Peugeot road bike stem steerer size? When is 22.2mm not 22.2mm?
05-10-23, 06:53 AM
#26
Not so New
I believe the serial number was originally on an aluminum plate riveted in those two holes on the bottom bracket. I think the the number you see was a later addition by a PO, possibly at the time of re-painting.
05-10-23, 07:46 AM
#27
Sunshine
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Don't think so.
The late Sheldon Brown gave the dimensions of a French metric steerer tube as having a nominal OD of 25mm (slightly less than 1") and a nominal ID of 22mm. That means the tube's wall thickness would be 1.5mm - part of which is threaded and thus already weaker than the unthreaded portion. Increasing the ID to 22.2mm would further reduce the wall thickness to 1.4mm.
In contrast, a standard ISO 1" threaded steerer tube has an nominal OD of 25.4mm and a nominal ID of 22.2mm. This means the normal wall thickness of an ISO 1" threaded steerer tube is 1.6mm.
A French steerer as designed (25mm OD/22mm ID) has a wall thickness 6.25% less than a 1" ISO steerer. Increase the inside diameter to 22.2mm and it's now 12.5% thinner.
I'd sand the stem.
The late Sheldon Brown gave the dimensions of a French metric steerer tube as having a nominal OD of 25mm (slightly less than 1") and a nominal ID of 22mm. That means the tube's wall thickness would be 1.5mm - part of which is threaded and thus already weaker than the unthreaded portion. Increasing the ID to 22.2mm would further reduce the wall thickness to 1.4mm.
In contrast, a standard ISO 1" threaded steerer tube has an nominal OD of 25.4mm and a nominal ID of 22.2mm. This means the normal wall thickness of an ISO 1" threaded steerer tube is 1.6mm.
A French steerer as designed (25mm OD/22mm ID) has a wall thickness 6.25% less than a 1" ISO steerer. Increase the inside diameter to 22.2mm and it's now 12.5% thinner.
I'd sand the stem.
Admittedly I hadnt even measured the steerer tube OD. The headset was already installed, so I just took it apart to clean and regrease- hadnt thought to measure the headset ID or the steerer OD.
Given that I would file down the area where threads are cut, and the math you did shows its about 1.4mm in that area, I will attack the stem. I just assumed the numbers were 25.4mm and 22.0mm.
Interesting for sure.
05-10-23, 07:57 AM
#28
Senior Member
Forgive me for stating the obvious but the steerer tube is steel while the quill is aluminum, a much softer, easier to sand down, metal
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05-10-23, 01:32 PM
#29
Senior Member
Well very interesting and thanks for the math.
Admittedly I hadnt even measured the steerer tube OD. The headset was already installed, so I just took it apart to clean and regrease- hadnt thought to measure the headset ID or the steerer OD.
Given that I would file down the area where threads are cut, and the math you did shows its about 1.4mm in that area, I will attack the stem. I just assumed the numbers were 25.4mm and 22.0mm.
Interesting for sure.
Admittedly I hadnt even measured the steerer tube OD. The headset was already installed, so I just took it apart to clean and regrease- hadnt thought to measure the headset ID or the steerer OD.
Given that I would file down the area where threads are cut, and the math you did shows its about 1.4mm in that area, I will attack the stem. I just assumed the numbers were 25.4mm and 22.0mm.
Interesting for sure.
Frame tube dimensions are often different (metric tubing diameters in even mm). Fork steerer? Slightly different size (25mm OD), with metric 25mm x 1mm threading for the steerer (and thus the headset topnut). Crown races? Often non-ISO (26.5mm and 27.0mm). Quill stems? Different insert size (22mm). Handlebars? Non-ISO clamp size, and also not the Italian standard 26.0mm (25.0mm was the standard French alloy road bar clamp size, and the grip size was also slightly smaller - 23.5mm vice 23.8mm for ISO and Italian). BB? 68mm shell, but 35mm x 1mm threaded and RHT on both sides. Seatposts? Sometimes odd-sized due to tubing size differences. Pedals? Different threading. Frames often had Simplex or Huret RD hangers vice the de facto standard Campagnolo style. Different gauge numbering scheme for spokes. And there are probably a few other deviations from the norm I'm forgetting.
That said: I do have a French stem (with what appears to be a legit 25.4mm clamp), headset, and set of French threaded 68mm BB cups squirreled away - just in case I ever lose my mind and decide to "go for it".
