How To Find The Right Size Seat Post For A Bike

hey viewers i picked this bike up local thrift store and among other problems it was missing a seat post so today i'm going to show you how to find the right size seat post to fit a bike now i recommend starting off by doing a little bit of research so i went online and googled trek 3700 seatpost size i found multiple pages saying that the 3700 had a 31.6 millimeter seatpost but you can't believe everything you read on the internet one issue is the different model years of bikes can have different sized seat posts but it gives us a starting point it's also possible that you might not even find the seat post size for your particular bike in either case we're still going to have to measure now before you measure you want to make sure that the seat post clamp is completely loose better yet just go ahead and remove it and get it out of the way if you can so that we're going to get the best measurement we also want to go ahead and clean around the inside of the seat post tube there's a seat tube because any little dirt grease grit and everything in there can go ahead and throw off the measurement just a little bit so now before we do the measurements you want to check the slot in the back of the seat tube here the spacing of this slot should be pretty consistent from the top to the bottom if you find it kind of compressed at the top then uh it's possible that somebody had tried to squeeze a seat post that was too small for this frame in in there and it got kind of squished down in in that case any measurements you make like this are going to be inaccurate you have to address that situation i did a video where i ran into a situation situation like that in the past go ahead and check the description for that video now don't even bother with a ruler or tape measure or anything like that it's just not going to be accurate enough now if you work on bikes a lot like i do uh something like this it's a seat post gauge is a three-piece set is really handy and how this works is you basically just kind of slide this in there now notice that this stopped at 31.6 so that is the size of seat post for this frame so now most people aren't going to have a seatpost gauge lying around i happen to have one but so you're going to want to use a like a digital caliper here in measuring millimeters and you're going to want to measure like a couple different angles preferably about 90 degrees apart and you're going to play with a little bit trying to find the largest numbers between there so let's go here get this here because as you move it around you'll see the numbers kind of jumping around right there is i hit about 31.61 right there and so let me see what i can get over here and there's about 31.65 right there now sipos come in increments of 0.2 millimeters there are some rare exceptions they're older bikes and like i said very rare probably don't need to worry about those so you want to find a seat post that's pretty close to the measurements you took out of there maybe hair smaller now i measured just over 31.6 millimeters in there so i'm pretty sure that's what it is so i have a 31.6 millimeter seat post here and i'll slide this in and it slides in pretty smoothly there if you have to force it in it's too big go to the next size down now this one here there's just a hair play which is what you want if there's a lot of play then the seat post is probably too small and you might want to try the next size bigger but this is 31.6 millimeters so i remounted the clamp here i put a little thin coating of grease on the seat post here i slide this in and clamp that down and that is how to measure a seat tote for what size of seat posts should be installed there hopefully you found this useful or interesting if you did please give my video a thumbs up if you're not subscribed my channel click that subscribe button down there be sure to click the bell so you get notified when new videos come out i'm over on facebook rj the bike guy go over there like that page i post a lot of stuff over there anyway thank you guys very much for watching

Channel: RJ The Bike Guy

Views: 97,316

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Id: BnKQHGPItgE

Length: 4min 5sec (245 seconds)

Published: Mon Jan 10 2022