Motion ratio and shock performance

[MSKrebs]

Originally Posted by FABRICATOR in other thread relating to running shocks mounted to the trailing links instead of directly to axle:
That, and keeping the shaft/piston under warp speed.

This brings up an interesting topic (to me at least).

Running a larger motion ratio decreases the shock velocity but also increases the force exerted on the shock proportionally, requiring a larger shock with gnarlier components (shaft, body, shims, bearings) to handle the forces. I don't have any experience with the thermal dynamics of oil, so... What does experience show about heat buildup in the shock when you change motion ratio? the oil is moving through the shock slower but under more pressure, so there has to be more friction and generate more heat... does this generate more/less heat than using a smaller shock with a smaller motion ratio (having less force fed into it but higher shock velocities) ??

Also, I think tuning would be easier with a smaller motion ratio (shock mounted closer to axle) because for higher motion ratios any change in the shock valving is multiplied over the motion ration and has a larger effect at the wheel, therefore harder to fine tune (same for spring rate changes).

Does that sound right?


Matt

[DUMP!]

Originally Posted by FABRICATOR in other thread relating to running shocks mounted to the trailing links instead of directly to axle:
That, and keeping the shaft/piston under warp speed.

This brings up an interesting topic (to me at least).

Running a larger motion ratio decreases the shock velocity but also increases the force exerted on the shock proportionally, requiring a larger shock with gnarlier components (shaft, body, shims, bearings) to handle the forces. I don't have any experience with the thermal dynamics of oil, so... What does experience show about heat buildup in the shock when you change motion ratio? the oil is moving through the shock slower but under more pressure, so there has to be more friction and generate more heat... does this generate more/less heat than using a smaller shock with a smaller motion ratio (having less force fed into it but higher shock velocities) ??

Also, I think tuning would be easier with a smaller motion ratio (shock mounted closer to axle) because for higher motion ratios any change in the shock valving is multiplied over the motion ration and has a larger effect at the wheel, therefore harder to fine tune (same for spring rate changes).

Does that sound right?


Matt

Yes that sounds right. You are correct in all your logic. The typical motion ratio of a offroad vehicle should be between 1-1 and 2-1 but no more the 2-1. Anything more then 2-1 and you will find it hard to keep the seals in the shock from melting. I'm also talking about a vehicle that is about 3500 LBS and heavier.

Dump

[FABRICATOR]

...

Does that sound right?


Matt

I know I don't know what I think I know. But IMHO, most of what has been said does not sound right, for dezert racing at least.

[Outcast]

Here you go... Suspension Linkage (http://www.race-dezert.com/forum/showthread.php?t=29860)

[MSKrebs]

Thanks for the referral, just what I was looking for.

Cheers-

Matt