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29er weight versus 26er weight.
NB: Originally posted elsewhere on the Global Riders Network and appears via syndication.
I'm of the opinion that a 29er bike weighs about half a kilo heavier than an equivalently specced 26 inch bike. What's everyones opinion on this?
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If it really is 'equivalent' spec - i.e. identical products (e.g. Stans Crest rims, Stans tyres) - then i think it would be slightly less.
The extra frame material is not massive, the extra length in the fork is not much either.
Just my opinion.
What about rotating mass?
what about it?
It doesnt make the bike actually 'weigh' more....mass is mass. Inertia (and therefore acceleration and deceleration - from rotation will be different.
You can get some ridiculously light 29er wheels and tyres these days - light enough that it wont be an issue if you really care....
I agree about the wheels but you can also get ridiculously light 26 inch wheels too. (Lighter than 29ers! ).
Rotating mass is IMO way overstated. the inertia only makes a difference for that moment when accelerating, if you are spinning round and round nicely, there isnt inertia, if you come out of a corner and stand on the pegs and go hard from 6kmh to 25kmh - then there's inertia!
As best i can figure out, multiplying the rim, and tyre weight by about 1.3 gets you the weight effect - if a 29er wheel is 11% heavier, then its 1.3 * that extra weight. say 1.8kg * 1.3 = effective weight of 2.34 versus 2.08 for a 26er effective weight.
Maybe 0.6 of a kilo for a 29er weight penalty? Up a reasonably steep climb thats worth 0.005 more time, no effect on the flat or the downs - so is the rollover advantage and the advantage on the flats worth the 1/2% on the climbs? - maybe maybe not
Gotta disagree. 'Unsprung mass' makes a big difference.
Your formulae are incorrect. You haven't taken centrifugal force into account at all. Im not going to bother looking up the correct formulae, wheel & tire weights etc, and applying those to typical mtb speeds, but needless to say, the centrifugal forces applied are greatest the further from the axle you go. I believe the rate of increase is close to exponential, so a small increase in diameter provides a large increase in weight which is concentrated at the circumference. Due to the greater gyroscopic stabilising forces of a bigger wheel, a 29 should feel more stable, roll over obstacles more easily, but at the cost of weight and manoeuvrability. Your preferences and riding style will determine whats best for you.
I just want to make it clear that the increased weight only really affects handling and ride characteristics. Carrying that extra weight up hills etc is almost meaningless given your body weight can easily fluctuate a kilo or two over a week.
Again, in the context of this forum and its riders, its not a question of lap times, its a question of which suits your riding style and preferences. I ride 26, and who knows... a 29 may give me faster lap times, but if i feel the bike is less manoeuvrable and fun to ride, whats the point?
Its why motorbike riders in particular obsess with getting this 'unsprung mass' lower. Carbon rims, light weight folding tires etc... all pretty standard at club level. And sure, the wheels are going a whole lot faster, but then they also have an engine to power them.
Bottom line is 26 vs 29 debate will continue forever as both have pros and cons. Anyone who is asking what the differences are is probably nowhere near fast enough to 'need' one over the other. It's just a matter of riding style and preference.
The people that tell you one is 'dead', are usually trying to sell you the other.
I'm not concerned too much with the handling debate, (except for that caused by rotating mass), more interested in the weight gain caused by going to a 29er.
In that case, the answer is "absolutely no difference that you could notice in speed, or measure in lap times"
If its weight you are concerned about, the first place to look is body weight. This can provide a 2 fold improvement, as every kilo you lose is obviously a kilo less to carry, but more importantly, a kilo less you have to fuel. This provides immediate improvements in important numbers like VO2 max (the ability of your blood to carry oxygen), and reductions in energy consumption (go faster using the same amount of energy).
The weight gain isn't that much, half to three quarters of a kilogram would be in the ballpark for equivalent spec.
26ers are more nimble without a doubt, but 29ers conserve kinetic energy much better, and not because the wheels are heavier. It is because they don't drop into the ruts as much, which means the axle path is smoother and less of your kinetic energy is expended accelerating the wheels up and down over the terrain.
On smooth groomed tracks the momentum conservation differences won't be as evident, but on on choppy terrain you really notice how much better 29ers maintain speed.
29ers are so much fun to ride you do more riding and lose more weight.
If it really matters honestly 20inch wheels are much lighter than 26 and 29inch wheels but it aint that simple is it.
I prefer 29 over 26.
I have two similarly specced bikes one 26 & the other 29, both frames weigh almost exactly 1.5kg. The 29er is about 300g heavier although it is running the lighter TL ready rather than full UST tyres which the 26 is. I could reduce that & make them even lighter by many small tweaks like cutting off excess seat tube I feel that it would be getting a little to anal, especially as I weigh 83kg.
10.7 & 11 kg by the way.
I have two similarly specced bikes one 26 & the other 29, both frames weigh almost exactly 1.5kg. The 29er is about 300g heavier although it is running the lighter TL ready rather than full UST tyres which the 26 is. I could reduce that & make them even lighter by many small tweaks like cutting off excess seat tube I feel that it would be getting a little to anal, especially as I weigh 83kg.
10.7 & 11 kg by the way.
i have both
08 specialized stumpy expert alloy 26er 12.5kgs (stock specialized tubed)
08 specialized stumpy expert alloy 29er 13.5 kgs ( nobby nic fr , crossmark tubeless rear )
11 stumpy carbon expert 26er 12.5kgs (stock specailized tubed tyres)
and i can see and feel the pros and cons on both
the 29er is better throu rock gardens rough stuff , but the 26 feel more fun .
to me more planted in the front end/cornering , better in the air/jumps.
overall depends on the purpose of the ride and location
but its obvious that the 29er weighs more cause the 2x 08 model bikes i have are exact same spec other then tyres.
i was suprised that the carbon bike weighs the same as alloy , but i spose carbon has diff frame flex characteristics.