Page 17 - Sound Rides April 2024

From: THE NEWSLETTER OF THE CANTERBURY BRANCH ULYSSES CLUB OF NEW ZEALAND

TYRE PRESSURES Thanks to Sherrel for sending this in..

Popped into MCDU for a bit of a chin wag and got talking to Ian Templeton. Ian had been part of a su-
perbike team and until recently the Michelin Agent in NZ so we got talking tyres. I’ve been running Mich-
elin Pilot Road 6 GTs for some time and I’m really happy with their performance but I had one niggle
with them. In an ‘Oh Shit’ moment, I did find the rear squirmed a bit when you braked hard, which can
be a little off putting. “What pressure are you running” Ian asked me. “42, 42” I replied, exactly what Su-
zuki recommends for the Hayabusa. “Not enough air” was Ian’s reply. Ian went on to explain modern
tyres with very soft side walls only the volume and pressure of air within the tyre was all that was keep-
ing the tyre profile as it was designed, for all angles of lean and when under load. “In the old days the
sides walls of a motorcycle were stiff because they were almost 10mm thick! Today, they’re as thin as 2-
ply toilet paper so you’ve got to stiffen them, to support them, and the only way you can do that is with
air, plenty of air. For you and the riding you do, I’d be putting in 46 rear and leave the front at 42, maybe
even going as high as 44.” Now that’s hard and I asked about what that would do to the contact patch
and suspension. Ian explained that while a tyre has a part to play with your suspension and ‘softness’ of
ride, it’s a minor part. Your suspension setup should take care of 95% of that, and you should not rely
on your tyre to make up the shortfall. As for a contact patch, it’s a fallacy that a lower pressure provides
better adhesion, even more of a fallacy when it's wet. Taking a tyre off the rack, he showed me what he
meant. By pushing on the center of the tyre, the side walls bulge and the grooves or sipes in the tyre
begin to close off and in doing so mitigating any water pumping action they were designed to do. Yes, it
was an un-inflated tyre, but it was a very visual demonstration of what he was explaining to me. And
while your rebound set up has a lot to do with it, the wrong pressures will also cause telltale feathering
on the leading edges of those water grooves while noticeably increasing tyre wear. “Your tyres act more
like a squeegee, and like the squeegee you use in your shower to wipe water off the glass, as the tyre
rotates, the rubber surface pushes the water into the next groove or sipe, where it is pumped out side-
ways. If those grooves or sipes are restricted, or even closed off, so to the ability of the tyre to get rid of
water and your grip is now seriously compromised.” I was flagging at Ruapuna one wet weekend, and I
remember commenting to Trevor Pierce how his son Jacob was riding really well despite the conditions.
Trevor told me that while others were dropping tyre pressures to improve adhesion, he’d pumped Ja-
cobs up and his son began carving his way through the pack because his tyres were doing what they
were designed to do, pumping the water away. Last year I had Trevor set up the suspension on Char-
lotte and the effect was very noticeable. She was a different bike and while a lot stiffer for sure, she was
a lot nimbler, turning in and out effortlessly, the old ‘point and squirt’, and my ride made a lot more en-
joyable. So, what about this 46psi? It was a big change until Ian explained that Suzuki had spent mil-
lions on developing the Hayabusa and if they recommend 42 front and rear, then that’s a good starting
point. But if I'm honest, and I think about it, they were set up for a ‘son of a samurai’ test rider, not the
‘son of a steak pie’! Oh well, in for a penny, in for a pound. If I didn’t like it, easily fixed by letting some
puff out. Yesterday, I went into MCDU and shook Ian’s hand thank him. Having just completed a shade
under 3k for the weekend, Charlotte had been transformed. Those extra psi had changed her aspect
and handling to the nth degree. No longer did she feel slightly arse down and saggy. The ride wasn’t no-
ticeably harder either, but boy could she corner now, and I found myself doing so effortlessly and at
speeds a lot higher than I thought I was doing because it was so
bloody easy. Charlotte was on rails, the extra few psi in pressure en-
suring the side walls were doing their job maintaining the tyre profile
and the difference was transformational. I’m a convert. I will be run-
ning those higher psi ratings from now on. It hasn’t affected the grip
of the 6’s one iota, in fact it probably has improved it, if the truth be
known. Not enough air. Three simple words but oh what a differ-
ence. Cheers Ian, you’re a legend! Regards, Chris

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