How/where do I measure modern frames?

[Framed]

As a long-time keen road-biker, I have various beautiful, elegant, vintage lightweight bikes, dating from the 1950's -1970's; all Classics, including Hetchins, Holdsworth, Harry Quinn, Alan, Claud Butler, etc. Vintage frames are so easy to measure, for size and frame angles, & I know exactly how to do this, but how on earth do I measure the new, weirdly-shaped modern frames?

Pre the first lockdown, I bought a Ridley (simply tried it out and it felt OK for size & performance) but having had an accident (not on the bike!) breaking an arm & wrist, I can't cycle at present & would like to re-sell it, but haven't a clue how to describe its measurements, as the modern frames are all such strange shapes & proportions, so I just don't know where/how to begin. Sorry to seem an idiot, but please can anyone explain?

[slowster]

Like most manufacturers, Ridley typically use 'small', 'medium, large' etc. to designate the sizes, and the various geometry measurements for each size are supplied on Ridley's website. Therefore, just state the size, model and year, and people can get the measurements themselves from Ridley's website. If it's a model that is no longer made or the geometry of which has changed since you bought yours, it may be possible to find the information elsewhere, e.g. https://geometrygeeks.bike/bike-directo ... /?q=ridley, but you need to be careful about vouching for the accuracy of third party websites.

[drossall]

I'm not sure there's much point because, having measured them, you also have to work out what your measurements mean. Whereas it was clear and obvious with traditional frames. The whole system has collapsed rather, and the only reliable way I can see to know whether a bike fits is to sit on it.

[mattsccm]

s above. You don't. You look at the size label and just say that. People then check manufacturers website to see if all the measurements and angles suit them.
No size label? Find an easy tube to measure such as the head tube, measure it and use that to find the size from the manufacturers website.

[Greystoke]

Why not just say how tall you are, inside leg etc and say what tolerance there is for near sizes

[peetee]

If you intend to buy a new bike or frame the best advice I can give you is to measure the horizontal distance between the seat tube and head tube on your existing bike and use this to choose your new purchase. As you say, frame design varies these days and seat tube lengths can be wildly different on two ‘medium’ bikes. The top tube length has always been a restricting factor in frame choice as the seat post height can be adjusted across a range that is greater than can be achieved by swapping handlebar stems.
Selling a bike is a bit different as the top tube length is not a widely recognised method of establishing the size. Most manufacturers include the frame size on a seat tube decal and you should quote this as a start on the assumption that yours will not be the only Ridley that a potential purchaser is interested in.

[CyberKnight]

yes
i agree with the above i usually go by the virtual top tube when looking at bikes

[Mick F]

What I did when I bought the Moulton, was to measure everything on my 1986 Mercian.
Handlebar height from the floor, saddle nose to stem, stem length, height of saddle to floor, BB height from floor, saddle setback from vertical from BB, saddle angle from horizontal ............ you name it, I measured it.

Then, I transferred all the measurements to Mouton so that when I sat on it with my eyes closed, and put my feet on the pedals and held the 'bars, I couldn't have told you which bike it was ............ well I could obviously, but you get the idea.

The two bikes are still exactly the same.

[peterb]

If you want to give dimensions for sale you could simply follow the format used by Ridley themselves [url][https://www.ridley-bikes.com/en_GB/bike ... RID318/url]

[drossall]

Hadn't thought about the angle of your purpose being to sell. I for one find it really helpful to have information about the current rider. I've seen various ads saying This is set up for me at 5' 10" or whatever, and it saves a fair bit of guesswork, even allowing for differences in body proportions.

[Jdsk]

Hadn't thought about the angle of your purpose being to sell. I for one find it really helpful to have information about the current rider. I've seen various ads saying This is set up for me at 5' 10" or whatever, and it saves a fair bit of guesswork, even allowing for differences in body proportions.

Agreed.

And very common in the recumbent world where there has never been even the pretence of standardised sizes of frames.

Jonathan

[Paul Smith SRCC]

With the variety of shapes and sizes it does confuse many, especially when S,M,L references are used. Fortunately most will list what seems to have become the industry standard which is 'Stack' and 'Reach'. 'Stack' is the vertical height between the bottom bracket centre and the top of the centre of the head tube. 'Reach' is the horizontal distance between the same points; I have added a BikeCAD drawing showing just those two points that may help clarify.

In your case as you are selling it I'd look at the model on their website and list all the supplied data, you will see in the example of a Kanzo Speed they have also focused on 'Stack' and 'Reach'.

In addition if you wanted to be more thorough they also have a "What is my size?" tab, you could morph your personal dimensions up and down until the 'bike size' recommendation changes, you can then list a the 'rider dimension size' range relevant to the very bike you are selling

Note these are only a guide but it is often a valid starting point and may prove helpful to whoever is viewing

[drossall]

The horizontal reach only measures the front end of the bike. Seat-tube angle will affect the additional reach from the rear section. Isn't equivalent horizontal top-tube length still a better measure?

[Paul Smith SRCC]

The horizontal reach only measures the front end of the bike. Seat-tube angle will affect the additional reach from the rear section. Isn't equivalent horizontal top-tube length still a better measure?

A very valid point.

Data is indeed useful to make comparisons, I personally can 'read' and gain more from the 'effective top top tube' more than I do initially from stack and reach, the latter in isolation can be just numbers; although I can relate to them far more when I compare the listed data of one model to another. Perhaps that maybe because as I am 58 years old I relate to a generic race bike with 73 degree parallel frame (in my size) with similar seat and top tube lengths, so yes to me the "equivalent horizontal top-tube length" is something that I personally relate to.

The key word above is 'initially'; I do look at the 'sum of the parts' of all the data. The beauty these days is that most list far more data than 'when I were a lad' so whatever data the rider personally relates to there is a good chance it's listed.

[peterb]

Virtual top tube measurement most useful for me too. I would find a virtual seat tube measurement useful too, the ones given are not very helpful unless specified centre to centre. All too often the seat tube length is shown to the top end of the seat tube, wherever that might be. If you have the virtual top tube, reach, stack and head tube measurements you can get a good idea of how a frame compares to one you already own.