Mechanics.....

[MrGrumpy]

This Yamaha Pic of the Maj400 seems to have the tread pointing the opposite way.....

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[michaelphillips]

on another point with the ARROWS.... why do rotor disks have an arrow on them???? as when i purchased TWO front disks, they were identical , yet the arrow would fase front direction on one side and rear direction on the other, the five fixing holes have shamfers in them so they had to go on this way, anyone technical minded, help with this as well please.. cheers

[tallpaul]

Well it shows what sort of Muppet I am , the last time I got my new city grips I asked the tyre fitter to take it back off and change the tyre round with the arrow rolling forward.

[MrGrumpy]

Well it shows what sort of Muppet I am , the last time I got my new city grips I asked the tyre fitter to take it back off and change the tyre round with the arrow rolling forward.

But surely thats the point of an arrow? If it doesn't point in the right direction, why is it there??????

[tallpaul]

Well it shows what sort of Muppet I am , the last time I got my new city grips I asked the tyre fitter to take it back off and change the tyre round with the arrow rolling forward.

But surely thats the point of an arrow? If it doesn't point in the right direction, why is it there??????

I know, the tyre fitter originally put the tyre on with the tread the same direction as the old one, it wasn't till I put the wheel back on the bike when I noticed the direction of the arrow, so I had it turned around.

[TmaX9]

That's correct. All bike tyres are labelled front or rear, or have an F or R in the code. The arrow always points in the direction of rotation which is clockwise when viewed from the offside (right hand). Like a rear tyre on a farm tractor, the deep treads are designed to dig in for maximum pulling traction. A tractor in reverse has much less grip than going forwards and it's the same principle that the grooves on a road tyre use to push water out from the centre of the tread to avoid aquaplaning.
Some brake discs also have directional arrows but technically their direction is irrelevant as they aren't dispersing anything. They will bed in whichever way they point but a correct set for a dual disk should have arrows pointing in the direction of rotation on both discs. A dual set should be a matched opposite pair.
I would only worry if an MOT tester spotted it and got pedantic but they don't look that closely do they?

[MrGrumpy]

That's correct. All bike tyres are labelled front or rear, or have an F or R in the code. The arrow always points in the direction of rotation which is clockwise when viewed from the offside (right hand).

I think I see...on the Michelins, the arrow points clockwise, which is towards the rear when viewed from the offside, despite unhelpfully having the word 'Front' by the arrow!

A little bit of knowledge is a dangerous thing!!!

[TmaX9]

The arrow doesn't point to the front just indicates the direction of wheel rotation so clockwise from the right and anti-clockwise from the left. The reason tyres are labelled front or rear is that really old tyres were the same width and rim size for both wheels, but modern tyres are designed differently for each wheel so are marked accordingly. A few modern small size tyres are universal and can be fitted front or rear and if there are no direction arrows marked on the tyre it doesn't matter which way it's fitted either.

On the subject of the red spots, all my current tyres have them next to the valve, but some years ago one fitter, who was an experienced racetrack tyre supplier and fitter told me they should go opposite the valve. He said the spot represented the heaviest part of the tyre, so if fitted opposite the valve, counterbalanced the valves weight. He fitted a pair of Pilot Sports like that for me and they required hardly any balance, but the same wheels now with the spots next to the valve, as that's how other fitters say it should be, have hunks of lead strip attached, so who is right?