hummmm. I'm needing my OWN set of calipers so that I can measure some of these other seatposts around the house and see if any of them are 27 and try them.

Off topic but where can I get calipers?

ah, the vagaries of human communication. You can find some pretty good calipers on eBay. That's where I'll look first when I finally spring for some. Dial calipers are better (but ya get what ya pay's fo, of course).

I think that you would have to measure down inside of the seat tube, below the level of the clamping area, to get an accurate measurement. If the clamp has been distorted, then you'll see what the seatpost tells you, that you need a 26.2. I don't have one of those bikes in the shop, but I seem to recall that it takes a 27.0. Other explanations are possible; Trek may have done a midyear technical change for some reason.

Normally, seatpost manufacturers will mark the seatpost size, although it may be hard to read after someone pushes it into a frame and pulls it back out a few times.

Aren't we talking about a Raleigh Marathon? Heck guys, I have no idea what size seatpost a Raleigh Marathon is supposed to take, I was just going by TrekSandra saying the LBS measured it and also that it seems to work fine. I will definitely stand by my statement that there's a huge difference betweeen a 26.2mm post and a 27.0mm post, though. I really can't imagine that you could get a 26.2mm post to "work fine" in a 27.0mm seat tube no matter what you did, unless you used a shim. But who knows-

yes communication does get wonky. the original post was regarding a bBridgestone MB-5. the specs for it call for a 27.0 seat post. the poster had said that what was in it was a 26.2 at which point 'treksandra' got involved saying she also needed a 26.2. the bikes and the their seatpost sizes have nothing to do with each other. in the catalogue for the Raleighs in 1985 the sport touring group, i believe, had a number of models in it. one of them was the 'Marathon' another was the Olympian. The seatpost size for the olympian according to sheldon brown's seat post data base is 26.6. and is likely the closest to what is spec'd foor the marathon. i don't know where anyone got the idea that anyone was talking about putting a 27.0 seatpost in the Raleigh Marathon. the talk around the 27.0 was soley to do with the Bridgestone. Clear as mud now, right. But it covers da ground.

MidwayUSA.com.

My apologies. The hijack was my fault. I also had a similar seatpost thread going recently and at one point forgot which one I was on. Thank you for all the good advice.

But one thing to note, the '85 Olympian and '85 Marathon don't use the same tubing.

'85 Olympian specs:
https://www.sheldonbrown.com/retroral...-olympian.html

'85 Marathon specs:
https://retroraleighs.com/catalogs/19...-marathon.html

Since TrekSandra had a seatpost that worked fine in terms of diameter but was just too short, had it measured by the LBS and found it to be 26.2mm, ordered a 26.2 and says it works fine, I don't see any reason to think TrekSandra has the wrong size seatpost.

I have studied the old seatpost as carefully as possible. I can see the 26 pretty easily, but right after that it get really hard to read and unclear. If I had to guess, I'd say it MIGHT just say 26.4! But that is just a guess. It's not clear at all. I feel sure this is the original seatpost because everything else on the bike down to the seat and tires are original Raleigh.

how horrible would it be to use a 26.2 seatpost if it called for a 26.4?

I'm so sorry for the hijack. I hope the original question was answered before I drifted off topic.

Well, they don't make them in .2mm increments for nothing.

But seriously, have you ridden the bike much with the new seatpost? Does it slip? When you put the seatpost into the seat tube, how snug is it? Is there any resistance at all, or does it drop in without even contacting the walls of the seat tube? If there's any resistance at all, you should be fine and you probably have the right size post. Even without any resistance, it doesn't necessarily mean you have the wrong size post.

At the top of the seat tube, where you tighten the seatpost binder bolt, look at the small slot and see if it's crimped noticeably inward at the top after you tighten the binder bolt enough to secure the post. If it is, then you may very well have the wrong size post. If the slot seems to be more or less the same width from top to bottom after the bolt is tightened, you should be fine. Again, the main thing is: does the seatpost slip while you ride the bike?

Just dropping in a note. This thread was really helpful. I have an odd 1970's Italian bike, and needed a higher seatpost because the original one is only 6'' high, and I need another 1-2". I took it to the local bike Bikeline shop, they measured it as 26.0 (they're much better qualified to measure & actually have the tool).

The links in the thread helped me find a selection of 26.0 seatposts and order on-line.

I am just passing this along because whenever you include links/feedback - it helps.
Thanks...

I've ridden the bike. The seatpost does NOT slip when I ride it. Now about the slot at the top. At the top, it's together/touching when the bolt is completely tightened. I can't imagine how a 26.4 would even give it much distance in the space!

These are about half the price of the ones suggested by bigbossman and Harbor Freight has even cheaper ones yet, but I really wouldn't trust anything under $10.

Sounds like luker may have been right about someone crimping it down so that a smaller post could be used, then. I'd take it to a bike shop and have them look at it, see if everything looks okay to them. Or can you post a pic of the binder bolt area?

and a 26.4 would not give it that much space, would it?

i believe it would give it enough space so the two 'ears' where the bolt goes through are not touching. if they are touching the likeyhood of getting the post really secure is slim, there should be a little space between those two points.. how easy was it to put the post in? like well-biked said 'is there any resistance'?

That's definitely crimped in, just like luker said. There's no way to tell exactly what size it should take from the photo, but I'd say luker's educated guess of 27.0, or the 26.6 mentioned earlier, or even 26.4mm would be possibilities. The only way to say for sure is to do as luker said earlier and get a caliper reading from further down inside the seat tube, where it would be unaffected by the crimping. I mean, I guess since you say it doesn't slip you could just ride it. Or you can carefully bend the clamp area back to shape and use a shim. Or you can get a caliper reading and get the right size post, which will also require carefully bending the clamp area back to shape.

Regardless, I stand corrected.

Thanks. and it's not your fault well biked. You were only going by what I told you.

Actually, the one I was referring to (and have on hand) is the dial caliper for $25 - still $10 more than the one's you linked to and SAE only, to boot.

Thanks for the link. I may have to "upgrade" and pick up one of those Harbor Freight ones, but I've had very poor luck with everything I've ever bought from them. Do you have that one? How does it perform?

it turns out that 26.2 IS the correct size for the XO-5 according to the Bridgestone brochure from that year. its different from the other XOs.

just a little disclaimer here- i have nothing against kalloy, the only reason the seatpost is crap is because its 14 years old, has been ridden hard, and is the only component of this bike that wasnt swapped out at one time or another. anything will look flashy compared to this dirty, scraped up post. most likely will get another kalloy, just looking to see if there were any other options.

I have no experience with that particular one, but here's a review.

I'm in Canada and Canadian Tire has a similar-looking caliper for $35 that's on sale for half price every so often. A couple of friends have these and while they don't feel as smooth as a Mitutoyo, they're great for the price.

good on ya dgleue for tracking that down! i knew one of the RB bikes had a small seat post andi think the mb-4 frin 1991 had one but i sure didn't think any of the xo's had one and somewhere i have a 1993 catalogue. duh!
I just found my catalogues and in the 1993 catalogue there is nothing indicating seat post size other than it is a kalloy #242 which likely came in many sizes. However the interesting thing is that in the 1994 catalogue th XO-4 is 26.2, so is the XO-5 and the CB-1. as well the MB-4 had a 26.6 post along with a number of other models. Maybe yours is a 1994.

some more info to go along with the above. the 1994 26.2 post was a Kalloy #200. this is a straight post ie; there is no clamp. also check the headset in 1994 it was a YST 8002G. dglue ,if you are interested email me and i will give you the specs for both years 93/94.

SandraTrek (edit: I must have name dyslexia...sorry TrekSandra): I've got either an '85 or '86 Raleigh Marathon...the seatpost definitely says 26.4 (I came to this thread because I'm about to get a longer one). Here's mine: https://www.bikeforums.net/classic-vintage/356754-just-got-mixte-new-c-v.html. Not sure how to tell if we have the same year or not.

treksandra, i just received a confirmation from an owner of a marathon with all original parts that the seatpost is definetly 26.4.