diff --git a/mercurial/bundle2.py b/mercurial/bundle2.py
--- a/mercurial/bundle2.py
+++ b/mercurial/bundle2.py
@@ -183,7 +183,7 @@
 _fpayloadsize = '>i'
 _fpartparamcount = '>BB'
 
-preferedchunksize = 4096
+preferedchunksize = 32768
 
 _parttypeforbidden = re.compile('[^a-zA-Z0-9_:-]')
 
diff --git a/tests/test-clone-uncompressed.t b/tests/test-clone-uncompressed.t
--- a/tests/test-clone-uncompressed.t
+++ b/tests/test-clone-uncompressed.t
@@ -199,7 +199,7 @@
   
 
   $ f --size --hex --bytes 256 body
-  body: size=112318
+  body: size=112222
   0000: 04 6e 6f 6e 65 48 47 32 30 00 00 00 00 00 00 00 |.noneHG20.......|
   0010: 68 07 53 54 52 45 41 4d 32 00 00 00 00 03 00 09 |h.STREAM2.......|
   0020: 05 09 04 0c 2d 62 79 74 65 63 6f 75 6e 74 39 38 |....-bytecount98|
@@ -207,7 +207,7 @@
   0040: 72 65 71 75 69 72 65 6d 65 6e 74 73 64 6f 74 65 |requirementsdote|
   0050: 6e 63 6f 64 65 20 66 6e 63 61 63 68 65 20 67 65 |ncode fncache ge|
   0060: 6e 65 72 61 6c 64 65 6c 74 61 20 72 65 76 6c 6f |neraldelta revlo|
-  0070: 67 76 31 20 73 74 6f 72 65 00 00 10 00 73 08 42 |gv1 store....s.B|
+  0070: 67 76 31 20 73 74 6f 72 65 00 00 80 00 73 08 42 |gv1 store....s.B|
   0080: 64 61 74 61 2f 30 2e 69 00 03 00 01 00 00 00 00 |data/0.i........|
   0090: 00 00 00 02 00 00 00 01 00 00 00 00 00 00 00 01 |................|
   00a0: ff ff ff ff ff ff ff ff 80 29 63 a0 49 d3 23 87 |.........)c.I.#.|