Quantcast

Suspension Kinematics Video Series

Happymtb.fr

Monkey
Feb 9, 2016
829
217
SWE
Thanks for the detailed answer, Hugh!

You're absolutely right about the 4 bars being enough to dissociate AS and AR. I was confused and meant dissociate AS from pedal kickback. My bad!

About the high pivot bikes with idler, the PK can be very low, and even negative for some gears, but the chain growth can be quite large. This combined with today's giant cassettes would require some longer derailleur cages, I imagine?
 

hmcleay

i-track suspension
Apr 28, 2008
116
102
Adelaide, Australia
Thanks for the detailed answer, Hugh!

About the high pivot bikes with idler, the PK can be very low, and even negative for some gears, but the chain growth can be quite large. This combined with today's giant cassettes would require some longer derailleur cages, I imagine?
PK relates to the chain growth of the 'tension' segment of the chain from the Chainring through to the cassette.
With a high-pivot, there's more AS built into the linkage kinematics (I call it 'Natural AS'), meaning that you need less (or negative) chain growth to get decent Total AS figures. So yes, PK can be very low or even negative for high-pivot designs.

The need for longer derailleur cages only becomes necessary if the overall chain growth (tension segment plus return segment) is significantly greater than that of a regular bike. Because with a high-pivot design, we usually have less chain growth in the tension segment, we can get away with having more chain growth on the return segment, without needing special derailleurs.
Most high-pivot designs do have a pulley on the return segment, to help reduce the chain growth there. And it seems that is sufficient to have it work with a regular derailleur.
 

hmcleay

i-track suspension
Apr 28, 2008
116
102
Adelaide, Australia
Hey guys,

The next video is up.
I wanted to fit Horst Links into this episode too, but ran out of time. I was even hoping that this episode would be shorter than the last one... but I failed. I'd rather have long boring videos that cover everything, than gloss over some important things.

What's the consensus so far? (all of the following answers are correct):
(a) I already know this stuff.
(b) I don't understand what you're talking about.
(c) I don't care about this stuff and just enjoy riding my bike.
(d) I don't have 30mins spare.
(e) This is interesting, but can you focus more on [insert sub-topic here].

Cheers,
Hugh.

 

Jm_

Turbo Monkey
Jan 14, 2002
9,036
1,460
AK
Hey guys,

The next video is up.
I wanted to fit Horst Links into this episode too, but ran out of time. I was even hoping that this episode would be shorter than the last one... but I failed. I'd rather have long boring videos that cover everything, than gloss over some important things.

What's the consensus so far? (all of the following answers are correct):
(a) I already know this stuff.
(b) I don't understand what you're talking about.
(c) I don't care about this stuff and just enjoy riding my bike.
(d) I don't have 30mins spare.
(e) This is interesting, but can you focus more on [insert sub-topic here].

Cheers,
Hugh.

Man I love that we have progressed far enough to be able to analyze this and it's not just some company's bullshit marketing. :thumb:
 

Happymtb.fr

Monkey
Feb 9, 2016
829
217
SWE
Nice Hugh, much better sound this time!
Keep them coming!

Any thoughts about commercializing custom rockers? :D
I am running a Devinci Django with a rocker from the previous generation of Troy. It changes the motion ratio from nearly flat to around 25% progression and also boosts the rear travel from 120 to 130mm. I can now run a coil shock with some limitations :
- the motion ratio is quite low with 130mm of travel for a 44mm stroke so that it require a high spring rate
- the progression might not be nearly enough to get a relatively good sensitivity at the beginning of the stroke and bottom out support (I realise that I am asking for a lot from 130mm of travel)
- the bb height is now somewhere in a no mans land which is too low for 27.5 wheel and too high for 29 wheel (the bike is a 29er stock)

A new rocker would easily help for the bb height, but I wonder if it could help with the progression?
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
15,859
955
01776
D for me. No offense, I just have kids that suck up all my time and I usually end up watching netflix when I have 30 minutes of downtime instead.

I do like that you are picking up on "natural antisquat" from high pivot designs. I always felt like brooklyns pedaled well, even though they have virtually zero quantifiable antisquat. Then switching immediately to a concentric BB pivot bike, which had virtually the same AS characteristics, pedaled so much worse. I realized it must be something in the way the rider's weight was cantilevered onto the pivot and therefore into the suspension system, but nobody has ever looked at it as a quantifiable and important value. It is certainly interesting to see all of the high pivot bikes coming out of the woodwork these days.

As for DW and axle path- none of his bikes have ever had anything to do with axle path other than manipulating AS figures, and he's never tried to sell a bike with a different axle path. Now that he's selling a fork with an adjustable axle path, he is concerned with it.