diff --git a/Lib/test/libregrtest/setup.py b/Lib/test/libregrtest/setup.py
index b76bece7ca08b5..ec021668553fb4 100644
--- a/Lib/test/libregrtest/setup.py
+++ b/Lib/test/libregrtest/setup.py
@@ -88,16 +88,19 @@ def _test_audit_hook(name, args):
     setup_unraisable_hook()
     setup_threading_excepthook()
 
-    if ns.timeout is not None:
+    timeout = ns.timeout
+    if timeout is not None:
         # For a slow buildbot worker, increase SHORT_TIMEOUT and LONG_TIMEOUT
-        support.SHORT_TIMEOUT = max(support.SHORT_TIMEOUT, ns.timeout / 40)
-        support.LONG_TIMEOUT = max(support.LONG_TIMEOUT, ns.timeout / 4)
+        support.LOOPBACK_TIMEOUT = max(support.LOOPBACK_TIMEOUT, timeout / 120)
+        # don't increase INTERNET_TIMEOUT
+        support.SHORT_TIMEOUT = max(support.SHORT_TIMEOUT, timeout / 40)
+        support.LONG_TIMEOUT = max(support.LONG_TIMEOUT, timeout / 4)
 
         # If --timeout is short: reduce timeouts
-        support.LOOPBACK_TIMEOUT = min(support.LOOPBACK_TIMEOUT, ns.timeout)
-        support.INTERNET_TIMEOUT = min(support.INTERNET_TIMEOUT, ns.timeout)
-        support.SHORT_TIMEOUT = min(support.SHORT_TIMEOUT, ns.timeout)
-        support.LONG_TIMEOUT = min(support.LONG_TIMEOUT, ns.timeout)
+        support.LOOPBACK_TIMEOUT = min(support.LOOPBACK_TIMEOUT, timeout)
+        support.INTERNET_TIMEOUT = min(support.INTERNET_TIMEOUT, timeout)
+        support.SHORT_TIMEOUT = min(support.SHORT_TIMEOUT, timeout)
+        support.LONG_TIMEOUT = min(support.LONG_TIMEOUT, timeout)
 
     if ns.xmlpath:
         from test.support.testresult import RegressionTestResult
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 29ea944a3bfce9..fb69d9f7af018d 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -74,13 +74,7 @@
 #
 # The timeout should be long enough for connect(), recv() and send() methods
 # of socket.socket.
-LOOPBACK_TIMEOUT = 5.0
-if sys.platform == 'win32' and ' 32 bit (ARM)' in sys.version:
-    # bpo-37553: test_socket.SendfileUsingSendTest is taking longer than 2
-    # seconds on Windows ARM32 buildbot
-    LOOPBACK_TIMEOUT = 10
-elif sys.platform == 'vxworks':
-    LOOPBACK_TIMEOUT = 10
+LOOPBACK_TIMEOUT = 10.0
 
 # Timeout in seconds for network requests going to the internet. The timeout is
 # short enough to prevent a test to wait for too long if the internet request