FJR Owners Forum banner
  • Hey Everyone! Enter your bike HERE to be a part of this months Bike of the Month Challenge!
1 - 11 of 11 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter · #1 ·
Can someone help me understand the power to weight ratio for bikes?

BMW R1200RT = 1:7.90

Honda ST1300 = 1:6.85

FJR 1300 = 1:5.28

Thanks,
 

·
Registered
Joined
·
66 Posts
This is how I understand it.

Power to weight is the power output of the engine divided by the weight of the bike.

It's a way to compare different machines. For example a tank may have a much bigger power output from its engine than the FJR does. But the tank weighs a heck of a lot more. Overall, the tank's power to weight ratio would be a lot less. The FJR would beat it in a drag race.

I guess the actual numbers quoted depend on how you measure power (kilowatts, horse power) and weight (pounds, kilogrammes) etc. Of course, when comparing different machines, they all need to have their power to weight ratio calculated the same way. The bigger the number, the bigger the relative power.
 

·
Registered
Joined
·
141 Posts
Actually, the smaller the number, the bigger the power.

It's 1hp to xx weight.

So the FJR has 1hp for every 5.28lbs, the ST 1hp for every 6.85lbs and the BMW 1hp for every 7.9lbs.

A GSXR1000 is at 1:1.

(BTW, I am guessing it's lbs, as kg sure doesn't fit.)
 

·
Registered
Joined
·
141 Posts
Another way of doing this is one that is often used with cars: pwer to weight ratio as the amount of power per metric ton.

At 145bhp and 288kg (feuled up weight) FJR has a power to weight ratio of 503.5bhp per metric ton.
 

·
Registered
Joined
·
1,618 Posts
Or you can use thrust (kg) per unit mass (also kg)
Anything more than 1:1 can do a sustained vertical climb.
Which is nice..... 8)
 

·
Registered
Joined
·
124 Posts
afterburn said:
A GSXR1000 is at 1:1.
GSXR is about 170 bhp and 170 kilos. So it's ratio is 1:1 bhp/kg, but 1:2.2 if the weight is measured in lbs like the others.

However, I'm not sure what the units of measure are in the original query.

At 145 bhp and a weight of say 250kg for the FJR then the ratio is 1:1.71 bhp/kg or 1:3.79 bhp/lbs.
 

·
Super Moderator
Joined
·
3,962 Posts
The closer to 1:1, the faster the bike will be (all other things being equal) when compared to a bike that is farther away from 1:1.

IOW: 1:1.5 is faster than 1:3 (given the same rider and same everything else).

It's a way to compare a 145 hp bike that weighs 600 lbs to a 145 hp bike that weighs 900 lbs.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #10 ·
PTW Ratios

All the ratios that I listed were taken from Motorcycle Consumer News bike review figures and are in pounds. Thanks for the posts. Interesting stuff.
 

·
Registered
Joined
·
949 Posts
I was being continually confused by variations in performance figures until I realised that some HP ratings are in imperial units and others are in metric HP or PS. For true apples vs apples performance specs I've gone to the Kilowatt as there is no confusion or overstated understanding:

- 1 KW = 1000watts
- 1 Imp HP = 745.7watts
- 1 metric HP = 735.5watts

For torque:
kg-m---------------lb-ft----------------N-m

1----------------7.2330138----------9.80665
0.1382553------------1---------------1.355818

Be afraid -- be very afraid !

Cheers
Lenz
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top