On a flat, weight is relatively insignificant but according to Jim Martin, a five lb weight drop will save a recreational rider about 57 seconds over a 40 kms at a 3% grade. This increases proportionally as the grade becomes steeper.

As I see it, your weight is a combo of your bike weight plus that of your body. It doesn't matter to physics if the weight loss is off your body or the bike. 20 Lbs of body weight is 4x more than losing 5 lbs of bike weight. And is a lot cheaper to achieve.

I've read that some people feel that rotational weight is a 2:1 ratio compared to non rotational weight, but I've also read that other authors dispute this. Maybe some of the engineers can help us out here.

I lost more than 50 lbs about 3 years ago. Much of my loss was a result of cycling. Here in Colorado almost nothing is flat and my ability to go uphill was dramatically better. Now, as part of my spring training, I tow my son behind me in a trailer on several good uphill training rides. When I ride without that extra weight I can climb much better. The weight of my son and the trailer is only slightly more than I used to have to carry around all the time.

I don't think it will make a huge difference in swimming unless you improve your techinque at the same time. Weight loss will definitely help you run faster.

Comparison wise I think it's much better and cheaper to get your body in prime shape than it is to spend money on wheels. In fact I would say it's better to hold off on major bike purchases until you get your body in top shape.

Congratulations on the weight loss. The benieits should be huge. You lost a whole bike from your body! When going uphill you are mostly fighting gravity. The force trying to pull you down the hill is directly proportional to weight (mass for the purists). Whether it is static or rotating doesn't matter much unless you are accelerating rapidly. (Going from 8 up to 9 mph while climbing is not significant acceleration)

You've done the hard work, now the real fun starts though. Shaving grams from the bike by freely spending hundreds of dollars is much more fun than losing weight! Explaining the significance of $1000. wheels to the wife can be interesting. :)

"Explaining the significance of $1000. wheels to the wife can be interesting. :)" Worst thing I ever did. Then she wanted a pair which I had to get for her for X-Mas!

When I started making noise about getting a new bike about a year and a half ago, I had to let my wife get the mini van she wanted. She did find a nice two year old and now I'm driving her old Volvo! I was then cleared to get the bike and got a KM-40 that I love to ride. When we decided to get a bigger house last summer I didn't hesitate. I got the race wheels while the cash flow was still good.

It's great that your wife wants race wheels! My wife just started a team in training program to walk a marathon. I heard her on the phone talking about stride length and her favorite energy bar. Man I hope she gets hooked. I figure if she gets into it she'll cut me more slack about my training. I'm adjusting my schedule as needed to help her get to her group workouts. Anyway, I'm rambling...

Lost the 20 pounds, Bought the P3, Hed 3 wheels and a HED disk, profile carbon cranks,

Depending on your body shape, and swimming proficiency, weight loss may actually SLOW your swim splits a little, but obviously not enough to outweigh (so to speak) the significant gains on the bike and run. Nothing like a little fat to help you float!

best thing to do is ride behind your little brother and hang on for as long as you can!! this will have to help with your climbing!!! also you could try buying a new QR redstone, heard anyone that rides this bike is one hell of a cyclist.