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Originally posted by Andy8982
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For the tightest turning radius at any speed you need the maxium lean angle you can sustain (as far as you can go without falling over in the corner). A lot of this is set by the tyres - but there's a lot of things going on in the chasis that affects the load the tyres see.
The total weight affects the cornering limit of the bike (grip limit as described above).
Additionally there's two types of weight. Unsprung weight and Sprung weight. How the weight is divided between them also greatly affects performance and so turning radius.
In short you want the unsprung weight as low as possible. Is essentially is a measure of the wheel/swing arm weights. Which affects rotational masses/moments of interia - which influence braking, acceleration, and rate of lean angle change (turning 'in' rate of the bike)
For the quickest corner you need a bike that want to tip in fast and has no resistance to direction changes (Inertia).
Sprung weight can be balanced out by suspension springs, but what you have to realise is that as you get into steeper lean angles more and more of the cornering load is carried by the chassis and swing arm. (If you don't believe me - think about where the suspension spring is at high lean and think where the weight of the bike is trying to go - straight down.) This acts to 'bend' your suspension rather than compress it.
To make the bike corner well you have to design to the cornering load and allow a certain amount of flexure of the chassis to suit. This is easy to do with low sprung weights but steel framed bikes tend to have high weights and very limited flexure in the chassis.
This is made worse by steel framed bikes having a tendency to have lower end/cheaper suspensions so amplifying the issue.
All this means that where chassis flexure would allow a bit of give in the cornering load without transmitting it to the tyres, steel (heavy) frames act like a welded rod and so when combined with the heavier weight overload the tyres quicker, so limiting your corner radius.
The total weight affects the cornering limit of the bike (grip limit as described above).
Additionally there's two types of weight. Unsprung weight and Sprung weight. How the weight is divided between them also greatly affects performance and so turning radius.
In short you want the unsprung weight as low as possible. Is essentially is a measure of the wheel/swing arm weights. Which affects rotational masses/moments of interia - which influence braking, acceleration, and rate of lean angle change (turning 'in' rate of the bike)
For the quickest corner you need a bike that want to tip in fast and has no resistance to direction changes (Inertia).
Sprung weight can be balanced out by suspension springs, but what you have to realise is that as you get into steeper lean angles more and more of the cornering load is carried by the chassis and swing arm. (If you don't believe me - think about where the suspension spring is at high lean and think where the weight of the bike is trying to go - straight down.) This acts to 'bend' your suspension rather than compress it.
To make the bike corner well you have to design to the cornering load and allow a certain amount of flexure of the chassis to suit. This is easy to do with low sprung weights but steel framed bikes tend to have high weights and very limited flexure in the chassis.
This is made worse by steel framed bikes having a tendency to have lower end/cheaper suspensions so amplifying the issue.
All this means that where chassis flexure would allow a bit of give in the cornering load without transmitting it to the tyres, steel (heavy) frames act like a welded rod and so when combined with the heavier weight overload the tyres quicker, so limiting your corner radius.
My brain feels like how a pretzel looks now......
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