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By Andy C
#96392
I was looking at the manual earlier today as need to adjust the chain, I also looked at the tyre pressure section, is anyone using the pressures recommended in the manual of 25PSI Front / 32PSI Rear?

Mine are nearer F 32 / R36, the recommended pressures strike me as a little on the low side - happy to be corrected.
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By windmill john
#96393
There is an article about running all tyres at 36 and 42. I ran road tyres at these pressures for years, but have gone back to either tyre manufacturers recommended or bike recommended.

I’m running 26 and 30 on my F650GS with TKC80 tyres and it rides very nicely.

I’ve discovered after tens of thousands of miles, many tyres, many bikes that all above works.

I did discover that on Transalps running at 25/30-ish and some Airheads running at book pressure, you could feel the difference in bends. They wallowed. Now wallow is too strong a word, they felt very safe. But running at the higher pressures, steering was faster and very precise.

But like I said, we are not Moto GP riders, so book pressures or the ‘default’ will be absolutely fine.

As long as you have at least 20 in there you can test. Make sure your tyres are definitely scrubbed in, i.e. you have covered at least 100 miles if new. Try about 24psi in the front. Go for a long ride and feel the corners. Come back and try 32 to 26 in the front; re-test.

I don’t like overly high pressures in the Winter on cold roads.
By Andy C
#96394
John - thanks for that.

Think I'll just leave "as is" because I am happy with the ride / handling, so it is a case of if it aint broke.......I was just curious as to what the recommended pressures were.

I know that if I run my 865 Speedmaster below the recommended pressures it feels really "wallowy" in the bends - even makes moving it around harder, which I guess it would, handbook recommended pressures seem to work fine.

On my H2 Triple I run 32 front 38 rear - cant recall what the workshop manual recommends, but at those pressures it suits the way I ride. Talking of riding, sun is out - time to get a leg over a bike.........
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By windmill john
#96395
Here's the thing I mentioned above, copied from elsewhere if interested:


Tyre pressures are a crucial factor in determining how your bike handles and how
quickly you wear out your (not exactly cheap) tyres.
There are lots of myths and misconceptions about what pressures you should run in
the wet, on track days or when you're loaded with luggage. Usually you'll find someone
propping up the bar who knows better than the manufacturers' recommendations. To
find out how close they are to being right we talked to a genuine expert - a man who
should know tyres if anyone does.

Leo Smith spent years as chief development tester at Avon tyres. He is now
motorcycle product manager. He said: "We probably get asked more about tyre
pressures than about any other aspect of a tyre”. There's so much bad information
kicking about that people can't separate the truth from fiction."

Smith says that is largely the fault of tyre companies themselves. Several years ago,
different tyre companies recommended different pressures for different tyres and
different bikes. But around 10 years ago, a decision was reached between the
companies to standardise pressures so that most bikes can run on the same no matter
what tyres they're on. That standard is 36psi at the front and 42psi at the rear.

There are some exceptions, like some 400cc grey imports which run 29psi at the front
and 36psi at the rear. Another notable exception is the Kawasaki ZX-12R - which is
meant to run 42 front and rear. But if you've got a modern, mainstream bike,
chances are you should be running the 36/42 standard.

That 42 figure in particular will have a lot of the gentlemen at the bar shaking their
heads. But it is not a figure chosen at random. Pressures determine how your tyres
deflect. The lower the pressure, the more the tyre will flex. That may make for a
comfortable ride when you're cruising in a straight line, but the tyre will flex too fast at
speed and make your bike unstable. The bike will feel vague going into turns and feel
like it's going to tip into the corner suddenly. This is because the tyre isn't "strong"
enough and it's literally buckling under you.

The bike will also feel wallowy through turns and it'll weave under acceleration.
Conversely, if you over-inflate a tyre, the flex will be slower but that will make your bike
more stable at high speeds. The ride comfort and the tyre's ability to absorb shocks will
be lost and your wrists and backside will take the brunt of it. The bike will feel so harsh
that many people will think they have a suspension problem.

Cornering won't feel as bad as when pressure is too low, but you will again lose feel
and feedback from the tyres. For example, if you ride over a stone, an over-inflated
tyre cannot absorb it and the tyre breaks contact with the road. Smith says the classic
myth about tyre pressures is that you deflate them for wet-weather riding. He says
most grip comes from the tyre's compound and the contact patch - and the shape of
the tyre where it contacts the road is everything.

Tread patterns stop water from building up under the tyres - which could cause a bike
to aquaplane. Smith says: "A good front tyre chucks enough water out of the way to
enable the rear to get the power down. If you reduce the tyre pressure, the tread
becomes compressed so it can't clear as much water." If anything, Smith recommends
you increase the rear tyre by 2-3psi in the wet but leave the front as it is.

Another widely held misconception is that the psi recommendations are the maximum
the tyre can take. They're not. The figure only tells at what pressures the tyres were
tested at for all-round use. You could actually safely inflate a type up to around 50psi if
you really wanted to, although it wouldn't do you much good.

But the biggest area for debate has to be track days. If you've ever been to one it's
almost certain someone has told you you'll be best off reducing your tyre pressures.
You get more grip that way, they tell you. Smith has radically different advice.
You should leave them alone, he says. "Racing tyres are of a totally different
construction and stiffness to road tyres so they need less pressure to maintain the
carcass shape. That's where the rumours and bad advice comes from. "If you drop the
psi in road tyres you will get more movement in the tread pattern. They will heat up too
much and that will eat into tyre wear. You'll almost certainly ruin a set in a day without
gaining any advantage in grip."

Smith says he's known people to drop their rear tyre to just 22psi when heading for the
track. His advice is to leave your tyres alone, saying a good tyre at standard pressures
will give more grip than you need on a track day because you almost certainly won't be
going as fast or for as long as racers. Track surfaces offer much better grip than the
road, too - another reason for leaving your tyre pressures the same for the ride to the
track as for the ride around it.

Many people also ask the experts at Avon if they should increase psi to take pillion
passengers. Again there's no need. The manufacturers' agreed pressures of 36/42
were arrived at after testing with pillions, luggage, cold tyres and every other
combination you could think of.

One of the few cases when Smith does recommend you change your pressures is
when your tyres wear. A worn tyre has lost a lot of its strength as the shape and
flexibility levels have changed. That means it will handle differently to a new tyre. Try
increasing the tyres by 2psi when you're down to around 40 per cent tread depth. It will
only make a marginal difference, but it should improve your bike's handling a bit.
You may not have to keep changing your tyre pressures, but you do have to maintain
them. Smith recommends that you check them once a week as an absolute minimum
but to be extra safe, you should really check them every day because a tyre can
change by as much as 3psi on its own just because of changes in the weather.

You should always measure your tyre pressures when they are cold. A few bikes are
now coming with tyre pressure gauges in their under-saddle tool kits. If you haven't got
one it's worth buying one. They only cost a few quid and take up about as much room
as a pen. Forecourt gauges are notoriously inaccurate.
By RocketRR
#96399
27 front 32 rear for me mainly lanes and byways with some A roads. Obviously drop pressure on byways, bought a cracking lithium pump makes life so easy and small to carry
By Andy C
#96403
John.

An interesting read, the 36 / 42 combination is what is in the book for my Speedmaster, and does seem to work OK.

What I really must do is buy myself a tyre pressure gauge, I have compressor in the garage to which I connect my tyre inflator, question is just how acurrate is the gauge on the inflator?
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By windmill john
#96404
My stick tyre pressure gauge could be out, but I’ve used it for years, so at least it will be constantly out....

I’ve have thought about comparing it to another, it does read roughly the same as the one on my £6 foot pump. But at the end of the day, reading the article, if I’m a psi or 2 out, I’lll still sleep soundly in my bed :D
By Andy C
#96405
I have a very old (was my Dads) Schroeder stick gauge out in the garage, I just tried it on my Speedmaster tyres as they have a 90 degree adaptor on it so they are easy to access.

Stick gauge reads 2 PSI lower than the gauge on my inflator and as you say not worth loosing any sleep over.
By vince
#96407
Hi, interesting comments. As an aside my Redditch manual for 350 bullet states front 18 psi, rear 23psi and with pillion 32psi but the tyres of the day were of a different construction. The sidecar tyre is quoted at 16psi which seems horrendously low. Vince

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