Frame Geometry

[juliensorel]

Hi All. This is not a what bike should I buy or model recommendation question. I'm considering buying a bike (first one). I don't want to visit tens of stores and try loads of brands/models/etc. Of course when the time comes for the actual purchase, I'll do that. But first, I want to narrow down my choices.

I have slightly short legs and slightly long arms for my height. I'm not flexible. I prefer a rather relaxed and upright position. A road bike my not be the right choice for me, but I want to give it a try. I'm open to fitness bikes and I'd ride women's road bikes as well, provided the frame is not forcefully painted to be cute...

Question is, how do I interpret frame geometry numbers? I'm not asking a full explanation of the parts; I can find that information some other place. What I need to know is, out of this multitude of lengths and angles, which ones are more likely to have an impact on my position. For example, Specialized Secteur is said to be more relaxed than Specialized Allez. How do I see this in frame geometry numbers?

Thanks

 

[Kajjal]

The two main numbers are reach and stack. Roughly speaking these are how long and tall a bikes frame is. You then need to account for stem and handlebar size. In reality most bikes of a similar size have similar stems and handle bars so this doesn't matter as much.

If you go to a good bike shop and do some test rides you will see which bikes you prefer and fit you best. Then check their geometry charts for reach and stack to give you an idea of what size fits you best. The main thing is don't get a bike that is too big for you.

 

[vickster]

How tall are you? Are you male or female? Given your dimensions, a women design may not be the most appropriate, we 'tend' to have longer legs proportionally to torso

As above, stack and reach important. Also to get the right width bars and flipping thr stem up can raise the bars. If a woman looking at roadbikes, you may also want to consider the size and shape of the shifter hoods

 

[Fab Foodie]

That's a tough question as I'm not convinced that geometry measurements between manufacturer ex are all that comparable.

You don't say where you lack flexibility but I'm assuming it's bending at the hips/back meaning you can't bend to reach low bars despite long arms.

Actually I think for you there are 3 measurements that are important, they are: seat tube angle, reach and bar height.
The seat tube angle affects how far you sit behind the bottom bracket and this impacts your 'balance' on the bike - how much weight your back/arms need to support.
Reach is self evident.
Stack height might be an issue as many bikes tend to have quite low stack heights, however there are some companies that do 'customised fit bikes' that can have short reach frames with high stack heights. Thorn, Hewitt and Oxford Bike Works come to mind.
Beyond that and budget depending, you can have a custom steel or Titanium frame made with prices starting around a grand.
I'll post a link shortly to a good article by Peter White on fitting a bike which is far more sensible than race orientated methods.

 

[Fab Foodie]

Here you go, ignore the crank length stuff for now but if you are particularly short legged you might want shorter cranks that the 170mm average:

http://www.peterwhitecycles.com/fitting.htm

 

[vickster]

@juliensorel what is your likely budget? A custom build could be the way to go but if wanting mid to high end components you'll be looking at some way north of £2k probably

Is your lack of flexibility due to anatomy or injury, or would a course of Pilates and a stretching regimen help?

 

[summerdays]

Here you go, ignore the crank length stuff for now but if you are particularly short legged you might want shorter cranks that the 170mm average:

http://www.peterwhitecycles.com/fitting.htm

Interesting article, thank you! I've been pondering some things like is my knee above the pedal and now I don't have to worry about that since I think I've got longer thighs than calves.

 

[SpokeyDokey]

Good luck in getting any meaningful test rides.

 

[juliensorel]

Thanks for all the responses

@vickster, Custom build: I don't have 2k+ to spend on a first bike but regardless of the budget I'm not sure I'd want to go after a custom build frame without knowing what I want to have in the first place.

@vickster, Height: around 179cm, male. 82cm inseam (self measured, may not be a reliable number). I feel comfortable with 52-53 cm frames.

@vickster, Frame geometry: Do women tend to have longer legs or shorter arms proportinal to torso? For longer legs I thought the frame would have a longer seat tube for a given top tube (and reach). But for shorter arms I thought the frame would have a shorter top tube (and reach) for a given seat tube. My reasoning was, with a shorter reach I'd have a more upright position. Sure, this is all speculation, I may be way off.

@vickster, @Fab Foodie, Flexibility: My lack of flexibility is due to a complete lack of exercise. And I'm not getting any younger. And I don't feel comfortable putting too much pressure on my wrists.

@Kajjal, Frame size: Is riding a slightly smaller bike generally more favorable than riding a slightly larger bike?

@SpokeyDokey, Test ride: Exactly. Once I test rode for more than 2 hours on different bikes. That was too much for me, and I had no idea anymore what was comfortable and what was not. First ten minutes, all the bikes seem ok but after the first hour I felt more and more this pressure on my wrists. That's why I want to narrow down my choices even for a test ride.

I have already read some articles on fitting. They are all very knowledgable and everything but they tend to fit a bike to you (crank length, seat height, seat position, handlebar width, ...). They all say that reach and stack and some angles are important, but they don't say exactly in which way they are important.

Looks like I should go for a shorter reach, bigger seat tube angle, probably smaller head tube angle, and maybe a shorter stem? Good luck to me. Thanks again for all the ideas.

 

[summerdays]

To the question about female proportions women tend to have longer legs than a male of the same height and so their torso is slightly shorter. Obviously not all, as my daughter is taller than me has shorter legs than me, so if she borrows my bike I have to put the saddle down a good inch or more.

 

[cyberknight]

I might be talking rubbish but i would have thought a bigger frame with maybe a shorter flipped stem would be better as you would have less drop from saddle to bar .
Pros tend to ride smaller frames for the opposite reasons to you as they want to get low .

 

[Kajjal]

I have a relatively long body compare to my legs and it causes no issues fitting bikes. Long legs and a short body makes things alot harder.

If a bike is a little small then it is easy to make it fit properly. If too big there is little you can do, people can waste time and money trying though. If far too small again don't bother.

My road bike bars are just over an inch below the saddle as i prefer a more upright position and also it is comfortable to ride in the drops for long periods.

Main thing is don't over think it, as long as the bike allows you to get the saddle and bars in the right position you will be fine. Road bike setup takes a little fine tuning but once done the are very good for riding hours at a time.

 

[vickster]

52-53cm sounds small for your height which is around 5'10.5, especially if you have long arms. I'm a couple of cms shorter, with longer legs (33-34") and shorter torso being female. My roadbikes are all 54cm with a flipped 100mm stem and 172.5cm cranks

If your wrists are hurting, assuming no anatomical issues with them, you are putting too much weight through them suggesting a bike that is too small, but perhaps with bars that are the wrong width, and possibly you are gripping the bars too tightly. All exacerbated if you have a weak core as you are putting your weight through your arms rather than your core supporting. You can work on this if so inclined, age has nothing to do with it really

Where are you based in the country (are you in the Uk?), someone might be able to recommend a good bike shop knowledgeable about bike sizing and fit. It is less likely that you will get that from a national chain

If you want to compare geometries for Allez and roubaix (no secteur anymore) the numbers for the current ranges are here (scroll down)

https://www.specialized.com/gb/gb/bikes/road/allez-e5-sport/106650

https://www.specialized.com/gb/gb/bikes/road/roubaix-sl4/106478

 

[Viking]

I've found that, for me, getting the horizontal top tube size "correct" is the main concern. Because I've got a long body / short legs that tends to mean a size up on frame suits me best. I've seen it stated elsewhere that dividing your height by your inside leg measurement gives a ratio where 2.2 is at the long body end and 2.0 is at the short body end. I have a ratio of 2.24, so that seems to work for me. Going to a size smaller causes me all sorts of problems e.g. the shorter top tube makes me feel cramped, the steeper seat tube puts the saddle too far forward, the head tube is shorter thereby lowering the handlebars and in some cases the bottom bracket is raised too much. Most of these can be adjusted "out" but the start point isn't right for me.

So I would suggest that you speak to a few LBSs and, at least, sit on a few different sizes and makes and just get an idea of what feels right for you.

 

[e-rider]

Hi All. This is not a what bike should I buy or model recommendation question. I'm considering buying a bike (first one). I don't want to visit tens of stores and try loads of brands/models/etc. Of course when the time comes for the actual purchase, I'll do that. But first, I want to narrow down my choices.

I have slightly short legs and slightly long arms for my height. I'm not flexible. I prefer a rather relaxed and upright position. A road bike my not be the right choice for me, but I want to give it a try. I'm open to fitness bikes and I'd ride women's road bikes as well, provided the frame is not forcefully painted to be cute...

Question is, how do I interpret frame geometry numbers? I'm not asking a full explanation of the parts; I can find that information some other place. What I need to know is, out of this multitude of lengths and angles, which ones are more likely to have an impact on my position. For example, Specialized Secteur is said to be more relaxed than Specialized Allez. How do I see this in frame geometry numbers?

Thanks

head tube length - longer means that you should have higher handlebars = more relaxed position. However, you might need some experience to interpret these as they need to be considered with all other measurements.
top tube length - shorter should mean slightly more relaxed position, but as above numbers need to be considered along with all other measurements, as you can easily end up not comparing like for like