Weight to Power : V-Twin Forum: Harley Davidson Forums

4XLT · 08-31-2009, 07:57 PM

i know weight effects hp and tq ..

my question would be how much hp/tq would 80lbs of weight take away from a bike ?

facn8me · 08-31-2009, 08:39 PM

ZERO I understand what your thinking but the hp/tq does not change. A dyno doesn't know what your bike weighs. What you lookin for is hp to weight ratio. Take the weight of the bike and divide it by hp. Then add 80 pounds and do it again so 100 hp and a 700 pound bike is a hp to weight ratio of 7 pounds per 1hp 780 is 7.8 pounds per hp

4XLT · 08-31-2009, 10:07 PM

thanks allot.... i am trying to figure out how this guy keeps pulling me, not much now but still pulls me...

C-Cat · 09-01-2009, 12:08 AM

some say every extra 100 lbs. of weight is a .10 of a second in a car, this would have a greater impact on a bike, lowerering the power to weight ratio even more. a tenth of a second at 120 mph is a decent margin. the .10 in a1/4 mile for a car is arbitrary, and would vary with weight and horsepower of vehicle in question.

Krash_Kinkade · 09-01-2009, 04:48 AM

think ever 30 pound will show some gain but less than 30 pound off does not show up much.
but with Nitro don't matter

Hillside · 09-01-2009, 08:58 AM

80 lbs. of weight on a bike is a TON!!!!!! We used to look to strip everything we could when racing. Even had a 7075 T-6 front axle.

Scott

dog155 · 09-20-2009, 05:05 AM

When it comes to your friend pulling you,are you comparing apples to apples.so many variables,of course hp&tq,others are final gearing,wind resistance,good tune up,exhaust systems,just to name a few.Good Luck in your hunt to roll on by your adversary.

4XLT · 09-20-2009, 12:03 PM

well its not apple to oranges but deffinately not the same either...

my bike is a 98 EVO E-Glide,, his bike is a 05 E-Glide SE 103" with a stage 1 kit only as far as i know but he also has a SE 6speed with lower gearing, i think thats whats helping him the most now..

also i realised while we were fartin around the one night i wasnt gettign full throttle ( my fault not twisting it enough) somethign i am going to have to remember lol..

i guess im just going to have to loose 100 lbs this winter damnit lol.... would be nice to be under 300lbs again anyway lmao!

i just thought with 105 lb tQ i would be able to pull away from him not just stay even... i think the 05 103's came with 257 cams, figuring with pipes and air cleaner he might be pushing 90 hp and 97 tq maybe..
where with my 93" i am at 100 hp and 105 tq... thats why i asked about the weight ratio figuring thats why we are close to even

Krash_Kinkade · 09-20-2009, 02:26 PM

what your talking about is power to weight.
But some say the weight of the opperator on a chassis dyno effects things. but with an engine dyno it don't.
back to you and your friend, just work on your launch off the line and work on shifting really quick @ the right rev, but do it at the track then you know its a fair square start don't race on the street.

mtnrcr · 09-20-2009, 07:09 PM

They are doing roll on races, not actually launching from a stand still. I think if they would do that 4xlt could probably take his buddy. Unfortunatley there are alot of bikes that show good #s on a dyno but on the street will perform much differently then a bike with lower #s. And sometimes it just comes down to having the stomach to twist it and hang on. Let me ride it Mike I am sure it will take him then. lol

4XLT · 09-21-2009, 01:13 PM

LMAO Joe.. no dought your porobably 100 lbs lighter than him !! LOL
hope the family is well

i think it was me not twisting it enough i havent had a chance to run him alone and all out yet.. just 2-3 gear pulls from a rolling start..

i think i can take him..im just not use to whaling on it right of the bat yet..

droped the hammer on it the other night for the first time from a stand still and the tire just fried, supprised me because i was expecting it to wheelie with my weight..

FXDRYDR · 09-21-2009, 01:32 PM

If you're running stock tires, they'll do that. Something stickier - like a Dunlop K591 or an Avon will help. Also, learn to feather your clutch - and practice some. Different pavement will affect how hard you can hit it from a stop as well. When you find your sweet spot for hard street launches, stick with it.

4XLT · 09-21-2009, 03:40 PM

been running a Dunlop E3 for the mileage i put on the bike they wear very well.... might have to think about something else..

about the clutch i been trying to go easy on it since its the stock clutch with about 77K on it,, planning on replacing it this winter

FXDRYDR · 09-22-2009, 01:13 PM

I like the 591s alot and think they're stickier than the Avons - IMHO. However, I expect only half the mileage.

I replaced my stock clutch just this year at about 20K. It was slipping just a bit and only needed to be adjusted. Since I was in there already and had the new extra-plate clutch, I decided to just replace it.

The original had about 100 drag strip runs on it and still looked good. When racing, I fan the clutch and shift WOT. No problems, no burned plates plenty of life left. FWIW, I run it with a VPC and an SE spring

IME, the stocker is a damn good piece and can take a little abuse. I wouldn't be afraid of getting on it.

4XLT · 09-22-2009, 03:32 PM

thanks Ryder... i have the SE spring on it also...