Ducati Monster Forum

if I could keep a 160 rear on a Carrozzeria that would be my wish (and probably me alone) So my newb question is....


what exactly ruins the flickablity of the bike?  is the flickablity based on the wieght of the bike movig from the left side to right side with minimal effort (width of the tire is shorter; less distance cover to get the bike left to right or vice versa)

or...

is weight the factor here...the effort to move the tire's weight and mass to make the bike lean left to right...

A multitude of things add up to make a bike "Flickable".  The first that I'll address is weight.  The rotational weight of a wheel is huge due to gyroscopic effects, but the overall mass of the motorcycle plays a big role as well.  The more mass an object has the more force that must be applied to it in order to change its direction. 

Secondly, a wider wheel means that when leaned over you are laying on a section of the tire that is further from the true center line of the wheel.  The best example for issues with this a goofy 300 series rear tires that people are compensating with. 

The amount of leverage provided by the handlbars can't be left out.  Shorter clip-ons have less leverage than longer tubular handlebars.  That is one of the big reasons a Monster feels so nervous to guys used to clip-ons.  You end up putting inadvertant control inputs because it is more sensitive.

And finally, geometry.  Rake, trail, wheelbase all play a big role.  The most common indicator to use is the steering head angle.  Steeper angles turn faster.

That is the cliff notes version.  You can spend a career studying this stuff.

The biggest difference in flickability is how hard you push on the bars! No joke.

Im a pretty big guy, and fairly strong. A few years back, I had Doug Polen ride my bike. He comes in with one of the clip ons turned foreward about 40deg. I asked HOW he did that, when I had been riding that bike for 6 months at the track and on the street, and Im about twice his size. He replied that he was pushing the bars "AS HARD AS I CAN" going from side to side. Changed how hard I push on the bars for SURE.

Second biggest thing would be tire profile. You can have a 140 rear that is super round, vs a 190 rear that is very triangular, and the 190 rear will flick faster, and work better. If you look at the profile of the Pirelli or Dunlop race tires, they are almost a V is cross section when mounted.

And lastly, its the nut that holds the handlebars. If you stand on the pegs, the bike flicks, sit down and its slow. Move your body to the inside of the bike before the corner, and it flicks alot easier. Proper body position plays a huge roll in how the bike handles.

I have to disagree with DW about the nervous feeling of the older Monsters tho, A big part of that is due to the really poor weight distribution F/R. The bike was a hugely poor design for the light weight 2V motor, and it made the front end feel like crap when pushed.

Pretty much every bike out there today (I mean real bike, not a HD) has a geometry that alows the bike to flick and turn in much quicker than an average street rider can deal with. (Go ride a GL1800 if you want to see a big bike FLICK) the rest really comes down to the rider.

Will

When I read this, my brain had to reboot. I was trying to figure out how the top triple nut would have a drastic effect on handling... Then I realized I'm a moron. You meant the pilot.   [bang] [bang]

ROFL... Well it COULD have a huge effect, but not wuite what I had in mind! lol

The bike knows JUST what its doing, and what it needs to do, its the rider that screws it up most of the time!

Will

the 160 tire is def. the wrong size for the 5.5" CZ wheel.

a 170 would fit, but as mentioned...you would be better off finding a 180 with a more triangular profile that turns in quicker (front tire too)

i think weight is a big factor in the way the bike feels turning too.
M750 with mag marchesini wheels changes direction like a dream

Weight distribution (top to bottom) makes a pretty large difference too.  I was reading a thing on Erik Buell and how he wanted to make all his bikes with the lowest center of gravity possible.  It's the same principle as a figure skater doing a spin (I'm sure that's the technical term).  With their arms and/or leg out they spin slower and as they bring their weight closer in to the axis of the spin they spin MUCH faster.  I ran just an open udder for a while maybe a thousand miles into owning my monster (first bike) and I almost drove off the road the first turn I took just because the bike was so much more eager to lean over.  They don't put 190s on race bikes for no reason and short of getting yourself an exbox, a well profiled wider tire will probably be your best bet.

The Ebox kills the motor, so why bother! lol

You brought up the race end of things Jarvicious, and that bears good fruit in this topic... If the smaller tire was the key to flickability, you would see 160's on  racebikes world wide..

in AMA we have run as big as a 210/65/420 in recent times but the norm is pretty much a 190 or 200 rear right now...

like retrosbk said, it's not about the width, it's about the profile.

the reason they put 190s (and 200s) on racebikes is because it gives them lots of surface area on the side of the tire.