R100S!

[Blackal]

To my way of thinking -

The relatively high CoG is countered by the rider using the inside leg as an additional prop.

I'm going out now - to try that on my GS, wearing rollerskates

If I don't report back within an hour - dial 999.


Al

[Corvus]

To my way of thinking -

The relatively high CoG is countered by the rider using the inside leg as an additional prop.

I'm going out now - to try that on my GS, wearing rollerskates

If I don't report back within an hour - dial 999.


Al

You're moving the c of g to the inside. According to Pythagoras that should lessen the angle of lean further. Although I believe that is true I also suspect there's a whole lot more to it as well.

Best use the roller skate just in case.

[Harry Lime]

Deleted

[Corvus]

Yep.


Oh, and, c of g. A motorcycle with a higher center of gravity requires less lean to maintain a given speed around a corner.

So if you're not keen on leaning and want to go quicker, buy a tall bike with skinny tyres

Counter intuitive stuff, this motorcycling. Counter steering, counter intuitive, but counter me IN, I love it.

H.

Cheers.

Yep, the high c of g and skinny tyre thang was my take on things too. A principle easy enough to get your head around when thinking about one tyre only. But two different widths on the same machine (as is usual) takes a bit of head scratching.

The difference in angle of lean between front and rear tyres is clear to see on your picture. But is that representative of road riding? I was under the impression that countersteer initiated the turn but once you're over the steering turns in the more expected way? But even if that is correct the two tyres are still not at the same angle of lean anyway, to my way of thinking. Don't know if you'd agree with that?

Then there are bikes, like trail bikes etc, with extremes of width differences plus diameter differences!

I'm not an expert. But I think if you look at a lot of road bikes with extreme differences between front and rear tyre widths, you'll see a proportionately bigger "chicken strip" on the front tyre than the back.

The big back tyre thing on a road bike is just "race chic", I believe. A racer needs to get as much traction as possible, particularly coming out of a corner. A bigger tyre gives a bigger contact patch (though there are other ways of achieving this). On the front though, the racer wants the bike to steer quickly, so fits the thinnest tyre which still gives sufficient grip.

I don't see many road bikes breaking traction coming out of corners though & when they do, it's more likely to be due to road surface than shortage of contact patch, methinks.

I'm lucky enough to own two bikes with identical chassis. One runs a 100/90 110/90 combination, the other a 110/90 120/90 combination (still OK with the rim sizes). The thinner tyred bike handles a lot more sweetly than the other.

H.

Very interesting. I agree with everything you have said. I've nodded in agreement after every paragraph.

Although you haven't ventured to give an explanation. Doh!

I ride two very different bikes so I get to feel exactly what you've said every time I swing a leg over the r100. I've just bought a Honda 250 RS and the tyres on that are similar width to a mountain bike! It needs work but I'm looking forward to getting it on the road.

Cheers

[Harry Lime]

Deleted.

[Corvus]

Although you haven't ventured to give an explanation. Doh!

Cheers

I refer you to (the now sadly deceased) John Robinson's "Motorcycle Tuning - Chassis" of 1990 - cost me £10.95 back then.

I could never do better.

I was trying to get my head around a Hejira framed Laverda Montjuic at the time.

If you're really into this, get a copy. But be prepared for some fairly big math.

This relatively simple stuff is covered pretty well in chapter 1. Then it gets serious........

H.

Thanks. You're a gent. I'm onto it.

[Corvus]

Although you haven't ventured to give an explanation. Doh!

Cheers

I refer you to (the now sadly deceased) John Robinson's "Motorcycle Tuning - Chassis" of 1990 - cost me £10.95 back then.

I could never do better.

I was trying to get my head around a Hejira framed Laverda Montjuic at the time.

If you're really into this, get a copy. But be prepared for some fairly big math.

This relatively simple stuff is covered pretty well in chapter 1. Then it gets serious........

H.

Chapter 4, pages 48 and 49 in "motorcycle design and technology" by gaetano cocco explains the principle in brilliant simplicity. Unfortunately it explains it showing only one wheel, so it doesn't answer my question. Trust me to be awkward! The book is very easy to access so I'll have a scout deeper, in case it is covered in a later chapter.

I have now received my John Robinson book as you recommended. This one may take a bit more time!

Cheers.

[Corvus]

Although you haven't ventured to give an explanation. Doh!

Cheers

I refer you to (the now sadly deceased) John Robinson's "Motorcycle Tuning - Chassis" of 1990 - cost me £10.95 back then.

I could never do better.

I was trying to get my head around a Hejira framed Laverda Montjuic at the time.

If you're really into this, get a copy. But be prepared for some fairly big math.

This relatively simple stuff is covered pretty well in chapter 1. Then it gets serious........

H.

Chapter 4, pages 48 and 49 in "motorcycle design and technology" by gaetano cocco explains the principle in brilliant simplicity. Unfortunately it explains it showing only one wheel, so it doesn't answer my question. Trust me to be awkward! The book is very easy to access so I'll have a scout deeper, in case it is covered in a later chapter.

I have now received my John Robinson book as you recommended. This one may take a bit more time!

Cheers.

Chapter 8 - interaction between ground and motorcycle through the tyres. Page 121 . In the above mentioned gaetano cocco book.

Relevant extract:

"When we lean the bike over, the contact patch shifts to the inside of the curve...... This fact, along with the difference in the two wheel sections, makes the direction of the bike opposite to the one it needs to go around the corner, requiring you to turn the steering more in order to keep the bike on the proper cornering path. This is another reason why a bigger tyre width leads to less maneuverability."

There is a diagram also, but I can't show that.

Let's see what I can fathom from the JR book.

Cheers