Bike Weight - How important?

Blue407
Blue407 Posts: 33
edited June 2011 in Road buying advice
Maybe a silly question, but how much does it really matter if your bike is 15lb or 25lb?

What effect does it have on your riding?

I am looking for a new road bike and am 17st, aiming to get down near 15st. So as a proportion I can easily lose quite a bit of weight and the bike is a very low % of my total rolling weight (Bike + rider)

From what I have seen looking at on-line prices, you pay an awful lot more for a lighter bike and therefore there must be a point of diminishing returns for a heavy rider......

Comments

  • markos1963
    markos1963 Posts: 3,724
    For the vast majority of us bike weight is totally irrelevant. As you have pointed out you have plenty of weight loss in reserve, only when our fat percentage has got to less than 7% do you really need to look at the weight of the bike.
    What's more important equipment wise is wheel/tyre weight and a good position on the bike.
  • inseine
    inseine Posts: 5,786
    There's a lot of truth in what you say, except a 25lb will of course junk, just because the quality would be awful. Up to a point lighter parts are better quality. We're taliking extreems here though.
  • marksteven
    marksteven Posts: 208
    similar weight to me i go for sensible / strong rather than light weight & keep your pedaling smooth , good quality tyres & tubes are a good buy as are pedals & shoes then wheels & so on
  • I would agree that getting the lightest bike possible isn't necessarily a priority. As mentioned you will lose weight as you ride which will help more than having the lightest bike. Plus, you can always upgrade components later to shed some weight from the bike if you need to.

    I personally think that you should focus on getting a bike that is not ridiculously heavy, but more importantly a bike that will be durable so you don't have to constantly fiddle with components or adjust things too much.

    So getting the best quality components for your money along with a decent frame would be better than just getting the lightest bike you can find.
  • Chris James
    Chris James Posts: 1,040
    cadseen wrote:
    Well its just not the weight itself.

    For example a frame on a 15LB bike will be much more responsive and probably stronger than a 25Lb bike.
    .

    Wishful thinking in my view.

    Frames are made lighter by using less material. So a light steel frame has thinnner walls than a heavy steel frame. A light carbon frame less material than a heavier one.

    Frame strength is a function of it's cross section, so all being equal thicker walls are stronger.

    Obviously there are design tweaks that can be made by using better grade carbon fibres or stonger materials, and complicated butting profiles. But there is a limit to how far things can be pushed.

    Light frames and wheels are designed to be just strong enough and no more. If you want strength then you should buy a tourer!

    'Responsiveness' is usually down to stiffness (which is marginally increased by thicker walls) and geommetry , eg trail, chain stay length etc.
  • Squillinossett
    Squillinossett Posts: 1,678
    Bike Weight not a huge issue, rotating weight (wheels & tyres) is noticeable
  • Keith1983
    Keith1983 Posts: 575
    I would almost ignore weight and certainyl not let it be a deciding factor in buying or not buying a bike. I think rolling resistance is more important and will be influenced by things like tyres, bearings etc.
  • Pinner
    Pinner Posts: 19
    Weight isn't super important, Many pro riders bikes are not even near the weight limit, it seems that amateurs worry about it much more than top riders do! The legs make the difference!

    As for frame strength though, A quality carbon frame is about as strong as your going to get without riding a mountain bike, Take it from someone who has seen a worse crash than you will ever see and seen which bikes survived best. The alloy bikes were in pieces less than a foot long, while the carbon frame nearly could have been ridden home on.
    Custom 2010 Stumpjumper FSR Pro AM
    Custom 2009 Specialized Tarmac Pro SL2
  • I'm understanding that the aim here is fitness related.
    15lbs versus 25lbs is not a reliable indicator. In the 15 lb range the choice is so numerous as to be confusing. The 25 lb range is perhaps adequate for a DH MTB, which I don't think flying down offroad DH courses is what you have in mind :lol:
    As for road bikes at that 25lb, that is extremely heavy and on the scrapmetal side of equipment.

    So from your brief description I would suggest a higher end / midrange, but even here, the choice is going to be numerous. A Cannondale Super Six or a Pinarello Dogma, a Cervelo S3, all in that range would be (IMHO ) overkill.
    Along the lines of a Cannondale Synapse, a Specialized Allez would give you an excellent bike, extremely versatile, equally capable of the consistent fitness rides, yet more than capable of handling the occasional group ride. An attention to components and dialing in that segment of bike fit, Saddle, Bars, drivetrain configuration is going to make or break your experience.
    I strongly advise against buying online for those reasons. You need to go into a reputable shop to get fitted, test ride a few models and most importantly have an expert bike fitter fit you to an appropriate ride.
    Cannot be done online, regardless of the sale's pitch.

    After a few years layoff, I've returned to full on cycling, training to race again next year as a Cat.2 and Masters. I raced in the past, stateside and in France, coached juniors and promoted a two day stage race. In all my years of cycling, the most important factor for anyone from juniors to the casual rider, has always been bike fit, that is the critical factor that will allow you to reach your goals....Good Luck.. 8)
  • cadseen wrote:
    Well its just not the weight itself.

    For example a frame on a 15LB bike will be much more responsive and probably stronger than a 25Lb bike.
    .

    Wishful thinking in my view.

    Frames are made lighter by using less material. So a light steel frame has thinnner walls than a heavy steel frame. A light carbon frame less material than a heavier one.

    Frame strength is a function of it's cross section, so all being equal thicker walls are stronger.

    Obviously there are design tweaks that can be made by using better grade carbon fibres or stonger materials, and complicated butting profiles. But there is a limit to how far things can be pushed.

    Light frames and wheels are designed to be just strong enough and no more. If you want strength then you should buy a tourer!

    'Responsiveness' is usually down to stiffness (which is marginally increased by thicker walls) and geommetry , eg trail, chain stay length etc.

    I have to disagree on most points, a pair of Mavic Ksyrium wheels are extremely light, but will outperform ( strenght ) a 32-28 spoke conventional wheel.

    As for frame material, Carbon Fiber is the choice for strenght to weight ratio, will outperform a conventional steel frame as well as an aluminum frame, though the question remains as to what is the rider's goals.
    Fitness riding, Racing, social club/group rides or just riding for the pleasure of it all
    Carbon fibers are aligned to complement comfort as well as strenght, today's bikes are a far cry than even 5-6 years ago, a steel frame might be cool in the retro sense, but it has it's limits as to the range.
    In racing, I have not seen anyone on a steel frame for a few years, Yes the exception is still out there but for the 99% steel is obsolete, unless you want a bespoke frame which is an entirely different spectrum and not conducive to the material stresses that racing demands.

    Aluminum Frames can be a bit harsh, but that can easily be offset with carbon fiber seatposts, stems and bars as well as front carbon fork.

    In the choices of steed, costs are going to determine the range, $900.00 to $15,000.00 is the price range and the choices in that variant are too numerous to list.

    Comparing tubing thickness between Aluminum, Carbon and Steel doesn't make sense as the materials are completely different in tensile strenght and strenght to weight ratio.
  • Chris James
    Chris James Posts: 1,040
    I have to disagree on most points, a pair of Mavic Ksyrium wheels are extremely light, but will outperform ( strenght ) a 32-28 spoke conventional wheel. .

    The strength of a wheel is given by its spokes. A well built high spokemcount wheel is stronger than Mavic Ksyriums. Leaving aside the engineering, just ask yourself what is specced on heavy touring bikes and tandems?

    How are you assessing that the factory built wheels will out perform the handbuilts? Perform in what sense?

    I have low spoke count aero wheels and 32 spoke 23mm deep rims. The factory wheels are probably slightly faster but they are certainly not as strong.
    As for frame material, Carbon Fiber is the choice for strenght to weight ratio, will outperform a conventional steel frame as well as an aluminum frame, though the question remains as to what is the rider's goals. etc.

    Indeed, but this doesn’t contradict anything I said. I merely pointed out that a light weight carbon fibre frame has less material in it than a heavy weight carbon fibre frame. Likewise a light weight aluminium frame has less material than a heavy aluminium alloy frame.

    A frame’s strength is related to its cross sectional area – i.e. stress = force / area. By using clever butting and tube profiling and you can try to ensure that material is thicker at the points of greatest load and you can also specify stronger materials. However, there is a limit to how far you can push this.

    A superlight sub 1Kg carbon frame is unlikely to be stronger than a more budget carbon fibre frame that has considerably more material in it. Likewise steel frame made from thin walled tubes like Columbus Life are probably no stronger than, say, a 631 frame. .[/quote]
    Comparing tubing thickness between Aluminum, Carbon and Steel doesn't make sense as the materials are completely different in tensile strenght and strenght to weight ratio.

    Indeed, which is why my original post didn’t do that – hence the comparing of frames of the same material and the use of the phrase ‘all being equal’

    The original poster actually was asking what benefit a 17 stone rider would get by dropping a load of extra cash to get from a 25lb to 15lb bike.

    The answer is likely to be ‘next to none’. Cycling performance at any speed is mostly determined by aerodynamic, not weight of bikes. And aerodynamics is mostly determined by the rider’s position not the bike or even the wheels that much.
  • rolf_f
    rolf_f Posts: 16,015
    The original poster actually was asking what benefit a 17 stone rider would get by dropping a load of extra cash to get from a 25lb to 15lb bike.

    The answer is likely to be ‘next to none’. Cycling performance at any speed is mostly determined by aerodynamic, not weight of bikes. And aerodynamics is mostly determined by the rider’s position not the bike or even the wheels that much.

    Admittedly I weigh barely half the quoted rider and a statistical sample set of two isn't meaningful but....

    Commute time inbound yesterday (18lb Ribble Gran Fondo Carbon) - 29:37
    Commute time inbound today (28lb+ 1990 Dawes Horizon Tourer in Reynolds 501) - 30:51

    Not much really (within the variances of weather and personal zinginess)
    Faster than a tent.......
  • Bozman
    Bozman Posts: 2,518
    Very important, for every lb in weight you lose from your bike you'll gain 1mph on your average speed! :D