Author Topic: Tyre technicals...  (Read 479 times)

Offline Lobo

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Tyre technicals...
« on: September 15, 2020, 12:01:51 PM »
Today had Michelin Road 5s fitted to my Guzzi. They are correctly orientated.

Intrigued, cause logic suggests to my wee brain that on a soaked road, the tread will gather water, and with further rotation trample / channel / squeeze it towards the centre of the thread... lifting / aquaplaning the tyre.

What am I missing here?

Ta.
« Last Edit: September 15, 2020, 12:06:46 PM by Lobo »

Offline royhall

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Re: Tyre technicals...
« Reply #1 on: September 15, 2020, 12:09:14 PM »
Push the water away from the tyre centre I would have thought, but I do see where your coming from with the tread pattern and rotation.
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Offline Nurse Julie

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Re: Tyre technicals...
« Reply #2 on: September 15, 2020, 12:42:50 PM »
I think its 'cos you're in Australia Simon. Gravitational pull of the moon, magnetic fields and all that, pulls the water out, not pushes it in 😊😊😊😊
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Offline K2-K6

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Re: Tyre technicals...
« Reply #3 on: September 15, 2020, 01:17:51 PM »
Ooh I like a good tire discussion.

"I think its 'cos you're in Australia Simon. Gravitational pull of the moon, magnetic fields and all that, pulls the water out, not pushes it in 😊😊😊😊"  ;D

It looks at first description as you see it Simon doesn't it.  I do that "if you roll it round, then which way up is it meeting the tarmac" thing too.

But believe it's because the front wheel has absolutely no traction requirements as it's just rolling along and the curved profile prevents any serious water buildup.

Now put the brakes on and the tire goes straight to traction, but that force is backwards,  so the tread orientation is correct as the tire comes under this load,  flattened a little and water having a wider gap to travel toward under maximum demand of grip.


Offline Oddjob

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Re: Tyre technicals...
« Reply #4 on: September 15, 2020, 04:24:57 PM »
By the look of the bike it never goes out in the rain so where's the problem  ;D ;D

My 5s are fitted the same way, the rear is fitted the reverse of the front, the way you'd expect it to be. Must work as I've had no problems in the wet, great tyres, grip is phenomenal and they last very well, which is a good bonus.

I got a free Michelin tyre pressure monitor system with mine, great piece of kit, great to look down and see what the tyre pressures are and at the start of a run you can see instantly if you need a bit of air in them, the pressure goes up around 4-5psi when the tyres heat up. Highly recommend.
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Offline SteveD CB500K0

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Re: Tyre technicals...
« Reply #5 on: September 15, 2020, 04:30:28 PM »
It’s all in the sipes.

You’ll have to look it up as I couldn’t possibly explain it


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Offline Lobo

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Re: Tyre technicals...
« Reply #6 on: September 16, 2020, 03:57:34 AM »
...so far I think Julie’s winning on the explanation given the Ozzies have a penchant for doing things, um, differently.

Nige, I want to get where you’re coming from, but (1) the tyre must at all times have some sort of friction (otherwise it’d be akin to riding on black ice)  so even when rolling along water appears to be pumped to just where ya don’t need it.

And (2), under heavy braking I’m struggling to see how the dynamics change in this respect ... the outside tread is ‘charged’ with water, and as the tyre rotated forward is even more compressed (due flattening) and pumped to, er, just where ya don’t need it. Yes the force is one of retardation, but the tyre is still rotating forwards....

I totally accept I am wrong in the logic... but still fail to ‘get it’

Ken, the rear is fitted with tread the other way ‘round... phew (I think.)

Daftly, I can’t find any ‘Direction of Rotation’ markings on the sidewalls. Maybe I’ve simply missed ‘em, but it does seem a tad dangerous given the front wheel can be put back either way ‘round.

Steve... that’s a total bloody cop out! (and god help me I tried to get these photos orientated up (ie held the phone vertical).... aargh.)

(PS - Ken... have been looking at TPMS... do yours replace the valve (and if so are you happy with that)... or are they bluetoothing up to a handlebar display?
« Last Edit: September 16, 2020, 04:06:52 AM by Lobo »

Offline SteveD CB500K0

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Re: Tyre technicals...
« Reply #7 on: September 16, 2020, 07:34:55 AM »
We had the Michelin guys present tyre design at our bike club.

“Forget the rotation”

A tyre is subject to a force from the road surface which squashes the tread.

If you look at your picture and imaging pressing a credit card sized contact patch into the tyre, you will see that the water is actually channelled away.

The sipes help too


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Offline K2-K6

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Re: Tyre technicals...
« Reply #8 on: September 16, 2020, 07:45:19 AM »
Think I'm using the wrong terminology  ::) it's spindle torque acting on each tire that causes the most demanding conditions of longitudinal traction,  which is opposite for rear wheel power torque and front brake applied torque.

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Similar as in above photo of wet race tire as they are fitted with opposed pattern orientation.  Although it looks differnt, if the rear is accepted in it's "correct" direction, then the highest rotatational torque on the front wheel is applied in the opposite direction.  It looks confusing as the bike is moving along but the tire is trying to resist just being pushed along the road under braking and under high demand gets into a percentage of slip at it's peak braking. 

Online cliff7

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Re: Tyre technicals...
« Reply #9 on: September 16, 2020, 11:36:36 AM »
Does this mean my back tyre is more likely to skid in the wet when braking than the front? At the moment my back brake seems better than the front and I am sure I can brake quicker than I can accelerate.

Offline Oddjob

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Re: Tyre technicals...
« Reply #10 on: September 16, 2020, 12:15:24 PM »
The TPMS system uses the same valve stem as fitted, mine have 90 degree ones fitted or you tend to burn your hands on the front discs trying to get the inflater valve on. They are just essentially dust caps (albeit largish ones) which send a signal to a small circular disc which displays the pressure. It alternates between front and rear pressures and is very easy to read, not too bright at night to distract you. Also has a tyre overheat warning as well as a low pressure warning inbuilt. Mounts inside a small 2" cup which you attach to your bike, charges via USB and holds a charge for ages. Mines been on now for 3 months and it's still almost fully charged.

The cup is magnetic in that it holds the display module magnetically, mine is mounted on the frame just behind the headstock on my 1300, fits perfectly there and is almost invisible to passersby.

It's not failed to display yet, starts working as soon as the wheels start turning, when stopped it hibernates. 

Oh forgot to add, the sensors lock onto the valve stem with a locking nut, you get a little tool to help unlock them when you need to inflate the tyre, tool is very small and easily stored on the bike. I tried to remove the sensors without using the tool and I couldn't do it so should stop kids nicking them.
« Last Edit: September 16, 2020, 12:18:37 PM by Oddjob »
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Offline Lobo

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Re: Tyre technicals...
« Reply #11 on: September 16, 2020, 12:28:24 PM »
...I’m gonna have to hang my head in shame and walk away from this one; I’m not sure how you can ‘forget the rotation’; if your garage told you this / “...the wheels only needed static balancing”, you’d raise your eyebrows. (no offence Steve!)

Nige... trying to make your explanation ‘fit’.... but alas I’m in a bloody mindset here.

Regardless... thanks gents,
Simon.....  and quietly awaiting a Michelin Red Bulletin 😂😂😂)

(Interesting Ken, have been looking at such things - what brand is your system?)

Offline Oddjob

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Re: Tyre technicals...
« Reply #12 on: September 16, 2020, 07:27:32 PM »
It’s a Michelin one, they were giving it away free if you bought a pair of Road 5s, oh and there is a rotation mark on the tyre, it’s next to the tyre size on mine, says rotation and a small triangle pointing forward.
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Offline bobv7

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Re: Tyre technicals...
« Reply #13 on: September 16, 2020, 07:37:10 PM »
Nothing gets a motorcyclist more excited than a bit of black rubber! :-X

Offline Lobo

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Re: Tyre technicals...
« Reply #14 on: September 16, 2020, 10:29:12 PM »
...too true Bob.

Bloody hell Ken, you did well on the deal... I paid (equiv) £280 for the tyres... and I see your TPMS @ £85 on eBay. Result...

 

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