Debating the wheels on my Giant 29er and thinking, should i get lighter wheels.
Mine come in at
Front is 959 grams
Rear is 1226 grams
So just under 2300gr, which seems fairly heavy
Looking around, wheels can seem to come in (according to Manf;'r) at about 1600gr without too many issues....
So, therefore saving me 700gr of weight ...
What's your thoughts then lads ?
700g off you wheels will (should) be very noticeable.
I put some Maxxis 2.4 tyres on the full sus.. they are nearly a kg each. I rode them twice, then put on the 2.25 versions at 600g (ish)
HUGE difference.
So the point is, yes wheel weight can make a difference!
Yes makes a huge difference, I can tell the difference between my old (now training) wheelset at 1800g and my race wheels at 1450g. Different tyres and rotors probably adds up to a 500g difference.
Even 100g difference is noticeable IMO - as above, if you don't believe, the tyre change test is pretty convincing
yes, especially on a 29er where there's more wheel moving around
yes but saving weight at teh rim/tyre matters more.
Different tyres - big difference
Same tyres, but different weight wheels - i can't tell
The 'rotating weight' thing is massively overstated; weight is weight whether it spins, twists or pirouettes.
700 grammes sounds like a huge saving, but from an overall weight of about 100 kgs it's not that much really.
I'm sure you will notice the difference, but I suspect that you won't actually go any faster.
OK, ordered them 
Extra £10 off at CRC with voucher too.
Be prepared for "how do i fit/do tubeless rims" etc coming to a forum near you soon.
1600g is pretty light for 29er wheels, probably good for racing but for general trail use I'd of though 1800g would be about right.
My 29er wheels weight 2600g (Bonty Superstocks)! Which considering they are on a SS rigid bike is a good proportion of the bikes weight let alone rotating mass.
The 'rotating weight' thing is massively overstated; weight is weight whether it spins, twists or pirouettes.700 grammes sounds like a huge saving, but from an overall weight of about 100 kgs it's not that much really.
I'm sure you will notice the difference, but I suspect that you won't actually go any faster.
Agree and disagree at the same time.
As you say, 700g is an irrelevant weight diffrence compared to an all up 100kg+ bike and rider weight...
... but that 700g is noticeable, becasue it is rotating weight.
It may not make you faster overall, but it makes a very noticeable difference in acceleration
Definitely noticeable, but nothing like as noticeable as changing tyres.
It might be noticeable, but that's not because it is rotating.
And unless bicycles operate outside normal physics, it won't make a 'very noticeable' difference in acceleration.
If it did, could you show me the difference?
rotating weight is really noticeable.
The whole rotating weight thing comes partly from the old idea that 'a pound off the wheels is worth 2 off the frame' and has, over time, become one of those secret bits of knowledge that cycling seems to accumulate.
Here is the best explanation I've found;
How can it be that wheel inertial forces are nearly insignificant, when the advertisements say that inertia is so important? Quite simply, inertial forces are a function of acceleration. In bike racing this peak acceleration is about .1 to .2 g’s and is generally only seen when beginning from an initial velocity of 0 (see criterium race data in Appendix D ). Furthermore, the 0.3kg/0.66lb difference in wheels, even if this mass is out at the rim, is so small compared to your body mass that the differences in wheel inertia will be unperceivable. Any difference in acceleration due to bicycle wheels that is claimed by your riding buddies is primarily due to cognitive dissonance, or the placebo effect (they paid a lot of money for the wheels so there must be some perceivable gain).
http://biketechreview.com/reviews/wheels/63-wheel-performance
In summary, wheels account for almost 10% of the total power required to race your bike and the dominant factor in wheel performance is aerodynamics. Wheel mass is a second order effect (nearly 10 times less significant) and wheel inertia is a third order effect (nearly 100 times less significant).
I've seen similar calculations to the one crikey posted on this and oldgits handbuilt road wheel thread.
In reality the weight is probably going to make minimal difference. Where it really matters is for elite athletes looking for "the aggregation of marginal gains". However, if you are going to buy new kit if everything else was equal* I would recommend going for lighter kit. If you look at a 30kg bike and a 20kg bike each indiviual component will ony be marginaly lighter on the 20kg bike. However, overall the difference will be noticeable.
I think you'd more likely notice the tubeless conversion if you start to run lower pressures.
*all things are not equal, "stong, light, cheap; pick two"
Not sure the above rationale applies in quite the same way to mtbing - yes the physics will be the same, but unlike a road bike, a mtb on singletrack is constantly accellerating, decellerating and changing direction...
Of course with wheel weight it's really the weight at the rim that's most relevant so lighter hubs aren't as important as lighter rims, tubes and tyres. Light tubes are the best weight saving per pound, can get 65 to 70g road tubes for not much money compared to normal tubes at 100g or so. Is 30g per wheel noticeable though?!
I think it will apply even more to mountain biking, the overall weight is larger, therefore any weight change at the wheels will be less significant, and speeds are lower, accelerations are lower and so on.
I think it will be noticeable, but not have any measureable effect on performance; bit like a different colour bike... (apart from red, naturally... :D)
I recenlty rode a 29'er, the wheels were larger than my 26'er. I noticed they took longer to spin up and I felt a flywheel effect. The 29'er bike was ligher in total to my normal 26 bike. But I still felt the effect of larger wheels.
So for me the rotating effect was noticable.
+1 for changing tyres. Makes a big difference.
IMO it makes a big difference. I made the mistake of leaving a pair of dual ply DH tyres on a recent second hand bike purchase and then pedalling it around the local trails.
Well believe me I was dying on my arse on trails I normaly fly over, massive difference. Thought I'd make a big mistake on the decision to purchase!!
Surely if you think of the wheel as a see-saw action with the hub as the pivot and you have a heavy tyre / rim you are muliplying the weight of that tyre by the distance from the hub making small changes in weight significant. Initail inertia will be high and acceleration / decceleration and changes in, poor. Even more so on 29" wheel, hence they are often reffered to as sluggish to get going.
Also once the mass is spinning a heavy tyre will have a larger gyroscopic effect. It will be stable but changes in direction will be more difficult, I believe this again rings true in 29ers?
Perhaps I am looking at this in a too simple fashion? I'm no physicist 
purser-mark - the problem with that is the tyres will also be much more draggy.
I ride the same bike with a variety of tyres and the difference in the feel of speed is huge but I couldn't say how much was weight and how much was drag and how much real difference to speed it made. with heavy tyres it felt a lot slower
I changed rims from Mavic 321 to 719 and I felt the difference between them, so yes, you will feel a noticeable difference IMO.
Lets see when they arrive then
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