diff --git a/tire/tire_81.6_50.scad b/tire/tire_81.6_50.scad
index 67cca1a..a2973aa 100644
--- a/tire/tire_81.6_50.scad
+++ b/tire/tire_81.6_50.scad
@@ -10,6 +10,18 @@ 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
+N_SPOKE=9; // number of spokes
+CUT_BASE=8;
+CUT_ANGLE=12;
+CUT_I_R=1.5;
+CUT_O_R=2;
+
+// 6-spoke variant
+N_SPOKE=6;
+CUT_ANGLE=21;
+CUT_I_R=2.5;
+CUT_O_R=2;
 
 rim();
 tire();
@@ -21,26 +33,43 @@ module rim() {
         cylinder(r=R_I-0.2, h=W-2*(B_P-2-0.2));
         cylinder(r=R_I+B-0.5, h=2);
         translate([0, 0, W-2*(B_P-2-0.2)-2]) cylinder(r=R_I+B-0.5, h=2);
-        translate([0, 0, B_P]) cylinder(r=R_I+B+2, h=2);
-        translate([0, 0, W-2*(B_P-2-0.2)-6]) cylinder(r=R_I+B+2, h=2);
+        hull() {
+          translate([0, 0, B_P]) cylinder(r=R_I+B+2, h=2);
+          translate([0, 0, B_P+B+2+0.2]) cylinder(r=R_I-0.2, h=2);
+        }
+        hull() {
+          translate([0, 0, W-2*(B_P-2-0.2)-6]) cylinder(r=R_I+B+2, h=2);
+          translate([0, 0, W-2*(B_P-2-0.2)-6-B-2-0.2]) cylinder(r=R_I-0.2, h=2);
+        }
+      }
+      for (i = [1 : N_SPOKE])
+        rotate([0, 0, i*360/N_SPOKE]) rim_cut();
+      translate([0, 0, SPOKE_THICKNESS+(R_I-2-CUT_BASE)/2])
+        rotate_extrude(convexity = 10)
+        translate([(R_I-2-CUT_BASE)/2+CUT_BASE, 0, 0]) circle(r = (R_I-2-CUT_BASE)/2);
+      translate([0, 0, SPOKE_THICKNESS+(R_I-2-CUT_BASE)/2]) cylinder(r=R_I-2, h=W);
+      translate([0, 0, -0.5]) linear_extrude(height=W+1) axle();
+      translate([0, 0, -1]) cylinder(r=CUT_BASE-3, h=5);
+      hull() {
+        translate([0, 0, -1]) cylinder(r=CUT_BASE-2, h=1);
+        translate([0, 0, -1]) cylinder(r=CUT_BASE-3, h=2);
       }
-      for (i = [1 : 8]) rotate([0, 0, i*45]) rim_cut();
-      translate([0, 0, -0.5]) cylinder(r=2.5, h=W+1);
     }
   }
 }
 
 module rim_cut() {
-  translate([5, 0, -0.5]) linear_extrude(height=W+1) {
+  in_angle = atan((R_I-2)*sin(CUT_ANGLE)/((R_I-2)*cos(CUT_ANGLE)-CUT_BASE-CUT_I_R));
+  translate([0, 0, -0.5]) linear_extrude(height=W+1) {
     hull() {
-      circle(r=1);
-      rotate([0, 0, 15]) translate([R_I-2-5-3, 0, 0]) circle(r=3);
-      rotate([0, 0, -15]) translate([R_I-2-5-3, 0, 0]) circle(r=3);
+      translate([CUT_BASE+CUT_I_R, 0]) circle(r=CUT_I_R);
+      rotate([0, 0, CUT_ANGLE]) translate([R_I-2-CUT_O_R, 0, 0]) circle(r=CUT_O_R);
+      rotate([0, 0, -CUT_ANGLE]) translate([R_I-2-CUT_O_R, 0, 0]) circle(r=CUT_O_R);
     }
     difference() {
-      circle(r=R_I-2-5);
-      rotate([0, 0, 15]) translate([-50, 0]) square(size=[100, 30]);
-      rotate([0, 0, -15]) translate([-50, -30]) square(size=[100, 30]);
+      circle(r=R_I-2);
+      translate([CUT_BASE+CUT_I_R, 0]) rotate([0, 0, in_angle]) translate([-50, 0]) square(size=[100, 100]);
+      translate([CUT_BASE+CUT_I_R, 0]) rotate([0, 0, -in_angle]) translate([-50, -100]) square(size=[100, 100]);
     }
   }
 }
@@ -96,3 +125,23 @@ module protector_single() {
     translate([0, 0, -10]) cylinder(r=R+10, h=10);
   }
 }
+
+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);
+    translate([-axle_gap/2, -HOLE_RADIUS, 0])
+      roundedRect(axle_gap, HOLE_RADIUS * 2, .2);
+  }
+}
+
+module roundedRect(x, y, radius) {
+  hull() {
+    translate([radius, radius, 0]) circle(r=radius);
+    translate([x - radius, radius, 0]) circle(r=radius);
+    translate([x - radius, y - radius, 0]) circle(r=radius);
+    translate([radius, y - radius, 0]) circle(r=radius);
+  }
+}