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#860717 10/13/21 11:46 pm
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Pelle Offline OP
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Does anyone know what the British industry actually meant by "dry weight", or perhaps just "weight", when publishing such data for a bike?

Apparently, "dry weight" can be very different things. A Wikipedia quote:

"As its weight changes during riding, the dry weight of a motorcycle typically excludes the gasoline (or other fuel). Dry weight, in this sense, can directly be used for comparison with (FIM) weight limits, which pertain to the motorcycle in operating condition. It is also part of the homologation tests, and it is found on the EC Certificate of Conformity as unladen mass. This dry weight could also be useful in comparing different models, with different fuel tank capacities. However, manufacturers may also exclude some or all of the following: engine oil, coolant, or brake fluid, and this makes such a comparison difficult. When any of these is excluded, the specified dry weight no longer pertains to the motorcycle in running order. Some manufacturers even exclude the battery, notwithstanding the weight of the battery is mainly in solid components (usually lead), not liquid (electrolytes)."

Was there a common British motorcycle standard for "dry weight", and what did it include?

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Pelle #860722 10/14/21 1:41 am
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"Dry Weight" in motorcycle specifications and ads is sort of like "Horsepower" or "Top Speed". There never have been any honest standards for any of them; it's sort of whatever the manufacturer thinks they can get away with in order to sell bikes.

Horsepower ... measured at the rear wheel? The crankshaft? The piston crown? By who, and what method?

Top Speed ... on a typical bike off the showroom floor? Ridden by Pee Wee Gleason? "Specially tuned but stock?" Lemme see the timing slips - oh, there aren't any?

Dry weight - Maybe USED to mean with an empty gas tank, but now they take out the oil, battery, coolant, gas, brake fluid (you DID say 'dry', now!). The difference between the published "dry weight" and "curb weight" on my Guzzi Stelvio with a 4.9 gallon gas tank is 95 pounds. That's a lot of fluid ...

A truck scale is more to the point!

Lannis


Be guided by facts that you can observe yourself, along with knowledge of how people have behaved during similar periods in history.
Pelle #860726 10/14/21 7:41 am
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Generally it is the weight as shipped from the factory so no fuel and in some cases no oil.
Remembering that as the bikes can have any one of a 1/2 dozen tanks that can change the weight considerably


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Pelle #860749 10/14/21 6:19 pm
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Pelle Offline OP
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In my opinion a useful weight specification will include all necessary fluids, except petrol. If that is what the British makers used, or if they invented another standard to "reduce" the weights, is unknown to me. Comparing weights of different britbikes seems to be pretty much guesswork.

Pelle #860920 10/17/21 1:02 am
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The standard measure for “Dry weight” is (and was) as measured at the press release. Same place hp, top speed, and 1/4 mile time are measured. If a bigger number sells bikes, well …. And if a smaller number helps sell bikes, hmmm…. Man, Bultaco (to cite just one notorious example) sure had some interesting dynamometers and scales!!

Pelle #860931 10/17/21 6:27 am
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Specifications have always been weighted to improve manufacturers' claims.
Horse power was measured at the crank without the alternator or clutch in place, etc..
It got even more fraudulent with audio equipment. "Peak" power ratings with no regard to distortion or at what frequency. Third-harmonic distortion turned to total harmonic distortion in order to make solid state gear spec better than tubes, never mind that the even number harmonics produced by tubes actually sound good.
Then the FTC stepped in to 'standardize' the tests, but only for 'consumer' electronics.
Can't trust anything without a scale and a dyno.


Knowledge speaks. Wisdom listens.

72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
92 BMW K100rs "Gustav"
DavidP #860968 10/17/21 3:44 pm
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Well'ard Rocker
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Originally Posted by DavidP
Can't trust anything without a scale and a dyno.

And timing slips from an independent entity .... The differences between "claimed" performance ("The new Yawasuki Hellfire reached an indicated 244 MPH on a local track" or "Yeah, buddy, had my Bonneville up to 121 on River Road last night") and timing slips (WIND SPEED/DIR 3.2 mph SSE, TEMP 81F, HUMIDITY 32% AVG SPD 1/4M 97.232 MPH) is usually pretty incredible ....

Lannis


Be guided by facts that you can observe yourself, along with knowledge of how people have behaved during similar periods in history.
Pelle #861136 10/19/21 5:36 am
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You left out relative air density.


Knowledge speaks. Wisdom listens.

72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
92 BMW K100rs "Gustav"

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