Who knows the answer?

[bigpantswheels]

Why is every part on every bike that I have owned over the last 40 years been measured in metric, seatpost diameter, stem length, frame size, crank length, wheel spacing 126-130,etc. but bearings are measured in inches, 1/4 inch 3/16 inch ,etc. I have Italian, Japanese, and American frames, some with Campy some with Shimano and all have the same size bearings. Did anyone make bearings in metric sizes, I can't say I have ever seen any. Anyone knows the answer?

 

[Jonny69]

I'm fairly certain the 25.4mm seatpost on your bike isn't metric, nor is the 25.4mm headset, 22.2mm stem, 633mm rims etc etc! Most of them are legacy imperial sizes which have been converted to metric. Sometimes it's just easier to quote the imperial size and be done with, else you start asking for 14.2875mm threads in something, which would scare all but the best machinists. But a 9/16" thread? No problem!

 

[KermitGKona88]

Re:

Loose bearings are Imperial 1/4, 3/16, 5/16, chain pitch is too 3/32, 1/8.

As above too 25.4 = 1 inch, 22.2 = 7/8.

Literally the list goes on and on

 

[keithglos]

Re:

This goes back to the origins of bicycle production and machine tools in Birmingham and Coventry.

Continental bikes had many 24 and 26 threads per inch on metric diameters.

Keith

 

[torqueless]

Re:

I don't know the answer, and, as a Brit who's never tried to buy bearing balls anywhere but Britland, it's difficult to talk about it without immediately falling foul of 'fog in the channel...Europe islolated' syndrome, but I cannot believe that 'continental' engineers have ever been in the habit of keeping an 'imperial' micrometer at hand just to measure ball bearing diameters.

I could be wrong, but I would think that Mr Campagnolo's original specification for a bicycle wheel hub- in Italian- did not include the phrase: '1/4 inch balls'..?

This leads to another question, or maybe the same question phrased differently, which would be: "How critical is ball diameter to the proper functioning of a bicycle component?" i.e. Is a cup 'n' cone race designed for 1/4" balls damaged or functionally compromised by being filled with 6mm balls instead? Or vice-versa?

 

[mdvineng]

This leads to another question, or maybe the same question phrased differently, which would be: "How critical is ball diameter to the proper functioning of a bicycle component?" i.e. Is a cup 'n' cone race designed for 1/4" balls damaged or functionally compromised by being filled with 6mm balls instead? Or vice-versa?

in answer to the above; Very and Yes

 

[sdp2112]

Re:

There are metric sized balls. I used 3.5mm in my 1960 Bianchi headset. Believe it or not 1/8 left a gap, (not much of a gap its true). I have not though used metric balls in my hubs and bb, perhaps I should.

 

[Woz]

Perhaps because the universal adoption of the metric system is not that old compared to the history of the bicycle?

Perhaps SKF being the largest supplier of ball bearings even through WW1 and WW2 had something to do with it?

Case in point, I have a Swedish carpentry ruler from the 70s marked with three different inch measurements; London, Verktum, Norsk
plus Metric.

As they say, the good thing about standards is there are plenty to choose from.

 

[torqueless]

Re:

This leads to another question, or maybe the same question phrased differently, which would be: "How critical is ball diameter to the proper functioning of a bicycle component?" i.e. Is a cup 'n' cone race designed for 1/4" balls damaged or functionally compromised by being filled with 6mm balls instead? Or vice-versa?

in answer to the above; Very and Yes

mdvineng, your handle, and decisive answer, both suggest that you are an engineer? I'm not, as you may have guessed, but I'm genuinely interested in this:

In cross-section, the bearing surfaces of both the 'cup' and the 'cone' in a cup 'n' cone race have a certain optimal radius compared to the radius of the balls it contains. Should the radii of cup, cone, and ball be identical, or should the the radii of the cup and cone be greater than that of the balls by some increment, to reduce friction?

I understand the criticality of ball diameter in a 'sealed' bearing with no 'side-load' (or whatever the correct term is), and I also understand the importance of all the balls in any given race having identical diameter, but I always thought, perhaps wrongly, that the adjustable cup 'n' cone bearing, by design, had a margin of adaptability in terms of exactitude of specified ball diameter..?

 

[t47b]

Re:

The outside diameter of the ball has to match the radius of the cup or it will bind, the adjustability is available to take up the slack when the parts wear, they will still retain matching shapes albeit smaller so will need to be moved closer together (Or packed out with more grease )