diff --git a/backend/server.js b/backend/server.js
index c984672..848bcbd 100644
--- a/backend/server.js
+++ b/backend/server.js
@@ -68,7 +68,6 @@ if (!carCols.includes('sort_order')) {
   db.exec('ALTER TABLE cars ADD COLUMN sort_order INTEGER DEFAULT 0');
   db.exec('UPDATE cars SET sort_order = id');
 }
-db.prepare("UPDATE cars SET tire_type = 'スタッドレス' WHERE tire_type = 'スタットレス'").run();
 
 // Migrate: add period fields to reservations if they don't exist yet
 const resCols = db.prepare("PRAGMA table_info(reservations)").all().map((c) => c.name);
@@ -100,17 +99,13 @@ function broadcast(message) {
   });
 }
 
-function normalizeTireType(value) {
-  return value === 'スタットレス' ? 'スタッドレス' : value;
-}
-
+// for future use
 function normalizeCar(car) {
   if (!car) {
     return car;
   }
   return {
     ...car,
-    tire_type: normalizeTireType(car.tire_type),
   };
 }