Stack and reach - im confused

spasypaddy

so im looking at a new frame, im bang in the middle of a 52 or 54cm frame looking at the geo charts.

my current frames have stack and reach of:
1 - s 559 r 383
2 - s 546 r 383

now the 546 feels 'smaller' and actually feels lovely. the 559 fits me fine but doesnt feel as small and tight as the other.

The bikes are set up identically.

the two frame sizes im eyeing up are:
52cm - s 530 r 368
54cm - s 542 r 375

now obviously i'd need a longer stem on either one of those options to get the same reach as my old frame. but how does stack change a bike? does it just make a bike feel bigger/smaller?

keef66

Lower stack just makes the bars lower, all other things being equal. Which can make a bike feel smaller

But so can a shorter reach...

spasypaddy

ha

well the two current bikes are exactly the same set up (saddle height, handlebar height, etc). two different frames just give different ride feels.

i just dont know what to do! i will try to get a sit on a 52 and a 54 and see what happens i guess

Matthewfalle

last month's cyclist mag did a write up explaining all - worth a gander.

spasypaddy

Matthewfalle wrote:

last month's cyclist mag did a write up explaining all - worth a gander.

gonna have missed that wont i?

Matthewfalle

or go on their website and look at the back issues.

or ask me if i could put the article on here as i have the magazine in question on the coffee table in front of me, which i would have done with pleasure but due to the tone of your post i think that you can jog on.

spasypaddy

ha taking tone from 6 words on a webpage.

if you must know i went straight to their website and had a good look. but you seem to have anger issues (which is different to back issues, which im trying to avoid by making sure i get the right frame) so if you decide to get off your high horse and want to contribute to the bikeradar community then i would gladly read the article.

my tone for this post is patronising if you need some guidance on how to read it.

N0bodyOfTheGoat

What's the stack and reach of the 56cm variant?

Matthewfalle

spasypaddy wrote:

ha taking tone from 6 words on a webpage.

if you must know i went straight to their website and had a good look. but you seem to have anger issues (which is different to back issues, which im trying to avoid by making sure i get the right frame) so if you decide to get off your high horse and want to contribute to the bikeradar community then i would gladly read the article.

my tone for this post is patronising if you need some guidance on how to read it.

its a great article. you should read it some time. quite useful when buying a new bike and you're unsure about stack and reach.

oh.

spasypaddy

NitrousOxide wrote:

What's the stack and reach of the 56cm variant?

s 562 r 388

bristolpete

Funny old issue.

I was riding and loved riding a Medium large TCR with a reach of 39.8 which a couple of bike shops, Giant included told me was too long. I felt great on it. But taking advice I sold it, bought a 56cm Cervelo R5 with 38.9 reach which is basically a cm shorter, but actually feels like a longer / bigger bike. Still works and fits, but such a strange thing. The stack of course is relative as is stand over as TCR super compact.

turbotommy

I know you’re asking specifically about stack, but for me the stem length play a big factor in bike feel and the way it handles. So I’d prob opt for the smaller frame. For me I’m somewhere between 58 and 61cm and I have bikes in both those sizes. It’s hard to make a direct comparison as the bikes have other differences but the 58, with me further over the handlebars, does feel more assured.

DeVlaeminck

So for the OP - you have two bikes one of which fits fine but the other - lower front end - just feels a better fit. You are considering two new bikes - both have a lower front end than either existing bike and both less reach.

Seems to me of those two the 54cm is the obvious pick - it's already shorter and lower than a bike you are happy with - 52cm is going to be too small IF your current bike fits you.

N0bodyOfTheGoat

54 with a +10mm stem over current "good fit" bike, perhaps with an extra 5mm spacer under stem.

joey54321

bristolpete wrote:

Funny old issue.
The stack of course is relative as is stand over as TCR super compact.

Compact or not won't change the stack values of a bike. The stack is the horizontal distance from BB to headset, doesn't matter what other angles are going on with the top tube in between.

spasypaddy

DeVlaeminck wrote:

So for the OP - you have two bikes one of which fits fine but the other - lower front end - just feels a better fit. You are considering two new bikes - both have a lower front end than either existing bike and both less reach.

Seems to me of those two the 54cm is the obvious pick - it's already shorter and lower than a bike you are happy with - 52cm is going to be too small IF your current bike fits you.

they both fit me perfectly. they are both set up identically. even if they have different stack/reach measurements.

you've said what i think is what i want to hear, but i always think i should size down especially as new bikes are bigger than they were previously (hence the need for stack and reach)

54 with a +10mm stem over current "good fit" bike, perhaps with an extra 5mm spacer under stem.

thanks! (wont do either of these as they aren't pro :P )

DeVlaeminck

Longer stem is definitely pro - spacer yeah maybe not so much.

cycleclinic

You can size a bike based on horizontal top tube length. Dear tube length is not very relevant as the post goes up and down. Head tube length is important for bar position. Stack and reach, why bother looking at numbers that font inform much.

Your better if getting measured up for a bike fit and get the idealised frame geometry then pick the bike with the top tube and head tube length then change the stem for the right length.

If you have a good fit currently measure the effective top tube length, the head tube length, saddle to handle bar drop, saddle to BB height and the saddle binder bolt to handle bar diagonal and simply replicate on the new bike. That's what I do.

Stack and reach can be ignored. These numbers try to simply bike fitting without helping much at all. Then again a size expressed as a small or medium or as a seat tube length dies not help much either.

First.Aspect

thecycleclinic wrote:

You can size a bike based on horizontal top tube length....Stack and reach can be ignored. These numbers try to simply bike fitting without helping much at all.

Oh thank god, someone has said it. Stack and reach are about as sensible as measuring the length of a car from the door pillar to the front bumper.

I size a bike based on bb to saddle, saddle to bar distance and drop. There are only three contact points so what else do you need?

For a road bike I'm renting, for example, if I need a 90cm stem to get to my measurements, the frame is too large, and if I need a 120cm stem its probably too small. Simple.

Designing a frame is hard. Choosing which stock size should fit really shouldn't be.

joey54321

No, stack and reach is like measuring the distance between the car seat and the steering wheel (i.e.
the bit that matters for your comfort).

So you have two options; compare stack and reach and use that to easily add or minus the difference on to your stem length and your spacers. Or you can measure all your existing bike tubes with a bit of string, get your protractor out and measure the angle of your head tube and top tube, compare that to the new bike, notice there is a difference somewhere but not sure how or why and then take a punt on a size that might be similar.

Stack and reach are now expected to be published by bike companies for this exact reason. They're are the best way of determining if a bike will fit. Effective top tube length can be changed by seat post angle, so you need to do some trigonometry to calculate your stem length, the same goes for head tube length and head tube angle.

spasypaddy

ok so i test rode a caad12 yesterday and a bowman.

the caad12 felt like a boat which was down to the size bars on it. but the frame is insanely smooth
the bowman felt much more alive than the caad12.

the s/r of the bowman is very similar to my caad9 both of which are classified as a 54cm frame, the 54cm caad12 is too big but if i sized down it would be too small.

i've had 2 professional fits in my time which is why i know what numbers to look at. s/r might be simplifying it but once i got my head around it it made a lot of sense to me (i did A LOT of reading and not of a magazine as i dont want to kill trees). but i do hear what youre saying about it being simplified.

also i know which of my bikes feels the most comfortable, and which feels 'big' even if it has exactly the same setup. so im working off getting a new bike that fits exactly the same as my most comfortable geo.


anyway all the stack reach measurements ive looked at:
look: 559/383 (m) own
caad9: 546/383 (54) own
bowm: 542/375 (54)
Cad12: 551/381 (54)
Cad12: 526/375 (52)

DeVlaeminck

First Aspect wrote:

thecycleclinic wrote:

You can size a bike based on horizontal top tube length....Stack and reach can be ignored. These numbers try to simply bike fitting without helping much at all.

Oh thank god, someone has said it. Stack and reach are about as sensible as measuring the length of a car from the door pillar to the front bumper.

I size a bike based on bb to saddle, saddle to bar distance and drop. There are only three contact points so what else do you need?

For a road bike I'm renting, for example, if I need a 90cm stem to get to my measurements, the frame is too large, and if I need a 120cm stem its probably too small. Simple.

Designing a frame is hard. Choosing which stock size should fit really shouldn't be.

How can bike companies size bikes on bb to saddle or saddle to bars when these points are not fixed though ?

Stack and reach are actually a better way of measuring the distance between the contact points - or at least the points on the frame to which we then fit stem, seat post and cranks - than ETT length and head tube length.

imposter2.0

DeVlaeminck wrote:

How can bike companies size bikes on bb to saddle or saddle to bars when these points are not fixed though ?

Stack and reach are actually a better way of measuring the distance between the contact points - or at least the points on the frame to which we then fit stem, seat post and cranks - than ETT length and head tube length.

Not to me they aren't. Seat tube, top tube and head tube length is all I've ever needed to understand whether a frame will suit me or not.

Wheelspinner

joey54321 wrote:

bristolpete wrote:

Funny old issue.
The stack of course is relative as is stand over as TCR super compact.

Compact or not won't change the stack values of a bike. The stack is the horizontal distance from BB to headset, doesn't matter what other angles are going on with the top tube in between.

:? :? Isn't that the reach? I thought stack is the *vertical* distance from BB to top of headset?

DeVlaeminck

Imposter wrote:

DeVlaeminck wrote:

How can bike companies size bikes on bb to saddle or saddle to bars when these points are not fixed though ?

Stack and reach are actually a better way of measuring the distance between the contact points - or at least the points on the frame to which we then fit stem, seat post and cranks - than ETT length and head tube length.

Not to me they aren't. Seat tube, top tube and head tube length is all I've ever needed to understand whether a frame will suit me or not.

Well seat tube, head tube and top tube only work as well assuming you are looking at bikes with similar geometry, tyre clearances etc.

First.Aspect

Imposter wrote:

DeVlaeminck wrote:

How can bike companies size bikes on bb to saddle or saddle to bars when these points are not fixed though ?

Stack and reach are actually a better way of measuring the distance between the contact points - or at least the points on the frame to which we then fit stem, seat post and cranks - than ETT length and head tube length.

Not to me they aren't. Seat tube, top tube and head tube length is all I've ever needed to understand whether a frame will suit me or not.

I suppose stack is potentially a tie breaker - i.e. to figure out if you can get the drop you really want, or if you'd need too many spacers, in these days of "sportive" geometry bike options.

Whatever you do, some mathematics may be required. What use is stack, without knowing the length and rise of your stem? Reach I just don't get at all - its just a rough guide how far your hands are going to be in front of your feet, which is just the same as how far your bum is going to be behind them. This is dictated mostly by the seat tube angle, which in turn is dictated by the type of bike and how its going to handle. In any case, reach is also pretty much a useless measurement without knowing the stem length (and to a lesser extent rise) and the seatpost setback.

All stack and reach do is complicate an obscure the important issues. They are more or less pointless sub-measurements related to the measurements you actually need. They weren't needed when bikes all had horizontal tt's and geometry tables were centre to centre, so I don't understand what you now need anything other than the "virtual" horitontal tt measurements.

DeVlaeminck

No, stack and reach give a more accurate measure of what the contact points with reference to each other will be than top tube, head tube and seat tube.

That is just fact, sure you could use the frame angles, fork leg length etc in conjunction with top tube, head tube length etc to work out if a frame fits but all you'd be doing is calculating stack and reach!

You may argue what use is stack without knowing the length and angle of the stem - well it'd tell you if you need a different stem for a start - but really you could make tat argument about ANY measure of frame size.

cycleclinic

No the seat tube length is not relevant to sizing as the seat post goes up and down. Seat tube length has relavcne to buying the right length seat post only. What the seat tube angle affects is how much seat post seat back you need to position the saddle correctly relative to the BB.

So sizing is then determined by effective top tube length almost entriely. Head tube length is relevant to avoid too many spacers but since axle to fork crown distance on road bikes using short drop calipers vary by not alot you can use those two dimension alone to buy the right frame size. I bought my Oranage stage 4 based on this method based on my road bike sizing and you know I then thought a 90mm stem on the XL frame will be give me the postion i want down to the mm (760mm centre of seat post to centre of bars diagonal). Bingo it did. Top tube length (effective) is telling. It guides everything. Maybe I can just see it in my head. Thats probably the maths teacher in me.

Devallmerick you are making it too complicated.

DeVlaeminck

I'm not arguing seat tube is important and only mentioned it to say stack and reach are better measures than the traditional ETT, head and seat tube - read what I wrote.

You say axle to fork crown on road bikes with short drop calipers doesn't vary a lot - again I said that myself a couple of posts above BUT fewer road bikes these days have short drop calipers and so stack is a more reliable measure.

I'm surprised you find the concept of stack and reach complicated, I think once you understand it you'll see why it is a better measure of frame size. ETT and head tube length are a good proxy for stack and reach on bikes with similar designs - no argument - but if manufacturers are publishing stack and reach why would you choose to use a proxy measure?

First.Aspect

DeVlaeminck wrote:

I'm not arguing seat tube is important and only mentioned it to say stack and reach are better measures than the traditional ETT, head and seat tube - read what I wrote.

You say axle to fork crown on road bikes with short drop calipers doesn't vary a lot - again I said that myself a couple of posts above BUT fewer road bikes these days have short drop calipers and so stack is a more reliable measure.

I'm surprised you find the concept of stack and reach complicated, I think once you understand it you'll see why it is a better measure of frame size. ETT and head tube length are a good proxy for stack and reach on bikes with similar designs - no argument - but if manufacturers are publishing stack and reach why would you choose to use a proxy measure?

So, would you chose a frame on stack and reach alone then?

I don't know about you, but whether or not a frame fits or not depends on whether I can reach the pedals or bars. Both of these are entirely dependent on where my ars3 is in relation to the pedals or bars. Stack and reach provide absolutely no information in this regard, so you would also need two new measurements to go with them.

Lets call these new measurements "crotch" and "heave". From these two new measurements, you could add crotch to stack and heave to reach, to find out whether the frame fits. From the relative values of heave and reach, you can figure out roughly how racy the overall geometry is.

Alternatively, you could use the tube angles and effective tt and st measurements.

DeVlaeminck

First Aspect wrote:

DeVlaeminck wrote:

I'm not arguing seat tube is important and only mentioned it to say stack and reach are better measures than the traditional ETT, head and seat tube - read what I wrote.

You say axle to fork crown on road bikes with short drop calipers doesn't vary a lot - again I said that myself a couple of posts above BUT fewer road bikes these days have short drop calipers and so stack is a more reliable measure.

I'm surprised you find the concept of stack and reach complicated, I think once you understand it you'll see why it is a better measure of frame size. ETT and head tube length are a good proxy for stack and reach on bikes with similar designs - no argument - but if manufacturers are publishing stack and reach why would you choose to use a proxy measure?

So, would you chose a frame on stack and reach alone then?

I don't know about you, but whether or not a frame fits or not depends on whether I can reach the pedals or bars. Both of these are entirely dependent on where my ars3 is in relation to the pedals or bars. Stack and reach provide absolutely no information in this regard, so you would also need two new measurements to go with them.

Lets call these new measurements "crotch" and "heave". From these two new measurements, you could add crotch to stack and heave to reach, to find out whether the frame fits. From the relative values of heave and reach, you can figure out roughly how racy the overall geometry is.

Alternatively, you could use the tube angles and effective tt and st measurements.

You'll have to clarify what you mean. Are you arguing that some frames have your arse further behind the bottom bracket than some others?

I don't want to misrepresent you but you are wrong in arguing stack and reach provide no information about where your arse is in relation to the pedals and bars - I can't tell you why you are wrong though as I don't follow why you think stack and reach don't give you any information. I'd agree they don't give you absolutely all the information - frame angles are also relevant - but they are more useful than ETT and head tube length.