One of the most popular modifications for any car owner is the suspension. There is a lot of information out there and it's super easy to get lost and confused. So here's this guide to help find the best suspension upgrade for you and your BMW Z3.
We'll be through this in stages of 'complexity', stage one being the easiest thing to do and stage 5 being the more complex one. Feel free to skip through stages if you already know what you're looking for!
Stage 1 - Replace your old parts with new OEM spec
BMW made the car this way then why change it?
If you're happy with how the car handles, how the ride feels or if you're just looking to replace worn parts then Stage 1 is for you.
Why should you stick to OEM? (Original Equipment Manufacturer)
- It's often cheaper than the alternatives. Not just from a parts and labour point of view but changing the suspension can adversely effect tyre wear and other parts of the car which can add to the cost of maintenance.
The car is set up from the factory for a balance between performance and longevity. If you change one part, like a spring, it changes how all the other parts interact with it.
- You like the current set-up. If it ain't broke, don't fix it. The Z3 is a good handling car as standard. If you're enjoying open roof cruises with the odd spirited country lane dash then there's no reason to give yourself a headache with all these suspension options.
- The new parts will instantly give you better performance than the old, worn out parts currently on the car. Sometimes all you need is a refresh to kick some life back into the Z3, similarly to how giving it a clean makes it feel newer.
Why shouldn't you keep to OEM?
- As good as BMW developed the Z3 from the factory, there are improvements to be made if you can make the investment or are specifically looking to increase the handling performance.
If OEM if the choice for you the next question is which brand to go for?
You can get them from Euro CarParts, AutoDoc or any other friendly stock holder.
For springs you have to order to your car. For example a Z3 2.2 came with sports suspension so the springs are lower than standard. If you have a 4 cylinder Z3 don't order springs for a 6 cylinder as the spring rates are made to handle the heaver engine up front.
As long as you know which Z3 you have, most websites will have a filter system that accurately shows you the options for your specific car.
Here are some of our suggestions:
For the shock absorbers the same applies as above, replace like for like in terms of specifications. For the fronts you'll have to order Left and Right as the mounting points can't be flipped if you order 2 lefts. The rears don't have this issue.
Sachs shocks are the OEM brand and are still available.
Important point to note. It's good practice to changed left and right at the same time. It's also a good idea to grab any rubber pads that may need changing.
Stage 2 - Lowering springs
Firstly, what are lowering springs? The simple answer is they are shorter springs than OEM. The shorter spring lowers the car. So we have lowering spring.
Why would you get lowering springs for your Z3?
- In short, better handling. The car is lower to the ground, center of gravity is lower, there's less body roll and all the other stuff that's better explained here.
- Just for the looks. The Z3 does have some pretty big wheel arch gap which isn't the most aesthetically pleasing. Lowering the car closes the gap and gives the car a more aggressive look in the process
_ Cheaper modification alternative. Getting a set of lowering springs is the cheapest way to lower your car to increase handling performance. Coilovers are a lot more expensive and we'll cover those a little later on.
Why shouldn't you get lowering springs?
- The ride can be harsher. This means that you'll feel more of the bumps in the road and depending of how stiff the springs are, your spine won't be thanking you as you drive over that unavoidable pothole. As long as you get good quality springs you'll end up with a more responsive feel and your spine will stay intact. However if you want smooth cruising then lowering springs may not be for you.
- If you go too low you can't get over speed bumps. Bumper scraping may look cool but it really isn't practical. Be aware of how much the springs are lowering your car. 30mm is the most common choice as it gives the Z3 a more aggressive look, is still drivable and you can still fit decent sized alloys.
- On the topic of alloys, if you have massive 19" or 20" alloys on your Z3, you won't be able to lower the car as much as someone on 16" or 17" alloys. Also tyre height can factor into this. Get the tape measure out and do some calculations to make sure you're not going to slam your wheel arch onto your wheel!
If lowering springs are the one for you then here's a couple of recommended brands:
- H&R Lowering Springs > 30mm drop
- Eibach lowering springs > 30mm drop
Important point to note. Keeping the standard shocks can cause them to wear faster. Keep this in mind as you may have to change to shocks made for lowering springs shortly after. Many people successfully run lowering springs and OEM shocks but faster wear is something to keep an eye on.
Stage 3 - Suspension Kits
A packaged deal for all your suspension needs, well kind of. A suspension kit consists of springs and shocks. The main point here is you can get lowering springs with matching shocks!
Why should you get a suspension kit?
- As above it matches the lowering springs to the shocks so they are balanced and will wear evenly. It also means you can change all 4 corners at the same time!
- You get all the benefits of the lowering springs with the shocks to match!
Why should you not get suspension kits?
- They are expensive compared to lowering springs
- No adjustability. If you're looking for something you can dial in then this isn't for you.
- Not a massive cost jump to coilovers which are adjustable.
If you want to lower your car properly, get all those lower car benefits and you're happy to keep one setting, then which one do you go for?
Everyone has these. Everyone loves them. It lowers the car but is still soft enough for daily driving.
Stage 4 - Coilovers
If you're looking for something to let you fine tune your suspension, change it between daily driving and track driving then coilovers are your friend. There's a lot of stuff to adjust so here's a video explaining coilovers, what they do etc.
Why should you get coilovers?
- Adjustability is the main reason. Most, if not all, sets let you adjust the ride height of your Z3. Some come with camber adjustment, dampening adjustment and rebound adjustments.
- All the performance benefits of lowering your Z3 with the added performance benefits of dialing in other settings as above.
Why shouldn't you get coilovers?
- They are the most expensive option. Getting cheap ones may not give you the full adjustability you're looking for
- The rears are not true coilovers. As the Z3 has the E30 rear suspension set-up it has the spring and shock fitted independently of each other. This means that a real coilover set-up will require some welding and a couple of extra parts.
If coilovers are the ones for you then here are a few recommendations:
- KW Series There a 3 variations.
KW 1 is the cheapest with height adjustment
KW 2 is next with height and rebound damping adjustment
KW 3 is the most expensive but with adjustable bump & rebound damping as well as height
- BC- Racing have a range just like KW with different adjustment levels and spring rates to choose from.
- Gaz Coilovers have a nice range but also offer a true coilover for the rear axel. You will need to purchase their offset rear top mounts to ensure the rear coilover units fits.
Many people have used one of these three options and are happy with the results.
Stage 5 - Racing Suspension
Don't really know! You have to look at spring rates and do a bunch of maths and testing.
We're still learning about this and really, it all comes down to what racing you're doing, your driving style, do you have aero etc etc.
Racing coilovers are best place to start, GAZ have got racing specific coilovers for sale which were used by the ZCars Z3s .
When we've learnt more about this we'll add to this blog!
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