MTB rear suspension fundamentals

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MTB rear suspension fundamentals
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flag andrextr
Posted: Dec 19, 2015 at 9:12 Quote
Hello guys!

Just wanna to share my video about the basic theory behind rear suspension / linkage.

Topics covered in the video: Leverage ratios (LR), LR variation & progressivity, suspension forces and shock (air & coil) forces.


Sorry for my portuguese accent Big Grin
Hope you enjoy it.
flag galuska
Posted: Dec 28, 2015 at 17:58 Quote
Hy mate!
Very amazing vids! Keep them coming!
I was always excited about suspension designs and i am drawing some when i have time but i havent understood the leverage ratio until i saw these vids. Thank you!
flag andrextr
Posted: Dec 29, 2015 at 8:53 Quote
You're welcome! More videos will come in the next weeks Wink
flag seanondemand
Posted: Dec 29, 2015 at 9:22 Quote
This is some great stuff man, props.
flag andrextr
Posted: Jan 4, 2016 at 13:51 Quote
Hi guys! Check my 3rd video.

The reason why you shouldn't use pre-load in your coil shocks and forks.


Bye Smile
flag andrextr
Posted: Jan 11, 2016 at 13:38 Quote
4th video !!

Which is the best suspension system in the market? Is it FSR? VPP? Singlepivot ? Check it out !
flag galuska
Posted: Jan 11, 2016 at 13:45 Quote
Awesome again!
What type of app do you use?
flag andrextr
Posted: Jan 11, 2016 at 13:48 Quote
Linkage software.

http://www.bikechecker.com/

You can try the demo with limited features, for 30 days.
flag ManiacInBlack
Posted: Jan 11, 2016 at 17:59 Quote
I'm interested in your opinion, axle path, relevant or not Salute
flag andrextr
Posted: Jan 12, 2016 at 6:19 Quote
Hi !

In my opinion axle path is relevant, but not in the way people think it is. The actual shape of the axle path its not the most important charactheristic of the rear suspension. Leverage ratios, anti-squat, pedal kick back and so on, are more important in my opinion. The ideia that axle path is important cames from the marketing myths of VPP showing the mythic "S" shaped rear paths. Which is false! However, the shape of axple path can influence how much the chain grows along the travel. And chain growth is directly related with pedal kick-back and anti-squat. Therefore, everything is linked together in the system. It's in my plans to address this issue in a future episode in a comphreensible way Smile

Meanwhile check this article:
http://www.santacruzbicycles.com/en/us/news/344

Bye Smile
flag galuska
Posted: Jan 12, 2016 at 7:26 Quote
My opinion: Axle path: Influence the activity of the suspension, if the axle path points backward then it will be very active and sensitivy unless you are pedalling. If you are pedalling or just standing on the pedals than the chaing growth would pull your pedals up but you are pedalling or standing so they cant move up so itt will hamper the suspension. This behaviour also occurs with a straight upward axle path. But thats good because the pedalling will be more efficient. It is good on xc, trail, Am and on enduro bikes. On dh bikes the industry would like to eliminate this but this depends on the racers too. Somebody likes if the pedalling is efficient. It also depends on the track.
See: Commencal dh bike or:http://m.pinkbike.com/news/sam-blenkinsop-norco-aurum-prototype.html
flag ManiacInBlack
Posted: Jan 12, 2016 at 7:47 Quote
Ok cool, that's kinda what I thought. I agree that the S shaped thing was/is nonsense but I do think axle path its very important ( see Sir Issac Newtons third law of motion, simple but applicable ). Though I also agree its pointless if you don't resolve all the things you've talked about before as well. The perfect combination is entirely possible, some have even got pretty close already, Canfield & Zerode for eg to name just two, waiting for your next vid Salute
flag andrextr
Posted: Jan 12, 2016 at 11:13 Quote
I agree with both of you! Galuska you are rigth Smile

BTW, a little offtopic, I did it a YT Capra 2016 linkage analysis. It's not a MTB rear susp episode, but give a look!
flag Waxy
Posted: Jan 21, 2016 at 10:26 Quote
andrextr wrote:
Hi guys! Check my 3rd video.

The reason why you shouldn't use pre-load in your coil shocks and forks.


Bye Smile

I don't think I agree with your premise or the graph you've shown regarding how pre-load affects suspension.

The force it takes to fully compress the spring does not change by preloading the spring. It is a pre-defined linear constant that is set by the spring rate (500lbs/in) and the amount the spring is capable of being compressed. The spring compresses at a constant rate, the only thing you've changed by adding preload is the point along the linear force curve of the spring at which the suspension will move/compress. From that point on, the spring and suspension react exactly the same as they would without preload, assuming linear shock calibration.

If you put 100 KGs of weight (or the equivalent weight required to overcome the effect of the spring preload tension) on the bike with increased preload, it would react exactly the same in the drop test as the bike with no preload, assuming shock calibration is also linear. They would also both bottom out at the same level of force, and that's the reason to increase the spring rate rather than simply add preload. The additional 100 KGs on the bike increases the max. forces exerted on the spring/shock, and in order to prevent bottoming and maximize the useable travel of the shock/suspension, a higher spring rate (stiffer) spring is required.

Matching spring rate to the rider weight/preference according to sag specs is always the best starting point, but preload is still the best (only?) way to adjust that initial travel to the weight and ride preference of the rider.
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