# Valving numbers for shocks - what do they mean?

Discussion in 'The Garage' started by **DONOTDELETE**, Oct 10, 2003.

1. ### **DONOTDELETE**Guest

I need some new shocks and decided on some Bilsteins. What do the valving numbers mean, like 170/60 or 255/70? /forums/images/graemlins/1zhelp.gif I know they correspond to compression and rebound but how do I know which one to select? It's an 90 Blazer if it matters.

2. ### rjfguitar3/4 ton statusGMOTM Winner

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I think the valving determines how stiff the shock is but I'm not positive. /forums/images/graemlins/tongue.gif

3. ### **DONOTDELETE**Guest

That's what I figured, but what do the numbers mean and how do they correspond to it?

4. ### scrappy881/2 ton status

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I'm pretty sure it has to do with Compression and Rebound damping of the shock. Depending on the valving, you could have a shock that is stiff on compression but soft on rebound, or the other way around. At least that's how I understand it. I could be wrong /forums/images/graemlins/grin.gif

Oh, and I think higher numbers are stiffer. Anyone else know about this? I'm kinda curious myself as I'm in the market for news shocks.

5. ### Bubba Ray Boudreaux1 ton status

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[ QUOTE ]
Understanding Bilstein Valve Ratings
Damping forces of Bilstein valvings for Off-Road are measured in Newtons at a velocity of 0.52 meters/seconds (approximately 20 inches/second). The ratings shown correspond to those measurements; rebound force is the first number, followed by compression force (rebound / compression). Conventionally, the ratings are written as one tenth the damping force in Newtons.
EXAMPLE: Valve rating: 275 / 78
Rebound force is 2750 Newtons at 0.52 m/s
Compression force is 780 Newtons at 0.52 m/s
Higher numbers mean higher (firmer) damping forces. For example, 360/80 has more control (is firmer) that 275/78, while 170/60 has less control (is softer) than 275/78.
For valving recommendations please refer to the Valving Guide.
Determining how many shocks to put on a vehicle.
A shock absorber transforms mechanical energy (suspension movement) into kinetic energy (heat). If a shock absorber builds up too much heat, it will not function properly. Shock absorbers exposed to excessive heat will fade (soften) or fail.
If you are experiencing excessive shock failure or fading, it may be time to add another shock.
By adding another shock, you are spreading the work load from one shock to multiple shocks. Increased cooling capability will be achieved from the following factors:
Decreased Friction
Dampening causes friction. When you use a multiple shock set up, lighter valved shocks can be used which will decrease friction.
Increased Oil Capacity
The more oil, the better. Higher oil volumes take longer to heat.
Other methods to consider which will increase oil capacity are to utilize a remote reservoir or to use a larger diameter shock.

[/ QUOTE ]

6. ### **DONOTDELETE**Guest

/forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif That's exactly the info I was looking for. Where'd you find that?

7. ### chulisohombre1/2 ton status

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good info.this will be saved under my favorite threads

8. ### Bubba Ray Boudreaux1 ton status

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9. ### BorregoK51/2 ton status

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More good info on how to set it all up

Since shocks move gas or liquid around inside themselves at certain rates to provide damping, it stands to reason that the faster the medium moves in the shock, the quicker the shock will compress or extend. Usually the compression and extension rates are very different. The reason is simple. When traveling down a road and encountering a bump, you’d like the wheel to deflect as quickly as possible so as not to upset the balance of the vehicle. This deflection is handled by the spring in large part. The softer the spring, the faster it deflects. You really don’t want the shock getting in the way of this because it would simply act like you added a stiffer spring. However, once the wheel deflects and that energy gets stored in the spring, you don’t want it springing back very quickly so you DO want the shock to slow it down. This is why compression valving on a shock is ALWAYS less than expansion damping. So how do you know what valving is correct? It’s basically a matter of looking at your spring rates. If we assume you have a spring with 100 LB/in of rate, and you typically encounter 2-5” bumps, you’d want a shock that could damp down that force. 5” of deflection x 100 LB/inch would give us 500 pound force inches of force. Or 56.49 Newton-meters in the international lingo. If we make this somewhat more realistic and use a 250 pound spring like you might find in a Land Rover, we’d then have 5” of deflection x 250 LB/in or 1250 pound-force inches or 141 Newton meters. If we use the vehicle off-road then we have to factor in that the spring may be compressed fully and then we would have to calculate based on an real-world spring having about 9” of compression. Using our 250 LB/in spring we would end up with 2250 pound force inches or 254 Newton meters.

Now we would go look for a shock that offered about 50 Newton meters of compression force (75-100 if we wanted to remove the sway bars) and expansion valving around 250 Newton meters. This assumes that the shock will be mounted vertically on the axle. If the shock will be mounted in a canted fashion, allowances must be made. You’d be wise to add a 10% stiffer shock for every 20 degrees of cant. You can now go to a custom shock manufacturer armed with your proper valving needs. Or you can take a visit over to Eshocks, and have a look at the off-road shock offerings from Bilstein and determine what might meet your needs."

10. ### Bubba Ray Boudreaux1 ton status

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[ QUOTE ]
More good info on how to set it all up

Since shocks move gas or liquid around inside themselves at certain rates to provide damping, it stands to reason that the faster the medium moves in the shock, the quicker the shock will compress or extend. Usually the compression and extension rates are very different. The reason is simple. When traveling down a road and encountering a bump, you’d like the wheel to deflect as quickly as possible so as not to upset the balance of the vehicle. This deflection is handled by the spring in large part. The softer the spring, the faster it deflects. You really don’t want the shock getting in the way of this because it would simply act like you added a stiffer spring. However, once the wheel deflects and that energy gets stored in the spring, you don’t want it springing back very quickly so you DO want the shock to slow it down. This is why compression valving on a shock is ALWAYS less than expansion damping. So how do you know what valving is correct? It’s basically a matter of looking at your spring rates. If we assume you have a spring with 100 LB/in of rate, and you typically encounter 2-5” bumps, you’d want a shock that could damp down that force. 5” of deflection x 100 LB/inch would give us 500 pound force inches of force. Or 56.49 Newton-meters in the international lingo. If we make this somewhat more realistic and use a 250 pound spring like you might find in a Land Rover, we’d then have 5” of deflection x 250 LB/in or 1250 pound-force inches or 141 Newton meters. If we use the vehicle off-road then we have to factor in that the spring may be compressed fully and then we would have to calculate based on an real-world spring having about 9” of compression. Using our 250 LB/in spring we would end up with 2250 pound force inches or 254 Newton meters.

Now we would go look for a shock that offered about 50 Newton meters of compression force (75-100 if we wanted to remove the sway bars) and expansion valving around 250 Newton meters. This assumes that the shock will be mounted vertically on the axle. If the shock will be mounted in a canted fashion, allowances must be made. You’d be wise to add a 10% stiffer shock for every 20 degrees of cant. You can now go to a custom shock manufacturer armed with your proper valving needs. Or you can take a visit over to Eshocks, and have a look at the off-road shock offerings from Bilstein and determine what might meet your needs."

[/ QUOTE ]

Or in Bubba's language, call Brett King down at King Shocks and say "Hey, what's kicking Brett? I need some 2.5" Bypass Shocks for my so and so that weighs 9 millions pounds with a spring rate of 7 lbs up front and 8 lbs out back and I will be floating over large rocks at approximately Mach 18."

So after you have robbed the bank to be able to afford these approximately \$500 a piece shocks, you can bolt them in, head to your favorite spot and dial your ride in exactly like you need it without taking the shock apart to revalve everything.

Right? /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

/forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif

11. ### BorregoK51/2 ton status

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Thats why the triple bypass shocks are so nice- you pay a boatload of cah for them, but you can dial them in externally out on the trail to get exactly what you want- without revalving! /forums/images/graemlins/thumb.gif

12. ### **DONOTDELETE**Guest

[ QUOTE ]
More good info on how to set it all up

[/ QUOTE ]

Indeed it is! /forums/images/graemlins/cool.gif ... and the missing piece of the puzzle. Now I can crunch some numbers. /forums/images/graemlins/thumb.gif

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