10mm

 

Thanks Bill! The head must be a little chewed up 10mm won't fit and 11mm is too loose.

 

Are you using a flare nut wrench?

 

Tried a flare nut wrench, I only have standard size. Did not fit. I put a regular metric wrench on their to gauge size.

------ Follow up post added March 20th, 2013 12:45 PM ------

Hm well it may be 7/16ths then. IIRC, the fittings are 3/8-28 straight with DIN flare. However some are 10mm metric, so that was my first guess. If it is chewed up I can make you another pipe with new nuts if you send me the length. Don't try to save questionable brake parts.

At this point I do not mind cutting the lines to get the cylinders off. I replaced the front lines, might as well replace the rear as well. Thanks for the offer, I can bend up a set myself

 

Hm well it may be 7/16ths then. IIRC, the fittings are 3/8-28 straight with DIN flare. However some are 10mm metric, so that was my first guess. If it is chewed up I can make you another pipe with new nuts if you send me the length. Don't try to save questionable brake parts.

 

When I roll under my truck to do brakes I bring a 10, 11, and 3/8. One of em usually works, but it's definitely not consistent.