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hi!

 

sorry for my english i’m in italy.

 

i ride bikes by many years, sometimes track.

 

i’m able to knee down, but i’m not a fast rider.

 

i’have searched extensively on web, read many books,

 

but still haven’t a answer to my question.

 

 

when i’m cornering with my bike,

i countersteer, and bike lean,ok.

 

but when leaned, i feel that handlebar, try to push against hand,(turn side, internal side)

 

i’m trying to understand the influence of suspension setup on this behaviour.

 

i think i  understood, that if the front end is lowered (reducind preload on fork spring or lowering fork tube in triole clamp)this behaviour is pronounced

 

instead if rise front end i fell this nearly gone,

 

i’m wrong?

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Your observation is correct. Lowering the front end increases the instability of the bike. Part of stability is the bike acting neutral while leaned over, a phenomenon that you described. Neutral means that it leans only when the rider countersteers and that it requires little or no effort from the rider to remain leaned over.

As the geometry is created by the full suspension it behooves us to consider the shock. A good suspension tuner will create an ideal height for the shock. Depending on the model of the bike they can many times add a few millimeters to the stock height. That raises the rear, creating the same type of geometry change as lowering the front. As they do this they make a judgement and avoid making the shock too high. Otherwise the bike will become unstable, fall over too easily, and require work to keep the bike leaned, the same problem that you experienced from excessively lowering the front. 

A benefit of setting the fork at or near the recommended height and lengthening the shock is that the bike will have the most road clearance possible.

It would be educational to hear from the riders and coaches here with regards to making any such compromises in the bike's stance for competition.

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In general, lowering the front will make the bike easier to turn into the corner, and cause it to hold a tighter line. It can also make the bike less stable - more steering response can make the bike feel "twitchy" and lowering the front too much can cause the front end to shake or wobble entering a corner. John (above) is correct that the rear shock or ride height can affect this also - is your rear suspension set much stiffer (or higher) than the front?

You may also want to take a look at the profile of your tires, and the pressures. A cold race tire can feel (and is) very stiff; when leaned over it resists compressing and tends to try to spring back into shape which makes the bike want to stand up, so the rider has to keep pressure on the inside bar to stay on line. If you are using racing tires with a V profile, or using full race tires or stiff track-day tires but not riding fast/hard enough to warm them up, the tires could be causing the feeling you describe. Possibly having the tire pressure too high could cause a similar problem. 

Another thing that makes the rider have to maintain pressure on the inside bar to keep the bike on line is trail braking. If you are applying the front brake while the bike is leaned over in a corner, it will tend to make the bike want to stand up, and you would have to press on the inside bar to counteract that.  (Watch A Twist of the Wrist II for a great CGI video explaining why this happens.)

Another potential cause for having to press on the inside bar is... pressure from your OTHER hand on the outside bar. Make sure you aren't unconsciously pushing on the OUTER bar, forcing yourself to have to counteract that force by pushing on the INSIDE bar. Check your body position to make sure you are not pushing accidentally on the bars, trying to support your body. Riders do this more commonly than you might think.

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ok i understood 

but the thing that has surprised me,

is that i was thinking that, when one say:

with more trail, fork more upright,bike has more stability, was meaning that the bike want stay more upright and not cornering, but instead i see that it is easy to go down without press on imternal handlebar.

 

i try to explain better,

on same bike ,with lower front,it has less  trail, fork more upright, it should be more flicker more unstable,

instead it try to stand up itself and in cornering it has to be pushed on internal handlebar

 

what intry to explain is that i understand why it physically do this,

but i don’t understand why it is sayd more unstable?

a bike that itself try to stand up, it shouldn’t be colled more stable?

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Less rake and less trail would make the motorcycle easier to steer into the corner, the front wheel will respond more quickly to steering change

"More stable" generally refers to straight-line stability - the bike is less reactive to accidental steering inputs, steering from wind buffeting or rider movement, less prone to head-shake or over-reactions to bumps. It is more resistant to initial turn-in, takes more steering pressure to start the turn.

Referring to "stable" IN a corner would usually just mean the bike holds a line (doesn't drift wide or fall in), the term "stable" would not usually mean that it wants to stand up IN the corner.

It is possible that front end instability could cause the bike to want to stand up - if the front is overloaded, shaking, or having tiny slide-and-catch motions from the tire, it could make it want to stand up because the varying load on the tire could create a countersteering effect. Or you could be experiencing the front pushing which makes you have to steer it in more to compensate for the bike not quite following the line you want.

Before you get too far into suspension or geometry changes, I would take a very close look at tire profile and tire pressures.  Is your front tire worn? If you have a lot of highway miles, the tire can become flattened in the center, and not provide a stable shape for cornering. It is called "profiling" when the tire gets worn unevenly and it can DEFINITELY cause the bike to want to stand up in the corner. Or, a tire that is too stiff (because it is cold, for example) can resist leaning over, and a tire that is too soft (low pressure) can flatten out and cause a counter-steering effect, too.                                   

 

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If I understand you correctly, Gianco, you must continue to countersteer all around every corner, otherwise the bike will want to straighten up. Is that correct?

My NT650V was like that with a Bridgestone BT30F on the front, demanding a very noticeable constant push on the inside handlebar grip. When I replaced it with a Maxxis M6029 Supermaxx, the bike actually went in the other direction, now demanding a miniscule pressure on the other end of the handlebar, otherwise the bike would slowly tighten its line.

I have had similar, although not quite as dramatic, differences on other bikes with other tires as well. As Hotfoot said, tires definitely have an impact on this matter.

 

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