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Where on the bike do manufacturers measure horsepower?

pismocycleguy

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When manufacturers post the horsepower ratings for their bikes, where on the bike do they measure the output? At the engine's crank or at the rear wheel?:confused:
 
Crankshaft.

Rear wheel dynos can vary so much between make/conditions/tires/etc., etc., that there would be a lot of potential error in a listed figure by a Manufacturer, compared to one of the many Dyno machines used by everybody else.
 
When manufacturers post the horsepower ratings for their bikes, where on the bike do they measure the output? At the engine's crank or at the rear wheel?:confused:

There are enough laws as to posted horsepower, to make that answer even complicated for any staff of attorneys, in many different countries.

Types of horsepower ratings are:

1. At the crank. (crank horsepower) This is before the transmission.

2. At the transmission output. (output horsepower) This is after the crank and transmission but before the rear wheel.

3. At the rear wheel. (rear wheel horsepower) This is after all the above where the rubber hits the ground. However, the dyno machines are set up quite different and have different operators.

Seems like everywhere has a different place of measurement as to this matter, so most companies do not what to give the consumer an answer to the horsepower question. If they do publish the horsepower it will be the lower of these answers, as they do not want to be sued.
 
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Why does it matter? :)

The key points for me when bike shopping are the bike's ability to keep up on the interstates and the range per tankful. If given the chance, I don't choose the slab but sometimes I need to cover lots of ground in one stint.

Motorcycle Consumer News has dyno figures in their road tests and since they're using the same dyno each time and in the same climate, it's pretty much an apples-to-apples comparison if you want to check one bike against another.
 
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Manufacturers like crank HP because they get a higher number that the Marketing Department likes. Rear wheel is all that matters because (reaching for it) that is where the rubber meets the road. Different transmission and final drive types have different HP losses. Driveshafts lose more than belts, which lose more than chains. Large chains lose more than small chains. CVTs (scooter trannies) lose more than DCTs. Right angle drives lose more than parallel drives (example: a bike with a transverse crank and chain drive has no right angle drives, but the same engine with a driveshaft would have two (one at the transmission and one at the rear wheel). A driveshaft on a bike with a longitudinal crank (like a BMW boxer) has only one right angle drive at the rear wheel. The longitudinal layout favors shaft drive and the transverse layout favors belts or chains.

So if two bikes both have 50 crank horsepower and significantly different drivetrain losses, then the simpler one will likely win the drag race even though the more complicated one might have other attributes that some buyers deem more important than speed. As Popeye said...

Popeye said:
Ya pays ya nickel and ya takes ya choice.
 
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