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Thread: forged fat rim

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    forged fat rim

    normally high end wheels are double walled, so forging is not possible, and normally a single wall rim is cheap, so forging is not practical.

    Now, with $220 single wall fat rims, maybe someone could try and come out with a forged rim. It would be stronger and definitely lighter than an extruded rim. there would be no joint at all. It would be cheaper than a welded rim if done in a fairly large quantity.

    If you extrude a large cylinder the size of the whole rim, and go straight from the extruder to a rotary forge machine, it could stamp out a lot of rims very quickly. Different dies could be used on the same extrusion for different rim widths and designs, and could apply cutouts or patterns of thinner and thicker walled sections around the rim, as well as domed indentations for the spoke nipples.

    Either way is a completely different process than any bicycle wheel manufacturer uses, so would be more easily done by manufacturers in other industries, and completely foreign to rim manufacturers. If the single wall forged rims turn out to be as strong as double wall but lighter in regular MTB widths though, someone could make high end rims for way cheaper than current double wall rims at the volume they could sell.

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    As you know, cost and profit are the usual reasons for business decisions. Forged wheels are common in the auto industry, and the flatter profile of fat rims probably better suits this area, but start-up tooling costs are still present, and volume probably couldn't justify it...yet.
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    Quote Originally Posted by autodoctor911 View Post
    normally high end wheels are double walled, so forging is not possible, and normally a single wall rim is cheap, so forging is not practical.

    Now, with $220 single wall fat rims, maybe someone could try and come out with a forged rim. It would be stronger and definitely lighter than an extruded rim. there would be no joint at all. It would be cheaper than a welded rim if done in a fairly large quantity.

    If you extrude a large cylinder the size of the whole rim, and go straight from the extruder to a rotary forge machine, it could stamp out a lot of rims very quickly. Different dies could be used on the same extrusion for different rim widths and designs, and could apply cutouts or patterns of thinner and thicker walled sections around the rim, as well as domed indentations for the spoke nipples.

    Either way is a completely different process than any bicycle wheel manufacturer uses, so would be more easily done by manufacturers in other industries, and completely foreign to rim manufacturers. If the single wall forged rims turn out to be as strong as double wall but lighter in regular MTB widths though, someone could make high end rims for way cheaper than current double wall rims at the volume they could sell.
    I have seen rim beads snap off of a high end lightweight racing wheel on impact with a crocodile strip on a track. Wouldn't a forged rim be susceptible to the same thing, especially considering the thinness of the bead? Correct me if I am wrong here.

    I though the bonus of an extruded rim is that the structure of the metal, the fibers whatever, crystalline structure is aligned by the extrusion process making the rim stronger. Again correct me if I am wrong.
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    Quote Originally Posted by autodoctor911 View Post

    Now, with $220 single wall fat rims, maybe someone could try and come out with a forged rim
    Here in Oz clownshoe rims are $250 each ($264us)
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    Quote Originally Posted by rockcrusher View Post
    I have seen rim beads snap off of a high end lightweight racing wheel on impact with a crocodile strip on a track. Wouldn't a forged rim be susceptible to the same thing, especially considering the thinness of the bead? Correct me if I am wrong here.

    I though the bonus of an extruded rim is that the structure of the metal, the fibers whatever, crystalline structure is aligned by the extrusion process making the rim stronger. Again correct me if I am wrong.
    Extrusions are quite a bit stronger than cast aluminum because the grain structure of the metal is algned, and compacted a bit when the semi molten metal is forced through the dies at high pressure.
    Cold forgings, or cold worked by other means are the strongest though, and sinter forged from powdered metal or parts formed from semi molten metal at very high working pressures by dies, or impacting. Then come extrusions, and after that the heavily machined from billet, or "CNC'ed", then at the bottom is gravity cast.

    A lot of people in the bicycle industry, like Sheldon Brown, for example recommend not using cnced boutique hubs because of the inferior strength of the machined from bar stock parts. And, bar stock is basically a straight round extrusion.

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    Quote Originally Posted by Stevob View Post
    As you know, cost and profit are the usual reasons for business decisions. Forged wheels are common in the auto industry, and the flatter profile of fat rims probably better suits this area, but start-up tooling costs are still present, and volume probably couldn't justify it...yet.
    yeah, I think to justify such a radical change in rim manufacturing technique, it would definitely require a bigger potential profit to be gained, than the sales of just Fatbike sales.
    But, I think there are a few high end motorcycles with wire spoke wheels that have forged rims, not only for strength, but for better tolerances to run tubeless, and for safety at high speed.

    Everybody knows how quickly a tubed tire can deflate, and come loose from the rim. At highway speeds, this can be deadly. The more precisely machined forged and cast motorcycle wheels have tight tolerance lips to hold the bead on, and tubeless motorcycle tires do not deflate as quickly from a puncture, which can cause a tube to rip a big gash, as it blows out. Of course, a big enough cut could do the same thing to a tubeless tire, but the bead will still stay in place well enough to provide some control still.

    Still, very few motorcycles have wire spoke wheels, and most of those are extruded Aluminum or cold worked chrome steel.

    Perhaps, instead of forging a rim, someone could cold roll some. The tooling required would be minimal, if any for a shop that can roll racecar rims. The difficult part will be finding the raw material in a thin enough extrusion. I don.t think you can roll the metal thickness down that much from thicker stock, at normal rim rolling temps.

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    Its the same argument on many threads here where people compare speed rated radial car tyres to fat bike tyres, saying the market is smaller therefore they are more expensive.

    The fat bike wheels we have at the moment are strong enough IMO, i beat the crap out of my single wall rims without any issues.

    Carbon wheels are good for regular MTB's as they increase stiffness, this isnt an issue with fat bikes and its common knowledge that alu rims are as light if not lighter than carbon rims, its only the stiffness that alu goes without.

    With rims like 690g marge lites selling well and the widest 100mm clownshoes the same, the game will probably move forward before stepping sideways to forged rims.... as said above the market dictates and its selling out as it is.
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    Quote Originally Posted by ozzybmx View Post
    Its the same argument on many threads here where people compare speed rated radial car tyres to fat bike tyres, saying the market is smaller therefore they are more expensive.

    The fat bike wheels we have at the moment are strong enough IMO, i beat the crap out of my single wall rims without any issues.

    Carbon wheels are good for regular MTB's as they increase stiffness, this isnt an issue with fat bikes and its common knowledge that alu rims are as light if not lighter than carbon rims, its only the stiffness that alu goes without.

    With rims like 690g marge lites selling well and the widest 100mm clownshoes the same, the game will probably move forward before stepping sideways to forged rims.... as said above the market dictates and its selling out as it is.
    well said

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    I really don't expect anyone will do it. I was just thinking out loud. The only way anyone would do it, is if it could be a high volume operation and cost less than current means to get a competitive product in the mainstream mtb or road bike scene. And they probably wouldn't even bother with the really wide rims for us. Unless a motorcycle rim maker does it for motocross bikes to get them a little lighter for competition, but they would be 21" which is an inch smaller than a 26" bicycle rim.

  10. #10
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    Forged rims are an interesting idea. Some of you know a company already known for some of the best forging of aluminum in the bicycle marketplace..........


    That would be Shimano. If anyone could do this, they could, but probably will not....

    My thought would be to have fat bike rims hydro-formed. They can control wall thicknesses on frames well with this method, and I would think the forged fat bike rim idea would be perfectly suited to this. Giant, for one, is heavily investing in hydro-forming and they think it may out-do carbon fiber at some point for light/strong/mold-able/price conscious bike frames.

    But as has been said, we don't really need it. But it could be cool.....

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    Quote Originally Posted by Guitar Ted View Post
    Giant, for one, is heavily investing in hydro-forming and they think it may out-do carbon fiber at some point for light/strong/mold-able/price conscious bike frames.
    It's already pretty close on Giant's frames- their carbon frames aren't a whole lot lighter than their aluminum frames, though the carbon frames are probably a little stiffer.

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    It would need to be double wall for hydroforming to work, and even then I'm not sure it would work, or what advantage hydroforming would have.

    What is made better on a hydroformed frame?
    doesn't it just turn a round tube into a weird shaped one?

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    Quote Originally Posted by autodoctor911 View Post
    ...What is made better on a hydroformed frame?
    doesn't it just turn a round tube into a weird shaped one?
    A question I have often pondered. Surely the metal is much thinner at the places where it has been stretched, and that often seems to be where it is welded, ie almost the opposite of what we look for in a butted tube. It seems to work ok though.

    I suspect the main advantage is to differentiate product from another manufacturer by having "prettier" tubes.
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    Quote Originally Posted by autodoctor911 View Post
    It would need to be double wall for hydroforming to work, and even then I'm not sure it would work, or what advantage hydroforming would have.

    What is made better on a hydroformed frame?
    doesn't it just turn a round tube into a weird shaped one?

    Why double wall? There is no need for a double wall.

    The reasoning for hydro-forming is to better control butted sections and to eliminate the need for welded gussets. Stronger structures are the result. It is like forging, only using a hydraulic means of moving the metal, instead of a mechanical one.

    Essentially the process could use a thin, flat piece of aluminum alloy and force it into the mold shape of a rim. The spoke bed section, bead seat, and the thinner sectors of the design could be precisely, and repeatably made. No weld joint, theoretically.

    Of course, it is all merely speculation on the rims, but hydro-forming is much more than a marketing trick.

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    What about a modified Raleigh or Westwick pattern rim in wide widths. There are still plenty of those and others like them kicking about on the road after so many years of abuse. Could something like that be done with aluminum? I wouldn't be scared off by a steel rim though. I think there might be something to forging or hydroforming.

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    Quote Originally Posted by autodoctor911 View Post
    Extrusions are quite a bit stronger than cast aluminum because the grain structure of the metal is algned, and compacted a bit when the semi molten metal is forced through the dies at high pressure.
    Cold forgings, or cold worked by other means are the strongest though, and sinter forged from powdered metal or parts formed from semi molten metal at very high working pressures by dies, or impacting. Then come extrusions, and after that the heavily machined from billet, or "CNC'ed", then at the bottom is gravity cast.

    A lot of people in the bicycle industry, like Sheldon Brown, for example recommend not using cnced boutique hubs because of the inferior strength of the machined from bar stock parts. And, bar stock is basically a straight round extrusion.
    Yeah I was thinking billet, not extrusion or forged rims. Just remembered that a few minutes ago. Thanks for clarifying, i was also thinking the boutique milled bar stock stuff that we suffered through in the 3DV era.
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