Part 2 Suspension setups info.

wagonmaster

Active Member
Lifetime Premium Member
Can I use standard shocks with lowered springs?

As stated previously above, standard shocks can easily be used with a 30mm lowered spring , possibly up to 40mm?, (That’s if KYB are leaning on the side of caution/fact), provided they are in good condition and the spring is under tension. The “spring under tension” requirement is very important, as the spring can become displaced from its upper or lower spring seat if the vehicle is jacked up or becomes airborne while on the road. This condition could seriously compromise the safety of the vehicle. With lowered springs upward of 40mm-60mm, a special shock is required, with a reduced stroke, shorter body and revised damping. The revised damping is necessary as the lowered spring has to do the same amount of work in a shorter space, so needs a higher spring rate. The higher damping rate means the shock needs less bump (compression) damping, but more rebound (recoil) damping. A standard shock has too much bump damping and not enough rebound damping for a shorter spring.

Can I lower my vehicle by more than 60 to 100 mm?

You can lower your vehicle by 60-100 mm or whatever you want using coils, air suspension/bags, but you have to ask yourself how practical it would be. You have to cope with speed bumps, steep driveways or rough roads that could rip the sump off your vehicle if conditions are right, so basically you would be breaking out in a cold sweat going over speed bumps at Coles, and we have all seen the guys driving over speed bumps sideways.

If you do this 100mm mod you would also have to take wheel arch clearance into consideration. You may have to go for rims with a different offset, tire size, or modify the body by rolling or flaring the wheel arches, to stop the front tyres from rubbing/ catching when the wheel hits a bump.

Another solution for the front wheels is to run negative camber so they clear the wheel arches when they move upwards. The drawback then is that tyres have to be rotated front to back every 5000 to 8,000 km to avoid excessive tread wear on the inside edge of the front tyres.

If you fit much larger and wider rims it just makes this whole problem worse, if you car is lowered by say 40-60 mm and you fit 18-20+ inch rims, the bigger rims & tyres have a bigger rolling circumference than the standard tyres, and apart from messing with the carefully selected factory gearing/speedo readings, they make the vehicle have a stand higher stance, they have less flex in the tire sidewalls the lower the profile, all this, in turn, demands a bigger drop, causes undue forces on the suspension, all of which is not possible without major modifications to the wheel arches.

If you lower vehicle too much (60mm-120mm+) you also introduce undesirable forces on the suspension joints; you may need some to bring the lower control arm back to the horizontal, and stop the joints working beyond their design range. If you use spacers they are safety-critical, and should only be made by a suspension-tuning expert using the best quality steel available.

Is it a good idea to fit aftermarket coil-over shocks or coilovers?

Yes, coilovers are good if you need to change the ride height of your vehicle often, a good example would be if you used your vehicle for car shows / cool daily driver or even for track work a few times a year.

Generally speaking, coilovers are most popular on many dedicated track vehicles where the ride height has to be set accurately, and corner weights (using special scales – one at each wheel) so that left and right weights are identical. Coil-over shocks are also used to give a vehicle a particular characteristic such as oversteer (making it tail happy). They can also be used to counter undesirable traits such as understeer (nose running wide in a corner), which is achieved by changing front to rear ride height. Coilovers are also popular on street cars for handling/adjusting ride heights, so usually the coilovers are set up once and never touched again. Vehicle owners do not often realise that from unladen to laden there is very little weight change at the front of their vehicle, but a very big change at the rear.

Cutting coil’s on my springs?

You could, but its dumb idea, because cutting coils results in the rate of the spring increasing (less coils doing the same work). This increase may be beyond the maximum design rate for the spring, so that it is forced to operate outside the tensile strength of the material, resulting in a broken spring. You cannot undo the act of cutting off coils, so to restore the ride quality back to standard; new OEM springs would have to be fitted. Another frequently encountered problem is that when the coil is cut off (using a torch or an angle grinder), if the cut off wheel nicks another coil or the torch touches or heats up the coil below the cut area, this can cause a weakness in the spring around and below the area cut, and the spring often fractures at this point, lowering springs/coilovers are always a better option than cutting.

Cutting/heating springs with torch to lower the vehicle?

This is a very bad idea as a DIY mod, as springs- coil or leaf – are manufactured to very precise standards to give exact spring rates, so there is little or no variation between the left and right spring on a vehicle. When springs are made they are heated to an exact temperature and cooled (tempered) using a fluid that is also at an exact temperature. Heating the coils on the vehicle with an oxy-acetylene torch is a far cry from a quality spring manufacturers, heated springs almost always fail where they have been heated. It is best is to stick to a 30mm 40mm or 60 mm drop, but if a drop of more than 60 mm is required, get the springs to a specialist spring works, where they will be heated and reset to a shorter free height, and re-tempered. This is only necessary if you cannot get standard lowered springs for your vehicle from one of the major manufacturers.

Advantages of a lowered vehicle?

1. You may get higher cornering speeds, especially if wheel alignment settings, such as camber, castor and toe-in, are re-set after the lowering has been done.

2. The frontal area will be lowered, and this may increase the top speed, as well as the steady speed for the same throttle opening. Fuel consumption may also reduce slightly, as you should use less throttle for the same speed.

3. The centre of gravity of the vehicle will be lowered, so that crosswinds will have less effect on it.

4. Lowered springs have higher spring rates than the standard factory springs, so the vehicle will roll less in a corner, nose dive less under braking, and squat less under acceleration. This will make the vehicle more responsive and give the driver more control.

5. A well-packaged suspension setup will go a long way to help reduce any nasties such as over- or understeer by careful selection of springs matched to the correctly damped shocks. Good quality kits are tested for many kilometres on the road, and on many differing surfaces, before being sold to the public.

6. The suspension will now have less travel from the ride position to full bump (compression), giving better wheel control, which equates to better vehicle control.

7. Coilovers give adjustable ride height so the vehicle can be trimmed to match local road conditions and varying load situations – for example, adjusting the rear up for a holiday to counter a full back seat (three people) and a packed boot.

8. By installing coil-over’s you can counter sagging springs and adjusting the settings upwards to restore ride height.

Disadvantages of lowering?

1. A badly fitted and drastically lowered suspension set-up can result in poor handling and slower cornering than on the standard suspension.

2. Lowered springs matched to incorrect shocks are likely to produce very unsatisfactory results.

3. The lower the ride height increases the risk of damage to the front bumper/skirt, sump and exhaust system.

4. The higher spring rate used for the lowered springs could give the vehicle a harsh ride.

5. Some drivers find the increased responsiveness makes the vehicle feel twitchy.

6. The lowered suspension, with its shorter travel, will give you a firmer ride vs standard factory ride.

7. Some people who buy coilovers just adjust and set them up once and never adjusted them again because they find the whole adjustment setup to time consuming, so why coilovers instead of lower springs in the first place?

8. Ride height cannot be adjusted on fixed drop suspension set-ups, so any settling of the springs is guaranteed over time and has to be accepted, or the springs have to be changed to restore ride height.

It’s important to remember that modifying a car’s suspension is a fine balancing act, manufactures spend millions of dollars on research and development to arrive at a all round compromise. This is why changes to the suspension will yield improvements to handling and looks, but there can also be inevitable disadvantages and dangers as well.

If any other forum members have something to correct or add, please do so to allow this to be reposted in the future with all corrections and or any additional information added to it.

These lowering heights mentioned are only a guide as results vary from car to car.
 

SDate42

Active Member
Lifetime Premium Member
My 2¢

I had evo7-9 OHLINS shocks with swiftsport springs 10kg and evo7-9 oem rubber strut top mounts fitted into my CH. I always had issues with changing wheel alignment and my castor was unable to be corrected. The mounting points to the body are the same CS to CT but the centre of the mount is different. This was the cause of my castor dilemma. Ride was too stiff with 10kg springs for the roads.

Recently I just upgraded to a full set of BC coilovers F+R. 8Kg and 6Kg respectively. 0-1mm preload as best as I could get. Fronts are 70mm collar to collar between the lower part of the strut and the spring perch lock. Rears are 36mm in the same space. Castor is back into a tolerable range. -0.7deg front -0.5deg rear camber. Toe at factory value for now. Shock stiffness 1/3 from softest.
If someone is looking for a base setting for coilovers on a CH - start here.
In this setup I clear evo 9 enkies with 225 RE003’s F+R. I also have lightly rolled guards. CT evo steering rack w/anti lift tie rods. The height is only slightly below stock VRX.

I will report back soon with some more data/info as I learn. Hope this can help someone.

EDIT: 2 hours of driving (wet). Straight line and cornering traction on acceleration are reduced. Higher speed and maintained speed cornering feels better than before. Definitely can feel the difference in the rear being stiffer finally. Relatively even body roll. I aim to reduce this with pre load. Going to confirm ride heights F-R asap.
 
Last edited:

unclepaulie

Well-Known Member
Lifetime Premium Member
My 2¢

I had evo7-9 OHLINS shocks with swiftsport springs 10kg and evo7-9 oem rubber strut top mounts fitted into my CH. I always had issues with changing wheel alignment and my castor was unable to be corrected. The mounting points to the body are the same CS to CT but the centre of the mount is different. This was the cause of my castor dilemma. Ride was too stiff with 10kg springs for the roads.

Recently I just upgraded to a full set of BC coilovers F+R. 8Kg and 6Kg respectively. 0-1mm preload as best as I could get. Fronts are 70mm collar to collar between the lower part of the strut and the spring perch lock. Rears are 36mm in the same space. Castor is back into a tolerable range. -0.7deg front -0.5deg rear camber. Toe at factory value for now. Shock stiffness 1/3 from softest.
If someone is looking for a base setting for coilovers on a CH - start here.
In this setup I clear evo 9 enkies with 225 RE003’s F+R. I also have lightly rolled guards. CT evo steering rack w/anti lift tie rods. The height is only slightly below stock VRX.

I will report back soon with some more data/info as I learn. Hope this can help someone.

EDIT: 2 hours of driving (wet). Straight line and cornering traction on acceleration are reduced. Higher speed and maintained speed cornering feels better than before. Definitely can feel the difference in the rear being stiffer finally. Relatively even body roll. I aim to reduce this with pre load. Going to confirm ride heights F-R asap.
on a spring with a linear/fixed K (constant spring rate) value: pre load will do nothing except compress the spring.

preload only works on old school coilovers where the spring has a varying K value / spring rate (aka: the spring coils are closer together one end and spread further the other end)

watch this
 

SDate42

Active Member
Lifetime Premium Member
Thanks @unclepaulie ! That confirms what I’ve had in my head for a long time and havent had any way of backing it up. One thing I will add to the MCA vid is that changing pre-load on a linear spring WILL have an effect. The ride hight is adjusted and also possibly the maximum compression stroke of the shock. (If spring is completely compressed before hitting bump stop).
 
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