How much difference does bike weight make?

I dont race but have made that change myself & it makes heaps of difference !

The biggest difference I noticed with my last upgrade was weight - in the wheels.

Overall, I didn't notice a big difference, except for climbing. Tubeless & lighter helps HEAPS. I'm assuming that both my wheels are around 700g lighter than my last set.

Weight makes almost no difference on the flat without accelerating, on hills, the more incline the greater the difference, but its not huge - put it this way, go and do 5 timed runs up your local hill on your bike, alternate between a full drink bottle and no drink bottle (750grams). 5 days do each alternating which is the first run and which the second, with a good 15 min rest between.

I would be amazed if there was a difference between them.

Rolling resistance of your tyres would make the biggest difference, but tends to be at the loss of grip. If you are under 5 10, finding a good racing position on a 29er will be harder, so i'd stick with a 26er - 29ers give better rollover on 6" rocks, and keep rolling better on fireroads (becasue of the rolling weight holds momentum - see how weight can help soemtimes? )

if a new lighter bike makes you feel better about riding more and faster, then it will speed you up

You are talking about the difference between a 2 litre hydration pack being full and empty. As others have said, lighter wheels will make the biggest difference to the feel of the bike.

Bike weight plays a big difference. You are talking about 2 kilos which is about a 16% weight reduction. The best way to maximise that 16% is if you can lose it from the wheels. Having reduced weight in the wheels means you're legs can work easier as they are not fighting the rotational weight. Easier acceleration should mean quicker times. As we are on trails braking and accelerating constantly, its the acceleration that can make all the difference.

Instead of 29er's, have you seen the 650B? Its basically right in the middle of 26" and 29" - 27.5". It takes the best of what a 26" and 29" bike have. This copy from a website explains it better than I could: 'So why 650B? The people behind the 650B movement claim that with 650B tires you get all of the same advantages of the 29" movement (lower rolling resistance, better traction, smoother ride, etc.) with less of the disadvantages (geometry limitations, toe clearance issues, higher center of gravity, suspension travel limitations).' I think this bike would hit the sweet spot for most XC riders, and its proving itself with a win in the World Cup 2012. http://www.bikeradar.com/news/article/nino-schur...

At the end of the day, it comes down to how comfortable you are on the bike frame, how much you're willing to spend (because you can buy speed!) and how serious you are. I simply race for fun and fitness and by no means a professional rider, but I can certainly feel the weight difference between having a water bottle on the bike or not, especially after having it for 4 days on the Cape to Cape, and then coming back to Perth and just carrying a camel back.

Just my 2c
Cheers
Steve

I understand what you are getting at but a 2kg weight reduction on the bike will make a bigger difference than taking a 2kg weight reduction from tools on your back. And if you could somehow miraculously lose 1kg from each wheel, then isn't that the most efficient way to lose that weight - as it impacts directly upon your leg strength / fitness / acceleration / time?

2kg back versus bike.

Bit of a fan of physics - there is no quantifiable difference between weight on the rider versus bike I can think of - potentially a very minor change in handling because of COG change, but 2kgs being driven by the leg muscles is the same amount of weight regardless.

Rotational weight is real, the multiplier is somewhere abouts *2. It only applies at the periphery of the wheel - ie rim and tyre/tube. It doesnt apply at the hub - maybe a 1.1 at the hub. Most wheelsets save their weight at the hub not at the rim. The tyre is the biggest gain by far in both rotating weight and also friction losses.

So losing 1kg at the wheel outside is indeed worth 2kg on uphill terrain and accelerating - you can save 500g on tyres easily, saving 500g on rims is very near impossible - most weight is hub, then spokes, then rims imo

there is a reason that elite road riders have virtually zero body fat - any extra weight is a disadvantage. Cav (hardly a giant) is deliberately losing weight to give himself a better chance at the Olympics road gold. Wiggins has lost heaps in his bid to convert from track to GC road rider. Pretty much any weight loss is positive for efficiency and speed with cycling. Save money by not buying ultra-light unobtainium bling and buy veggies and lean meat. Save even more by not drinking alcohol. Or sign up for dry July....

Having said that, shaving some weight off the wheels does have a noticeable impact. I recently changed from Crossmax UST's, with tubes (because I had wanted a reasonably heavy duty tyre without the rolling resistance of a DH type tyre) to non UST Ignitors, which were at least .5kg lighter overall. Made my Niner Jet feel much easier to accelerate out of corners. Just have to keep an eye on the sidewall wear as I've always had problems with lighter tyres getting a cross-hatch wear pattern and getting down to the canvas too easily.

If I could get enough weight off to be able to run a lightweight rim, it'd be a double bonus...... but I'm unlikely to get much below 100kg without chopping a limb off

At the Mont this year I had a test ride on a Carbon Merida XC job - 96 or something, which weighs about 10kg. (Compared to my Epic at about 12.2 bare)

I really noticed that the bike was easier to accelerate out of tight corners, particularly going up hill. It wanted to jump out of the corner with far more enthusiasm than the Epic. Unfortunately I'd not ridden for the 6 months leading up to the Mont, so the legs weren't a willing participant!

So yes, the difference was noticeable, BUT as everyone has rightly pointed out, there are plenty of other ways to reduce weight.

For me, I'm sticking to the Epic - can't justify forking out $$ for a lighter bike when I can just reduce the weight of the thing attached to the handlebars.

In an ideal world, I'd have 2 bikes. The epic for every day riding / training etc... and then a carbon featherweight job for race duties... but then, I'm kinda like you and never going to set the world on fire in a race... but the thought is nice anyway!

For what its worth - You can create your own data at http://www.analyticcycling.com/ForcesLessWeight_...
To establish the benefit of less weight for an MTB requires a few assumptions be made about various factors. These include, amongst others, wind resistance, rider wattage (power output), rolling resistance of tyre/ground interaction, the slope, frontal area and drag apart from the difference in weight between two bikes/people.

So by assuming all those factors are static and we just vary weight maybe we can get an indication of what difference weight makes? Assuming the rider puts out 250 watts for the climb, going up the same slope with the same tyres, skill, same wind, temperature, etc. etc. the only difference is reducing the weight by half a KG for each climb.

The following is the difference the above page indicates it would make going up a one kilometer long slope. Some assumptions are flawed and arbitrary. For example there may be few MTB trail slopes that are consistent for one km in WA.

Lets assume myself and bike weigh 80kg for an XC race (these are my weights ) So how much time would be saved over a set distance on a set slope? Approximately how much faster would I be if I lowered my bike weight from 80kg to 79.5; 79.25 and 79kg to go up this hill. Increasing the slope/grade would increase the time differences.

79.50kg I would be 2.1 seconds faster
79.25Kg I would be 3.15 seconds faster
79.00kg I would be 4.2 seconds faster

BUT - as already noted the advantage of weight loss may depend on where on the bike you lose the weight - wheels may be better as the energy required to turn them is claimed to be less. There are many other assumptions being made all of which are arbitrary.

So power to weight differences can be seen in this table which are about low/average for those in training. As the weight goes up the P:weight figure reduces.
weight | watts | P:wght
80.0 |||| 245 |||| 3.06
80.5 |||| 245 |||| 3.04
81.0 |||| 245 |||| 3.02
81.5 |||| 245 |||| 3.01
82.0 |||| 245 |||| 2.99

But it is claimed that weight is an advantage going downhill, but more of a penalty going uphill. Just to rub in the weight issue, on a road bike, it is claimed that a 0.5kg saving is the same difference over 40km that removing the airdrag of a pencil would make. Lets hear it for low drag shorts and tops = Lycra -

A question that comes to mind, for the average rider, is focussing more on skills, personal weight and diet more effective than being a weight weenie? Probably going on a proper sports diet would lose that 1kg and cost a lot less than those $2000 dollar rims I've been drooling over! But, can't I have both?

FWIW!

Woah, imho this is all getting far to technical for the subject where there's a few more important factors that are being left out. That is the rider's physicality & ability plus a few of the less measurable factors that some above have already mentioned like the way heavier bikes or wheels seem to hold speed better (More stored energy).

I remember one of the old MTB pro hacks Steve Waugh commented years ago that despite riding around a set race circuit on several quite different bikes his times were remarkably similar & I believe that this is because as long as the bikes are not ridiculously dissimilar the rider still has the greatest influence on the ultimate speed.

That aside, it's always nice to have bits that make the bike go better & if we take the rider as a fixed weight & output some parts will have a greater influence than others.

I personally feel that fast rolling tyres make the biggest difference to speed on the flat. Light wheels accelerate & climb well but will also hesitate on rocks where heavier would have enough momentum to carry on & stiffer suspension allows a more aggressive out of the saddle type of cranking. A good efficient riding position is also very important, especially on longer rides where you're sitting a lot more.

Once you get the bike down to around the 11kg - 12kg mark though the $ per gain equation starts to become far steeper & a few hundred grams can cost a lot. It makes far more sense to get stronger & lose the love handles (He writes while finishing his beer while in cyberspace).

Oh, & big wheels do roll well...

All the best

most of the upgrades to my bike have dropped the weight but the big plus has been the better function and more reliable kit. i replaced a an x7 nack end with an x0 - i'm guessing there is a weight difference but its the durability and shift quality that is the biggest plus. 9.7 kilo's for a dually is pretty light in my world, my 26 dually is 11.something. i've probably dropped it over time from nearer to 13 and as mentioned above i can feel the difference in the handling. i'm a bit of a large portion so getting sub 10kg's isn't really a priority - but whats people's opinion on the butter zone for weight? i'm in with the 11-12 before coin becomes prohibitive.

In my experience a heavier bike is actually faster and better for XC racing. Traction is increased as the tires are more planted into the trail surface. This means that 100% of produced power (and sometimes more) goes straight to the rear wheel resulting in improved climbing performance.
I have found this year my racing results have improved significantly since installing weightier components (approximately one place better for each added kg).

the only way increasing weight increases traction is by grippier tyres that by necessity weigh more.

The more weight on bike/rider, the higher the psi should be, so contact patch would remain identical. However with bigger bagged tyres that weigh more, the psi can be less, and thus greater contact patch, plus usuallu bigger knobs for side grip.

Although a heavier bike can give someone more confidence in the down and corners, lets face it, the rider who is comfortable sliding both wheels occasionaly when grip gives out, is usually pretty damn fast. For speed, i think confidence is everything, and so "feel" while often misguided can improve performance: ie your fast bike is fast because you think so.

Drugs are not needed for additional performance once you know a few of the weight gaining secrets that the Elite guys use. At first I was sceptical, but after breaking a number of Strava KOMs with my upgraded heavier setup I was convinced.

if you're upgrading to heavier components, I'm more than happy to take some of that old stuff that's too light to be useful off your hands for me pub bike

That explains why my carbon bike feels slower...

I'm going back to the Huffy to compare.

Mate, if you are at 78 kgs.....and you want to race and stay with the front bunch.....and you train your bum off....spoil yourself and get a 29er with carbon frame and wheels, target weight of 8kgs. I built mine with imported unbranded carbon frame and wheels. I have two forks, one rockshock and one rigid carbon fork, it's real easy to swop out your fork to suite the race conditions. The whole bike all in,two forks too, cost around the 2.5k mark. I run a 2.35 schwalbe in the front and a 2.25 rear....lotsa traction in the single track. Oh and at your weight a Dueley may not be needed if you aren't doing really hectic technical tracks.