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Don't you just love the way Triumph seemed to mix and match parts for their bikes in the late 60s. I've slowly been dismantling the T90 I bought recently and as we all know, there's a mixture of thread forms used on the various studs, bots and screws. What I wasn't expecting (although I suppose I should have been) was the different wheel bearings they used. The QD rear wheel hub has a pair of 'Imperial' size bearings... 3/4" I.D x 1.7/8" O.D. x 9/16" wide. The front wheel hub has metric bearings 20mm I.D. x 47mm O.D. x 14mm wide. Why was that, do you suppose? The imperial bearings for the rear wheel are about 4 times the price of the ones for the front.
 

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This is a bit like the 71/72 engine,some of which had a metric bearing on one side of the crank and imperial the other.From reading various books,it was said that bearings were in short supply for a time so the engine parts were machined to make a bearing fit that was available.May be a tale but it was in a book.
Be nice to hear from anyone who knew what happened at that point.
 

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I would think its was always a cost / availability thing -- "back in the day" i would guess that imperial bearings were probably cheaper than metric
 

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I would think its was always a cost / availability thing -- "back in the day" i would guess that imperial bearings were probably cheaper than metric
I would think it's the other way around, the metric bearings were cheaper so they changed from Imperial to metric because the bean counters bitched. When supply of the expensive bearing dried up they made the change. I can't remember anytime where Imperial or Standard was cheaper than a metric counterpart.
 

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I LOVE Triumph's "mix-and-match" nature.

Case in point: My 66/67/68/69/70 Bonneville vintage roadracer. There is at least one major/core part from each of those years on the bike, and it performs admirably.

 

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I LOVE Triumph's "mix-and-match" nature.

Case in point: My 66/67/68/69/70 Bonneville vintage roadracer. There is at least one major/core part from each of those years on the bike, and it performs admirably.

Johnny Cash bike?:grin2: One part at a time.
 
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