Author Topic: Tyre guru's  (Read 498 times)

Offline paul G

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Tyre guru's
« on: December 07, 2020, 08:07:39 AM »
Just taking the Z650 wheels in for the tyres to be removed so I can do a bit of work on the alloys and have new tyres fitted.
I always mark the direction on the disc or hub to avoid any confusion but that got me thinking.
If a tyre is directional, and runs in one direction on the front, why is this reversed when the same tyre is used as a rear  ???
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Offline Tomb

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Re: Tyre guru's
« Reply #1 on: December 07, 2020, 08:11:49 AM »
Braking on front accelerating on the rear
Tom
'73 CB550 with CB500 engine café racer
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And a load of old Yamaha 1100's

Offline paul G

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Re: Tyre guru's
« Reply #2 on: December 07, 2020, 08:25:15 AM »
Braking on front accelerating on the rear
I thought it was to do with the ability of the tyre to remove water which does not change from front to back !
Honda CB400 4
Honda CB550 K3
Honda CB750 UK K1
Kawasaki Z650 C2
Kawasaki Z650 cafe racer

Offline paul G

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Honda CB400 4
Honda CB550 K3
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Kawasaki Z650 C2
Kawasaki Z650 cafe racer

Online K2-K6

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Re: Tyre guru's
« Reply #4 on: December 07, 2020, 09:08:26 AM »
There's a couple of different aspects to this,  construction being one.  They were produced by wrapping a tread compound round a completed carcass and overlapped to "join" that component,  which would allow torque to pull the leading edge up and start to unwrap the tire if braking or traction were applied in the "wrong" direction.  That's obviously the structural element in addition to which production may have moved to complete bands of tread compound currently used with no join.

We had an explore recently in this area http://www.sohc.co.uk/index.php/topic,23441.0.html as to the tread pattern,  orientation etc.

Since which time I asked a tire engineer the same question,  the answer to which was,  the front tire particularly has no real prospects of aquaplaning.  It presents to the road surface in a "canoe" shape and as such doesn't build water between the two as a flat tire would. The two sides of the centre line can be considered as separate parts as you lean it over with the opposing side  simply not in contact.

The pattern is solely designed to give the correct feel to the rider as they lean it over and approach the tire slipping. This is obviously a compromise in terms of ambient temperature and just how much force the rider puts through it at extreme loading.  Hence high speed/load tire for high temperature will usually have minimal cuts and harder compound to support its intended use,  as a pure road tire for general temps will ordinarily be away from that to give the same feeling at much lower loading.


Offline Lobo

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Re: Tyre guru's
« Reply #5 on: December 07, 2020, 12:51:41 PM »
Interesting.

Fully appreciate the construction overlap aspects, but this surely has no bearing on tread pattern which can subsequently be orientated as required?

If we are all agreed that the rear tyre tread is designed to actively pump water to the outside as it progresses, surely the front tread should follow the same pattern & logic? (braking or cruising.... no difference as the rotation is always forward / ie trampling & squeezing the water into an angled groove)

No matter, you quote Nige that is all about ‘feel’ versus aquaplaning. Which still leaves me confused as both tyres are canoe profiles; does the forward versus aft angle of the sipes really translate into very different handling qualities?

Really enjoy this stuff, albeit struggling to get my head around it!

 

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