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Car weight reduction guide and tips

Car weight reduction guide and tips

Posted by Matthew Marks on 15th Dec 2021

Weight saving guide header image

Benefits of making your car lighter

You may hear people talking about the power to weight in their car and its importance, and they are 100% right. If we go back to basic principles and Newton's second law of motion Force = Mass x Acceleration in simple terms, the less mass you have to move, the less force is required to move it at the same rate.

An excellent example of this is an Ariel Atom 500, which can beat a Bugatti Veyron to 100mph at half the power due to the difference in weight!

Many factors also come into play, such as gearing, traction, and aerodynamics. However, you are off to a good start with less weight!

We will break down the easiest, simplest and cheapest ways to remove multiple kilograms from your car. Not only is the benefit from weight reduction making your car faster you get:

  • Increased acceleration
  • Improved braking
  • Improved cornering
  • More responsiveness
  • Reduced Wear on components

"Simplify, then add lightness" – Colin Chapman.

What should I remove?

What you remove is entirely up to you and will solely depend on why you use the car. If it's a daily driver, I doubt you'd be wanting to remove parts such as the stereo, but in a dedicated track, race or drag car, they would already be long gone!

We will be covering as many points today as possible, but there will be particular items on each car that we will have missed. If you are unsure about anything on this list, please talk to a mechanic or race car driver as they will clarify any points.

We will try to touch on as many car points as we can, but you can also go to the extreme and modify things such as OEM chassis and engine brackets that you do not need. For this, the difficulty will increase massively and involve fabrication work etc.

We are now going to run through the easiest and most effective ways to reduce the weight of your car and a rough estimation of the weight saved (varies from car to car).

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Sprung vs unsprung weight reduction

Before we go into parts you should be removing or changing; you need to learn the difference between sprung and unsprung weight.

Sprung

Sprung weight is anything carried by the car’s suspension, which would include parts such as the engine, seats, chassis etc. Generally, as the sprung weight increases, it will gain traction, but on the other hand, it will decrease mpg and increase weight transfer, ultimately leading to more body roll and instability, which you don’t want on a track car!

Unsprung

On the other hand, unsprung weight is the opposite, including parts such as the wheels, tyres, hubs, driveshafts etc. If unsprung weight were to increase, you would generally have a more significant effect on the vehicle as most of the unsprung weight will be rotational, which will have more inertia than sprung.

Sprung v unsprung infographic

Which one has more impact?

If you are going for all-out weight reduction, then unsprung would be the way to go as you would always gain more than reducing sprung weight. As a general rule, unsprung mass is the equivalent of 1.7-2 times what sprung weight is. So saving 1kg from the unsprung mass is equivalent to 1.7kg – 2kg of sprung mass (such as your interior parts).

As for rotational mass, this has even more of an effect. Let’s take your wheel, for example; not only is the wheel part of the unsprung weight, but it also spins so it has angular momentum and the further away the mass is from the pivot point (centreline driveshaft), the more of an effect it will have.

Rotational mass can have an equivalency of up to 10 times sprung mass. There are many variables such as wheel size and where the mass is taken off from (tyre or wheel spacers, for example)

Rotational mass would apply not only to wheels and tyres but to anything rotational in your assembly. Fitting a lighter flywheel will make the engine rev quicker; the same applies to the wheels and tyres, as an example. When braking the less force is required to overcome the inertia of the wheel, more responsive braking, less heat and ultimately fewer losses.

Because of this, the further down the line you go with your weight reduction, the more you will be changing out items such as a wheel, wheel nuts, brakes, driveshafts etc., for a lighter version.

The more weight you can remove from both sprung and unsprung, the quicker you will be getting the lap times down, but if on a tight budget, you now know where to spend your money first!

Interior weight saving header image

Interior

The interior of your new track car is where most of the weight reduction will be. Removing the interior parts is one of the most straightforward modifications you can do. Of course, it is primarily free, making it the first go-to modification for most enthusiasts.

All you need is a bit of time and to be able to use simple tools such as a socket set, and you will be on your way!

Seats

The factory seats in many cars have multiple extras, such as electric adjusters, which generally have heavy motors. They are made from heavy materials due to their production, which is counterproductive to what you are trying to achieve.

Start by removing the Rear seats and replacing the front seats with lightweight racing bucket seats. There are hundreds of options on the market, ranging from a few hundred pounds to thousands.

You will likely be going with the cheapest option if this is your first track car. Bear in mind that if you ever enter a competition, you may need a particular seat specification, such as FIA approved seats for many events in the UK.

For the most cost-effective option, fibreglass seats will be the best bang for your buck, but when moving into the more expensive seats, you will see carbon fibre and Kevlar being used instead.

Once these are removed, you may have extra rear seat mounting brackets that you can also remove but be cautious as once drilled out; it will be much more challenging to fit the seats again in the future.

Changing these parts over won't save you a vast amount, but it will be more than you think combined with removing the rear seats and the front seats changed to lightweight versions!

Boot Spares

The majority of cars from the factory will come with many extras in the boot, such as a spare wheel, tool kit etc. For a road car, these are very important if anything were to happen, but on a track car, you can massively condense these down, and the majority of the tools you need will be waiting in the pits.

Remove your spare wheel, tool kit and any other junk you have been collecting in the boot. Lastly, you can remove the old plastics and boot carpet and any other extras that do not need to be there for that extra bit of weight saved.

Extra interior parts

Interior and sound deadening is a little bit harder but can save you massive amounts of weight! Remove everything you do not need, such as carpet, interior plastics, door cards, sound deadening and seam sealer.

While still being on the interior, the roof lining and sunroof are a large amount of weight to save and can also bring your centre of gravity down, which will increase handling.

If you want to go to the whole extreme on the interior, you can cut out non-structural metal such as door skins or Fixed parcel shelves, but we always recommend going with a roll cage to keep the cars' structural integrity.

In a nutshell, you can go as far as you want to with the interior, but this ultimately depends on the car's function and if you ever plan on driving it on the road again.

Carbon and fibreglass weight reduction header

Carbon And Fibreglass panels

We’ve all seen how beautiful carbon fibre panels are, but there is a massive weight advantage to be gained from them as well. The first panel most track day enthusiasts will look at is the bonnet, as in most cars, the bonnets are made from heavy steel.

Moving over to carbon fibre can save up to 15kg, which is a massive amount on any car. The next panel worth replacing would be the boot, which will be your next heaviest panel.

If you are going to the extreme, you can change parts such as the wings, bumpers, and roof skins, but again at this point, you would also need a roll cage to keep it as safe as possible.

Consider removing weight from high up on the car; this will lower your centre of gravity and reduce weight transfer and roll. For example, the E46 BMW M3 CSL came with factory fitted carbon fibre roof skin.

The downside to carbon fibre is the cost, and you will be looking from £300 up to £1,500 for each carbon panel you decide to replace.

If you want a more cost-effective option, fibreglass replacement panels are the next best thing. You may need to paint, wrap, or skin them, but they are generally much cheaper than their carbon fibre counterpart due to the finish.

Even with fibreglass, you can sometimes opt for certain skinning levels to make sure that it is as light as it can be!

If in doubt about anything so far in this article, make sure to get advice from a professional as they will be able to guide you in the safest possible manner to make sure you have fun but are also safe!

Polycarbonate windows

Unlike glass, polycarbonate windows are so strong they are almost unbreakable, and in the majority of cases, are lighter than their glass counterparts.

What is polycarbonate?

Polycarbonate is a thermoplastic polymer and is incredibly strong as a material. More importantly, it is completely transparent, making it a perfect substitute for glass in a track car.

Some regulations and circuits would ask to use polycarbonate instead of glass as it will not shatter, ruining everybody’s track day, including your own, if you were to crash.

Polycarbonate also has extreme impact resistance and is around 250 times stronger than glass, making it incredibly popular in everyday applications such as safety glasses or car headlights.

The one downside to changing glass for polycarbonate is that it is not as scratch-resistant, so most companies who manufacture polycarbonate automotive windows will have developed a hard coating to prevent this.

In terms of weight, generally, polycarbonate panels are around 50% lighter than their glass counterpart. They have so many other advantages that make them easy to go with. For costing, they are also not massively expensive, as you will be only looking around £200-£600 for a complete set.

suspension and wheels category header

Suspension And Wheels

Moving onto suspension and braking, you will be killing two birds with one stone to be fully set up for being a track or race car; you will need a mixture of good handling and weight reduction.

Luckily, most of the aftermarket products that will help you towards this will be much lighter than their OEM counterpart.

Coilovers

Coilovers are a good starting point here, as they will make up most of your handling and cornering, plus there is some good weight to be shed here! In terms of pound per kg of weight saved, these aren’t the most cost-effective option but will transform your car!

When you remove the stock suspension for a Coilover setup, you will be looking to save anything up 5kg over the stock suspension.

There are hundreds of Coilover options on the market, but we always recommend yellow speed racing as our first choice, as we have personally used them on many of our cars and supplied for customers race cars, with the least amount of problems with them.

Arms and bushes

For this section, we will specifically talk about the arms and bushes in one, as if you are changing out bushings generally, the weight will not be saved massively just from here.

Many different suspension arm brands are on the market, but our go-to brand would be hardrace for this. Again, like yellow speed racing, we run all Hardrace arms on our 4wd turbo civic and never have any issues with them.

Because of how cars are designed, generally, there is quite a bit of weight in the lower and upper arms. For example, the OEM rear lower control arms on a Honda are made from steel, whereas hardrace makes sets from billet aluminium which will save weight.

Also, due to how they design the bushes, you can either use their hardened rubber bushes or spherical, giving you the added advantage over the OEM bushes out on track.

Once you have gone through and changed all your arms for lightened or aluminium versions, you will add up quite a weight reduction over the car and handle much better than with your old, cracked bushes.

Brakes

Brakes will be the next thing on the agenda, and like the coilovers being unsprung, you will be able to gain quite a bit of an advantage here as generally, aftermarket setups are lighter.

As you will be going much faster out on track than a road car, you will naturally be wanting to upgrade your brake pads, discs and Calipers for better braking and pedal feel than OEM.

Starting with the main weight saver, you will more than likely be going from steel stock Calipers to something such as a 4 or 6 pot piston setup.

Generally, these will be aluminium, so you should be able to save a few kg here and disperse the braking force more evenly over your new pads.

There won’t be a significant saving in weight with the discs and pads you are using, but you should be able to go with much more aggressive versions than stock, such as the PBS Prorace brake pads and RPB grooved brake discs. You should also increase your disc size and still save weight, so a win all around.

The discs and pads combined with the Calipers will allow you to brake much later, and with the extra weight saving, you will be reducing the lap or ¼ mile times!

Less fuel and body weight

The next point is obvious but also very easily missed! If you are using a stock fuel tank, let us say 40ltr for the sake of argument, you do not need to fill it to the brim.

If you are going to be taking spares to the track with you, you can always invest in some fuel cans, and only half fill your tank. Fuel, on average, will weigh around 800g per litre, so if you are only filling your tank halfway with 20ltr, you will instantly save 16kg.

If you’ve ever seen full drag cars such as the SFWD cars, they will run small fuel tanks in their front bumpers for two reasons. One is for weight disbursement over the vehicle for as much traction as possible, and secondly, they only need enough fuel for one run and will save themselves a tremendous amount of weight in the process.

Lastly, if you are going to the extreme in your car, the most obvious thing is to save your body weight. Going from 100kg to 80kg will save as much as removing an entire passenger seat!

Lightweight wheels

Referring to the sprung v unsprung debate earlier in this article, the next thing to look at changing up is your wheels. Just replacing your OEM wheels for lightweight racing wheels can save up to 5kg per wheel!

Because of the massive advantage you gain with items such as wheels being part of the rotational mass, you will notice a considerable difference by dropping even 2kg off each wheel.

Exhaust system weight saving header

Exhaust system

Your exhaust system won’t be the most significant loss of weight over this guide, but as we try to make this guide cover as many points as possible, we thought it was best to include it!

Materials

Oem exhaust systems are generally made as cheaply as possible from varying grades of steel, which in turn tends to rust badly over a period.

Because of this, most of the cheaper aftermarket exhaust systems are made from stainless steel, which will be lighter than OEM, plus you will gain the extra resistance to corrosion that the OEM exhaust system won’t offer.

If budget isn’t the biggest problem for you, titanium is the lightest option. Generally, this will cost much more than the stainless counterpart, but being around 40% lighter on average will save a considerable amount over the entire exhaust system.

There are other things to consider when getting a custom exhaust, such as removing silencers, reducing the number of joints, and thinking about the wall thickness of the pipe. These things will all help you on your weight loss journey.

How much weight can be removed?

The amount of weight being removed is entirely down to you, but if you are fully stripping the car and changing everything in this article, we have seen some cars removing up to 100kg from the stock weight of the vehicle.

As every car will vary from their factory weight, we cannot put an exact number on anything in this article, but the more you decide to remove or change out, the lighter you will possibly get the car.

Is it worth removing everything?

Suppose you are going for a dedicated race car, then yes. The majority of the factory parts on vehicles, especially the interior, will be made for comfort so you can remove them without needing to worry.

In some cases, you do not need to remove the functionality of a product; you can replace it with something much lighter weight that will do the same job, such as the t7 design lightweight race heaters.

These can sometimes be outputting the same heat, if not more, than your factory heater plus can save up to 9kg!

Conclusion

Now you’ve been through our entire list in-depth, you should be able to decide what you would like to keep or remove. Most of the time, with racing, this will come down to budget, but you shouldn’t need to worry too much to get started with many free options available to you.

Good luck in your new weight reduction journey, and if you need any of the products we have mentioned in this article, make sure to check out the rest of our website, where we stock thousands of different parts.