Speed of steering?

[snerkler]

I've just tried out the ESA in 2-up rather than 1-up plus luggage. I'm obviously sat a little higher, and the rear shock doesn't soak the bumps up as well, but what I also seem to have noticed is that the bike seems to turn quicker, as though the steering is more precise. Is this my imagination or is this what you'd expect by increasing the preload, and if so why is this?

Cheers

 

[cookie]

if it raises the back relative to the front, the steering will get quicker

 

[Schtum]

Is this my imagination or is this what you'd expect by increasing the preload, and if so why is this?

Yes, it's exactly what you'd expect. Jacking up the rear of the bike, decreases the effective rake of the steering head which reduces the trail and hence the caster effect of the front wheel. The wheelbase will also be slightly shorter and this means that for any given angle of lean the radius of the turning circle will be smaller.

I used to run both my '04 & '07 GSes with almost maximum preload on the rear shock to achieve the same effect. ISTR that '08 and later bikes actually have a slightly steeper steering head and shorter wheelbase as standard. I run my current bike on 1+luggage all the time when ridden solo to achieve slightly quicker steering than the base setting.

 

[snerkler]

Yes, it's exactly what you'd expect. Jacking up the rear of the bike, decreases the effective rake of the steering head which reduces the trail and hence the caster effect of the front wheel. The wheelbase will also be slightly shorter and this means that for any given angle of lean the radius of the turning circle will be smaller.

I totally understood this

Thanks for the reply, bit over my head I'm afraid but at least I understand the end result

But, how can the wheelbase be shorter? Surely the distance between the wheels is fixed, and no amount of fiddling with the suspension will alter this?

 

[RickG]

The forks are at an angle, leaning backwards OK?

If the wheel slides up it has also to move to the rear, hence wheelbase reduces.

However, it's the angle of the forks that is the bigger influence as the steeper the angle (the more your arse is in the air) the faster bike will turn.

Choppers vs trails bikes for eg

Google "caster angle" as it's too long to explain here and pictures are worth a thousand words

 

[Wapping]

I totally understood this

Thanks for the reply, bit over my head I'm afraid but at least I understand the end result

But, how can the wheelbase be shorter? Surely the distance between the wheels is fixed, and no amount of fiddling with the suspension will alter this?

Happy reading:

http://www.gostar-racing.com/information/motorcycle_suspension_set-up.htm

http://www.calsci.com/motorcycleinfo/Suspension.html

http://www.carbibles.com/suspension_bible_bikes.html

http://www.sportrider.com/suspensio...spension_setup_guide/preload_and_damping.html

 

[snerkler]

The forks are at an angle, leaning backwards OK?

If the wheel slides up it has also to move to the rear, hence wheelbase reduces.

Aha, that makes sense. The wonders of physics eh

 

[snerkler]

Happy reading:

http://www.gostar-racing.com/information/motorcycle_suspension_set-up.htm

http://www.calsci.com/motorcycleinfo/Suspension.html

http://www.carbibles.com/suspension_bible_bikes.html

http://www.sportrider.com/suspensio...spension_setup_guide/preload_and_damping.html

Cheers, I'll read through this later