyres were at 55psi or so.
I do think worries about tyre pressures are generally over-rated!

And on that, for the OP, it's possible that it's the composition of the white line's themselves that are getting a bit slipper as they get hotter.

However, you could always try running your bike at a colder time and seeing what pressure your tyres are when 'hot' - then ride at a hot time and set them to the same pressure.

[robbieguy2003]

I cant believe no one has called this guy a bastard, solely on the fact he wont see rain till november!

On another note, i'd drop a few PSI out of each, maybe 3 or 4 to start, see how it feels and go up down. If you're making changes though, try and do one thing at a time, then you can get a measure or feel for the change.

Swapping lots of stuff at the same time wont help work out what does/doesn't work.
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Current Bikes: Honda CBR 600RR - '07, Suzuki GSX1250 FA ST '11
Old Bikes: Suzuki Intruder 125 LC - '2001, Honda CBR 600F - '92, Honda CBR 600RR - '03

[Acemastr]

Throwing this one out there, 34c air temp must be close to 45c road temp? painted white lines/tar/asphalt are going to start melting at that temp. Even my stand dug into the ground the other day when it was 20c here.
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2017 KTM 350 XC-F - 2014 Yamaha R6 - 2005 Yamaha YZ125
2016 Toyota Tacoma Limited

[DrDonnyBrago]

I'd just drop 2 or 3 psi out of each.

IMO though regardless of what it says in the book you KNOW when it is all working properly, if the bike feels right then that is enough .

[c-m]

Hang on... doesn't he want to increase tyre pressure? As that will lead to the temperature lowering.

I thought the issue is that the tyres are getting too hot? Decreasing pressures will see them get hotter.

[Dibble]

p1*V1/T1=p2*V2/T2


p=pressure

V=volume

t=temp.

If we take the volume to be constant-it isn't as the tyre is elastic, and use psi for ease

p1/t1=p2/t2

p1=42psi

t1=288k (Kelvin in the uk-15celsius)

p2=x

t2=307k

42/288=p2/307

p2=307(42/288)

p2=44.7psi

So if you set your "cold" pressure in the UK at 42 psi shipped the bike to Cyprus and measured the pressure would be 44.7psi.

You would need to know the particular characteristics of the tyre in regard to Black body Radiation to work out the different pressures at operating temp to find out if it actually runs at a different temp/pressure.

[Suntan Sid]