ElectraGirl: The Difference 15mm Can Make

Saturday 5th March 2016

After the success of putting the lowering springs on our i3, we started thinking about wheel spacers, then the bad weather arrived and we put that thought to one side for a couple of months. But now the weather is mostly getting better, we started to think about them again.

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15mm Wheel Spacers and 43mm bolts

Wheel spacers are disks placed between the wheel and the hub to push the wheel out a little. They can look a bit silly when too big but when done just right, they give the car a broader stance filling the wheel arch looking good and improving handling. Getting the right thickness led me to asking a couple of questions about sizes of spacers to some owners that had already fitted them. Within a couple of hours of the response the spacers and bolts were ordered and we sat back and waited for them to be delivered.

We chose to go with 15mm spaces on all four wheels and we got 43mm bolts for the wheels to compensate for the extra reach.

We didn’t have long to wait, they were ordered on Wednesday 24th February and they were here in two days, on Friday 26th, so we knew what we would be doing on the coming Sunday.

Sunday arrived and my sidekick said that this was going to be an easy job to do, did that mean he expected me to do it?!! I’m not sure about that, won’t my hands get dirty?! Anyway, apparently I wasn’t expected to do it – phew!! I was just being told it was an easy job.

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43mm bolts


Spacer on hub



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So – with the spacers and bolts unpacked, it was time to head outside. First task was to jack the car up on one side and remove the wheels. Oh no! My lovely lowering springs are all grubby from the winter weather – should I clean them?  Apparently not as when I turned around the spacers were on and being aligned with the bolt holes and the wheels were already being put back on. Then the new longer bolts were put in and tightened a little; the car was lowered and the bolts tightened up so the wheels don’t fall off – because that might be a problem! And – Viola! That’s one side done. Now repeat on the other side. I didn’t get to clean the springs on the other side ether. It did indeed turn out to be a simple job! Maybe I could have done it – maybe, hmm maybe not! Turns out that when asked to release the jack on the back whilst my sidekick lowered the front, I couldn’t even get the jack to lower slowly – Oops!

Wow – the car does look different, it’s not a huge difference just a subtle difference but a really good difference.

Next up was the test drive. Oh my goodness, what a difference. You can feel that the car is sat more firmly on the road, it feels more squatted, like there really is a wheel on all four corners. Because, you know, it really didn’t feel like that before. With the lowering springs and now the wheel spacers on it has made a real difference to the i3. A really good difference – I like it – A lot.

My sidekick will now write his little piece as I had to get out of the car for this. I got stuck in the car for one turn but not again – no way.

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Results recorded on my iPhone

So, it’s not just vanity that drove us to add the wheel spacers but, they do look good! The extra 30mm of track has again lowered the center of gravity. To test it, I pulled out my test kit and headed to open flat tarmac.

The results speak well of the i3’s tires and suspension setup, the result was a healthy 0.91G of lateral acceleration, on a warmer day, Edmunds managed 0.78G by comparison.

Safety first

What dos that mean? Well, they say that the best way to survive an accident is to avoid getting into one in the first place. The extra lateral grip means that our i3 can now corner faster than almost any 70’s super car and comes close to a modern day Porsche 911 – only 0.04G short and, on super-efficient wheels and tires.

Thanks to Shaun Wooten, Marcus Pugh and the i3 community for their recommendations and help on selecting the perfect solution.


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  • Mark Melocco

    I hope you have told your insurance company that you have modified your vehicle in this way as many will not insure cars fitted with wheel spacers.
    Wheel spacers affect the ‘Scrub Radius’ of you suspension and can adversely affect the steering performance of a car in situations where the level of grip is different on each side such as if you drop over the edge of a road or hit a patch of ice. In these situations kick – back and stability can be adversely affected.
    I really think you should do some research into the likely effects so that if you choose to keep this modification you will at least be aware of the potential changes to your cars behaviour.

    • Electra Girl

      Following the BMW community forums it seems that opinion is split, some say any more positive scrub is bad, others claim not to be able to feel any difference, especially with only a 15mm change. Many say it has a bigger impact on those off-roading but I guess that’s what you’re saying if I fall off the road 🙂

      I had my sidekick give it a work out (my stomach can’t handle that) to see how things had changed and apart from some black lines where my tires had had enough, he couldn’t find a problem other than greater grip overall.

      I wonder it there’s a test that could be carried out, any ideas?

      • Mark Melocco

        As you have discovered, adding wheel spacers is a bit controversial with opinions on both sides. I was a bit concerned that you may not be fully aware of the potential drawbacks as this was not mentioned in your article, in particular that some insurance companies will refuse cover or worse refuse to pay a claim if you don’t disclose this modification to them. Your local wheel alignment guy may be able to tell how far the scrub radius has been affected but I’m not aware that there is any objective test that can be done. In the end it’s your car and armed with the correct knowledge you can make a more informed decision.

        • MPugh

          As common as wheel spacers are I have not ever once heard of an insurance company that required such a disclosure and further denied a claim. Some cheap wheels spacers have given wheels spacers a bad wrap, as long as you buy high quality products your rush of failure is minimal.

          • info

            Even the cheap ones don’t fail – they are simple discs afterall – its the overall handling as well as suspension wear and tear that is affected.

    • MPugh

      Are you new to wheels spacers? They are very common amongst enthusiasts, I believe your concern is misplaced.

  • In an electric car and especially in one with the aerodynamics of a tall SUV extra steps are taken to lower the weight, the aerodynamic drag and the tire rolling resistance.
    Lowering the car was good for lowering the aerodynamic drag, but extending the wheels out its the opposite.
    It disrupts the smooth flow of air around the car.

    • Electra Girl

      Yes, you can definitely see at the rear how the tires stick out a bit more than before. I’ll take it out on the highway today to see if I can hear any extra wind noise and report back. I suppose that pushing them out does place them into the flow though I don’t know how far out they have to get to really have an impact and, at the same time they’re subtracting from the resistance to the air flowing underneath.

      I’m getting about 5.1 Miles/kWh at the moment as it’s the coldest part of the year, we’ll see if that changes but with my typical driving seldom reaching 40mph I think the warmer weather might play a bigger part.

      • vdiv

        You may have to disrupt the airflow even more and add mud flaps 😉

    • MPugh

      The i3 is a city car, at speeds of 45mph or higher the slab front end hinders the cars drag more than anything. Spacers are the least of the i3’s troubles at highways speeds, but make the car look amazing at city speeds, well worth it.

  • info

    Increased unsprung mass, puts additonal strain on wheel bearings and changes steering fulcrum point, reduces spring rate…..Overall BMW spent 100,000 USD on i3 why mess with the set up? Spacerd are about looks not perforamnce or handling – sounds more psychosomatic to me. Lowering and increasing negative front camber would have a better handling result with only downside being inner tyre wear.