Bottom Bracket Height

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deliquium
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Bottom Bracket Height

Postby deliquium » 21 Aug 2014, 5:31pm

I have 2 x 1948 bicycle frames, one is a 23" Leach Marathon with 531tubes and the other is a 22" PT Stallard 'Montlhéry' with Accles & Pollock tubes. The Leach's chainstays are 17½" and the Stallard's 18"

The former's BB is 292mm from the ground with 700c wheels and 32mm tyres, the latter's is 270mm with same wheels and tyres. A difference of 7/8".

What could be the reasons for this difference?
Last edited by deliquium on 23 Aug 2014, 10:04am, edited 1 time in total.
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timdownieuk
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Re: Botoom Bracket Height

Postby timdownieuk » 21 Aug 2014, 5:59pm

deliquium wrote:I have 2 x 1948 bicycle frames, one is a 23" Leach Marathon with 531tubes and the other is a 22" PT Stallard 'Montlhéry' with Accles & Pollock tubes. The Leach's chainstays are 17½" and the Stallard's 18"

The former's BB is 292mm from the ground with 700c wheels and 32mm tyres, the latter's is 270mm with same wheels and tyres. A difference of 7/8".

What could be the reasons for this difference?


Is this a trick question?

At a wild guess, I would say that the frames were constructed with different geometry.

Maybe I'm not understanding the question....

tatanab
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Re: Botoom Bracket Height

Postby tatanab » 21 Aug 2014, 6:07pm

It could be that the former was built for 26" wheels and the latter for 27". Or maybe the former is a racing frame built for tubs (700C) and again the latter is for 27".

Brucey
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Re: Botoom Bracket Height

Postby Brucey » 21 Aug 2014, 7:03pm

I agree, 26" wheels for the one with the short stays is very likely.

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deliquium
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Re: Botoom Bracket Height

Postby deliquium » 21 Aug 2014, 7:25pm

Thanks folks. Not a trick question, just me going :roll: :?:

I'd not considered 26" rims.

But then there's brake drop to consider? Given that at the moment both frames have identical 700c wheels and tyres mounted:

Leach has a rear brake drop of 62mm and a front brake drop of 55mm

Stallard has rear brake drop of 50mm and a front brake drop of 66mm

???
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Keith Bennett
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Re: Botoom Bracket Height

Postby Keith Bennett » 23 Aug 2014, 9:39am

It maybe that the clue is in the year of manufacture. The Leach frame may very well have been designed for use with a fixed wheel giving a little more ground to pedal clearance when cornering than the Stallard which almost certainly would have been designed for gears. Keith Bennett

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deliquium
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Re: Botoom Bracket Height

Postby deliquium » 23 Aug 2014, 10:03am

Keith Bennett wrote:It maybe that the clue is in the year of manufacture. The Leach frame may very well have been designed for use with a fixed wheel giving a little more ground to pedal clearance when cornering than the Stallard which almost certainly would have been designed for gears. Keith Bennett


At the moment the age of the Leach Marathon is only a guess based on the 531 decal being one that was used between '48 and '53.

The Stallard does indeed have Benelux dropouts, with the DS hanger sawn off at some point.

The brake drops on both frames are quite strange in my ignorance :o
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Keith Bennett
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Re: Bottom Bracket Height

Postby Keith Bennett » 23 Aug 2014, 10:15am

In 1948,other than track frames, most would be automatically built to take mudguards for most of us one bike had to do for all purposes from a weeks tour to time trials and even at times on the track, could account for the odd brake height

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531colin
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Re: Bottom Bracket Height

Postby 531colin » 28 Aug 2014, 8:13am

"Brake drop" doesn't apply if Resilion Cantilevers were fitted....http://www.classiclightweights.co.uk/components/resilion-story.html