In our fun little MIKO community last week, I asked YOU to be the teachers!
Here was my question:
Deep creases, wedgies and excessive buttcrack gathers (😅 I know there’s a better description, but this gets straight to the point) indicate that the bikini is too large for the body. This occurs even in the most minimal of cuts. How do you fix it?

Two main remedies were proposed:
- Decrease the width through the crotch
- Shorten the rise
Both of these remedies are correct! But today, I’ll go over what I approach first and why. Let’s dive right in!
Defining the Problem
Whenever you encounter excess fabric buildup down the back centerline, it’s most likely an indication that the suit is too large. The instinctual response is to reduce the width throughout the crotch and back. But, what if you’re in a position in which you cannot reduce the width? For example:
- Reducing width may not be an option for competitors with strict coverage guidelines. Or, let’s expand beyond bodybuilding competitions: reducing the width is not always an option for gymnastic leotards, figure skating costumes, competitive swim…etc. And,
- You’ve reduced the width as much as possible, yet this problem still occurs
Personally, my first check is the back crotch length. It’s a little counter intuitive, but hopefully this blog post will explain why.
Just a little refresher: The crotch length is the distance from your front waistline to your back waistline, where the waistline is defined as the smallest circumference of your torso.
The crotch length is different for every body. However, most commercial patterns, including the MIKO Sewing Patterns, use crotch lengths based on ASTM industry standards.
Many women will fit within the standard sizes. But many of us will still need adjustments for the best fit.
Todays discussion will be limited only to the back crotch length.
Before moving on, it’s also important to note that this summary will not go over any specific measurement magnitudes. It is simply an overview to help you in hands-on fitting for yourself or your client.

Why Length is Important
The easiest way to explain why length is important is through simple geometry! We’re going to use a right triangle, as given in the image below.

Based on this image, you can see that measurement ‘c’ (the triangle’s hypotenuse) is directly related to and affected by measurement ‘a’. Let’s go over why this is important and what it represents:
The triangle’s hypotenuse (measurement ‘c’) represents the bikini’s leg hole. Measurement ‘a’ is the back centerline. If ‘a’ is too long, then ‘c’ will be too long. Ultimately, the area of the triangle will be too large, where the area of a triangle is defined by

So even if you insert your leg hole elastic to induce more negative ease through measurement ‘c’, you’re still left with too much area (e.g. too much fabric). The image below shows a comparison between a fitted triangle and a large triangle.

With nowhere to go, the excess fabric loosely bunches up down the back centerline.
What if the opposite occurs?

If ‘a’ and ‘c’ are too short, you’ll just end up with an uncomfortably tight wedgie!
What’s the Fix?
If you recognize this problem at your first fitting with your client (or your first fitting if you’re making your competition suit), then the first step is to evenly pinch out as much excess fabric as possible along a horizontal line, as shown below:

Start at the back centerline and work outward toward each leg hole. Where should your horizontal line fall?
The MIKO Sewing Patterns give two locations at which you can adjust the back centerline. However, when you’re physically fitting yourself or your client, don’t worry about those locations. I’ll go into more detail in my upcoming Ultimate Fit Guide for Figure Bottoms.
For physical fittings, the horizontal fitting line can be placed AT your hip line (i.e. the widest part of your glutes/hips) or just below it.
Important factors when doing this include, but are not limited to:
- You MUST also pinch out the excess at each leg hole. The diagrams below will show why.
- Do not pinch out more than you need to. You’ll know that you’ve gone too far if you start pulling on the crotch seam and the back waistline.
- After your first run of pinching out the excess, assess the fit. You may have to take in a hair more fabric, so two to three more pinching iterations might be necessary .
Let’s see this method in action using our right triangle example:
1. Define the placement of your horizontal fit line

2. Pinch out the excess, working from the back centerline outward. You must pinch out the leg holes as well. Remember, the leg holes are proportional to the centerline.

3. Take note of the excess that you pinched out, then transfer that measurement to your pattern. True your leg hole.

et voila!
In conclusion, the back length is the first measurement that I evaluate when excess fabric pools in the butt crack. Secondary to that is the width measurement, and there are definitely occasions in which you’ll need to do both. For the most part, if you adequately address the back length (measurement ‘a’), then you’ll have the right amount of tension through your leg holes (measurement ‘c’) to keep your bikini from pooling.
I will be publishing an Ultimate Fit Guide for the MIKO Figure Pattern that will go into much more detail. It’ll show you how to preemptively determine if the pattern will be too long or short for you or your client. And it will go in depth with the steps to take for adjusting your pattern before cutting into fabric.
But in the meantime, I hope this blog post helps you in your physical fittings! As always feel free to contact me with any questions.
I’ll talk to you soon 🙂
xo,

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