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Confused by headset measurements

Old 07-13-18, 07:06 PM
  #1  
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Confused by headset measurements

I am rebuilding a Ross Aristocrat road bike and the chrome on the races is very worn and pitted and so I am looking to replace the races. Assuming I have the part names right, these would be the upper pressed race, the lower pressed race and the crown race.

It seems there are a bewildering amount of sizes for headset components. I looked to Sheldon Brown (Sheldon Brown's Bicycle Headset Dimension Crib Sheet) and saw for
1" ISOStandard the Crown race Inside diameter is 26.4 mm and that the Stem diameter, Steerer I.D. is 22.2 mm (7/8") . In large font is says "This is the standard 1" size.
(I tried to load his chart and failed).

Based on that, I assumed that I was looking for 1 inch ISO standard.

But then I measured the inside of the crown races and saw that they were actually a bit larger than the stated numbers so wondering if the Ross required a special size or if they compress when swagged back on the head tube and that is why they are now larger?

I have photographed the cups first using SAE measurements then metric

Upper Crown race SAE


Upper crown race metric


Lower crown race SAE


Lower crown race metric

No one seems to have anything in my specific sizes and then some companies list stem sizes as .883 (presumably of an inch) instead of 22.2 mm or 7/8".

So, having said all that, can I just go ahead and order a complete standard 1" headset from any online retailer or do I need to order a Ross specific headset**********
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Old 07-13-18, 08:35 PM
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Why are you measuring the inside bore of the headset cups? It's the outside diameter that matters.

The inside measurement is only relevant to the crown race, as it mounts on the fork.
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Old 07-13-18, 08:36 PM
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It seems to me that you're focusing on the wrong measurement. To fit in the head tube, the OD of the race where it fits into the head tube is critical. The ID (as long as it is greater then the steerer OD) is pretty irrelevant. You want an interference fit with the head tube.
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Old 07-13-18, 08:40 PM
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Well, to start the dimensions of a headset are usually either a reference to the fork's steerer OD (and this is not the crown race seat) or the press fit diameters the headset is made for. So the 1" headset, regardless of the other sub specs for it, is not the inside of the press fitted cup skirts that fit in the head tube. Of course their ID has to have a tad of clearance to allow a 1" steerer to pass through them.

So go back to the measuring caliper and headset parts nd measure the interfacing surfaces/diameters. The skirts' ODs, the crown race seat's ID. then measure the frame and fork's mating points to confirm or find out how tiny a measuring variation you can end up with. Don't assume what is currently called a standard is what has/was done years before. Standards come and go. When a brand is big enough it's common for specific dimensions to be sourced as to prevent lower quality part subs (read up on the history of Schwinn and remember that Ross was a wanna be Schwinn). So always go to the measured dimensions as your guide.

Ross did use some Ross speced stuff. That they are long gone will make our search for replacement parts only harder. Good luck. Andy
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Old 07-13-18, 08:47 PM
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Similarly, the 22.2 inner diameter of the steerer tube is relevant for picking a stem, not a headset.
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Old 07-13-18, 09:57 PM
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You need to measure the crown race of your fork 26.4 mm = 1 inch standard 27mm = JIS. Either one will fit your head tube but only one will fit your fork, that is the one you want.
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Old 07-14-18, 07:00 AM
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https://www.parktool.com/blog/repair...eadset-service
Servicing Bicycle Headsets

YOu also need to know the stack height


​​​​​​​
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Old 07-14-18, 09:59 AM
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Ok, I remeasured. I measured 1st in inches and 2nd in metric

fork crown external diameter (1.185 inches).
fork external diameter - measured on a thin line made in the paint by the crown when it was compressed (1.05 inches)
fork crown external diameter (30.08 mm)
fork external diameter - measured on a thin line made in the paint by the crown when it was compressed (26.14mm)

lower race external diameter (1.184 inches).
lower headset internal diameter (1.182 inches)
lower race external diameter (30.08 mm)
lower headset internal diameter (30.17mm)

upper race external diameter (1.185 inches).
upper headset internal diameter (1.184 inches)
upper race external diameter (30.10 mm)
upper headset internal diameter (29.83mm)

dedhed

You said, "You also need to know the stack height"

I checked the link you provided https://www.parktool.com/blog/repair...eadset-service

I can't see any reference to the stack height. What do I need to watch for?
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Old 07-14-18, 10:24 AM
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If your replacement headset stack height is too tall, your locknut will not engage enough threads

Measuring Threaded Stack Height
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Old 07-14-18, 11:01 AM
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Measure the inside diameter of the frame, head tube, instead, yet?
and outside diameter of the fork crown race seat, at the fork crown..
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Old 07-14-18, 11:42 AM
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dedhed - I see what you mean and will watch for that. Thank you.

Fietsbob - I did those measurements and have posted them.


I measured 1st in inches and 2nd in metric

fork crown external diameter (1.185 inches).
fork external diameter - measured on a thin line made in the paint by the crown when it was compressed (1.05 inches)
fork crown external diameter (30.08 mm)
fork external diameter - measured on a thin line made in the paint by the crown when it was compressed (26.14mm)

lower race external diameter (1.184 inches).
lower headset internal diameter (1.182 inches)
lower race external diameter (30.08 mm)
lower headset internal diameter (30.17mm)

upper race external diameter (1.185 inches).
upper headset internal diameter (1.184 inches)
upper race external diameter (30.10 mm)
upper headset internal diameter (29.83mm)
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Old 07-14-18, 11:49 AM
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best fit ? insert a few thousandths larger than the frame ID, for a good press fit.
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