The block 136x53 is put longways with one end pushed to touch the back rest
You then measure from the front top edge of the block vertically up 450mm
Then draw a horizontal line back, your belt mounts should be at this height or higher, its prudent to add a few mm to this minimum height.
The block longways achieves 2 aims
1. Makes the horizontal and vertical measurment point transect the center of the top of the theoretical shoulder
2. Takes into account any rake on the seat base (some have more rake than others)
Last edited by snapper : 9th March 2013 at 08:52 AM.