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  1. #1
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    Aug 2008

    Rubber v. metal, where is the compliance?

    This isn't just theoretical, I am really considering this project right now.
    Anyhow, I know that certain materials and technology will make a bike ride nicer. I also know that high volume tires can drastically change how a bike feels, on and off road. So here is the Q:

    Bike A) An aluminum hard tail with a carbon fiber rigid fork. 29 x 2.0 low tread tires.

    Bike B) A steel hard tail with a steel rigid fork. 700 x 38c low tread tires.

    ***Assume all other components are equal

    Intended use: riding with noobs, exploring local parks. Riding around town. Light trail use. Gravel rides. Maybe bike packing later on.

    Question: which will ride nicer? i.e. more forgiving and compliant.
    no chain no gain.

  2. #2
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    Aug 2008
    no one knows. now i feel better about asking
    no chain no gain.

  3. #3
    > /dev/null 2&>1
    Reputation: Procter's Avatar
    Join Date
    Feb 2012

    Re: Rubber v. metal, where is the compliance?

    Because they're both fully rigid, I'd bet the main factor in how forgiving the bikes are will be the 1.5 inch vs the 2.0 inch tires. After you rectify that, I don't think you'll feel a difference in the forgiveness due to the wheel size difference ( 700 vs 29er), unless you are riding more aggressive (rocky) terrain.

    So, the first bike will be more forgiving. But, beyond that, it's a question that can't be quantified.

  4. #4
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    Oct 2010

    Re: Rubber v. metal, where is the compliance?

    The bike with the fatter tires wins always. I have had the opportunity to try this, many times on mt bikes, road bikes and gravel grinder bikes.

    Coming from me that's a lot. I love steel bikes. I just had a custom steel mt bike made. However, the resiliency of steel... I just don't know how much you can really feel. Tires, handlebars, seats and seat posts seem to be the biggest differences in that order for me anyway.
    Btw, 700c and 29er are the same diameter.
    CRAMBA Chairman

  5. #5
    mtbr member
    Reputation: Flamingtaco's Avatar
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    Mar 2012
    Quote Originally Posted by thickfog View Post
    The bike with the fatter tires wins always.
    Pretty much. More volume=more compliant, tire design notwithstanding. You can also run a lower psi with that larger tire.

    Steel Vs. aluminum, meh. Maybe 20+ years ago, when they were building alum frames pretty the same as steel frame and the thicker alum tubing made for a harsher ride, but not with today's frames.

  6. #6
    Trail Ninja
    Reputation: Varaxis's Avatar
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    Mar 2010
    No brainer: Bike A.

    Reasoning: a metal's cross section is a big factor to consider in stiffness. An object with smaller cross section (smaller diameter tubing) is less stiff than one with a larger cross section made from the same material. I'm not sure about vibration damping, but I think density, thickness, material stiffness, and atomic structure (ex. crystalline, or composite matrix) play a factor. I reason that because a solid cylinder of low density foam-like material can damp vibration and other waves a lot better than a thin brass tube or glass tube of the same dimensions. I believe perceived comfort comes from a lack of unwanted feedback. Maybe designers make it a goal to make something light, responsive, yet comfortable. Stiffening up the bike makes it more responsive, yet can introduce sharper feedback, and compromise weight or durability. It's a delicate balance.

    Based on basic scientific research (AKA googling, but still favoring credible info), and not just eating up marketing or generally accepted beliefs, I know that steel is a very stiff material. It is much stiffer than aluminum and titanium, and I believe even stiffer than carbon, though stiffness to weight ratio is another story. It's so stiff that bikes use smaller diameter tubing, compared to other materials, to find that stiffness sweet spot, where it's not too stiff and not too flexy. If all things are equal, and I take that literally, that means the aluminum alloy tubing is the same diameter, and therefore super flexy. Cannondale is one brand in the past gave aluminum a reputation for being harsh, since they had super large diameter downtubes and such and thin-walled tubes. I suspect if the Cannondale's tube walls were thicker, it would be a little less harsh. If the tubes were smaller diameter, there would be less stiffness and less feedback. I would predict an alloy frame with thick yet small diameter tubing would handle poorly, due to the flex, but it wouldn't be harsh. Higher volume tires definitely would offer more compliance. I trust the carbon fork will mute more buzz than a steel one, based on anecdotal reports. I'll just assume Bike A is like many other modern alloy frames and it's not using super oversized tubing, instead a bit more moderate sized tubing. Assuming that, I can say the alloy bike will not be really that harsh, to counter what people generalize about aluminum frames.

    Comfort and ride qualities are a subjective thing. This is where choices come into play. Do you want your frame to have larger diameter tubes because you actually like to feel feedback to feel connected with the trail/road, or do you want to not feel it and only want to pedal and focus on other things like the scenery? Do you know what you are exactly after besides something "comfortable"? Or are you the type that just wants to be sold on a material based on some marketing or cliched sayings such as "steel is real" (whatever that means)? Even steel bikes feel different from other steel bikes, with lower cost steel bikes actually feeling more comfortable in a blind test vs top of the line steel with identical geo. Alloy bikes also feel different from one another. Easiest way to decide is to choose something that a manufacturer actually designed with your intentions in mind.

    You need to have a head full of knowledge that probably wouldn't do much good for much of anything else, to be able to figure this stuff out without test riding. Or you can just test ride and figure out answers to such questions yourself. Beware that some bike shops will try to sell whatever they got in stock to you, even if it might not suit you very well compared to what another shop might have. Shop around and don't get stuck on any one brand or model before going in, as those shops might not have it, let alone have it in your size. Perhaps a shop carrying Kona, Focus, Jamis, Fuji, Focus, Diamondback or another brand you haven't considered might have just want you need that the Trek, Giant, Spec, Cannondale, etc dealer(s) didn't have.

    To add on to what I said above about compliance, check out the diameter and shaping of the tubes in the seat stays. Check the diameter of the seatpost and how high up the seatstays connect to the back of the seat tube. I think that's the general area that new cutting edge models are focusing on, to create compliance. Small diameter, carbon composite, decoupling the seat stays from the back of the seat tube (instead attaching it to the top tube), flattened seat stays, small diameter seat post (ex. 27.2mm instead of 30.9mm or bigger), etc. are features of new bikes designed for more compliance. If you are planning on loading the bike down with gear, packing a heavy pack, etc., perhaps frame reliability will play a larger factor in your decision. Steel is generally accepted to be a very strong, durable, reliable/trusty choice, and I cannot argue with that, esp compared to alum and carbon. When you got to compromise to meet a price point, it's a tough choice, eh? People are spending 6k+ on bikes to not have to deal with many compromises, so that's your other option.

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