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Using Styrene to increase Rim Size

It's not a very common practice to try increasing the rims size of our builds. Usually, we simply opt to replace the whole rims to ones that are already the required size. However when I was building the Tamiya Lexus LFA and using the HD detail-up set to turn into a Nurburgring Edition, I discovered that the rims supplied with the transkit are actually smaller than the original LFA items! This would have made them look small beneath the Lexus body and the Tamiya tires were simply too big for them. At this stage, I decided to use styrene to make them bigger and get them the same size as the originals! 

The procedure below shows you exactly how I did this job of turning a set of 19" to 20". This can be performed to any rims that have a flat circumference, like the ones I'm using.

Picture above shows the original LFA rims in 20". The resin rims on the back is the original HD supplied with the Nurburgring set. The one in front wearing the tire, is an already modified one which became the same size as the originals and tire fits perfectly

Here's a comparison with the original vs HD rims where the discrepancy in size can be noted. At this stage my options were to replace the Tamiya tires with a set of 19s, or modify the HD rims to become the same size as the originals. I chose the latter!

In the picture above we can see how loose the original tire from the LFA fits around the rim supplied with the Hobby Design detail set. As explained before, this is due to the smaller size of the new rims. Time to take out the tools and make them fit!

I have several different thickness of styrene and made some tests to find out the best size possible to increase the rims from 19s to 20s. The ideal thickness was 0.01" (0.25mm)

First thing I did was mark the width of the rim on the styrene. I marked it around 2mm wider on each side to be sure the whole rims is covered when gluing. Extra will be sanded

Then I measured the circumference of the rims. For this I took several pieces of scrap masking tape I had lying around and attached them to the circumference of the rim. Always leave it a little longer, as seen above, so that you'll have extra to cut later on

The tape was then removed as a whole piece from the rim and attached in between the lines I drew earlier, to mark the circumference on the styrene. This will be where I cut

Now I cut out the styrene sheet I had just marked earlier. Since the sides will be sanded out once the styrene is attached, it's not important to cut into a perfect straight line

Now, before starting to glue the styrene in place, make sure that the circumference of the rims doesn't have any raised pieces, like I had on mine (as seen above). These will obviously affect you in attaching the styrene perfectly with the rim, so sand these away

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Here it is, all sanded smooth and ready to start attaching the styrene sheet

Now, the gluing can begin! For this I use a quick drying superglue as it helps to have such a glue. I start with attaching a small piece of the first side, let it dry and then keep attaching piece by piece until arriving at the last stage seen above, where only about a 1cm remains to be glued. I stop at this stage so that I could mark the extra piece exactly. While gluing it's important not to leave any gaps between the styrene and the edge of the rim, especially on the front. This will look ugly once paint is applied, so avoid at all costs!

So at this stage I press the extra part down onto the already glued styrene and using a blade I mark on both sides where the styrene meets. These will be as guides where I cut

Now lift the extra part back up and using a scissors cut along the two blade marks

Once the extra piece is cut, check that both sides now match well. If not, take a sand paper or file and slowly sand away any extra pieces of styrene which might still be there

Using a sand paper or file, sand down the line where the styrene has been joined together until you achieve a smooth finish as seen above. Now, it's time to take care of the extra lenght of styrene on the front and back. So, first I used a scissors to remove the larger pieces, then a sand paper placed flat on the desk to remove the smaller styrene pieces

When sanding the front of the rims to remove the extra pieces of styrene, it's important to do it slowly and check the progress every few seconds. Once the styrene is fully sanded, you'll start sanding away details from the rim, and I'm sure you don't want that!

Do the same for the back until all the styrene is sanded flat with the rim. And, that's all! You're done with the modification and if you chose the same thickness as me, your rim is now an inch bigger! You can also opt to leave the styrene at the front a little longer so that you'll create a deep dish in front of the rim! All up to you to adapt to your requirements!

There they are, four rims modified with styrene and ready to go for primer an inch bigger!

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Related Video

I have also documented this tutorial into a video, uploaded to my YouTube channel. You can see this from the viewer below:

And that’s my whole procedure! Really hope you find it interesting and that it'll help you out when you need to modify your rims to make them bigger or add a little deep dish to them! If you have any questions, feel free to sign the guestbook or ask on the jdm24scale facebook page. Keep modelling friends!


Building the Tamiya Lexus LFA

Tutorial: Fitting wheel adaptors

Review: The HD LFA detail set

More info inside