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  1. #1
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    Grease Alloy Seatpost?

    Hello,

    I'm a newbie, and I need tor replace my seat post. I hope this is in the right forum.

    I currently have a 26.4 alloy seat post, and need a longer one. I was fitted at a bike shop today, and the post is too short. They don't stock this size. So I will buy online. I don't understand what "alloy" means here. When I install, do I need to grease the alloy seat post? What should I use to grease it, if anything? My current seat post has not been greased. It's lasted since 1989. This is not a high end bike. It is a steel bike.

    Thanks for any help. By the way, it is hard to find a 26.4 sized seat post that is not aluminum. I need something that will hold 275lbs, so aluminum is out.

  2. #2
    如果你能讀了這個你講中文 genericbikedude's Avatar
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    Yes

  3. #3
    如果你能讀了這個你講中文 genericbikedude's Avatar
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    Wait--after actually reading, DO grease the seatpost, and alloy (alluminum) WILL hold your weight.

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    Alloy means Aluminum. For any decent quality seatpost the material choices are aluminum and carbon. You can be sure it will take your weight. A lot heavier than you haven't broken them.

    Yes, be sure to grease it and any auto or bike grease will do. The grease is used to prevent corrosion from causing the post to seize in your frame. It's lubricating properties are not important.

  5. #5
    Senior Member Brian's Avatar
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    Quote Originally Posted by HillRider
    Alloy means Aluminum. For any decent quality seatpost the material choices are aluminum and carbon. You can be sure it will take your weight. A lot heavier than you haven't broken them.

    Yes, be sure to grease it and any auto or bike grease will do. The grease is used to prevent corrosion from causing the post to seize in your frame. It's lubricating properties are not important.
    "Alloy means aluminum"? That's news to me. Last I checked, an alloy was a mixture of a base metal and 1 or more metallic or non-metallic elements. Brass is an alloy, as is cro-mo. And you're suggesting that this rider use a carbon fiber seatpost on a steel bike that is at least 16 years old, and needs to handle a load of 275lbs?

    Back to you now, Fleet. Any local shop that orders from J&B Imports can get you a post in that size. Pyramid makes one 350mm in length, and Rockwerks makes one 400mm in length. If they're charging more than about $20, they should have a mask and a gun. There's at least one rider on the forums that I know of who weighs over 300lbs. If his aluminum post hasn't broken, you shouldn't have any problems. As Hillrider pointed out, a light coat of grease will keep the two dissimilar metals from forming an unfriendly bond.

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    Quote Originally Posted by Expatriate
    "Alloy means aluminum"? That's news to me. Last I checked, an alloy was a mixture of a base metal and 1 or more metallic or non-metallic elements. Brass is an alloy, as is cro-mo.
    To a metallurgist, yes, you're correct. In the common bicycle vernacular however, "alloy" is understood to mean an aluminum alloy....

    HTH!
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  7. #7
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    Quote Originally Posted by Expatriate
    "Alloy means aluminum"? That's news to me. Last I checked, an alloy was a mixture of a base metal and 1 or more metallic or non-metallic elements. Brass is an alloy, as is cro-mo. And you're suggesting that this rider use a carbon fiber seatpost on a steel bike that is at least 16 years old, and needs to handle a load of 275lbs?
    I assume you are being obtuse just to show you can be. In this context of bicycle components, alloy is synonymous with aluminum. We aren't talking general materials science here.

    I was not suggesting a carbon seat post would be suitable but it most likely would be. He specifically asked if an aluminum seatpost would be suitable for his weight and I believe it would be as they have supported heavier riders quite successfully for decades. And, what does the frame material or its age have to do with the suitability of a seatpost?

  8. #8
    Senior Member Brian's Avatar
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    Quote Originally Posted by HillRider
    I assume you are being obtuse just to show you can be. In this context of bicycle components, alloy is synonymous with aluminum. We aren't talking general materials science here.

    I was not suggesting a carbon seat post would be suitable but it most likely would be. He specifically asked if an aluminum seatpost would be suitable for his weight and I believe it would be as they have supported heavier riders quite successfully for decades. And, what does the frame material or its age have to do with the suitability of a seatpost?
    The original poster doesn't seem to familiar with bike components, or their metallurgic properties. Had you stated in your post "In the context of bicycle components, alloy generally means aluminum" you would have been factually correct. Aluminum, or aluminium as it's called here, is rarely even pure aluminium. It contains traces of Zinc, Iron, and Titanium, among other elements. And even at only 97% pure, it's nto considered an alloy.

    You'll find that some CF parts have a suggested weight limit, and it's not usually 275lbs. You're also right about the material and age of the bike having nothing to do with the suitability of a seatpost. I'm sure that if he's riding a 16 year old steel bike he wouldn't hesitate to drop $60+ on a carbon fiber seatpost, rather than $15-20 for an aluminum one.

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    It contains traces of Zinc, Iron, and Titanium, among other elements. And even at only 97% pure, it's nto considered an alloy.

    The use of "alloy" as a synonym for aluminum was in a bicycle context from the very beginning as he was dealing with a bike shop.

    I don't know of any bicycle components made of pure aluminum. It's too soft and too weak to even be considered. Every one is made of one grade or another of aluminum alloy. That's where all the 4-digit numbers you see in the ads (2XXX, 5XXX, 6XXX, 7XXX) come from.

    If the manufacturer of a component has a suggested weight limit, it should be clearly specified and the bike shop would be very remiss if they sold it to an unsuited rider. However, I don't know of any alloy (as in aluminum alloy) seat post with a published weight limit, which is what started this entire thread.

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    Well wasn't that banter fun?

    Anyway, if you get a Aluminum (AL) seat post IT SHOULD hold your weight, especially if you get a good one and not a expensive lightweight racing one. Nitto makes longer seat post that are very strong and very high quality. Whatever post you get make sure it has 2 adjustment bolts and not just one-two is generally stronger then 2.

    If you get a AL seatpost you need to slather the post with grease before inserting it into the seat tube, then insert and just wipe off the excess grease that piles up from lack of space for most of it. If you get a CF post-which by the way proberly would not be strong enough, you can't use grease because then you won't be able to keep the post from slipping even after tightening it as hard as you can.

  11. #11
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    how long of a post do you need? 26.4 is not a common size these days, and 400 mm is about as long as they come, and generally pretty low end in quality. unless you find a chromoly seatpost, an aluminum one (don't start on alloys again guys) will be stronger than a steel one; cheapo steel seatposts are pretty soft. the only carbon ones i've seen are short aero/road jobbies.

    if you do need an extra long seatpost, i think the leverage and your weight may be possibly considerations.

  12. #12
    Senior Member Brian's Avatar
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    Quote Originally Posted by HillRider
    It contains traces of Zinc, Iron, and Titanium, among other elements. And even at only 97% pure, it's nto considered an alloy.

    The use of "alloy" as a synonym for aluminum was in a bicycle context from the very beginning as he was dealing with a bike shop.

    I don't know of any bicycle components made of pure aluminum. It's too soft and too weak to even be considered. Every one is made of one grade or another of aluminum alloy. That's where all the 4-digit numbers you see in the ads (2XXX, 5XXX, 6XXX, 7XXX) come from.

    If the manufacturer of a component has a suggested weight limit, it should be clearly specified and the bike shop would be very remiss if they sold it to an unsuited rider. However, I don't know of any alloy (as in aluminum alloy) seat post with a published weight limit, which is what started this entire thread.
    I deal with about 6000 tonnes of aluminium each week, so I know a little bit about it. My comment about weight was for the guy that suggested the CF seat post.

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    Quote Originally Posted by Expatriate
    I deal with about 6000 tonnes of aluminium each week, so I know a little bit about it. My comment about weight was for the guy that suggested the CF seat post.
    I assumed you knew a lot about it. That's why I asked if you were being obtuse when you posted the comment about the term "alloy" not being limited to aluminum alloys. My note about various families of Al alloys was for the original poster's benefit.

    Always fun corresponding with posters from "Down Under". The huge time difference usually makes replies occur at 12 hour intervals.

  14. #14
    Senior Member Brian's Avatar
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    If anyone is interested, a typical analysis contains the following trace elements:

    Silicon, Ferrite, Manganese, Magnesium, Chromium, Zinc, Vanadium, and Titanium.

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    Quote Originally Posted by Expatriate
    If anyone is interested, a typical analysis contains the following trace elements:

    Silicon, Ferrite, Manganese, Magnesium, Chromium, Zinc, Vanadium, and Titanium.
    Gee, I'm sorry, but I for one am not interested! I wouldn't know a ferrite rod from a magnesium rod it they were sitting side by side!!! I have all I can do trying to understand my VCR!!!!!!!!!!!!!!!!!!

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    Wow! That's a lot of info on alloy seat posts! Now I know that Alloy means Aluminum. Thank you for that. I'm now in the process of finding a 26.4 seat post that is at least 350mm. My current one is about 200mm. My LBS doesn't have any - they said they haven't sold this size in about 15 years! So I'm checking online. Thanks for your help everyone!

  17. #17
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by raleigh_fan
    To a metallurgist, yes, you're correct. In the common bicycle vernacular however, "alloy" is understood to mean an aluminum alloy....

    HTH!
    So if you tell a lie enough times that a great many people come to believe it does that somehow make it true?

  18. #18
    Senior Member Brian's Avatar
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    I'm sure QBP has them in their catalog as well. Your LBS must just be too slack to order one for you.

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    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by Fleet
    When I install, do I need to grease the alloy seat post? What should I use to grease it, if anything?
    I'm a believer in greasing not the seatpost itself, but the inside of your bike frame's seat tube. If you grease the frame tube, any excess is carried down into the bike frame by the seat post. If you grease the seat post, the excess is scraped off onto the exterior of your bike. The purpose of the greasing is to prevent the post from galling in your frame. Virtually any lubricating grease will do. I use Park Poly-Urea because that's what I happen to have on hand for other bicycle uses.

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    Quote Originally Posted by Retro Grouch
    So if you tell a lie enough times that a great many people come to believe it does that somehow make it true?
    You are hereby elected to head the committee to correct the usage of the word "alloy" in the bicycling community. Keep us posted on how it's going for you....
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    In case it is helpful.

    I am not sure of the seat post length, but the alloy/aluminum/aluminium seat post on my Sedona held up to my weight when I was 365. The Sedona has a compact frame, so the seatpost is pretty long.

    I have a bolt for the seatpost and don't want to undo it, but I currently have 240 mm between the collar and the top of the seat clamp. It is a suspension post in case that matters in the analysis (although I recently tightened the mechanism in order to make it act like a solid post without buying a solid post).
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  22. #22
    Senior Member Don Cook's Avatar
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    Quote Originally Posted by Expatriate
    The original poster doesn't seem to familiar with bike components, or their metallurgic properties. Had you stated in your post "In the context of bicycle components, alloy generally means aluminum" you would have been factually correct. Aluminum, or aluminium as it's called here, is rarely even pure aluminium. It contains traces of Zinc, Iron, and Titanium, among other elements. And even at only 97% pure, it's nto considered an alloy.

    You'll find that some CF parts have a suggested weight limit, and it's not usually 275lbs. You're also right about the material and age of the bike having nothing to do with the suitability of a seatpost. I'm sure that if he's riding a 16 year old steel bike he wouldn't hesitate to drop $60+ on a carbon fiber seatpost, rather than $15-20 for an aluminum one.
    If you guys don't stop it, I'm telling your moms!

  23. #23
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    Quote Originally Posted by raleigh_fan
    You are hereby elected to head the committee to correct the usage of the word "alloy" in the bicycling community. Keep us posted on how it's going for you....
    I'll join Retro Grouch's committee. It's very annoying when people start accepting shortened or incorrect wording for things. It typically leads to confusion later down the line, makes it difficult for newbies to gain knowledge, and looks ignorant to those that actually took the time to learn something. And please STOP saying that "alloy is synonymous with aluminum." Aluminum usually implies alloy, simply because you don't usually use pure aluminum. But alloy does not have to imply aluminum, especially not to anyone outside of the bike world (which you have to consider when a newbie is the one asking questions).

    To illustrate: If I told YOU I had an "alloy" seatpost, you might ASSUME (you know what that does) that I have an aluminum (or properly: aluminum alloy) seatpost. Yet, I could correctly have a chromoly (a steel alloy) seatpost.

    Using proper terminology is most important in situations like this, when the material selected determines whether the seatpost is suitable (due to length and weight demands). If we were talking about how to measure a seatpost, saying "alloy seatpost" would have no bearing.

    In this case, it would have been nice if the first reply had just answered the OP questions:

    Alloy is a mixture of metals. Typically, when talking about bikes, alloy implies an aluminum alloy. It has excellent material properties for the right price. It's probably stronger than plain steel, much lighter, and rust resistant. If you could find a chromoly seat post, that may be stronger, but a bit heavier and not common. Carbon fiber is typically suited for lighter riders, and/or on road use where weight is more important than strength and cost.

  24. #24
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    To illustrate: If I told YOU I had an "alloy" seatpost, you might ASSUME (you know what that does) that I have an aluminum (or properly: aluminum alloy) seatpost. Yet, I could correctly have a chromoly (a steel alloy) seatpost.

    Go into any bike shop and ask for an "alloy" seatpost, being no more specific, and see what you get. Will the shop guy bring out a Cr-Mo steel post? A brass post? Of course not. Go into the same shop and ask to see "a frame". Do you expect to be shown something that surrounds a painting? How about a fork? Will you get an eating utensil?

    The use of alloy in this regard falls into the category of jargon, that is terminology specific to one industry or profession. There are a huge number of term that have been co-opted by various professions, hobbies and industries that have a specific meaning there but a far different one to outsiders. Get used to it.

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    Quote Originally Posted by HillRider
    The use of alloy in this regard falls into the category of jargon, that is terminology specific to one industry or profession. There are a huge number of term that have been co-opted by various professions, hobbies and industries that have a specific meaning there but a far different one to outsiders.
    So what part of: "Hello, I'm a newbie, and I need to replace my seat post" did you not understand?

    Further, I still contend that alloy is not synonymous with aluminum. Jargon is field specific, but is technically accurate. ie stem, head tube, hub, spoke, tube, etc. "alloy" is jargon, but your usage (and the incorrect truncation so common) conflicts with the technical non-specific definition. No other commonly accepted, and correct jargon does that. For a computer analogy, a CD is a disc, but a disc does not imply a CD (could be a DVD).

    Quote Originally Posted by HillRider
    Go into any bike shop and ask for an "alloy" seatpost, being no more specific, and see what you get.
    Just because a bike shop knows what you're talking about when you say "alloy", doesn't mean its correct. If you had a Toyota Celica and a Toyota 4Runner next to each and you said the "sports car" is faster, I would know you're talking about the Celica, even though its a sports coupe, not a sports car.


    Quote Originally Posted by HillRider
    Get used to it.
    No thanks. There's enough misinformation spreading in the world as it is. It's really annoying when people think experience equals truth.

    Confucius says: A reasonable man is content with the world around him. An unreasonable man is not content and seeks to change it. Therefore, all progress is the work of unreasonable men.

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