Bike weights - surprising?

[loudlashadjuster]

Having recently bought a new road bike I was interested to see how it compared in terms of weight with my old MTB.

I've no particularly special scales, just a basic digital Salter bathroom set, but at least the relative weights should be fairly accurate.

The results surprised me, not the road bike because it's pretty much exactly the weight I thought it would be, but the relative lightness of what is a relatively cheap yet 'tooled-up' MTB in comparison.

Weights are those quoted on manufacturer/retail websites. Method: Me holding each bike then deducting my weight.

Genesis Volare 10 2015 - 10.4kg - Manufacturer quoted weight 9.75kg (no pedals)
58cm frame
Shimano PD-M520 pedals (420g)
Standard except for a plastic cage (50g?)

Specialized Hardrock Sport Disc 2012 - 14.8kg - Manufacturer quoted weight ~13kg (inc. pedals)
19" frame
Shimano XT-T780 pedals (394g)
Changes from shipping spec:
Alivio rear mech (replaced Acera +/- ?g)
2.2" Continental Mountain Kings (replaced Specialized tyres +/- ?g)
SRAM rear wheel & freehub (replaced Specialized bag of crap +/- ?g)
Alloy bottle cage (50g?)
Ancient Topeak minipump (?g)
Moon Comet rear light and mount (33g)
Lifeline flasher front light (29g)
Mount for Cateye front light (?g, light not fitted)
Topeak all-weather Tribag (65g)
- Crank Bros. B14 multitool (206g)
- patches, plastic tyre levers (30g?)

The (steel) Genesis is never going to be the lightest bike around but it is almost exactly the weight I imagined it would be, 10kg without pedals (Genesis' quoted weight will inevitably be for the smallest, or at least a medium, frame).

The Specialized, even with a load of old crap nailed to it, was only 4.4kg heavier than the roadie which was a bit of a shock and well within believable reach of the manufacturer's quoted weight before all the additions/changes. I really did assume that the quoted weights for bikes were very "aspirational", but unless my scales are under-reading quite a bit (a real possibility I suppose) then these two at least look to be bang-on.

OK, in percentage terms looking at the bike-only weights the Hardrock is a lot heavier, but considering my heft (I'm about 12st 4lbs, or 78kg) it's not a huge difference when the "wet weight" rolling package is considered. All in, with me, clothed, spare tube, phone, money etc. I'd imagine the difference would be less than 5% overall weight (~93kg vs ~97kg).

I could easily imagine a day riding the Genesis when I've got a full bidon, stomach and bladder and me and my "light" road bike is barely any more than me and my "heavy" MTB on a day I'd popped out without lights, tools, water etc.

The difference in speed then must almost all be down to friction (road and air) and not weight which surprised me.

Anyone else weighed their bike to see how it compares to manufacturer figures?

[Dammit]

Rolling resistance (knobblies vs little/no tread) and aerodynamic drag are going to be the difference on the flat - much above 5% and weight's going to come into it.

The other thing to consider is how much power you can output in the positions each bike puts you in - it's usual for someone on a TT bike to be unable to deploy the power which they would on a road bike, but the reduction in drag more than makes up for it.

I got my old Cannondale down to 6.4kg, with first gen Di2, deep carbon rims and a powermeter - current bike is a lot more than that though.

[ecsrobin]

Remember manufacturers weights are normally for a particular frame size which they state.

Giant don't list weights as they say there are to many variables.

[Daveyraveygravey]

On the flat, the only time you notice the weight is accelerating and decelerating, so if you're away from traffic the weight difference won't make it's presence felt that often.
If it's hilly, then you will notice it more.

[Batfink]

Except due to aero drag and friction even on a flat it will be harder to maintain a given speed. I remember the first time I rode a friends fixie after riding his £3k mountain bike and it was a revelation

[rdjohn]

My Aluminium Hybrid weighs 13.7kg and has the same 25mm tyres and chain ring as my 9.6kg Carbon road bike. At the rear the difference is 6-10 speed.

Back to back, my average speed over the same circular 40km route is an average 5kph quicker on the Carbon. My guess is this is more to do with me being in a more aero position rather the difference in weight, or gearing.

[Some Gump]

Why do you lot insist on using kph? We're not in france!

[Janosh]

Some Gump said:

Why do you lot insist on using kph? We're not in france!

Because it's in 'The Rules'

[cirian75]

Janosh said:

Some Gump said:

Why do you lot insist on using kph? We're not in france!

Because it's in 'The Rules'

http://www.velominati.com/the-rules/

Rule 24.

I break 30 because I commute and my boss would go "what rules!?!?!?! you are late"


and no way will I do rule 33 !

Edited by cirian75 on Thursday 30th July 12:18

[Craikeybaby]

Vitus quote 13.6kg for my bike, but when I weighed it (with pedals) it was 14.9kg.

[Roger Irrelevant]

It's not that surprising really - weight is way overrated as a factor in the 'performance' of a bike. But then (unlike cars where you have bhp, torque, weight, 0-60, mpg, all sorts of roll-on acceleration figures, drag co-efficients etc), it's basically the only number that's easily comparable between one bike and another so perhaps it's not surprising that a big fuss is made about it. I bet that if you could make your road bike weigh the same as your mtb but keeping everything else the same (e.g. fill the frame with concrete), then your time for a given route would still be far closer to the time you'd usually do on your road bike than the time it took to do it on the mtb.

[2Btoo]

Batfink said:

Except due to aero drag and friction even on a flat it will be harder to maintain a given speed. I remember the first time I rode a friends fixie after riding his £3k mountain bike and it was a revelation

Sorry to be slow but what would have made the difference? Thin, smooth tyres on the road rather than fat knobbly ones I can understand, or is a fixie lower-drag because it doesn't have gears?

[BadgerBenji]

As long as a bike rides nicely I've tended to find the weight is kind of irrelevant in the grand scheme of things.

[MC Bodge]

The weight of the bike is fairly insignificant compared to the combined weight of bike and rider.

I have a cyclocross bike currently fitted with a flat bar and 23mm slick tyres (and a front crud catcher!). It is consistently significantly slower than my road bike (again on 23mm slicks) that I can comfortably ride with a flat back on the drops for sustained periods (thanks to experimenting with fit, stretching/yoga and 'core' strengthening). Fitting aero bars (and adjusting the seat and stem position) can make it even faster.

The aerodynamic drag difference is noticeable on the cyclocross bike as speeds rise.

[P-Jay]

Published MTB weights are bobbings, in years gone by they'd remove consumables like brake pads, tie-wraps that hold on the cables and such like to get the published weights down, or use an accumulative weight based on the (fictional) weight of their frame added to the (fictional) claimed weights of all the parts - but I think they've long given up - now they weight their bikes, look what their competitors claim and chuck something ball park in, if they bother at all.

[loudlashadjuster]

P-Jay said:

Published MTB weights are bobbings, in years gone by they'd remove consumables like brake pads, tie-wraps that hold on the cables and such like to get the published weights down, or use an accumulative weight based on the (fictional) weight of their frame added to the (fictional) claimed weights of all the parts - but I think they've long given up - now they weight their bikes, look what their competitors claim and chuck something ball park in, if they bother at all.

That's what I assumed, so it was slightly surprising to find that the quoted weight for mine wasn't a mile out.

[Batfink]

2Btoo said:

Sorry to be slow but what would have made the difference? Thin, smooth tyres on the road rather than fat knobbly ones I can understand, or is a fixie lower-drag because it doesn't have gears?

the weight of an MTB wheel will be vastly greater as well as the spinning components so it will have far greater rotational inertia. The thinner tyres will have lower drag as well. The overall heavier weight will also have an effect on acceleration but not to the same extent.

[P-Jay]

loudlashadjuster said:

The difference in speed then must almost all be down to friction (road and air) and not weight which surprised me.

I've been trying to find a link, but it's alluded me - someone credible once released a short list of the 'friction points' on a bike and their respective importance.

Far and away tyres were the biggest factor - a road tyre is tiny compared to a MTB tyre, it's also 2-4 times the pressure which reduces the contact patch further still - weight and aero play their part of course - but rolling resistance trumps them all by a good margin - but you'll rarely hear the people who make carbon / aero stuff mention it of course with far less resistance you can turn bigger gears with the same amount of force so the effect is compounded.

[Kawasicki]

P-Jay said:

loudlashadjuster said:

The difference in speed then must almost all be down to friction (road and air) and not weight which surprised me.

I've been trying to find a link, but it's alluded me - someone credible once released a short list of the 'friction points' on a bike and their respective importance.

Far and away tyres were the biggest factor - a road tyre is tiny compared to a MTB tyre, it's also 2-4 times the pressure which reduces the contact patch further still - weight and aero play their part of course - but rolling resistance trumps them all by a good margin - but you'll rarely hear the people who make carbon / aero stuff mention it of course with far less resistance you can turn bigger gears with the same amount of force so the effect is compounded.

Rolling resistance of a knobbly tyre is obviously much higher than a pure road tyre, but rolling resistance overall is a small fraction of aero drag. Aero drag is accepted as the biggest factor.

[2Btoo]

Batfink said:

2Btoo said:

Sorry to be slow but what would have made the difference? Thin, smooth tyres on the road rather than fat knobbly ones I can understand, or is a fixie lower-drag because it doesn't have gears?

the weight of an MTB wheel will be vastly greater as well as the spinning components so it will have far greater rotational inertia. The thinner tyres will have lower drag as well. The overall heavier weight will also have an effect on acceleration but not to the same extent.

Interesting, thanks.