Sheldon Brown v Chris Boardman, who's right

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  • Sheldon Brown v Chris Boardman, who's right
  • Premier Icon mtbfix
    Subscriber

    Presumably a grooved tyre has slightly more contact area and more deformable edges so grip may be enhanced.

    Chris Boardman was very careful with his words. He said something along the lines of ‘wider, treaded tyres give riders more confidence’. He didn’t actually say they had more grip.

    They are both incorrect.

    They are both incorrect.

    Because,????…come on, the suspense is killing me.

    fisha
    Member

    It depends on whether you consider aqua-planing the same as lowered friction due to a wet surface cause there is a film of liquid between the surfaces.

    I dont.

    To me, aquaplaning is where deep water is built up in front of the tyre at a speed faster than the water can move away from the tyre to allow it to cut to the surface below. This grip is lost. As sheldown says, its not realistically an effect that a bike would get into. The speed required is too high for a bike to acheive.

    A film of water which reduces friction is different. IIRC, sheldons thoughts are that the bumps in the road surface provide grip edges that a smooth tyre can purchase grip on. Water in the dips reduces the edge effect. So as mtbfix suggests, a light grooved tyre would then be surface that provides the edges from which t he grip can be purchased.

    mauja
    Member

    Not related to aqua planning but I thought most of the peloton had now decided wider tyres were actually faster in all conditions

    Reinventing the Wheel: The 25mm Revolution

    I_Ache
    Member

    I aquaplaned my MTB on Cannocks famous braking bumps! I was going bloody fast and it was really wet. I crapped myself.

    steezysix
    Member

    Slipping and aquaplaning are not the same – I’ve slipped while walking on wet pavement. Pretty sure I wasn’t aquaplaning when I did it. 🙂

    I_Ache
    Member

    Oh I definitely aquaplaned, I know what a slipping front wheel feels like.

    mattsccm
    Member

    Sheldon is right. CB is simplifying things for telly. Wide grippy tyres do feels nicer in the wet and that can count.

    FunkyDunc
    Member

    It would be impossible to aquaplane off road on braking bumps! You need a smooth surface.

    I assume road grooved tyres could create more friction as the groove basically creates 2 or more differing height contact points on the road and therefore cuts through crap on the wet dirty road surface.

    Ive used slicks in the wet plenty of times with no problems.

    mrmo
    Member

    mauja, read the article, most are still on 23’s not 25’s and it is not the tyre but the rim that matters. The rim decides what tyre makes sense.

    Jamie
    Member

    Because,????…come on, the suspense is killing me.

    Because George says so. That should be enough.

    avdave2
    Member

    So Sheldon tells us it’s impossible to aquaplane a bicycle so tread on tyres on the road is of no benefit on wet roads, in fact with a smaller contact area you actually loose grip.
    Chris Boardman on the Tour highlights tonight suggested that on a wet course some of the riders might opt for wider treaded tyres.

    So who’s right or are they both a bit right.

    Premier Icon supercarp
    Subscriber

    Not sure you go fast enough to aqua plane on a bike as i thought to process involved hitting standing water at speed which overwhelms the tyre tread causing the car to lift up and travel across the top if the water.

    since road bikes have such narrow tyres and low speed i cant see it is possible as the tyre would cut through the water not lift.

    dantsw13
    Member

    Aquaplaning speed is a function of tyre pressure.
    Speed = 9 x square root of tyre pressure in psi.

    So on a Mtb about 50 kt or 55mph
    On the road 90 kt or 100 mph.

    Premier Icon wwaswas
    Subscriber

    So on a Mtb about 50 kt or 55mph

    so I_Ache hit the braking bumps at 55mph?

    *chinny reckon*

    bencooper
    Member

    That formula doesn’t take into account lots of factors, like tyre width, tread pumping capacity or rider weight – I think there’s more to it than that.

    I_Ache – Member
    Oh I definitely aquaplaned, I know what a slipping front wheel feels like.

    Were you riding on slicks?

    dantsw13
    Member

    I Ache may well have “waterskied” through a deep puddle as opposed to pure aqua planing. Both cause brown pants!!

    ChunkyMTB
    Member

    This thread is screaming for TJ

    ChunkyMTB – Member

    This thread is screaming for TJ

    ^^ and GW (coughs).

    dantsw13
    Member

    Bencooper – the formula comes from my dayjob as a pilot. Yes, some other factors change it, but not much.

    If Anybody is bored try this! Aquaplaning article

    thomthumb
    Member

    wider, treaded tyres give riders more confidence

    boardman was right.

    Wider, treaded tyres give rides confidence because they think that’s what they need. Not because they’re better.

    you cannot aquaplane a bike. Riders feel confident on treaded tyres.

    The statements don’t contradict.

    Premier Icon gofasterstripes
    Subscriber

    Having ridden through some of the worst rain possible [Cornwall], I would confidently say, no it’s not possible to aquaplane.

    IMHO

    I think if you made a concerted effort with a huge entry hill and a specialist lake, it might be possible on a chunky tyred mtb, or better yet a fatbike, but road tyres are just too skinny to offer enough resistance to give sufficient lift.

    We need these fellas to try it:

    [video]http://www.youtube.com/watch?v=MAaOFfcwAlE[/video]

    sugdenr
    Member

    Road tyre tread is designed to allow a certain amount of water to be transported out of the way from a smooth surface when the tyre pushes into it, aquaplaning is where a tyre is overwhelmed by the volume of water and is in effect waterskiing on the water.

    MTB tread of course totally different, is designed to allow the tyre to dig in and grip on an uneven loose surface, a bit like studs on a snow tyre.

    A road tyre that is not aquaplaning but is loosing grip due to wet surface is merely slipping, technically it is probably experiencing hydrodynamic lubrication.

    To minimise aquaplaning on the road you probably want skinnier tyres – more concentrated weight will cut through the water better and less ‘ski’ area. The issue for TdF riders will be that they are not comfortable/experienced in sliding and their bikes like modern F1 cars are not designed for sliding, their high psi fast rolling tyres have a kife edge of grip in corners, so they want wider tyres to make their bikes more slip tolerant with a lesser kife edge of grip — and to make them feel more confident.

    That’s my tuppence anyway.

    avdave2
    Member

    [video]http://www.youtube.com/watch?feature=player_detailpage&v=EKymcCHCttU#t=1422s[/video]

    I wonder if he had tread on his tyres for this stage? 23:40, I don’t seem to be able to get it to link to a specific time in the VT

    clubber
    Member

    aquaplaning is not slipping. Slipping/sliding on a wet surface is just reduced friction between the road and the tyre due to a lubricant (the water)

    To aquaplane, you need to be going fast enough that there is a layer of water between the tyre and the surface – eg so that the tyre is no longer in contact with the road.

    To do that, you have to be going fast enough that the water does not move out of the way of the tyre fast enough so the tyre rides onto the water (effectively as though the water was a solid rather than a liquid). The speed for this is really quite high (as per the calculations above).

    klumpy
    Member

    The wider a tyre, the flatter its profile, and the smoother its surface, the more likely aquaplaning is. Road bicycle tyres are rounded profile and very narrow, can’t talk in absolutes but aquaplaning is unlikely.

    That said, compared to dirt tarmac has a not very progressive transition from grip to slide and wet tarmac is even worse, so a loss of traction is likely to be sudden and catastrophic. That’s why motorcycle racing in the dry tends to have more deliberate sliding than in the wet, when riders are more wary of approaching a narrower limit.

    Tread doesn’t just move water, it allows a tyre to heat up quicker (but wear faster) as the blocks get smoodged about. I understand they may also allow more progression in a slide as blocks deform before letting go and not all blocks on the road let go at once.

    clubber
    Member

    I think that blocks/treads causing heating of a tyre is not significant on bikes compared to motor bikes/racing cars where the loads and speeds are way higher.

    So Sheldon tells us it’s impossible to aquaplane a bicycle so tread on tyres on the road is of no benefit on wet roads, in fact with a smaller contact area you actually loose grip.
    Chris Boardman on the Tour highlights tonight suggested that on a wet course some of the riders might opt for wider treaded tyres.

    They’re both right.

    avdave2
    Member

    So can we actually conclude that it is not categorically proven whether tread on a road bike tyre on wet tarmac offers more or less grip than a tyre without?

    We know that we can’t actually ride fast enough to aquaplane and we know that some riders choose treaded tyres for psychological reasons. But we don’t know if they are actually increasing or decreasing their level of grip. Is that a fair summary?

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