because it has yer fat ass on it! ;D Or would that be mine? :'( That is a good ? premie, that I myself can not answer. So are single sided swingarms usually heavier devi? I've never had a single arm off, but I have had a regular swingarm off, and they are not that heavy at all!
SSSA design requires all the loading be taken on one side and one pivot point. This requires a stronger part (heavier) than would be needed by spreading the load on both sides with dual pivot locating points.
I tell you! Speedy should get off its fat ass and loose some weight! And don't try tell me "It's not fat, it's got big bones!". That's what your momma tells you, but everybody else seems to know it's BS. ;D
to lighten: Use lighter exhaust, lighter wheels, polish and lighten every nook and cranny, and fastener. lots of plastic - lights, and other bits hidden behind fairings.
Triumph doesn't have the money to press-weld the frame with layers of aliminum sheet making a light but strong part. So they use a frame that is a bit heavier than many Asian bikes. Also many Triumph castings seem to be a bit thicker than some Asian parts.
I like the looks of the SSSA over a lighter standard part. The tube frame and design of the bike has more character than a tube frame trellis or aluminum composite frame - at least to me. I have had the dime-a-dozen crotch rockets, and am very pleased with my Speed Triple.
" Less metal = less weight, right? "
I used to weigh the metal I removed from engines by porting - even ground off every bit of casting flash and casting boss I could remove to reduce weight.
Now I just take the porting shavings and drop them in water to figure what volume they displace.
Let's say a rider weighs 200 pounds, and the bike weighs 450 pounds. Then using an old racer's "rule of thumb" and calculating backwards - each 2.32 pounds removed from the bike (or rider) makes the bike 0.1 seconds faster in the quarter mile. Where can you remove 2.32 pounds easier - the bike or the rider?
This is why a 20 pound lighter rider can be considerably quicker - especially out of turns.
Adding 2.32 hp has the same effect - roughly. Power-to-wieght ratios are not as accurate for acceleration as torque-to-weight ratios.
Now IF that same 2.32 pounds you removed is rotating weight (wheels, chain, sprockets, brake rotors (For kahulka), crank, rods, pistons, etc.) it can be 50-100% more valuable. Depending on how far from the center of rotation the weight was removed. Inertia is a big deal - especially in the first two gears.
Now if the bike weighs 400 pounds, and the rider weighs 180 pounds - it takes 2.07 pounds or 2.07 hp to get the same improvement. The lighter the total weight, the less amount is required to get the same improvement, but the harder, and more expensive, it is to get each pound removed.