israeloros

Hello all,

I am a newbie to Bike Forums and I would like to pick up your brain to resolve an issue I am currently facing. I recently sold a Pinarello Prince on eBay, size is 55cm. Unfortunately the person who I sold the bicycle to is claiming all sorts of things and stating it is not a true 55cm frame. Because I was the second owner of this bike, I do not have the papers stating the correct size of the bicycle. Therefore I am trying to figure out if there is a way to determine the frame size, based on the serial number of the frame or something along those lines. The only reason I sold my bicycle was due to financial hardship and now this person is trying to take advantage of me. Obviously if the frame is not the size I claim, I will take the hit and take it back. But what I do not want is this other person messing up with the bike, then realizing it was not his size and send it back in a bad shape.

I hope you would be kind enough to provide any guidance.

Best regards!

jtarver

Try here: https://sheldonbrown.com/frame-sizing.html

joejack951

I've seen bikes listed with the most ridiculous sizing numbers in the title. I would NEVER buy a bike off Ebay (or anywhere for that matter) and ASSume the lister measured the frame the same way I would have. Bike frames are measured so many different ways even by different manufacturers that a simple frame size number is meaningless. If the buyer didn't ask for specific measurements of the frame and is now complaining that it doesn't fit the way he expected to, I'd be the first person to say "too bad."

well biked

Frames can be measured in several different ways, and sometimes a manufacturer will even measure different models in different ways to get the stated frame size. The best way to have no doubts in a situation like an ebay auction is to not simply say "this is a 55" or whatever, but take specific measurements of the frame and then post the dimensions and what exactly you measured to get them. My '97 lugged steel Pinarello Vuelta with traditional frame geometry is a 54cm, measured from the center of the seat tube to the center of the head tube. It's also 54cm from the center of the bottom bracket to the center of the top tube.



But your Prince may be measured differently, you'd almost have to contact Pinarello with the model year, etc. and find out how they measured the frame to determine the stated size. Whatever it is, it doesn't sound like it fits whoever bought it from you, unfortunately. That's why it's important for the buyer and seller to communicate regarding the specific dimensions, no matter what the stated frame size-

Panthers007

Usually the measurement is from the center of the bottom-bracket to the top of the seat-tube. At least in my experience.

dvs cycles

I find more manufacturers use C to C than C to T.

Panthers007

Oh great. I use the other and it is accurate on both my Trek hybrid, and my PUCH frame from 1982. No wonder so many things never fit right! LOL

HillRider

I don't think you meant this. At most the measurement would be from the center of the bottom bracket to the top of the seat[b]tube[/] and this is not how frames are commonly described.

There are two commonly used dimensions for level top tube frames; center to center (aka c-c, center of the bottom bracket to the center of the top tube, measured along the seat tube) and center to top (aka c-t, center of the bottom bracket to the top of the top tube measured the same way). The difference for the same frame can be as much as 2 cm so a claimed 54 c-c frame might also be advertised as a 56 c-t frame.

Usually, but not always, American and Japanese frame sizes are defined by c-t and European frames, particularly Italian are specified by the c-c distance.

For sloping or "compact: frames, the sizes are often based on an imaginary level top tube and can be c-c or c-t also.

joejack951

How would you get an imaginary c-t measurement? The only way I can imagine is to take the current protrusion of the seat tube above the top tube and then add that to the imaginary c-c measurement. Seems completely ridiculous but so is sizing bikes by the seat tube measurement, in my opinion.

norwood

It's sometimes called a "virtual" measurement, but you project from the center of the top tube/ head tube junction back along a "virtual" level line to the spot where that line would intersect the seat tube. That point to the center of the BB. That would be your virtual C to C seat tube measurement for a sloping top tube frame equating to what it would be on a level top tube frame.

joejack951

I understand "virtual" c-c measurements. My question was in regards to virtual c-t measurements. And it was a bit of a rhetorical question since I probably know the answer but I guess I just felt like pointing out the pointlessness of such a measurement. Not only are you drawing imaginary lines but you are also offsetting those imaginary lines (imaginary imaginary lines?) to get a virtual c-t measurement.

FlatSix911

How to determine Pinarello frame size?

A special formula is required ... check your bank account ... spend until it hurts!

Al1943

I've found that the most common frame measurement is c-t, center of bottom bracket to top of seat tube. Every bicycle I've owned over the last 15 years (mostly Treks and Colnago) has been measured this way. My son's Specialized Allez with a level top tube was measured c-c. The difference between c-c and c-t on an OCLV Trek is 4 cm. The standover height on my son's 52 cm Allez was nearly the same as my 56 cm Trek. But the top tube length on my Trek was at least 4 cm longer.

Al

norwood

I agree on the pointlessness of the C-T measurement. The placement of the actual top of the seat tube means little, as far as bike fit goes.
But if I were in the market for a sloping tube frame, I would want to know the virtual measurments of the frame to compare to the "normal" size frame that I ride. Then I could get a frame that should fit basically the same, only it would have somewhat less standover height.
What's somewhat pointless to me also, is actual measurement of the seat tube of a sloping TT frame because alot of it is adjustable seatpost anyway.

Panthers007

Fixed - and thank you! Yes - seat-tube.

jland

This pdf might help - Frame size = bb center to top of seat tube minus "K" factor from chart.

HillRider

Your are correct but c-t measurements aren't taken to the top of the seat tube. They are taken to the top of the TOP tube and have a major implication for standover clearance. The seat tube can project a little or a lot above the top tube and it doesn't change the frame size.

well biked

That's not always true, and is a good example of there being NO "standard" way of measuring frames. Schwinns, for example (and there were millions of them), were measured by the length of the actual seat tube, all the way to the top.......AND, they were measured in INCHES, not centimeters.

norwood

Yes, you are absolutely correct. C-T (top of top tube) is important. I didn't make myself clear, I was refering to what I often times see on ebay and c-list where the top of the seat tube is refered to.

Panthers007

2.54cm = 1 inch.

25.4mm = 1 inch

10mm = 1 centimeter (cm)

HillRider

I don't think old Schwinns set the standard for current frame measurement conventions. Also, did the seat tube end nearly flush with the top of the top tube? Many frames were made that way before seat collar clamps became common so the seat tube end and top tube top coincided.

For the record, older Treks were specified in inches as were the lower line Bridgestone road bikes. My '83 Trek 400 is listed in their catalog as 22". BTW, the seat tube is very nearly flush with the top of the top tube.

Panthers007

My Trek 7.5 FX was marked as a 17.5 inch. And from the center of the BB to the top of the collar-clamp - 17.5 inches.

DaveSSS 

The whole concept of c-c and c-t is really not relevant these days, with so few bikes having horizontal TTs and most of the tubes no longer being round.

What really defines a bike's vertical size, is the head tube length with the headset. If the bike has a horizontal TT, anyone complaining about the bike not being a "true" 55cm needs to specify whether they truly mean c-c or c-t. In the old days a 53cm c-c and 55cm c-t were about the same and you always had to clarify which you were speaking about.

If you want some dimensions for a "true" 55cm frame then the older Colnago geometry chart can provide those. A totally traditional Colnago in a 55cm c-t or 53cm c-c size had a 134mm head tube. To that you have to add at least 25mm for the headset. I'd just call the total 160mm. From there you can extrapolate just about any size.

Referring to the geometry Pinarello geometry chart, I see that the 53cm has a 144mm head tube. With the most common 15mm headset top section, that would make the total 159mm. That means to me that the frame is a 53cm c-c or 55cm c-t.


https://www.pinarello.com/else/technical_data.pdf

joejack951

I'm pretty sure this is wrong but if you can show me a geometry chart that specifies c-t and shows center to top of top tube (and not the seat tube) then I'll be quiet. I've never seen that measurement on a geometry chart though I have seen standover and center to top of seat tube quite frequently.

For example: https://www.gunnarbikes.com/crosshairsspecs.php

well biked

How far above the top tube the seat tube extended varied depending on model, but the measurement was the actual length of the seat tube, all the way to the top. I have a couple of Schwinns with seat tubes that extend about an inch above the top tube. I also have Raleighs that were measured differently.

Some brands these days measure their various road bike models in different ways to get the stated size. My point was, and is, that there is no "standard" way to measure a frame size; never has been and probably never will be. Again, even c-t can mean different things. And with sloping top tubes, things get even more confusing. I know of one group of road bikes from one brand where the center of bb to top of top tube, along the seat tube, is used for the manufacturer's stated size of the bike. This group of bikes has sloping top tubes. Crazy stuff.

That's why, for the OP's purposes, better communication with the potential buyer is essential, stating what exactly is being measured and what the measurements are. To say a bike is a "55" ísn't precise enough, I'm afraid. Also, the buyer should have asked more questions and gotten precise measurements of whatever he wanted measured.