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Why the big difference between calculated and advertised bike weights?

I've just been calculating the weight of a build using a Cannondale SuperSix Evo 105 as the basis. The bike weighs 8120g according to reviews but if I add up the weights of all the components I get nowhere near that. This seems to always be the case for Cannondale (whilst Canyon bikes typically add up to what you'd expect). Why is this?

Here's the breakdown:

Wheelset: 1735

Tyres: 460

Tubes: 200

Bar: 320

Stem: 149

Shifters: 486

Rear mech: 234

Front mech: 89

Brakes: 378

Saddle: 250

Crankset: 600 (guess... it's around the Ultegra mark)

Cassette: 251

Chain: 257

Frame "system" (i.e. forks, frame, seatpost): 1600

TOTAL: 7009g

Conspicuously missing are the bearings and cables but even then I'm  at least  700g out. How? Same happens when I calculate the weight of the SuperSix Evo Hi Mod and my Synapse. Do they hide some lead blocks somewhere after assembly?

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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14 comments

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trohos | 7 years ago
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 90% of manufacturers give their weights without pedals and with the smaller sizes of components.

The weight you take from web may differ  up to 10%. Also the frames for the same model has a little variation in the weight.

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rjfrussell | 7 years ago
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If every item manufacturer has gone 10% low (what cads, they'd never do that, would they), you are there.

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part_robot | 7 years ago
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Bike, frameset and wheelset from reviews. Groupset from a site that has all the groupsets weighed. Some other from blogs/forums. The rest from wiggle etc.

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Nick T replied to part_robot | 7 years ago
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part_robot wrote:

Bike, frameset and wheelset from reviews. Groupset from a site that has all the groupsets weighed. Some other from blogs/forums. The rest from wiggle etc.

 

You're comparing claimed individual component weights to a claimed full bike weight and you wonder why there's a discrepancy? No two components will weigh the same from the same production line, the advertised weight is usually best case scenario so add a few % onto the advertised weight before buying. 

 

Youll only get an accurate weight for an item when you have the part on a set of scales in front of you

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Nick T | 7 years ago
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Where are you getting these component weights from 

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Giles Pargiter | 7 years ago
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I really think that when one considers that people often pay over a £1 a gram to lose weight on their bikes - that is way outside margin of error territory. . . then again ..?

I have noticed in the past that the labels one would expect to be are often not the lightest. I distincty remember weighing a Stronglight chain set against a Campag' one and the Stronglight was over an ounce (28g) lighter, to my surprise.

That in no way explains the divergence in weights mentioned though. Rather it adds to the inexplicable inaccurracies in advertised weights. Could be some kind of fraud maybe?

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mtbtomo | 7 years ago
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Do the review(s) give actual weight or catalogue weight?

 

The manufacturer might weigh an actual bike for a given size, and the component manufacturers do it differently (minimum weight of one from a batch of components)?

 

5 - 10% weight discrepancy is not a lot.

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beezus fufoon | 7 years ago
1 like

did you weigh the air in the tyres?

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HarryTrauts | 7 years ago
1 like

Grease.  300g of grease.  Problem solved! smiley

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part_robot | 7 years ago
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So if Natrix is right we are down to just 300g missing. I suspect that's margin of error territory unless I've missed something else?

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part_robot | 7 years ago
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Could be. There's 200g right there maybe! Good spot. Perhaps the other review included pedals (I don't recall where I found it however)

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Natrix | 7 years ago
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Frame size??  The review I read had it as 7.9kg anyway http://www.cyclingweekly.co.uk/reviews/road-bikes/cannondale-supersix-ev...

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part_robot | 7 years ago
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Doesn't look like it:

Bar tape: 50g

QR: included (but I'll add 170g just in case)

BB: 100g

Bolts: stem only not accounted for - 30g max I'd guess?

Cables:  250g

NEW TOTAL: 7600g

STILL MISSING: 500g

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sergius | 7 years ago
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Cables, Bar Tape, Nuts and Bolts, BB, QRs...

700g really isn't a lot of weight for all of those bits

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