blackwarlock
braap
So there's a lot of suspension stuff on the internet, people running this and that.
I'm posting my knowledge here to give you specific details regarding how to work out what will fit on your car
I'm hoping this will give people a baseline to work out what they want
Car and Wheels
Car is important as you get a starting point (i'll explain later) and different cars will react differently to suspension mods. This comes down to weight and suspension setup.
For example
A VS is lighter than a VZ, therefore the same spring will sit lower on a VZ than a VS - because it weighs more.
Also, throughout the history of the third gen commodore (VT-VZ), they made the suspension a little better.
For example
When lowered (just shocks and springs) a VT will run more negative camber than a VZ. Keep in mind its not a huge different, the VZ suspension wasn't great compared to the VT. VE's are wear its at if you want a commo with good suspension - but that's another story.
Moving on from the car is the wheels you are running. Thankfully you won't run into any differences between the VT to the VZ when fitting wheels, regardless of how low you are. This is because they all used the same rear quarter panels.
The width, tyre profile and diameter of your rim will affect how low you can go before you rub your guards, either through turning or through bumps. Offsets will also affect this but I that is again another story which requires a separate thread (please ask for more info)
I'll break down wheels into the three sections as above:
Width
Obviously, how wide your wheel is. Notice i said wheel and not tyre. This is because a wheels width will not change, however you can fit different width tyres on the same wheel. It's a little confusing but tyre width will be in miller meters and wheel width will be in inches.
For example
An 8.5" wheel can fit from 215 - 235mm tyres and be roadworthy and within VICTORIAN road rules. I cannot speak for other places. You can also 'stretch' tyres. This is the process of putting a narrow tyre on a wide wheel. I've seen 205 (think barina width tyres) on 10" wheels (that's corvette width). Crazy stuff.
So why am I mentioning all of this? Well going back to my example, a 8.5" wheel with a 215mm tyre on it will have a narrower (albeit slightly) footprint than a 235mm tyre on the same wheel. So technically speaking you could go slightly lower on with that setup. And your wheel could be slightly closer to the wheel arch of your car without touching. it's all very slight stuff but can be the difference between rubbing and not rubbing. And it's a big complaint people have when they put new tyres on their already lowered car. Suddenly they've gone to a wider tyre package without realising and they're getting rubbing where there wasn't before. I could go on more but I think i'll keep it as simple as a can and stop there.
Tyre Profile
Tyre profile is the second digit you get when reading a tyre's specs.
For example
235/35R18. Basically, the tyre is 235mm wide and will fit on a wheel of 18" in diameter. The R is a speed rating. and the 35 is your profile. NOTE this is not 35mm. It is 35%. Biggest mistake people make is reading the 35 as 35mm. It is actually a percentage of the tyre width. so in this case you're looking at 35% of 235 which is 82.25mm.
Another way to look at this is having two tyres with the same profile but different width
225/40 = 40% of 225mm = 90mm
245/40 = 40% of 245mm = 98mm
Note: The diameter of the wheel designated on the tyre will not change the profile. Only the width will.
As you can see the wider tyre will give a slightly larger profile, even though both will say 35 on the tyre. Note also, it is only a small difference, but again this can be the different between rubbing and not.
Wheel Diameter
This one is pretty straight forward. The larger your wheels, the higher they will make your car.
For example
If you have the same car with lowered suspension and you put 18's on it then 20's. It will sit up a further inch. Why 1 inch? Because although the diameter has increased 2 inches, the radius has only increased by 1. This is effectively the measurement from the hub (centre of the wheel) to the ground (edge of wheel)
Now there's only little kicker to all of this. And it's the tyre profile. Because you must add the tyre profile to the wheel radius to get an accurate measurement of how much higher the car will sit. Because as we've demonstrated above, the same profile on different tyre width will change the actual profile in mm. This is especially important when talking about different sized rims because generally the higher you go the wider you go, due to structural challenges. Although it must be said this is not always true.
For example,
215/35R18 = (35% of 215mm) plus 9 inches = 75.25 + 228.6 = 303.85mm
235/35R20 = (35% of 235mm) plus 10 inches = 70.5 + 254 = 336.25mm
So as you can see although you've increased your wheel radius by one inch 25.4mm. The actual hight increase is 32.4mm. Because the profile is bigger when changed from a percentage to mm. To negate this you would need to choose a narrower tyre of a lower profile - 235/30R20 would actually give you a lower ride height than the 18's plus tyre would.
Now we can actually start considering what springs to put on.
Three things to consider: height, spring rate, roll.
Height
Pretty simple, how low do you want to go. If you know your wheel and tyre information you should be able to pretty accurately understand how low you *can* go, which is always a good baseline.
Once you have that, its a matter of deciding what springs to put in. I'll use the king springs guide here because I have the most experience in it.
King springs have pretty accurate springs for commodores. I know for a VZ, they've different part numbers for V8's vs V6's in the fronts. This is due to a V8 being heavier (slightly) and so for the two engine models to sit at the same height, the V8 would need slightly stiffer springs. Now keep in mind the difference is almost non-existant and given the amount of ebay people selling 'front SL springs VT-VZ V6&V8' i wouldn't get too bogged down looking for your exact spec. If you do buy second hand ask the seller what he had them in. If they were in a V6 and you put them in a V8 if may go lower than you expect. Or vice versa, may sit up higher than you want.
I buy new from reputable dealers who want to know things like body style, engine size and model. Because there is a difference between fronts on a VT V6 than a VZ V8. The beauty of these slight variations is you can get pretty accurate springs in your car if you choose right. VZ SL V8 springs will sit slightly lower than VZ SL V6 springs, but not as low as VZ SSL V6 springs. It's all very nit picky but there are differences. So if your friend has the same car as you and is lowered use theres as a baseline and chose slightly different variants if you want to go lower or higher.
Spring rate
This is a tricky one because most 'cheap' springs done list spring rates. I'm not sure if king springs lists them anywhere. If you go coil than you'll get that information. But in any case you can still affect spring rates without knowing the exact rates.
A basic lesson on spring rates is quite literally the rate at which they spring. Because there are two ways you make a spring, stiffer with less coils (making the spring shorter) or looser with more coils (higher spring). Both can actually sit at the same exact height, but the stiffer spring will obviously be a less forgiving ride. But it will roll less and handle better. This is because a shorter spring has less room to contract under load. So it is stiffer to compensate.
In terms of part numbers, I know in king springs lingo, HD is the stiffer counterpart of standard springs and as such will be a harsher ride.
Roll
This is an obvious one, the lower and stiffer your spring/shock setup is the less roll you have. This will mean your car is a more aggressive cornering machine. It will also make it more tail happy, including snap oversteer - you have to be much quicker with your steering inputs. Another thing to consider is that a car which rolls less will rub less. Because the car rolls, not the wheels. The less it rolls the less change you have of the car 'leaning' on your tyres.
A quick note on shocks
The cheap suspension upgrade negate shocks. They're the most expensive thing to buy and most people just want the lowered look. And if that is all you want then you don't need shocks. Shocks don't lower your car. They just cope with lower springs better than standard shocks.
Important to note, commodores have two different types of shocks, FE2 and standard. FE2 shocks are slightly more sporty and shorter. So they'll cope with slightly lowered vehicles better than standard. Having said that, if you're by any means a passionate driver, do yourself the favour and get some shocks to suit your springs. It makes the world of difference.
What are the truths,
Standard and FE2 shocks will both take just about any springs you put on the car. They won't be happy about it. And will eventually fail due to being bottomed out almost all of the time. It also puts more stress on other suspension components because the shock has less time to absorb impacts so the impact is thereby transferred to the rest of the car, and you. Which equals and less refined ride.
Standard shocks are of pretty poor quality and i wouldn't recommend any spring upgrade without tossing them.
What cars come with standard shocks?
Anything below a Calais or SV6 has standard. Anything above and including Calais and SV6 have FE2 or better (HSV/Grange etc get the better)
FE2 shocks will cope with SL springs okay. SSL in the rear will most likely be fine too. Although ride quality will deteriorate over time. Just think that the shocks you have are made for the springs you have. So if you buy springs, buy shocks to suit.
I'll add shocks are simple to buy. Don't worry too much on part numbers. Just get them to suit your model. They'll be shortened to suit lower springs and a bit stiffer. This will reduce roll and cope with the lessened spring travel of shorter springs.
Rolling guards
Comes down to how low you're going (ie if you're tucking rim under the guard) and how wide the wheel/tyre combo is. Generally speaking SSL's may just tuck rim. Anything lower will.
I know from experience that an 8.5" wide 18" wheel on 235/40 tyres and SSSL springs won't hit the guard lip. Most people's wheel/tyre combo will be around this (or less wide) so it won't be needed. Of course, under severe cornering, where body roll occurs, you may get rubbing. Rolling the guards may resolve this although it may not be enough. It's worth noting the rubbing is minor (no tyre damage) and only happens under really harsh cornering.
~~
If you search my threads you'll find one of my spring/suspension setup that you can use as a baseline for your own suspension build.
Thanks for reading.
I'm posting my knowledge here to give you specific details regarding how to work out what will fit on your car
I'm hoping this will give people a baseline to work out what they want
Car and Wheels
Car is important as you get a starting point (i'll explain later) and different cars will react differently to suspension mods. This comes down to weight and suspension setup.
For example
A VS is lighter than a VZ, therefore the same spring will sit lower on a VZ than a VS - because it weighs more.
Also, throughout the history of the third gen commodore (VT-VZ), they made the suspension a little better.
For example
When lowered (just shocks and springs) a VT will run more negative camber than a VZ. Keep in mind its not a huge different, the VZ suspension wasn't great compared to the VT. VE's are wear its at if you want a commo with good suspension - but that's another story.
Moving on from the car is the wheels you are running. Thankfully you won't run into any differences between the VT to the VZ when fitting wheels, regardless of how low you are. This is because they all used the same rear quarter panels.
The width, tyre profile and diameter of your rim will affect how low you can go before you rub your guards, either through turning or through bumps. Offsets will also affect this but I that is again another story which requires a separate thread (please ask for more info)
I'll break down wheels into the three sections as above:
Width
Obviously, how wide your wheel is. Notice i said wheel and not tyre. This is because a wheels width will not change, however you can fit different width tyres on the same wheel. It's a little confusing but tyre width will be in miller meters and wheel width will be in inches.
For example
An 8.5" wheel can fit from 215 - 235mm tyres and be roadworthy and within VICTORIAN road rules. I cannot speak for other places. You can also 'stretch' tyres. This is the process of putting a narrow tyre on a wide wheel. I've seen 205 (think barina width tyres) on 10" wheels (that's corvette width). Crazy stuff.
So why am I mentioning all of this? Well going back to my example, a 8.5" wheel with a 215mm tyre on it will have a narrower (albeit slightly) footprint than a 235mm tyre on the same wheel. So technically speaking you could go slightly lower on with that setup. And your wheel could be slightly closer to the wheel arch of your car without touching. it's all very slight stuff but can be the difference between rubbing and not rubbing. And it's a big complaint people have when they put new tyres on their already lowered car. Suddenly they've gone to a wider tyre package without realising and they're getting rubbing where there wasn't before. I could go on more but I think i'll keep it as simple as a can and stop there.
Tyre Profile
Tyre profile is the second digit you get when reading a tyre's specs.
For example
235/35R18. Basically, the tyre is 235mm wide and will fit on a wheel of 18" in diameter. The R is a speed rating. and the 35 is your profile. NOTE this is not 35mm. It is 35%. Biggest mistake people make is reading the 35 as 35mm. It is actually a percentage of the tyre width. so in this case you're looking at 35% of 235 which is 82.25mm.
Another way to look at this is having two tyres with the same profile but different width
225/40 = 40% of 225mm = 90mm
245/40 = 40% of 245mm = 98mm
Note: The diameter of the wheel designated on the tyre will not change the profile. Only the width will.
As you can see the wider tyre will give a slightly larger profile, even though both will say 35 on the tyre. Note also, it is only a small difference, but again this can be the different between rubbing and not.
Wheel Diameter
This one is pretty straight forward. The larger your wheels, the higher they will make your car.
For example
If you have the same car with lowered suspension and you put 18's on it then 20's. It will sit up a further inch. Why 1 inch? Because although the diameter has increased 2 inches, the radius has only increased by 1. This is effectively the measurement from the hub (centre of the wheel) to the ground (edge of wheel)
Now there's only little kicker to all of this. And it's the tyre profile. Because you must add the tyre profile to the wheel radius to get an accurate measurement of how much higher the car will sit. Because as we've demonstrated above, the same profile on different tyre width will change the actual profile in mm. This is especially important when talking about different sized rims because generally the higher you go the wider you go, due to structural challenges. Although it must be said this is not always true.
For example,
215/35R18 = (35% of 215mm) plus 9 inches = 75.25 + 228.6 = 303.85mm
235/35R20 = (35% of 235mm) plus 10 inches = 70.5 + 254 = 336.25mm
So as you can see although you've increased your wheel radius by one inch 25.4mm. The actual hight increase is 32.4mm. Because the profile is bigger when changed from a percentage to mm. To negate this you would need to choose a narrower tyre of a lower profile - 235/30R20 would actually give you a lower ride height than the 18's plus tyre would.
Now we can actually start considering what springs to put on.
Three things to consider: height, spring rate, roll.
Height
Pretty simple, how low do you want to go. If you know your wheel and tyre information you should be able to pretty accurately understand how low you *can* go, which is always a good baseline.
Once you have that, its a matter of deciding what springs to put in. I'll use the king springs guide here because I have the most experience in it.
King springs have pretty accurate springs for commodores. I know for a VZ, they've different part numbers for V8's vs V6's in the fronts. This is due to a V8 being heavier (slightly) and so for the two engine models to sit at the same height, the V8 would need slightly stiffer springs. Now keep in mind the difference is almost non-existant and given the amount of ebay people selling 'front SL springs VT-VZ V6&V8' i wouldn't get too bogged down looking for your exact spec. If you do buy second hand ask the seller what he had them in. If they were in a V6 and you put them in a V8 if may go lower than you expect. Or vice versa, may sit up higher than you want.
I buy new from reputable dealers who want to know things like body style, engine size and model. Because there is a difference between fronts on a VT V6 than a VZ V8. The beauty of these slight variations is you can get pretty accurate springs in your car if you choose right. VZ SL V8 springs will sit slightly lower than VZ SL V6 springs, but not as low as VZ SSL V6 springs. It's all very nit picky but there are differences. So if your friend has the same car as you and is lowered use theres as a baseline and chose slightly different variants if you want to go lower or higher.
Spring rate
This is a tricky one because most 'cheap' springs done list spring rates. I'm not sure if king springs lists them anywhere. If you go coil than you'll get that information. But in any case you can still affect spring rates without knowing the exact rates.
A basic lesson on spring rates is quite literally the rate at which they spring. Because there are two ways you make a spring, stiffer with less coils (making the spring shorter) or looser with more coils (higher spring). Both can actually sit at the same exact height, but the stiffer spring will obviously be a less forgiving ride. But it will roll less and handle better. This is because a shorter spring has less room to contract under load. So it is stiffer to compensate.
In terms of part numbers, I know in king springs lingo, HD is the stiffer counterpart of standard springs and as such will be a harsher ride.
Roll
This is an obvious one, the lower and stiffer your spring/shock setup is the less roll you have. This will mean your car is a more aggressive cornering machine. It will also make it more tail happy, including snap oversteer - you have to be much quicker with your steering inputs. Another thing to consider is that a car which rolls less will rub less. Because the car rolls, not the wheels. The less it rolls the less change you have of the car 'leaning' on your tyres.
A quick note on shocks
The cheap suspension upgrade negate shocks. They're the most expensive thing to buy and most people just want the lowered look. And if that is all you want then you don't need shocks. Shocks don't lower your car. They just cope with lower springs better than standard shocks.
Important to note, commodores have two different types of shocks, FE2 and standard. FE2 shocks are slightly more sporty and shorter. So they'll cope with slightly lowered vehicles better than standard. Having said that, if you're by any means a passionate driver, do yourself the favour and get some shocks to suit your springs. It makes the world of difference.
What are the truths,
Standard and FE2 shocks will both take just about any springs you put on the car. They won't be happy about it. And will eventually fail due to being bottomed out almost all of the time. It also puts more stress on other suspension components because the shock has less time to absorb impacts so the impact is thereby transferred to the rest of the car, and you. Which equals and less refined ride.
Standard shocks are of pretty poor quality and i wouldn't recommend any spring upgrade without tossing them.
What cars come with standard shocks?
Anything below a Calais or SV6 has standard. Anything above and including Calais and SV6 have FE2 or better (HSV/Grange etc get the better)
FE2 shocks will cope with SL springs okay. SSL in the rear will most likely be fine too. Although ride quality will deteriorate over time. Just think that the shocks you have are made for the springs you have. So if you buy springs, buy shocks to suit.
I'll add shocks are simple to buy. Don't worry too much on part numbers. Just get them to suit your model. They'll be shortened to suit lower springs and a bit stiffer. This will reduce roll and cope with the lessened spring travel of shorter springs.
Rolling guards
Comes down to how low you're going (ie if you're tucking rim under the guard) and how wide the wheel/tyre combo is. Generally speaking SSL's may just tuck rim. Anything lower will.
I know from experience that an 8.5" wide 18" wheel on 235/40 tyres and SSSL springs won't hit the guard lip. Most people's wheel/tyre combo will be around this (or less wide) so it won't be needed. Of course, under severe cornering, where body roll occurs, you may get rubbing. Rolling the guards may resolve this although it may not be enough. It's worth noting the rubbing is minor (no tyre damage) and only happens under really harsh cornering.
~~
If you search my threads you'll find one of my spring/suspension setup that you can use as a baseline for your own suspension build.
Thanks for reading.
Last edited:
cheers
