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weight - time differences
Funny question but what is the general consensus regarding weight and time. My argument is that my particular bike is 4Kg's heavier than the next bike down in the group I ride with. What I try to maintain is that I must be a lot fitter than them as I can just about keep up with them (they hang back for me) and if I had a bike that weighed the same as theirs, then I should at least be able to ride 'with' them rather than behind.
So - 4kgs weight diffference - what would that equate to round Manly Dam? 2 mins,5?
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More weight = more energy required to move it.
On the flats and downhill would be negligible I reckon, but a lighter bike would make you faster on the climbs surely.
4kg isn't going to make a measurable time difference on a lap of Manly Dam.
My previous bike was easily 4kg heavier than my current one and my lap times were consistently faster - mainly because the heavier bike absolutely bombed the downhills which more than made up for any time lost on the uphills.
To all those racers out there: yes of course extra weight *does* make a difference - but only at the limit of performance and Manly Dam is not the same as climbing the Alpe d'Huez after 180km of road riding.
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NB: and of course, as my Wife would observe, I may have saved 4 kg on the new bike but I still could lose 8kg myself
here's some not so scientific thoughts ...
So if you had a lighter bike you'd be 4kgs lighter. So when you consider your weight plus clothes, shoes, backpack plus bike weight that's probably about 4% of the total mass you have to push up the hill? So you would put out 4% less effort while you were climbing if you had a lighter bike.
So if you're climbing about 70% of the time you spend riding a circuit then you're down to about 3% easier overall so let's say that makes you 3% faster. That would be 1min 20secs if you're doing it in about 45 minutes at the moment.
If you look at my lap times at the Dam the fastest 2 are on a Yeti 575 when it was running 2.35 tires. In this configuration I'd say it's 2kg heavier than my Rush. That said, I haven't timed a 'hot' lap of the dam on the Rush for a long time, especially since the recent changes that make the lap easier and therefore faster.
These tire sizes, geometry and other factors probably pay an equal part. Eg. the Rush has more XC geometry and lower rolling resistance tires so is more efficient pedalling along the road and firetrails but the Yeti has more grip and more relaxed so is faster DH and on the technical sections you can just float down.
Maybe one day I'll go and do back to back laps and see if it we can get any conclusive results.
not wanting to make an ass out of u and me by assuming too much I'm going to ask you two questions before I give you and answer.
Is your bike 4kg heavier than your mates because it is an older, lower specced bike of a similar style to theirs, ie are you all on xc rigs?
Or is it 4 kgs heavier because you are riding a 6 - 8" DH rig and your mates are on xc or light all mountain rigs?
If it is the second option then swapping to a lighter weight xc bike will not make much difference to your overall lap times. You will be faster going up, probably enjoy it more and will more than likely be able to keep up with your mates. This will normally be offset by slower speeds / times heading down hill or on techincal stuff for the reasons given above. (Unless of course you are a sub 25 yr old male in which case the decision making / risk taking department of your brain isn't fully developed and you'll just bomb through everything
)
If on the other hand you are all riding similar style bikes but yours is heavier because steel is real, it has lower specced components and heavier wheels / tires etc then swapping to a 4kg lighter bike will most certainly be rewarded with faster over all lap times.
Hope this helps
Just buy it anyway as N+1 is always a good thing
It's a heavier lower specc'ed entry level dualie. Just by upgrading the mechanical brakes to hydraulic I've seen an increase in my overall speed - comes down to confidence I would think. Plus its a 24 speed - I have no idea how this would affect the ride if I went to 27?
I'll look to upgrade the bike in the next few months and see how I go with the times. At least I should be able to keep up with them, although upgrading the bike takes away my last excuse!!
Another twist to the bike weight issue is to consider your own weight. I only weigh about 69kg, but a friend who is much much bigger and stronger (similar fitness) weighs about 103 kg. Although his bike is 2kg heavier than mine, it is effectively lighter for him than my bike is for me. The result of the conversation was that a bit of extra weight in good chunky tires does not affect him like it would me. So he runs chunky tires and I run light ones. He is much faster on fast 'loose over' downhill sections as I don't have the traction, but I get him on the uphill bits.
Noel:NoelsBike = 70kg:12kg = 17%. Noel's bike is 17% of Noel's Weight.
Friend:FriendBike = 105kg:14kg = 13%. Friend's bike is 13.3% of Friend's weight.
Summary: Noel will notice weight change to a bike more than the Friend as the heavier friend is much bigger and stronger.