Hello,
The seat seam is ripping open under fairly extreme movement e.g. lifting foot right up to put a shoe on, crouching right down. They feel completely comfortable otherwise and look good.
Following Rory's comment on a video (can't remember which!) I always use weakish cotton thread so the cloth never rips. However should I be either making an alteration here, or using stronger thread?
Thanks!
Robbie
As for soft thread, I don't use polyester for fear if the seam comes under pressure, the cloth will tear rather than the thread in the seam.
It's not the thread that's the issue here, but the allowance over the on skin seat measurement.
The seat expands 2" when you bend over or sit down.
So the finished seat measurement should be 3" bigger for expansion and ease.
If your seat is 42, your trousers should finish at 45.
I had the same problem with a pair of trousers earlier this year. I ended up reinforcing the machined seam with a row of hand-stitching. I used thicker, cotton thread: Guterman 30 wt (though it might have been 12 wt, I can't remember). It's sometimes referred to as 'Sulky' (a type of embroidery thread, apparently). I used stem stitch. It's the same as back stitch, but done from the other side of the cloth (so to speak), which allows one to direct the thread and make a neater job of it. Outline stitch is the same, but the thread is directed from above, rather than below (check some youtube vids and you'll see what I mean). Which one you use depends on any curvature. You direct the thread in the opposite direction to a curve in the seam, otherwise the end row of stitching will have an angular look. Hand-sewing supposedly has more give, which was my reasoning for doing the above. It worked, but the material was quite sturdy (cotton drill). Might simply be better to add a little more ease across the seat. Or stay the seam and use stronger machine thread?