My motorbike runs at 36psi front 42psi rear so the front tyre will break loose at 62MPH which is why we have tread to channel the water away.
And does that mean grip will be significantly reduced at say 50mph, or is there a sudden transition at 62?
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62 is the speed at which the water builds up in front of the tyre faster than the tyre can drain it so yes, you suddenly go from contact with the road to no contact.
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Any loss of grip on the front end of a motorbike usually ends expensively, painfully, or worse. To lose total front end grip at speed doesn't bear thinking about.
My old motorcycle instructor who was a police motorcycle instructor for 15 years, and RoSPA advanced rider reckons recovery from a loss of the front end slide comes down to nothing more than pot luck. He drilled this into us on the CBT, and it remains the only thing I ever heard him say a rider could do nothing about (apart from not get into the situation in the first place). It always stuck.
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Cue the Gates of St Peter.
AE: " I shouldnt be here, gmac told me I was ok up to 62 mph. I was only doing 58 round a gentle bend when i lost the front tyre in a very deep river of water running across the road, came off and went unmder the artic coming the other way."
St peter "Dont wory GMAC is due here soon he can explain where it all went wrong"
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How would slicks behave on a slightly muddy road or where there are wet leaves or a bit of oil mixed in with the water? I've never ridden a motorcycle but it's obvious to me that on a public highway slicks would be dangerous - Even on a pushbike bald tyres are more likley to slip in the wet than treaded ones. Try it and see.
Also, aren't racing slicks made of a special soft compound that wears very quickly? So if you used slicks on the road you'd need to carry a spare tyre on your bike!
Edited by Sofa Spud on 13/11/2009 at 12:05
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Even on a pushbike bald tyres are more likley to slip in the wet than treaded ones. Try it and see.
Have you tried it to see? I currently have a bald tyre (brand new continental, bald by design) on the front of my bike. It didn't come with any warning to say dont use in the wet. What you are saying goes against everything that the cycling experts say.
All the cycling guys seem confident that a bald tyre will grip better, even in the wet. I'm curious as to at what point does it make sense to have treaded tyres for the wet. Certainly for cars it makes sense to have tread, motorbikes fall somewhere inbetween.
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How does the shape of the tyre effect the calculation? Surely the sqaure profile of a car tyre is going to behave differently to the curved profile of a bike tyre?
Trying to get my head around how the shape of the contact patch would effect it. For example isnt a wide profile car tyre more likely to aquaplane than a skinny car tyre? I think there was a thread on here a while back about that.
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Never seen them stop for wet tyures on the Tour de France. . . .
They ride at 80kph plus down some of the hills.
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How does the shape of the tyre effect the calculation?
Contrary to what would apparently make sense, it has no affect.
The calculation given is as applicable to a 747 landing in pouring rain as it is to your pushbike. The size of the contact patch or weight of the vehicle doesn't come into it.
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Aquaplaing can commence when the speed reaches 8.6 times the Square root of the tyre pressure. Not knowing much about bike tyres I'd hazard a guess that we could be talking about as little 60mph. Added to motorcycists justified comments about the slipperiness of oil patches at traffic lights and diesel spillages anwhere I would think a bit of tread would be a good thing
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There's repeated reference to tyre pressure in this thread.
As I understand it, it's the pressure the tyre exerts on the road surface, not the air pressure inside the tyre!
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There's repeated reference to tyre pressure in this thread. As I understand it it's the pressure the tyre exerts on the road surface not the air pressure inside the tyre!
If BB tom is cottect then I can understand how the shape and size of the contact patch would no longer matter.
My gut feeling is that BBT is correct.
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Added to motorcycists justified comments about the slipperiness of oil patches at traffic lights and diesel spillages anwhere I would think a bit of tread would be a good thing
I can see how tread is good at dispersing water at high speed, but how does it help grip on slippery surfaces such as oil?
Edited by Focus {P} on 13/11/2009 at 14:19
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how does it help grip on slippery surfaces such as oil?
Thankfully it's never happened to me, but judging by the people I've spoken to who have hit diesel spills on roundabouts, even with brand new tyres on, it doesn't. :-(
Edited by DP on 13/11/2009 at 14:23
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>> how does it help grip on slippery surfaces such as oil? Thankfully it's never happened to me but judging by the people I've spoken to who have hit diesel spills on roundabouts even with brand new tyres on it doesn't. :-(
My thoughts exactly - if you hit an exceptionally slippery surface such as mud, oil or diesel, you are going slide no matter what type of tyres you have.
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I don't know Focus but motor cyclists complain about it a lot!
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I don't know Focus but motor cyclists complain about it a lot!
Sorry AS - I know oil etc. is a nightmare for 2 wheelers, but what I don't understand is how having tread on your tyre helps you to cope with it.
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If you look at the typical road bike tyre which is 23 or 25mm in section, the contact patch (because of the curved profile) is smaller than the tread blocks between the grooves on a car tyre, so it is narrow enough to disperse water on it's own.
Another way is to ride a treaded road bike tyre through a damp patch and then look at the pattern it leaves on the dry. There is just a single unbroken line with no dry line from the tread grooves. Any tread on the tyre is too shallow to have any water dispersal effect, it is little more than marketing bling.
A road biker who gets on one of those hideous MTB's with knobbly tyres is usually scared to death the first time he banks into a corner, they are horrible on tarmac and the lack of grip can be felt straight away.
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Neither do I Focus! I suppose sipes and treads that can lift water off a road or break thru a film of water might achieve something with an oil/water mixture? Re comments on knobbly tyres ISTR a news item about somebody who went up the M1 on some trail bike and set fire to his rear tyre! All that flexing of the tyre I suppose.
Edited by Armitage Shanks {p} on 13/11/2009 at 15:05
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The most infuriating thing about off road MTB tyres on tarmac is that horrible brrrrrrrrrrrrr noise.
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The most infuriating thing about off road MTB tyres on tarmac is that horrible brrrrrrrrrrrrr noise.
And the fact that they knock about 10mph off your speed. Mountain bikes are one of the most successful consumer cons of the past 25 years, with apologies to those who do actually use them off road.
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Shoes with smooth, untreaded rubber soles are much slippier in the wet than ones with a tread on. When I was a boy, the rubber soles of my Clarks black school shoes used to wear smooth and they used to be all slippy in the wet. My dad used melt new corrugations into the soles with a red-hot poker, and then the shoes were grippy again.
If this is the case for shoes, it must also be the same for motorbike tyres, except more so!
Edited by Sofa Spud on 13/11/2009 at 15:29
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I have a Claud Butler Cape Wrath MTB which I use primarily for leisure. I'm not a serious MTB'er, but I do enjoy heading out with the dog of an evening just to muck about. A lot of my use is across dirt trails and through woodland etc. The bike came with fairly aggressive looking "Kenda Klaw" tyres which are fabulous on the rough stuff, but irritating as hell off it. I will be looking for some hybrid tyres when these wear out (too much of a skinflint to bin tyres with wear left in 'em). It is fun to chuck it about on dirt though, and I wonder how much of a compromise the hybrid tyres are. I'm not a professional or anywhere close to it, but grip is grip, and more importantly lack of grip = pain. ;-)
Where I ride is a mix of trails, and two beautiful 800m disused tarmac runways with associated taxiways and aprons. It really is a mix of terrain which makes tyre choice difficult.
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A smaller diameter Maxxis Highroller might be better. Run at high pressure they are not too bad for a 'proper' off-road tyre as the centre line has a fairly continuous run of knobs. Very stable and controllable off road as well.
Worth a look, but possibly still too biased for off-road.
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a cycle may need a high speed to aquaplane on normal road surface
but thats not all cycle tyres are for, they are also there to grip when driven through a patch of mud or similar
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but thats not all cycle tyres are for they are also there to grip when driven through a patch of mud or similar
But the treads on a cycle tyre will not provide any grip on a patch of mud or similar.
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oh yea they do, it may not be as much grip as you would like, but its a lot more than a slick, and accident rates would go through the roof if slicks were used routinely on cycles
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oh yea they do it may not be as much grip as you would like but its a lot more than a slick and accident rates would go through the roof if slicks were used routinely on cycles
Slicks are already routinely used on cycles. Take a look at the road bikes in Decathalon, they all come with slicks.
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Riders in Paris-Roubaix use slicks. Much of the race is run over cobbled roads which are covered in mud, maybe they just haven't cottoned on to the need for tyre treads yet?
Bloomin' foreigners, eh ;-)
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My 2 main road-bikes are: a Claud Butler Levante flat-bar "hybrid", mostly used for commuting to-from work (about 40 miles or so) and a Felt F95 racer, mostly used for mild racing/long hacks.
The CB has 23mm treaded tyres, and the Felt 21mm slicks. In a straight line in the dry or wet there's no difference in grip whatsoever, and more speed with the Felt. Different story if you are turning on an uneven or slippery surface in the wet, like cobbles or high road-markings, where the treaded tyres offer a bit more grip somehow. I'm still trying to work out why exactly,
but suspect its to do with the profile of the side-walls.
My mountain bike (ancient but venerable Marin Mt. Vision) has Panaracer Fire XTs front and bike- very knobbly, and extremely slippery on a wet paved surface if turning- IF! you have a lot of pressure in the tyres (>45psi). Dropping the pressure for a wet road makes it grippier but of course massively increases the rolling resistance. Much harder work.
tt
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Aquaplaning is out of the question for nearly all cycles. Therefore the issue for grip seems more likely to be compound rather than tread. Having high hysterisis, silica enhanced rubber in close contact with tarmac gives ample grip, assuming correct pressure. Slick tyre makers for bikes are no doubt well aware of the issues. As for smooth shoe soles giving rise to slipperiness, this again is more likely to be the choice of compound.
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The CB has 23mm treaded tyres and the Felt 21mm slicks. In a straight line in the dry or wet there's no difference in grip whatsoever and more speed with the Felt. Different story if you are turning on an uneven or slippery surface in the wet like cobbles or high road-markings where the treaded tyres offer a bit more grip somehow.
The lack of grip when you are turning is down to the 21mm tyre, not the lack of tread. 23mm is the universal choice for road racing, 21s are the territory of time trialists and track riders.
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>> >> How does the shape of the tyre effect the calculation? >> Contrary to what would apparently make sense it has no affect. The calculation given is as applicable to a 747 landing in pouring rain as it is to your pushbike. The size of the contact patch or weight of the vehicle doesn't come into it.
Wikipedia says otherwise:
"The longer and thinner the contact patch, the less likely a tire will hydroplane. Tires that present the greatest risk are wide, lightly loaded, and small in diameter. Deeper tread dissipates water more easily."
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