Underwires are not all same. Their shape, length and width differ a lot from one brand and model to another. Have you ever had underwires poke you in the wrong places, even though the cups fit perfectly?
Firstly, I recommend underwired bras for these reasons. They keep the breast tissue from escaping under the band. And underwires need not be uncomfortable. The first reason for uncomfortable underwires is wrong bra size. Even if you have been measured by a fitter, measure yourself like this.
Why the width of the underwires mattersAfter you've found your correct size, you need to find out whether you need broader or narrower underwires. Some breasts have a very narrow base or root, some have a much wider one. To see what a difference the width of underwires can make, take a look at these photos; the girl is wearing broad underwires in photos on the left, and narrow in the right side photos. She clearly need narrow underwires. The broad underwires go way beyond her breasts, and don´t support it. Also, the bra band pulls the underwires even further, and they stretch, and pull the cup fabric with them, flattening the breasts.
How to find out whether you need narrower or broader underwiresFirst, look at the imprint the underwires leave on your breasts*. Ideally they should perfectly outline the breast. If the go on top of the breast or they go way beyond the breast, you will know they are the wrong width. I also want to quote Drüber und Drunter's method of finding out where your breast tissue ends:
"In order to decide if your wires are just right or too wide/narrow, it is important to know where your breast tissue ends. Best thing is to lift your breast and push it a little to the side. Mark the line with an eyeliner or a similar pencil. Then, just like in a breast examination, feel for breast tissue beyond this line to make sure there are no glandular tissue outside the visible breast area. The wire should enclose all breast tissue!" read the rest of her postA person with wider breasts can easily tell when the underwires are to narrow for them: the breasts look (and feel) as if the underwire is cutting off a part of them. A girl with narrower breasts might feel that some underwires end on her back, leaving parts of the cup empty.
If you still have no idea which underwires you need, I advise you to try on a bra each from Panache and Freya -- Panache has the widest underwires and Freyas are narrow.
Don't confuse the width of underwires with their length. Long underwires are problematic for petites and ladies with highly set breasts: the tips poke upwards into the armpit. For the rest, long underwires keep the breast tissue in place, and prevent migration of breast tissue. Long underwires are on bras that have a lot of fabric under the armpit. Both long and short underwires can be narrow as well as broad.
Don't confuse the width of underwires with your breasts being close together or far apart. More on that here.
Also, some underwires are elastic, some not. Very springy underwires mean that when you put on the bra, the band pulls the underwires, making them wider. So, the underwires are wider when worn, that makes the band wider, and the cup flatter. *Example pics*
Where to buy narrower or broader underwires ?
Underwire width differs from brand to brand, and sometimes from model to model. I highly recommend checking out bra reviews on Bratabase and bra-fitting blogs before you order bras. Some brands like Panache almost always have wide undewires; Freya and Lepel have the narrowest ones. Ewa Michalak and Fantasie are medium. More on other brands here.
Measure the length and width of the underwires of bras that fit you well (distance between the tips) -- compare this to the numbers that you find on Bratabase.
Can you just bend the underwires ?That works only for small adjustments. Bending the underwire wider 1. makes the cup flatter, and 2. the band wider, so you´re distorting the whole shape and fit. However if it´s not the width that´s bothering you but the shape of the underwire: feel free to experiment.
* Underwires and bra bands usually leave marks on the body, just as panties and socks do. That's normal, and doesn't mean you need a looser bra; unless it's hurting.
Photo by basakina