Index: ../trunk-jpl/src/m/classes/friction.py
===================================================================
--- ../trunk-jpl/src/m/classes/friction.py	(revision 22874)
+++ ../trunk-jpl/src/m/classes/friction.py	(revision 22875)
@@ -37,10 +37,8 @@
 		self.p=project3d(md,'vector',self.p,'type','element')
 		self.q=project3d(md,'vector',self.q,'type','element')
 		#if self.coupling==0: #doesnt work with empty loop, so just skip it?
-		if self.coupling==3:
+		if self.coupling in[3,4]:
 			self.effective_pressure=project3d(md,'vector',self.effective_pressure,'type','node','layer',1)
-		elif self.coupling==4:
-			raise ValueError('coupling not supported yet')
 		elif self.coupling > 4:
 			raise ValueError('md.friction.coupling larger than 4, not supported yet')
 		return self
@@ -70,7 +68,7 @@
 		WriteData(fid,prefix,'object',self,'fieldname','p','format','DoubleMat','mattype',2)
 		WriteData(fid,prefix,'object',self,'fieldname','q','format','DoubleMat','mattype',2)
 		WriteData(fid,prefix,'class','friction','object',self,'fieldname','coupling','format','Integer')
-		if self.coupling==3:
+		if self.coupling in[3,4]:
 			WriteData(fid,prefix,'class','friction','object',self,'fieldname','effective_pressure','format','DoubleMat','mattype',1,'timeserieslength',md.mesh.numberofvertices+1,'yts',md.constants.yts)
 		elif self.coupling > 4:
 			raise ValueError('md.friction.coupling larger than 4, not supported yet')