Please help me understand spacer lift.

[slooowr6]

Hi All,
I'm not doing any mod, I've a 2wd Vanagon. :ylsmoke:
Most spacer lift I seen is installed between the top plate and the coil spring which essentially raised the preload of the coil which in term raised the truck. But does not this reduce the up ward travel of the shock? So it's easier to top out? I read a lot of people who did the spacer lift said they don't feel the ride is stiffer which should be the correct, if the coil is not progressive then a spacer lift does not change the spring rate so the ride should be about the same.
I've spacer on my Vanagon but the reason for that is to increae the preload cause a camper Vanagon is known to lean towards driver side cause all the camper stuff is on the driver side.
I know I can get real answer on this site, I don't have any off road experience but I would imagine it's important to keep the ratio of upward travel and downward travel close to the factory spec. I can understand adding a spacer on top of the top plate, this just extend the overall length of the shock so travel stay the same but geomety will chage a little.
So does a spacer lift (one that is between top plate and the coil) consider a good offroad mod?

Thanks for any tip you can spare!
Alex
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local headshop

 

[goodtimes]

A spacer between the spring and the upper spring mount (bucket, plate, whatever you wish to call it) will not change the spring rate, it simply pushes the axle down however far the spacer is tall.

I am not real familiar with the suspension setup on the VWs, but most of this info is pretty generic, and likely applies.

On any linked, or radius arm suspension, moving the axle down in relation to the frame (installing a lift), moves the axle down and towards the center of the vehicle slightly. The more lift, the farther towards the center the axle will sit at rest. This moves the tire closer to the rear of the wheel well (on the front axle), so watch for interference here. As your axle droops, the castor changes, which will affect handling, so be cautious with how much lift you use. A little lift is generally not a big problem, but as you lift higher, it will get to a point where corrections need to be made.

It also extends your shocks, so at a neutral position (vehicle sitting at ride height), you will effectively gain compression (up travel), and lose extension (down travel). Again, the more lift, the more severe the change. What this can do to your shocks, is you can over-extend them easier (when your axle droops). This can cause damage to the seals, and premature failure.

This also lets your axle travel farther up, because there is more distance between the axle and bump stops. Your axle will still stop upward movement at the same point (relative to the frame/body), but if you have installed bigger tires, you now have a problem with the tires hitting the body. So extending the bumpstops to prevent this is advisable. Once again, the bigger you go (with tires this time), the more problem you will have.

The ride quality will suffer a bit, and you can expect a bit more road noise as the links (or radius arms) move away from being parallel to the ground. Again, bigger lift = more problems to overcome.

Generally speaking, a small lift has minimal effect on these things, but they should be checked, and adjustments made to compensate for them. As you go higher and higher with the lift, the effect increases on a almost exponential scale.

Sorry this info is a bit vague...but without having a VW in front of me, it is hard to see what exact effects you will have....I don't work on VW's much (OK, virtually never....).

 

[slooowr6]

:sombrero: Thanks for all the info. I'm not asking this for the Vanagon, the van is a 2wd 4400 lbs with 90hps/112lb-ft on a good day.
I'm trying to understand is spacer lift a worth while mod for off road, just adding a spacer? With minor 2"-2.5" lift the change in geometry should be mild but it does have noticeable affect on the up/down stroke ratio cause it's a 1:1 change in the extension of the shock, if you put a 2" spacer in the sock should loose 2" downward travel. Does this affect offroading? Doesn't the tire loose traction when the shock tops out?

Thx again.
Alex
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Honda CD175

 

[goodtimes]

A spacer lift in general (not specific to any vehicle), is an inexpensive way to make room for larger tires, and thus added ground clearance. Yes, you lose some droop if you keep the same shocks (for the reason you mention). Most people will add longer shocks to make up for this. It is an economical way to lift a coil sprung vehicle...but this type of lift does not address any factor other than lift. Often times a different spring rate is desired on a lifted vehicle to induce or control body roll, allow better articulation, compensate for added gear (heavy bumpers, winch, etc), or compensate for gear that has been removed (rear seats, fiberglass tops, etc). In addition, a proper spring rate for your anti-sway bars will greatly improve performance. Again, a spacer lift does not address these issues.

(side note here: There is a common misunderstanding about having a tire in the air while off road. Most people think you lose traction if you do not have all 4 tires on the ground. On soft surfaces such as sand, mud, etc, this is correct. But on hard surfaces, having a tire in the air can actually increase traction. Physics and gravity being what they are....a vehicle that weighs 4000 pounds will ALWAYS exert 4000 pounds of pressure on the ground, less any force lost or gained due to kinetic energy. It is simply a matter of how large of an area that force is distributed over. Once you lift a tire, all of the force that was distributed through that tire is transferred to a different tire, or combination of tires, which increases the contact pressure on those tires. Obviously, for you to make use of that contact pressure, you need to be able to add rotational force to that tire---which requires either a locker or a spool in the differential)

In addition, if the bump stops are not set properly, it is possible to bottom the coil spring on full compression (where the each coil is touching the coil above, and below it). This can damage a coil spring, as they are generally not designed to compress this far. This leads to fatigue, and premature sagging of the spring. This is less likely with a aftermarket, longer spring (instead of the spacer), but can still happen---so the installer must pay attention when setting the bumpstops.

To answer your question directly---yes. A spacer lift can improve off road performance of a *vehicle* because it allows you to use a larger tire, and thus improve your ground clearance and reduce the angle of incidence to an obstacle. But a spacer lift does not allow your *suspension* to work any better (for the reasons cited above).

 

[slooowr6]

:bowdown: Now that makes a lot of sense. Cool info!
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Honda CD100

 

[asteffes]

Most dampers work less well when forced to operate at the extremes of their travel. It follows that by forcing a shock toward extreme extension by the use of a spacer it will not properly damp suspension movement just off full extension. So while riding around town at the maximum shock extension you will be largely riding on the springs with less damping than normal from the shocks. This is perhaps why people perceive spacer lifts to ride harshly - they do so because the spring motion at that extreme level of extension is not properly damped.

Coilovers or other shocks intended for lifted vehicles are valved to operate within their optimum range, as well. In the case of these shocks, they are tuned to operate properly with the vehicle lifted N inches by adjusting the body length and piston length of the damper to leave enough fluid or nitrogen gas where it is needed to damp the shock travel. Your stock dampers are intended for a vehicle lifted zero inches. Forcing them to operate at N inches over stock means they are not operating within that sweet spot of the middle 80% or so of their total travel.

 

[slooowr6]

Good point!
BTW, your truck is my model truck. When time comes I'll just follow what you did and save me the trouble of a lot of info gathering! Oh, and you are local does not hurt either.
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R51

 

[asteffes]

I haven't tried anything else, but I imagine it's hard to beat the Donahoe setup. Where are you located? We could meet up sometime.

 

[slooowr6]

I'm in Sunnyvale so we are next door/city neighbor. I don't have a truck/expedition vehicle yet, at least not for another year or two. I have a 20year old vanagon :smileeek: it's a fun old van.
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Yamaha XT225