Originally Posted by
North Coast Joe
I can only gauge by how much better my current bike performs after replacing both steel rims with alloy,
That's where you made your improvements.
Think about how a wheel works. The rim is that huge distance from the hub and for the bike to do anything, you have to accelerate that rim. This is called rotational mass because you have to turn it and keep it turning to ride your bike. Removing weight from the rim makes that rim and hence the wheel, much easier to accelerate and to stop. Going from a steel rim to an alloy rim will make a massive difference in rotational mass and very noticeable. It's one place where real improvements can be made ... depending on where you're starting from of course.
Losing weight elsewhere on the bike is more problematic. Sure, you have to carry that weight but you need to consider it as part the whole package ie, the bike and the rider. People get excited about losing half a kilogram from their bike. A 500ml bottle of water weights about half a kilogram. Do you notice the difference when you either lose or gain a bottle on water on your bike? Consider then that, depending on how heavy the rider is, a 100kg total package is not unrealistic (I weigh 110kg on my own, but I'm a big ***** cat) and that half a kilogram that so many riders get so excited about is only 0.5% of the total package. For a small rider, this might get as high as 1% and, not being rotational such as weight in the rims, all it does is just sit there.
The effect of weight is grossly exaggerated but it sells bikes to people who don't bother to think about things beyond the marketing blurb.
What IS important, is the design of the frame and how it's built. The material is only part of this equation, any of the popular frame materials (steel, titanium, aluminium, carbon fibre) are capable of making very good or very bad frames, also very light or very heavy frames.
Realistically, if your bike is designed and built well, if it fits you properly (because the frame is the right size and you've put time and thought into adjusting things) and you've equipped it properly (fenders in the wet, carriers if you carry stuff, enough drink bottles, etc), it will ride well and you will love riding it ... just as I love my old Europa which weighs just less than an Abrams Battle Tank and cuts through errant taxis rather than shuddering to a halt
