Quantcast

frame design-an effort

Bikael Molton

goofy for life
Jun 9, 2003
4,010
1,141
El Lay
I think Ridemonkey needs a thread where only Udi, No Skid Marks and Norbar discuss this kind of stuff FOR THE REMAINDER OF TIME.
 

freeriding

Monkey
Jun 5, 2011
138
1
in subject now, progressive is muchos better for me, cause it has much improved small bump compliance, and support in heavy hits.

it may seem a bit wallowy, but i think this can be easily fixed with some lsc.

the bike i own, has a fully linear/progressive lr, 2.33:1, and with a ccdb feels a ****ing beaut!
 
Last edited:

Steve M

Turbo Monkey
Mar 3, 2007
1,991
45
Whistler
to make it more simple:

the blue lr is progressive.

the red is regressive.

for the same bump, which do you think will reach easier 150mm of wheel travel???

red of course...

the same for 50mm wheel travel (since the starting LR is the same value for both)

View attachment 112241
The way you are defining "progressive" and "regressive" is a bit strange - standard nomenclature is that:
Progressive bikes have a leverage ratio that decreases as the bike compresses. Also called "rising rate" even though the ratio is actually dropping.
Digressive (some call regressive but this technically never happens) bikes have a leverage ratio that increases as the bike compresses, also called "falling rate" even though the ratio is increasing.

Please just stick to these rather than referring to a "regressive leverage ratio" as a leverage ratio that drops, it becomes unclear who's talking about what otherwise!

In any case - what you're talking about with the red and blue lines is only correct based on the assumption that both bikes are running the same spring and damping rates at the shock - which is an unreasonable assumption, because a bike with the red curve would run a substantially higher spring/compression curve than the bike with the blue curve, in order to prevent it blowing through travel and bottoming out all the time.

I believe what you may also be overlooking is the fact that percieved "harshness" is related strongly to peak force values at the tyre, which are not necessarily directly related to how much travel a bike is using, but more to do with how flat a force response vs time plot is. For example, a stiffer spring rate at the wheel can reduce the initial response of the wheel to the beginning of a bump input quite substantially, causing the wheel to accelerate relatively slowly initially, which then means that as the bike moves over the bump, the wheel needs to move the height of the bump in less horizontal distance (ie time), causing it to both accelerate faster, to a higher peak speed AND have more resistance per unit displacement of the suspension - causing increased harshness in both spring and damping. Being able to effectively lower the spring rate early in the travel by using a progressive linkage (decreasing leverage ratio) can greatly reduce this effect, whilst also providing a way to control the total amount of travel used at peak compression (aiding stability). Go too far with this concept, and the bike becomes unstable and wallowy, and runs into a "wall" at a certain point.
 

no skid marks

Monkey
Jan 15, 2006
2,511
29
ACT Australia
It is good to see these kind of discussions on RM again.
Yeah for sure, can be quite informative, and great to see different views on things. The debating on what's the best way to phrase the same thing is painful, but I guess necessary:think:
I'm curious to know what your current thoughts are on what is more ideal for DH Socket, Linear, or Progressive(leverage curve, not shock), and why. Or is that to broad a statement as different pivot locations, wheel paths, shocks and pedal induced anti squat change the equation to much? Do you think high speed rebound is an issue with progressive leverage curves?
 
Last edited: