Seatpost diameter sizes (standards)
Apr 04, · what size clamp for a seat post. Thread starter alex; Start date Apr 4, ; Forums. Biking Forums. Downhill & Freeride. A. alex Chimp. May 20, 70 0. Apr 4, #1 need to know what size seatpost clamp for a post. Dogboy Turbo Monkey. Apr 12, 3, Durham, NC. There are only three common sizes of clamp - , and is mainly for steel frames with post. is most common for alloy or titanium frames with post and anything.
There may be different reasons why we need to change our bike seats. It may have become worn out because of use, weather, or unexpected events.
Whatever the cause, it is of great importance to whaf attention to measurements so as not to get the wrong one. Should we make an error in this aspect, it may either slip downwards while in use or be too big to fit the seat tube. Ride along with us, and skze out what you need to know about this accessory. First, we need to understand the difference between seat tubes and seat posts.
The former is the part of the frame where the seat post is inserted. Next, we need to know what a seat clamp is and why or when we should get one. Imagine how uncomfortable it would be to feel our saddle how to make a jolly rancher mixed drink or rotating as we ride our bikes!
Seat clamps may be included in the seat tube, as part of the frame. Otherwise, they may be acquired as an external part to add to the seat tube. They look like incomplete collars, attached to their tips by a bolt, used to adjust tension. They may also have a quick-release lever to make it easier for you to remove or modify the position of your seat. As we mentioned earlier, measures vary, and this may cause some headaches if you do not pay enough attention to it. There are some standard post measurements out there, namely Differences in the measure may correlate to quality, material, or weight.
Nevertheless, clzmp non-standard measures can be found too. Getting a wrong clamp size will not only affect its functioncausing your seat to wiggle up and down, or to rotate sideways.
It may also damage your frame. It may slide downwards if it what are the documents required for applying passport too big, or crack your seat tube if it is too tight. The first thing you need to do is to c,amp the in-frame clamp —if any- to its fullest. In this way, we make sure only the actual diameter is measured. These tools come in very handy when deciding which clamp is the correct one for your ride.
Even though some seat tubes may have their measurements imprinted somewhere, or your bike manufacturer may give you this information, it is always recommended to measure it yourself so that you can be sure. Gear For Venture is reader-supported. When you buy through links on our site, we may earn an affiliate commission. Click to learn more. Tips and Advice. Related Posts.
May 20, · totaly depends on the outside diameter of the tubing that the manufactutrer speced on the bike. As an example, I have a Trek hardtail with a seatpost that requires a 35mm Salsa lip lock clamp. My Stumjumper FSR has a seatpost diameter but uses the same 35mm diameter clamp! So it can vary quite a bit between frame manufacturers. Nov 16, · So high quality frames with 1 1/8? seat tubes usually had mm wide seatposts. More modern trend, mostly on mountain bikes, where stronger seatposts are required (without too much extra weight) lead to a new “oversized” standard of mm (and Estimated Reading Time: 4 mins. rows · This has resulted in a de facto standard of mm for high-quality bicycles that have 1 .
To help prevent mistakes when purchasing or changing seatposts, this article explains what kinds of seatpost diameters are most commonly used and how they are measured. Only diameter width is dealt with here. The length of the seatpost depends on frame geometry design and size — i.
A separate article explains the maximum amount of seatpost extension from the frame minimal insertion length. For seatpost height in terms of bicycle fitting, see: Setting up comfortable riding position. The first bicycle frames were made mostly from steel, with steel tubes of a standard outer diameter. Older French bicycles used 28 mm tubing. Standard outer diameter dimensions were important so that derailleur clamps etc.
Higher quality frames are usually made with thinned down tube walls to reduce the weight of the frame. This meant that a wider seatpost diameter usually meant a higher quality and lighter frame. How to measure the seatpost diameter? The easiest and most accurate method is to use calipers Vernier, or digital , as shown in picture 2. It can be seen from picture 2 that the seatpost is marked as This means the seatpost will probably not fit firmly enough to stay in place inside a seat tube meant for Always measure!
Measuring a seat tube diameter is often necessary before purchasing, or changing the seatpost. How should one do that? Three methods will be explained here, but one can always be creative.
Method 3: using special seat post sizing rods. These are rods with an increasing diameter from one end to the other, with a scale noting the diameter in standard sizes. The rod is simply placed in the seat tube and the matching diameter is the one just above the end of the seat tube the first visible number on the rod still sticking out of the tube.
If a measured diameter differs, it can be assumed that the correct diameter is the standard one that most closely matches the measured diameter. Seatpost diameters are usually a multiple of 0. If a measured value differs and most closely matches a value that is not a multiple of 0. For example, a measured A rule of thumb is that the widest post that slides in without being forced other than pushing or twisting by hand is the right one.
If it drops in, with play, before the pinch bolt is tightened, the seatpost is probably too narrow. For easier managing, table 2 gives an overview of seatpost diameters most commonly used on modern bicycles from the end of the 20th century to now. Related post — How to choose a comfortable saddle the first in a series of 5 posts explains saddle materials :. Amazon search affiliate link : Seatpost reducer adapter, shim. It might take time to source the particular needed combination, but Google and local bicycle shops are a way to go.
Thank you. Another way to measure the circumference, albeit not super exact, is to use a measure tape and tie it around the seatpost. If memory serves me well, dividing that with the number Pi should give the diameter.
My question is will I have to purchase to seat post clamps for this to work and be safe? Measuring the circumference of the post and dividing by Pi is a good method. There are even circumference tape measures to do it. An adjustable wrench can be used as calipers, then measure the gap on the wrench. But measuring the circumference means you only have to distinguish a 0. Measuring the size of the hole in the seat post—well, that requires ID calipers, gauges, or sticking something into it then marking it so you can measure it like the seat post.
That will introduce more error. For example, take some poster board stiff paper , roll it up, insert it, and let it expand to fill the hole. Pull out the paper, unroll it, and measure between the edge and the mark and divide by Pi. Thanks, Greg. Your article is confusing, because of some obvious errors. Also, at several parts you refer to Vernier calipers, but none of your images have Vernier calipers. Look up what a Vernier caliper actually is.
Finally, the suggestion that a less than 0. Any halfway decent clamp should easily account for 1mm error or more. Although it seems a bit snarky, your comment has been very useful. One of the WordPress updates seems to have removed labels on picture galleries where more than one picture is placed side by side.
I will correct the term once I double check the proper English technical terminology. As for the 0. Thank you for what is in effect a very helpful, constructive feedback.
If you find any other mistakes, feel free to note them. I try to keep this as correct, and up-to-date as possible. Most of your information is geared towards the later 20th Century bicycles. I measured it with a digital caliper and it reads So far I have not found any seat posts that are that small no clue what became of the original Any advise would be greatly appreciated. Machining the sidewalls down would weaken them tremendously in my opinion. Painting, or chrome plating could also be done — just take it into account when machining to not have the new seatpost too narrow, or too wide.
More than happy to help however I can. Good luck! If all else fails, and taking a frame to a certified carbon repair shop is not an option, that could be attempted. Will it work well? What I would try is to create leverage to remove the seatpost. Fred here again. I read your article and it prove most useful.
I measured my seatpost diameter and it turn out to be 40mm. I know it is large by modern standard do you have any idea where i can find such a seatpost clamp. Save my name, email, and website in this browser for the next time I comment. Notify me of followup comments via e-mail. You can also subscribe without commenting. Home » Technical part » Standards » Seatpost diameter sizes standards.
Picture 1 shows a seatpost 1 , and a seat tube 2 : Seatpost 1 , and seat tube 2 Pictures 1a, and 1b 1. A bit of history The first bicycle frames were made mostly from steel, with steel tubes of a standard outer diameter.
Measuring seatpost diameter using calipers. Source: forums. Method 2: using calipers, as shown in picture 3. Measuring the inner diameter of the seat tube. Source: bikeforums. Standard seatpost diameters Table 1 gives a list in mm of standard diameter sizes: Standard seatpost diameters Table 1 Seatpost diameters are usually a multiple of 0. A few notes, just in case: If a seatpost wobbles or rocks left-right before tightening the clamp , it is probably too narrow.
Forcing it in makes it very, very difficult to move or take out later. It might even damage some frames. Table 2 Related post — How to choose a comfortable saddle the first in a series of 5 posts explains saddle materials : Bicycle saddle materials.
Share this article Thank you, Will do. Reading this with a smile on my face — a lovely idea for a birthday surprise. HI, I read your article and it prove most useful.