Directional arrow on tyre

[King29]

A work friend took his bike for an mot. Mot bloke rang him at work as requested to report outcome and said he's failed it because directional arrow on tyre is going the wrong way?

Mot bloke wants £25 to take tyre off and put in on right way? does that sound legit or is mot place taking the mick? I wouldn't have thought it mattered and was there as a guide rather than YOU MUST DO THIS?

Can anyone clarify?

[MarJay]

It's dangerous to ride on a tyre with the directional arrow the wrong way. This is because the tread on the tyre is directional, and moves water outwards to the edges of the tyre with the forward motion of the tyre. If the tyre is on backwards, the water is forced to the centre of the tyre, basically forcing an aquaplane.

£20 is the usual ride-in ride-out tyre fitting price, so it's not excessive. Why bitch about it? The tester has him bang to rights.

I'm actually surprised you'd even go to the effort of asking about it, because surely the tyre direction arrow is there for a reason, and that's fairly self evident? *shrugs*

TL:DR, he needs to get it swapped, and the MOT tester is right.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[King29]

Fair enough, thanks for your help. I asked because I was not sure if it was an mot failure but your explanation make sense. Cheers.

[MarJay]

[colink98]

this was the result of my last MOT

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Date tested 13 June 2018
Pass
Mileage 75,077 miles
MOT test number 3580 3094 9302
Test location
View test location
Expiry date 13 June 2019
Monitor and repair if necessary (advisories):

Rear TYRE FITTED INCORRECTLY, DIRECTION ARROW WRONG WAY ROUND Dangerous

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So it wasn't a failure as of June 2018 but may have changed since then.
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PCX125 (stolen) - CBF600 (current)
Ride it like you stole it.
ride sensible and not like an idiot and you wont get 6 points in one week.

[Kawasaki Jimbo]

[kgm]

[Pjay]

If it's the front tyre and it has dual discs, maybe he's put the wheel on backwards?
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struan80 - I'll go first - satisfied tick 1

[doggone]

There seems some ambiguity about whether it's a guaranteed fail as tyre patterns aren't always so directional, at least on other vehicles.

[MarJay]

[Monkeywrenche...]

[Polarbear]

Is it not something to do with the drive as well. As in it's one way for a back tyre and the opposite if put on the front, or have I imagined this?
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Triumph Trophy Launch Edition

[Monkeywrenche...]

[Polarbear]

I was right, Avon roadrunners Showing my age now,

https://www.feked.com/images/detailed/38/IMG_8156-1000.jpg
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Triumph Trophy Launch Edition

[G]

[Pete.]

[weasley]

The tread on the front tyre is opposite to the rear too, because when leant over the front tyre clears water to the outside of the turn, so it is not pushing in inwards to where the rear tyre is about to arrive.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[doggone]

[iooi]

[weasley]

[Kawasaki Jimbo]

Tyres aside, I think the front wheels on both my bikes would fit either way but the ZX6R has an obvious directional arrow on one of the three spokes, and it is mentioned in the service manual. The R1 service manual makes no mention but I have found a subtle arrow on one spoke (3-spokes again) and the tyre fitter has matched it. I recall the ZX6R has a circlip on one side whereas the R1 bearing fitment is the same both sides, so the construction is different but they are both directional.

I guess this means the hub direction on at least these two bikes is important because the spokes are subtly designed to resist braking forces. Pjay's comment ("maybe he's put the wheel on backwards") might apply, although you'd expect the MOT guy to know. It could be that simple though.

Looking at drilling patterns I think some brake discs might also be directional.

[Pete.]

More likely the bearing seats are at different offsets so fitting the wheel backwards would move it off the centre line.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good