Jump to content

Damping for trials


Niro
 Share

Recommended Posts

I have a follow up question in my search for new rear shocks for vintage trials competitions.

What does "Damping" mean and what is the actual different in riding with "standard damping" or with "light/ super light damping"? 

Thanks. 

Link to comment
Share on other sites

 

This link talks about car suspension, but explains what dampers are.

 

Compared to the vast majority of motorsport trials bikes perform best with a low level of damping, on modern bikes it's typically adjustable to suit individual riders' weight and / or preference.

Edited by turbofurball
Link to comment
Share on other sites

 

Lighter damping in the shocks makes for less effort from the rider when un-weighting the bike, or getting a bigger lift with the same effort.

Your 247 will handle fine in trials sections with either standard damping or light damping in the shocks. Standard trials damping is slightly better if you are also going to use the bike for trail riding. Lighter damping is slightly better if you only use your bike for trials riding.

Suspension damping is the conversion of kinetic energy into heat for the purpose of controlling the up and down motion of the wheels and the up and down motion of the bike. Bike shocks use oil moving through small passages to absorb the kinetic energy. The heat energy gained by the oil is transferred to the atmosphere.

Edited by feetupfun
  • Like 1
Link to comment
Share on other sites

 
 
3 hours ago, Niro said:

Thank you! Valuable information. 
I think I will choose the lighter damping version, since I am riding only trials with the bike. 

It's very important to have the correct spring rate, one that does not require much pre-load to achieve 25~ 30% sag with rider on pegs. I started with a 45# spring and should have started with 60# with a low leverage system and 157 KG of bike/rider.

Link to comment
Share on other sites

 
12 hours ago, Ftwelder said:

It's very important to have the correct spring rate, one that does not require much pre-load to achieve 25~ 30% sag with rider on pegs. I started with a 45# spring and should have started with 60# with a low leverage system and 157 KG of bike/rider.

You mean 60LB? 
and by "low leverage" you mean light damping? 

Link to comment
Share on other sites

 

Leverage is the ratio of axle travel to shock travel. On a 247 the ratio is about 1.1:1, so if the shock travel is 100mm then the axle travel is 110mm.

The bigger the leverage ratio, the stiffer the springs need to be to achieve the right sag. Also, the heavier the rider, the stiffer the springs need to be.

For example I'm 94 kg and on a 1.1:1 rear end, 45 pounds per inch springs are about right.

40 pounds per inch springs on a Cota 247 would probably suit riders weighing between 70 kg and 85 kg.

Link to comment
Share on other sites

 
 
10 hours ago, Niro said:

Is 1.1:1 considered low leverage?
 

Falcon shocks offered me 50lb springs. I'm around 80kg with gear. 
Is 50LB will be much of a difference from 40LB? 

1:1 is zero leverage (Sherpa T pre-1970)

1.5:1 is high leverage for twinshock trials bikes (Godden Majesty 250/320, Fantic 240). Some twinshock MX and enduro bikes are even higher leverage.

1.1:1 is a typical for trials bikes made 1970-1975.

With Falcons and your weight, if you get the 50 lb springs you will have zero risk of bottoming out the rear end during landings but the the rear end wont work quite as well as it could in rocky stream-bed sections. 40 lb springs would give a more supple rear end in stream bed. You should use the lightest springs you can get away with because if you aren't using all the suspension travel, the suspension action is not as good as it could be.

If I was your weight, I would try the 40 lb springs first.

  • Like 3
Link to comment
Share on other sites

 

Would you say that the NJB Ultimate shocks are better option because they allow the rider to adjust the shock length? 
Is the length is critical as the spring pre load?

Link to comment
Share on other sites

 
 
9 minutes ago, Niro said:

Would you say that the NJB Ultimate shocks are better option because they allow the rider to adjust the shock length? 
Is the length is critical as the spring pre load?

I bought the NJB ultimate because of the adjustable body length which is independent of the the preload adjustment. The damping is very light and seem to be quite good.

Coil spring exact length is not critical as long as it's both short enough to be installed and long enough to prevent the spring coils from contacting each other known as binding. 

 

 

Link to comment
Share on other sites

 
 

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
  • Create New...