diff --git a/tire/tire_81.6_50.scad b/tire/tire_81.6_50.scad
index bc7d607..cfa6fab 100644
--- a/tire/tire_81.6_50.scad
+++ b/tire/tire_81.6_50.scad
@@ -5,10 +5,15 @@ $fn=60;
 
 // 81.6x50:
 
+// rim offset is (SPOKE_THICKNESS+(R_I-SPACING-RIM_THICKNESS-CUT_BASE)/2),
+// so offset=4mm if SPOKE_THICKNESS=12.85
+
 R=40.8; // outer radius
 R_I=26.5; // innermost radius
 BEVEL=2;
+BEVEL_OUTER=0.8;
 THICKNESS=2.5;
+BORDER_THICKNESS=2.5;
 PROT_DEPTH=1;
 PROT_L_WIDTH=2;
 PROT_A_WIDTH=2;
@@ -19,14 +24,15 @@ B_P=4; // position of edge for the rim
 W=50; // tire width
 N_L=4; // number of lateral protectors
 N_A=10; // number of angular protectors
-SPOKE_THICKNESS=10; // thickness of solid spoke part
+SPOKE_THICKNESS=12.85; // thickness of solid spoke part
 RIM_THICKNESS=2;
 N_SPOKE=9; // number of spokes
 CUT_BASE=8;
 CUT_ANGLE=12;
 CUT_I_R=1.5;
 CUT_O_R=2;
-SPACING=0.2;
+SPACING=0.6;
+HOLE_RADIUS=2.4; // my Wanhao Duplicator 4 makes no errors with Slic3r, 2.4mm is ideal lego hole
 
 // 6-spoke variant
 N_SPOKE=6;
@@ -36,56 +42,65 @@ CUT_O_R=2;
 
 // small
 R=22;
-BEVEL=1;
-THICKNESS=1.5;
-FIX_WIDTH=1;
+BEVEL=0.6;
+THICKNESS=1.2;
+BORDER_THICKNESS=0.8;
+PROT_DEPTH=0.4;
+SPOKE_THICKNESS=8;
+FIX_WIDTH=1.2;
 PROT_A_WIDTH=1;
 PROT_L_WIDTH=1;
 B_P=3;
-B=1;
+B_W=1;
+B=1.6;
 R_I=15;
 CUT_O_R=1;
 CUT_BASE=5;
 N_L=2;
-W=20;
+N_A=0;
+W=16;
 
 difference() {
   union() {
     translate([0, 0, W]) rotate([180, 0, 0]) {
       rim();
-      // Support ...
-      translate([0, 0, SPOKE_THICKNESS+(R_I-SPACING-RIM_THICKNESS-CUT_BASE)/2+SPACING]) cylinder(r=CUT_BASE, h=W-(SPOKE_THICKNESS+(R_I-SPACING-RIM_THICKNESS-CUT_BASE)/2+SPACING));
-      translate([0, 0, W-(B_P-FIX_WIDTH-SPACING)+SPACING]) cylinder(r=R_I+B-SPACING, h=(B_P-FIX_WIDTH-SPACING)-SPACING);
-/*
-      translate([0, 0, W-(B_P-FIX_WIDTH-SPACING)-2-B+SPACING]) difference() {
-        cylinder(r=R_I+B+THICKNESS, h=(B_P-FIX_WIDTH-SPACING)+2+B-SPACING);
-        translate([0, 0, -1]) cylinder(r=R_I+B+SPACING, h=1+(B_P-FIX_WIDTH-SPACING)+2+B-SPACING-((B_P-FIX_WIDTH-SPACING)-SPACING));
-      }
-*/
     }
-    tire();
+    difference() {
+      tire();
+      // first layer usually becomes slightly bigger...
+      difference() {
+        cylinder(r=R, h=0.3);
+        translate([0, 0, -0.1]) cylinder(r=R-BEVEL_OUTER-0.2, h=1);
+      }
+    }
+    /*
+    // "Manual support material" needed to print tire
+    difference() {
+      hull() {
+        cylinder(r=R_I+B-0.2, h=B_P-0.2-(BEVEL-0.2*(2-sqrt(2))));
+        cylinder(r=R_I+B-0.2-(BEVEL-0.2*(2-sqrt(2))), h=B_P-0.2);
+      }
+      translate([0, 0, -0.1]) cylinder(r=R_I+B-0.2-2, h=B_P);
+    }
+    translate([0, 0, B_P+B_W+0.3])
+    difference() {
+      cylinder(r=R_I+B+THICKNESS, h=W-2*(B_P+B_W+0.3));
+      cylinder(r=R_I, h=W);
+    }*/
   }
   // to cut and look inside :)
   translate([0, 0, -0.5]) cube(size=[R+10, R+10, W+1]);
 }
 
 module rim() {
+  V_SPACING=0.2;
   color([0.5, 0.5, 1]) {
     difference() {
       union() {
-        cylinder(r=R_I-SPACING, h=W-(B_P-FIX_WIDTH-SPACING));
+        cylinder(r=R_I-SPACING, h=W-(B_P-FIX_WIDTH-V_SPACING));
         // outer fixing edges
-        cylinder(r=R_I+B-SPACING, h=FIX_WIDTH+(B_P-FIX_WIDTH-SPACING));
-        translate([0, 0, W-(B_P-FIX_WIDTH-SPACING)-FIX_WIDTH]) cylinder(r=R_I+B-SPACING, h=FIX_WIDTH);
-        // inner fixing edges, 45 degree slope for easier printing
-        translate([0, 0, FIX_WIDTH+(B_P-FIX_WIDTH-SPACING)+(B_W+SPACING)+SPACING]) hull() {
-          cylinder(r=R_I+B+THICKNESS, h=FIX_WIDTH);
-          translate([0, 0, B+THICKNESS+SPACING]) cylinder(r=R_I-SPACING, h=FIX_WIDTH);
-        }
-        translate([0, 0, W-(FIX_WIDTH+(B_P-FIX_WIDTH-SPACING)+(B_W+SPACING))-FIX_WIDTH-SPACING]) hull() {
-          cylinder(r=R_I+B+THICKNESS, h=FIX_WIDTH);
-          translate([0, 0, -(B+THICKNESS+SPACING)]) cylinder(r=R_I-SPACING, h=FIX_WIDTH);
-        }
+        cylinder(r=R_I+B-SPACING, h=FIX_WIDTH+(B_P-FIX_WIDTH-V_SPACING));
+        translate([0, 0, W-(B_P-FIX_WIDTH-V_SPACING)-FIX_WIDTH]) cylinder(r=R_I+B-SPACING, h=FIX_WIDTH);
       }
       // make spokes by cutting space between them
       for (i = [1 : N_SPOKE])
@@ -104,9 +119,9 @@ module rim() {
       translate([0, 0, -1]) cylinder(r=CUT_BASE-2, h=5+(B_P-FIX_WIDTH-SPACING));
       // make spokes convex using another toroidal cut
       difference() {
-        translate([0, 0, -1]) cylinder(r=1+R_I+B-0.5/*R_I-2*/, h=1+(B_P-FIX_WIDTH-SPACING));
-        translate([0, 0, (B_P-FIX_WIDTH-SPACING)])
-          scale([1, 1, (B_P-FIX_WIDTH-SPACING)/((R_I-SPACING-RIM_THICKNESS-CUT_BASE+2)/2)])
+        translate([0, 0, -1]) cylinder(r=1+R_I+B-0.5/*R_I-2*/, h=1+(B_P-FIX_WIDTH-V_SPACING));
+        translate([0, 0, (B_P-FIX_WIDTH-V_SPACING)])
+          scale([1, 1, (B_P-FIX_WIDTH-V_SPACING)/((R_I-SPACING-RIM_THICKNESS-CUT_BASE+2)/2)])
           rotate_extrude(convexity = 10)
           translate([(R_I-SPACING-CUT_BASE)/2+CUT_BASE-RIM_THICKNESS, 0, 0]) circle(r = (R_I-SPACING-CUT_BASE)/2);
       }
@@ -131,38 +146,55 @@ module rim_cut() {
 }
 
 module tire() {
+b_i = BEVEL;
+bo_i = max(BEVEL, BEVEL_OUTER-THICKNESS*(2-sqrt(2)));
 difference() {
   hull() {
-    translate([0, 0, BEVEL]) cylinder(r=R, h=W-BEVEL*2);
-    cylinder(r=R-BEVEL, h=W);
+    translate([0, 0, BEVEL_OUTER]) cylinder(r=R, h=W-BEVEL_OUTER*2);
+    cylinder(r=R-BEVEL_OUTER, h=W);
   }
   // center hole through all piece
   translate([0, 0, -0.5]) cylinder(r=R_I, h=W+1);
   // top hole
-  translate([0, 0, W-B_P]) cylinder(r=R_I+B, h=B_P+1);
+  hull() {
+    translate([0, 0, W-B_P+BEVEL]) cylinder(r=R_I+B, h=B_P+1);
+    translate([0, 0, W-B_P]) cylinder(r=R_I+B-BEVEL, h=B_P+1);
+  }
   hull() {
     translate([0, 0, W-BEVEL]) cylinder(r=R_I+B, h=BEVEL);
     translate([0, 0, W]) cylinder(r=R_I+B+BEVEL, h=1);
   }
   // bottom hole
-  translate([0, 0, -1]) cylinder(r=R_I+B, h=B_P+1);
+  hull() {
+    translate([0, 0, -1]) cylinder(r=R_I+B-BEVEL, h=B_P+1);
+    translate([0, 0, -1]) cylinder(r=R_I+B, h=B_P+1-BEVEL);
+  }
   hull() {
     translate([0, 0, 0]) cylinder(r=R_I+B, h=BEVEL);
     translate([0, 0, -1]) cylinder(r=R_I+B+BEVEL, h=1);
   }
   // inside cut
-  translate([0, 0, B_P+B_W]) cylinder(r=R-THICKNESS-PROT_DEPTH/2, h=W-(B_P+B_W)*2);
+  translate([0, 0, B_P+B_W]) cylinder(r=R-THICKNESS, h=W-(B_P+B_W)*2);
   difference() {
-    translate([0, 0, THICKNESS]) cylinder(r=R-THICKNESS-PROT_DEPTH/2, h=W-THICKNESS*2);
+    hull() {
+      translate([0, 0, BORDER_THICKNESS]) cylinder(r=R-THICKNESS-bo_i, h=W-BORDER_THICKNESS*2);
+      translate([0, 0, BORDER_THICKNESS+bo_i]) cylinder(r=R-THICKNESS, h=W-BORDER_THICKNESS*2-bo_i*2);
+    }
     cylinder(r=R_I+B+THICKNESS, h=W);
+    translate([0, 0, W-BORDER_THICKNESS-b_i])
+      linear_extrude(height=b_i, scale=(R_I+B+THICKNESS+b_i)/(R_I+B+THICKNESS))
+      circle(r=R_I+B+THICKNESS);
+    translate([0, 0, BORDER_THICKNESS])
+      linear_extrude(height=b_i, scale=(R_I+B+THICKNESS)/(R_I+B+THICKNESS+b_i))
+      circle(r=R_I+B+THICKNESS+b_i);
   }
   // lateral protector
   if (N_L > 0) for (i = [1 : N_L])
     translate([0, 0, -PROT_L_WIDTH/2+i*W/(N_L+1)])
       difference() {
         cylinder(r=R+1, h=PROT_L_WIDTH);
-        translate([0, 0, -0.01]) linear_extrude(height=min(PROT_L_WIDTH/2-0.1, PROT_DEPTH/2)+0.01, scale=(R-PROT_DEPTH)/(R+0.01)) circle(r=R+0.01);
-        translate([0, 0, PROT_L_WIDTH]) rotate([180, 0, 0]) translate([0, 0, -0.01]) linear_extrude(height=min(PROT_L_WIDTH/2-0.1, PROT_DEPTH/2)+0.01, scale=(R-PROT_DEPTH)/(R+0.01)) circle(r=R+0.01);
+        translate([0, 0, -0.01]) linear_extrude(height=PROT_L_WIDTH/2+0.01, scale=(R-PROT_DEPTH)/(R+0.01)) circle(r=R+0.01);
+        translate([0, 0, PROT_L_WIDTH]) rotate([180, 0, 0]) translate([0, 0, -0.01]) linear_extrude(height=PROT_L_WIDTH/2+0.01, scale=(R-PROT_DEPTH)/(R+0.01)) circle(r=R+0.01);
         translate([0, 0, -0.1]) cylinder(r=R-PROT_DEPTH, h=PROT_L_WIDTH+0.2);
       }
   // angular protector
@@ -185,7 +217,6 @@ module protector_angular() {
 
 module axle(height) {
   axle_gap = 1.95;
-  HOLE_RADIUS = 2.55;
   union() {
     translate([-HOLE_RADIUS, -axle_gap/2, 0])
       roundedRect(HOLE_RADIUS * 2, axle_gap, .2);