Serious AT question

Goodness me ..... !!


A skinny tyre will dig in. Probably the best example I can give you is aquaplaning. Think of a big wide fat car tyre hitting just a few inches of water hard - it will skim over the top of the water like a flat bottomed barge. A thin tyre will cut through the water and continue to make contact with the tarmac below.

Off roading is much the same - a skinny tyre on dirt will perform much better than a fat wide one.


On tarmac, the downside (in my opinion) is pretty much only contact patch. Jump jim and Arsey may not think so, but they ride like a pair of girls :D If you really are going to push the envelope on corner entry then front end feel is your whole world, and a 90/90 won't give you quite the confidence that a conventional front tyre will. (pretty subjective though)

For the benefit of that welsh Cock mellors I will now bang on about slow steering and stunt kites :D





This bend is just down the road from me. It's a good example of real road riding (as opposed to 1190 pannigale developed from the track riding..). If you swiftly take this corner, eyes into the vanishing point etc, a sports bike will want to come off line and follow your eyes. But I don't want that to happen. I want my eyes to steer faster than my bike! I want my bike in the above example to track that nearside hedge row and ..... almost under steer! I want it to be just slightly lazier than my brain and to catch up with it half a second later - like the kite tail!

If the bike BANG followed my eyes BANG every where I looked BANG :)D) ..... then long lazy lines are harder to achieve because every turn of the head and that moto GP inspired 17" front wheel with geometry that puts it under my bollocks will follow me.

Of course ... of course .... a 21" front wheel never has and never will win the IOM!! But for you and me, who play a more gentle serenade on the public roads, (not that gentle Arsey ... keep up FFS ..) then the laziness of under steer, has real benefits.

:thumb2

All very good but for Engineer, that doesn't answer his question which is why I was 'trying' to encourage him to work it out and non of that explains why my trial bike also has a 21" front ...... flippin Stite Cnuts indeed :D:D
 
So skinny tyres don't sink into mud or sand off road as much as fatter ones?

I guess trial and error have favoured, on balance, skinny for off road and fatter for road.

Anyway have to go out now I am on a promise :)
 
OK here's a stupid question then:blast

Why do you deflate your tyres in snow or mud to get better grip.....:nenau

Isn't it to spread the load over a larger area?
 
OK here's a stupid question then:blast

Why do you deflate your tyres in snow or mud to get better grip.....:nenau

Isn't it to spread the load over a larger area?

Off road a knobbly tyre clear it's tread better at lower pressures as the carcass will deflect more - or something like that ;)
 
OK here's a stupid question then:blast

Why do you deflate your tyres in snow or mud to get better grip.....:nenau

Isn't it to spread the load over a larger area?

Complies to the irregular surface, adds to the suspension (so it complies to the surface better..).
 
Speaking as an engineer I think skinny tyres on larger diameter wheels has to do with gyroscopic effect. A thicker tyre will weigh quite a bit more and have significantly greater gyroscopic resistance to changes in the rotational plane of the disc (wheel) which is effectively what is happening when you change direction on a bike. Off road is generally lower speed than on road so the advantages of grip and smoother ride outweigh the negatives of the effect so larger diameter wheels can be used. On road or on bikes designed to be ridden quickly with rapid changes of direction a smaller wheel reduces the gyroscopic effect considerably. If you don't believe me when you next take your front wheel off and get it spinning quickly while holding the spindle in your hands then try to tip the wheels plane of rotation.

Sent from my GT-I9505 using Tapatalk
 
Speaking as an engineer I think skinny tyres on larger diameter wheels has to do with gyroscopic effect. A thicker tyre will weigh quite a bit more and have significantly greater gyroscopic resistance to changes in the rotational plane of the disc (wheel) which is effectively what is happening when you change direction on a bike. Off road is generally lower speed than on road so the advantages of grip and smoother ride outweigh the negatives of the effect so larger diameter wheels can be used. On road or on bikes designed to be ridden quickly with rapid changes of direction a smaller wheel reduces the gyroscopic effect considerably. If you don't believe me when you next take your front wheel off and get it spinning quickly while holding the spindle in your hands then try to tip the wheels plane of rotation.

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Hold it right there !!! What the f*** do you think you are doing,coming on here and using facts and logic to explain something !!!!
 
Speaking as an engineer I think skinny tyres on larger diameter wheels has to do with gyroscopic effect. A thicker tyre will weigh quite a bit more and have significantly greater gyroscopic resistance to changes in the rotational plane of the disc (wheel) which is effectively what is happening when you change direction on a bike. Off road is generally lower speed than on road so the advantages of grip and smoother ride outweigh the negatives of the effect so larger diameter wheels can be used. On road or on bikes designed to be ridden quickly with rapid changes of direction a smaller wheel reduces the gyroscopic effect considerably. If you don't believe me when you next take your front wheel off and get it spinning quickly while holding the spindle in your hands then try to tip the wheels plane of rotation.

Sent from my GT-I9505 using Tapatalk

this ^^^

and also what giles said about manhandling a slower steering bike rather than trying to keep on top of a twitchy one.
 
Speaking as an engineer I think skinny tyres on larger diameter wheels has to do with gyroscopic effect. A thicker tyre will weigh quite a bit more and have significantly greater gyroscopic resistance to changes in the rotational plane of the disc (wheel) which is effectively what is happening when you change direction on a bike. Off road is generally lower speed than on road so the advantages of grip and smoother ride outweigh the negatives of the effect so larger diameter wheels can be used. On road or on bikes designed to be ridden quickly with rapid changes of direction a smaller wheel reduces the gyroscopic effect considerably. If you don't believe me when you next take your front wheel off and get it spinning quickly while holding the spindle in your hands then try to tip the wheels plane of rotation.

Sent from my GT-I9505 using Tapatalk

So smaller wider tyres are generally better for road riding, how 'twitchy' a bike feels has a lot to do with geometry too - my Ducati Monster had 17" wheels and not very fat tyres but had built in tendency to understeer a bit.
 
Under steer? Are you sure? Most Ducatis have pretty quick steering ....??!
 
Ran my tyres between 5 and 6 psi today, didn't stop me from coming home battered and bruised from a front tyre slipping down a bank and into a stream :blast
 


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