moving the shock mount further along a arm???

[forum]

Ok if the shock mount on the a arm was moved out toward the tire would this cause any problems?? of course the leaverage would change and my shock builder would have to know this in order to build the shocks corectly but i was wondering about other problems.

[BigThumper33]

with a more horizontal angle of the shock I could see more pressure being put on the shock shaft. If this would cause any real problems I do not know. The predators front is set up in such a way.

[beerock]

it depends on how far you move it.

I read somewhere that putting the shock mount in the wrong place is a no no. I forget where I read it though. I think john arens said it.

[boogiechile]

moving the lower shock mount out will remove leverage from the shock. If the shock is then set up for the correct leverage it will usually work better. Lower motion ratios (shock moved out)are good for setting up shocks. The problem is that as you go out with the mount the travel is reduced and it would take a shock with more travel to give the same wheel travel. Moving the shock mount as close to the frame side as possible without causing the motion ratio to go too much past 2 to 1 gives the most wheel travel for a given shock while allowing it to work like it should. Motion ratios higher than 2 or at the most 2.2 to 1 are hard to get the shocks set up right.

If your shock has 4.75 inches of travel and you keep the motion ratio at 2-1 then 9.5 inches is what the wheel travel will be. If you move the shock mount out to lower the ratio to say 1.7-1 then the wheel travel is reduced to 8.075 inches.

The motion ratio is a ratio of the total wheel travel through the shocks range to the travel of the shock itself.

[forum]

ok well the reson im asking is because. rp's long travel a arms are moving the shock mount out. and they are using a 19 inch shock. so should this be a good setup?

[Jnine]

Wheel travel also depends on what the original length of the shock is, and how much stroke it has. It's not just leverage ratios alone.

[boogiechile]

If the a arms are long like +3 that is used on many long travel setups then the shocks almost have to be moved out to keep the motion ratio from getting too high. With +2 arms and the shock in the stock location in relation to the inside, I think the motion ratio is already at or above 2-1. if you extend the arm another inch the ratio will go even higher, unless you move the shock mount out. Shocks are difficult to tune with high motion ratios. For example Elka prefers to never go over 2-1.

Now it is true that there is more to travel then just the motion ratio. The other factor is shock travel. multiply the motion ratio times the shock travel and you get wheel travel. I would call the manf of the arms you are looking at and ask what the motion ratio is. It should not exceed 2.2-1 in my opinion. if they can't tell you what it is that should tell you something. Once you get the ratio from them then find out from the shock maker you are going with what the travel of the shock shaft is. Multiply by the motion ratio and you will have the wheel travel. The only problem could be if the ball joints are at the wrong angle or do not have enough range of motion causing all the travel to not be there or they are designed where some of the travel is actually after the frame bottoms, making it useless. It happens. A good a arm manf should have all this accounted for, but I have seen these type problems before.

Go to the custom axis site and download their tech manual. It has some good info on motion (leverage) ratios and how to check it.