Mismatched tyres

**McDuck** · 18th July 2009, 23:27

Originally Posted by koba

Can you get a 100 wide radial front or a 120 wide crossply front?

Non spacific example. Could have been the other way round, could be anything

**Jantar** · 18th July 2009, 23:29

Originally Posted by Mikkel

In which way would a narrower rim benefit from a tyre manufactured with a, supposedly, less ideal construction method?

I am asking this in all seriousness, I quite simply don't know that much about other construction methods than radial.

It isn't so much a less ideal construction method as one that is designed for a different purpose. Radial tyres have more flex which allows more tread on the road and also allows the tyre to heat up to a more optimum temperature. Crossply tyres are generally stiffer and hold their shape more. Have a look at racing tyres of a couple of decades ago. They are crossply with an almost triangular profile so that there is more tread on the track when leaned over than when upright.

Also remember that most crossplys were desinged for spoked rims which means they must be fitted with a tube. Radials are generally designed to run tubeless.

**Jantar** · 18th July 2009, 23:32

Originally Posted by Katman

"Benefit" may be stretching it.

See if you can find a set of crossplys as similar as possible to the old Pirelli Phantoms to put on that silver beast of yours. you'll be amazed at how quickly it will turn in and remain stable right through the turn.

**Mikkel** · 18th July 2009, 23:36

Originally Posted by Jantar

It isn't so much a less ideal construction method as one that is designed for a different purpose. Radial tyres have more flex which allows more tread on the road and also allows the tyre to heat up to a more optimum temperature. Crossply tyres are generally stiffer and hold their shape more. Have a look at racing tyres of a couple of decades ago. They are crossply with an almost triangular profile so that there is more tread on the track when leaned over than when upright.

You must mean by cross-section - not area - surely...

**Katman** · 18th July 2009, 23:37

Originally Posted by koba

Can you get a 100 wide radial front or a 120 wide crossply front?

The situation that McDuck is talking about is the one that a number of Ducati owners are now facing. The 906 Pasos and 750 Sports that ran a 160/60-16 rear have the problem that no tyre now exists in that size. Michelin used to be the only manufacturer that made a tyre in that size and they have recently discontinued making that tyre. Those owners now have to look at replacing their rear end with a 17" wheel (and the swing arm conversion that this entails) or going to a crossply of similar (but not very similar) dimensions (and then changing the front to a crossply when they need to).

**Jantar** · 18th July 2009, 23:54

Originally Posted by Mikkel

You must mean by cross-section - not area - surely...

I do indeed mean by area.

**Katman** · 18th July 2009, 23:58

Originally Posted by Jantar

See if you can find a set of crossplys as similar as possible to the old Pirelli Phantoms to put on that silver beast of yours. you'll be amazed at how quickly it will turn in and remain stable right through the turn.

I am gutted that Pirelli are only putting out those Phantom replica tyres in 17".

**McDuck** · 19th July 2009, 00:04

Originally Posted by Katman

I am gutted that Pirelli are only putting out those Phantom replica tyres in 17".

Dose my 400 have 17s or 18s?

**Mikkel** · 19th July 2009, 00:05

Originally Posted by Jantar

I do indeed mean by area.

I thought we had already agreed that vehicle weight and tyre pressure dictates the contact patch area

**Chrislost** · 19th July 2009, 00:06

Originally Posted by riffer

I thought it was a no-no, as the biasply front and radial rear would cause massive understeer problems and the opposite would cause oversteer.

HOWEVER, this was ages ago and times change.

The Harley-Davidson Rocker runs a radial rear and a biasply front.

And they wouldn't sell anything that could be that dangerous given that they're from USA - the land of the law suit.

I dont think harleys can go fast enough or corner well enough for it to matter. (one would expect harley rear tyres are specially picked to work with harley front tyres!??!)

My workmate put a radial front and a bias ply rear on his Cb400. At about 160 his bike started to weave.
Still cornered fine.

**Ocean1** · 19th July 2009, 00:07

Originally Posted by Mikkel

I thought we had already agreed that vehicle weight and tyre pressure dictates the contact patch area

You've contended that before.

You were wrong then also.

**Jantar** · 19th July 2009, 00:07

Originally Posted by Mikkel

I thought we had already agreed that vehicle weight and tyre pressure dictates the contact patch area

With radial tyres that would be correct, less so with crossply.

**Katman** · 19th July 2009, 00:08

Originally Posted by McDuck

Dose my 400 have 17s or 18s?

Well it clearly has a 17" front. That is the reason behind this whole thread. I don't know offhand whether the rear is 17" as well. If it turned out that the Pirelli Phantom repilcas fitted then they would be the absolute dog's bollocks!