Stack and reach - im confused

First.Aspect

drlodge wrote:

First Aspect wrote:

So, I can tell within a few mm which size of frame will fit, based on a single measurement.

Which is what cycleclinic said two pages ago. It really is very simple.

Pretty much. 1 degree difference in seat tube angle is 1cm in eTT. Most frames are 73.5 give or take, may be 1/2 a degree either way, which is a 5mm error. Not much. eTT for me, is the benchmark, then I look at the other aspects like STA and head tube length to get a more refined feel.

Wrong. Ett is completely independent of seat tube angle. Change your frame of reference.

timothyw

First Aspect wrote:

So, I can tell within a few mm which size of frame will fit, based on a single measurement.

Lucky you.

Allow me to take the example of two bikes that I've owned.

Fuji Sportif 1.1 - https://archive.fujibikes.com/2017/Fuji ... f-11-disc2

Giant TCR Advanced 3 - https://www.giant-bicycles.com/gb/tcr-advanced-3-2015

Because I'm a large man, let's take the example of the two largest sizes.

Fuji in XXL - 598mm effective top tube.
TCR in XL - 605mm effective top tube.

Near as damnit the same fit right, give or take?

Then you look at the stack and reach measurements.

Fuji has 66cm of stack. The TCR has 59.5cm. Reach measurements are fairly close - the TCR has about 1.5 cm more.

The TCR fit. The Fuji most definitely didn't. There's not a stem in existence that will drop the front end by 6cm, unfortunately.

Still, good luck with your sizing approach, ultimately it doesn't matter to me how you fit your bikes, I'm perfectly happy sizing up mine.

DeVlaeminck

First Aspect wrote:

I think the problem for stack and reach devotees is that the bb is considered to be a fixed point. In which case if you change the angles all of the other relevant positions change.

This is similar to the early models of the solar system with the earth in the middle. Very complicated machines they were.

I *think* you are arguing that if a bike has a relaxed seat tube angle then your saddle will be further behind the bottom bracket - whereas the "reach" measurement assumes that riders have a fixed distance they position their saddle relative to the bottom bracket by means of using seat post set back or sliding the saddle on the rails.

It really just depends which of these approaches you take whether ETT or Reach is the better measure of the "length" of the bike.

Stack seems to me to be just a better measure than head tube length though.

First.Aspect

TimothyW wrote:

First Aspect wrote:

So, I can tell within a few mm which size of frame will fit, based on a single measurement.

Lucky you.

Allow me to take the example of two bikes that I've owned.

Fuji Sportif 1.1 - https://archive.fujibikes.com/2017/Fuji ... f-11-disc2

Giant TCR Advanced 3 - https://www.giant-bicycles.com/gb/tcr-advanced-3-2015

Because I'm a large man, let's take the example of the two largest sizes.

Fuji in XXL - 598mm effective top tube.
TCR in XL - 605mm effective top tube.

Near as damnit the same fit right, give or take?

Then you look at the stack and reach measurements.

Fuji has 66cm of stack. The TCR has 59.5cm. Reach measurements are fairly close - the TCR has about 1.5 cm more.

The TCR fit. The Fuji most definitely didn't. There's not a stem in existence that will drop the front end by 6cm, unfortunately.

Still, good luck with your sizing approach, ultimately it doesn't matter to me how you fit your bikes, I'm perfectly happy sizing up mine.

Well, you chose the right size both times, without needing to know the reach, but one time you chose the wrong type of bike. You didn't check that the head tube of the Fuji is 5m longer, no? Didn't the name "sportive" give it away? You'd have been alright with this one though - https://archive.fujibikes.com/2017/Fuji/sl-11-disc

Funnily enough though, the reach differs by more than the ETT. What d'ya know.

You'd have problems getting to your preferred position on a mountain bike as well, but I bet you'd get the right size.

First.Aspect

DeVlaeminck wrote:

First Aspect wrote:

I think the problem for stack and reach devotees is that the bb is considered to be a fixed point. In which case if you change the angles all of the other relevant positions change.

This is similar to the early models of the solar system with the earth in the middle. Very complicated machines they were.

I *think* you are arguing that if a bike has a relaxed seat tube angle then your saddle will be further behind the bottom bracket - whereas the "reach" measurement assumes that riders have a fixed distance they position their saddle relative to the bottom bracket by means of using seat post set back or sliding the saddle on the rails.

It really just depends which of these approaches you take whether ETT or Reach is the better measure of the "length" of the bike.

Stack seems to me to be just a better measure than head tube length though.

Not really. You can put your seat wherever you want either way. All I'm saying is that the ETT measurment is more representative of where it will need to be, all things being equal. That's just maths.

Look, ETT is not the be all and end all, but it does get you most of the way there. My experience is also calibrated against seat tube angle in terms of how "over the BB" I like to feel, and my spidey sense detects a potential problem if the effective seat is longer than the ett. Then you start to look at how long the wheel base is and wonnot. Other options are available.

But lets be honest here, at that stage most of us are probably looking at a shortlist based on things like colour, type of bike, price, brand etc., rather than how low the bottom bracket is, the fork rake or the trail. For me, its all about aesthetics and brand, so I look cool at traffic lights.

DeVlaeminck

First Aspect wrote:

DeVlaeminck wrote:

First Aspect wrote:

I think the problem for stack and reach devotees is that the bb is considered to be a fixed point. In which case if you change the angles all of the other relevant positions change.

This is similar to the early models of the solar system with the earth in the middle. Very complicated machines they were.

I *think* you are arguing that if a bike has a relaxed seat tube angle then your saddle will be further behind the bottom bracket - whereas the "reach" measurement assumes that riders have a fixed distance they position their saddle relative to the bottom bracket by means of using seat post set back or sliding the saddle on the rails.

It really just depends which of these approaches you take whether ETT or Reach is the better measure of the "length" of the bike.

Stack seems to me to be just a better measure than head tube length though.

Not really. You can put your seat wherever you want either way. All I'm saying is that the ETT measurment is more representative of where it will need to be, all things being equal. That's just maths.

.

Where your seat "needs to be" is dictated by ETT length ? I'm not actually sure what you mean by that - it sounds like you are moving the saddle forwards or backwards depending on top tube length to get the "right" distance from saddle to bars.

Assuming you aren't on a wind up I do genuinely think you are confused about this.

First.Aspect

Nope not confused. Forensic analysis of internet chat forum posts may lead to disappointment.

I simply mean that where the position the seat will be, is more closely related to ett than reach. There's a dull page of trig to read again if you are enthusiastic enough.

Reach tells you where the top of the head tube and bb are in relation to one a other and that is all. From that, just as with ett, you can also infer where a saddle will end up, just less accurately.

Put another way, the bb is further from the seat than the notional intersection between seat tube and ett. Hence more potential variance if you don't know the angle. It's shi7 simple.

DeVlaeminck

First Aspect wrote:

I simply mean that where the position the seat will be, is more closely related to ett than reach. There's a dull page of trig to read again if you are enthusiastic enough.

Reach tells you where the top of the head tube and bb are in relation to one a other and that is all. From that, just as with ett, you can also infer where a saddle will end up, just less accurately.

Put another way, the bb is further from the seat than the notional intersection between seat tube and ett. Hence more potential variance if you don't know the angle. It's shi7 simple.

For most people the position of the saddle isn't determined by reach or ETT.

The bottom bracket is a fixed point - and if you assume we have a preferred crank length the saddle position is set from that.

There is a reason the industry has moved towards stack and reach, they aren't all making a huge mistake only you can see. Yes it isn't the end of the story, the guy that listed the calculator explained why, but your arguments as to why it's s backward step make no sense.

joey54321

First Aspect wrote:

It is all quite interesting though.

I completely disagree with:

"The problem with the top tube measurement is that it doesn't matter how long the top tube is - what matters is whether you can position the saddle in the position you like, relative to the bottom bracket. This can be accomplished on almost any bike just by sliding the seatpost in and out and sliding the saddle fore and aft - in extreme circumstances you might have to replace the seatpost for one that is inline/set back - but basically, I don't care how long the top tube is, or how long the 'effective' top tube is."

For me, precisely where the bb is relative to my feet is not very important, because I have knees. the exact position of the bb makes no real difference to the angle between my hips/back and thighs, which is the main determinant of whether or not I'll end up in agony. I just did a scientific test. I moved my keyboard further away and it was hard to type and my shoulders were tense. I then stuck my legs out and it made no difference whatsoever.

Now to the maths. Good effort, but you forgot to use the 20 cm of exposed seatpost in your calculations anywhere. C-.

If you have 20 cm of seatpost above the level of the effective seat tube, then by your calculation, the variance in saddle position drops from 1.8 cm to 4.8 mm.

Actually, I think 20 cm is quite a lot of seat post above the level of an effective tt, and for most people it would be more like 10 cm. Think about it - are your bars really 10-15 cm above your top tube? Or do you have a 20 cm seat to bar drop? So actually, effective tt gets you to within a couple of mm in most cases. So I think your maths is off by about an order of magnitude.

I used this: (740-200)* Sin (Seat angle). That 200 is the exposed seatpost.

I used 20 to be generous as the more seat post showing the less TT length is impacted.

I think I could actually have about 20 as my race bike has a sloping TT.

svetty

DeVlaeminck wrote:

For most people the position of the saddle isn't determined by reach or ETT.

The bottom bracket is a fixed point - and if you assume we have a preferred crank length the saddle position is set from that.

Bingo! We have a winner

drlodge

First Aspect wrote:

drlodge wrote:

First Aspect wrote:

So, I can tell within a few mm which size of frame will fit, based on a single measurement.

Which is what cycleclinic said two pages ago. It really is very simple.

Pretty much. 1 degree difference in seat tube angle is 1cm in eTT. Most frames are 73.5 give or take, may be 1/2 a degree either way, which is a 5mm error. Not much. eTT for me, is the benchmark, then I look at the other aspects like STA and head tube length to get a more refined feel.

Wrong. Ett is completely independent of seat tube angle. Change your frame of reference.

It depends what you're trying to measure. Perhaps I wasn't clear - my main reference is how far forward the head tube and hence bars are from the saddle, eTT gives me this. All things being equal, if the seat tube angle differs by 1 degree, then the eTT length will need to change by 1cm to give the same head tube position fore-aft. I want eTT=545mm with 73.5 STA. If STA is 73 degrees, then eTT moves to 550mm

First.Aspect

Your "fixed point" is arbitrary. Here we are concerned with three points - A - the intersection of the ett and seat tube, B - the intersection of the head tube and ett C - the bb. If you fix the relative positions of two of them and change the angles of the seat tube, the other one moves.

If any of you own meccano, have a play with a triangle, undoing a different corner each time. If you can't grasp it I guess you struggled at school.

If you state that the ett must change if the angles change, you are effectively asserting that there's only one triangle you can draw for any length of horizontal line. Which is clearly nonsense.

Whether of not your tt slopes is irrelevant to ett. That's the point.

The maths is still very wrong. 740mm isn't relevant at all, only the distance through which your 10 cm of seatpost above the level of the ett sweeps around point A with angle.

Since bike fit is more sensitive to the longitudinal distance between your seat and hands than it is to the longitudinal distance between your feet and your hands (not least because your feet move anyway), it is illogical to use a measurement which is less representative of the distance between your seat and hands as your starting point. All the calculations showing how much "ett changes" with seat angle if you take this approach merely confirms my point.

Stack is helpful - I agree. Reach is helpful to assess potential f/r weight distribution, although not on its own. And, to a lesser extent since how extended your hamstrings will be also depends on reach (for a given distance between the seat and bars), it is indeed somewhat relevant to bike fit. Just not as much. There are proxies for both, but for their intended purpose they are probably a step forward.

The industry is not wholsale moving to stack and reach. They are useful bits of info along with lots of other things on a geometry table.

What's happened is that the industry has standardised these two new measurements, and they've been misunderstood as being a substitute for something they are not.

I have a custom bike and I've had a couple of custom fits. In both case First question - what size is your current bike. Answer a 56 cm. (cue setting the tt length on the rig). Second question - how much saddle to bar drop do you have. Answer, about 8 cm. Cue, changing the height of the bars.

That was a Retul guy.

The bb position relative to either is not considered.

Kent Eriksen then took the Retul geometry, and adjusted the stack and reach slightly to accommodate a custom stem (stack) and to give a better handling bike (reach, at least in part). To do so he changed the tube angles slightly and lengthened the rear triangle a bit. Two additional factors relevant to weight distribution. He did not change the length of the tt.

Are these people just as stupid as me? Or just not as clever as you guys?

joey54321

Love the classic "I'm losing my argument so I'll use bigger words and make less sense" internet forum response.

First Aspect wrote:

Are these people just as stupid as me? Or just not as clever as you guys?

Hard to say, it could be either.

First.Aspect

drlodge wrote:

First Aspect wrote:

drlodge wrote:

First Aspect wrote:

So, I can tell within a few mm which size of frame will fit, based on a single measurement.

Which is what cycleclinic said two pages ago. It really is very simple.

Pretty much. 1 degree difference in seat tube angle is 1cm in eTT. Most frames are 73.5 give or take, may be 1/2 a degree either way, which is a 5mm error. Not much. eTT for me, is the benchmark, then I look at the other aspects like STA and head tube length to get a more refined feel.

Wrong. Ett is completely independent of seat tube angle. Change your frame of reference.

It depends what you're trying to measure. Perhaps I wasn't clear - my main reference is how far forward the head tube and hence bars are from the saddle, eTT gives me this. All things being equal, if the seat tube angle differs by 1 degree, then the eTT length will need to change by 1cm to give the same head tube position fore-aft. I want eTT=545mm with 73.5 STA. If STA is 73 degrees, then eTT moves to 550mm

Oh, sorry. In which case I think I agree, assuming you are quite fussy about where your feet are. I would guess then that you would take up the difference with a different stem. Personally, I'm more fussy about the stem length for some reason.

First.Aspect

joey54321 wrote:

Love the classic "I'm losing my argument so I'll use bigger words and make less sense" internet forum response.

First Aspect wrote:

Are these people just as stupid as me? Or just not as clever as you guys?

Hard to say, it could be either.

What is wrong exactly? Retul, Kent Eriksen cycles, me and everything I stand for, my maths, or long words like "longitudinal"?

First.Aspect

DeVlaeminck wrote:

First Aspect wrote:

I simply mean that where the position the seat will be, is more closely related to ett than reach. There's a dull page of trig to read again if you are enthusiastic enough.

Reach tells you where the top of the head tube and bb are in relation to one a other and that is all. From that, just as with ett, you can also infer where a saddle will end up, just less accurately.

Put another way, the bb is further from the seat than the notional intersection between seat tube and ett. Hence more potential variance if you don't know the angle. It's shi7 simple.

For most people the position of the saddle isn't determined by reach or ETT.

The bottom bracket is a fixed point - and if you assume we have a preferred crank length the saddle position is set from that.

There is a reason the industry has moved towards stack and reach, they aren't all making a huge mistake only you can see. Yes it isn't the end of the story, the guy that listed the calculator explained why, but your arguments as to why it's s backward step make no sense.

Step 1 - steal underpants. Step 3 - profit. Wait, what's step 2?

Step 1 - seat post height. Step 3 - stack and reach. What's step 2? The average ratio of leg length to arm length of northern Europeans?

DeVlaeminck

First Aspect wrote:

I have a custom bike and I've had a couple of custom fits. In both case First question - what size is your current bike. Answer a 56 cm. (cue setting the tt length on the rig). Second question - how much saddle to bar drop do you have. Answer, about 8 cm. Cue, changing the height of the bars.

That was a Retul guy.

The bb position relative to either is not considered.

...........

Are these people just as stupid as me? Or just not as clever as you guys?

I've never used the services of any retul guy but I thought I'd google retul stack and reach.

Forgive me if I've misunderstood what this link is but it appears to be a list of frames and their geometry published by retul or someone associated with them so people can use their retul fit to find a bike.

You'll notice they include stack and reach in their chart but not ETT.

https://b2b.retul.com/frame-finder/stac ... ch-tables/

DeVlaeminck

First Aspect wrote:

DeVlaeminck wrote:

First Aspect wrote:

I simply mean that where the position the seat will be, is more closely related to ett than reach. There's a dull page of trig to read again if you are enthusiastic enough.

Reach tells you where the top of the head tube and bb are in relation to one a other and that is all. From that, just as with ett, you can also infer where a saddle will end up, just less accurately.

Put another way, the bb is further from the seat than the notional intersection between seat tube and ett. Hence more potential variance if you don't know the angle. It's shi7 simple.

For most people the position of the saddle isn't determined by reach or ETT.

The bottom bracket is a fixed point - and if you assume we have a preferred crank length the saddle position is set from that.

There is a reason the industry has moved towards stack and reach, they aren't all making a huge mistake only you can see. Yes it isn't the end of the story, the guy that listed the calculator explained why, but your arguments as to why it's s backward step make no sense.

Step 1 - steal underpants. Step 3 - profit. Wait, what's step 2?

Step 1 - seat post height. Step 3 - stack and reach. What's step 2? The average ratio of leg length to arm length of northern Europeans?

That actually makes as much sense as all your replies on this thread - f all!!

First.Aspect

DeVlaeminck wrote:

First Aspect wrote:

I have a custom bike and I've had a couple of custom fits. In both case First question - what size is your current bike. Answer a 56 cm. (cue setting the tt length on the rig). Second question - how much saddle to bar drop do you have. Answer, about 8 cm. Cue, changing the height of the bars.

That was a Retul guy.

The bb position relative to either is not considered.

...........

Are these people just as stupid as me? Or just not as clever as you guys?

I've never used the services of any retul guy but I thought I'd google retul stack and reach.

Forgive me if I've misunderstood what this link is but it appears to be a list of frames and their geometry published by retul or someone associated with them so people can use their retul fit to find a bike.

You'll notice they include stack and reach in their chart but not ETT.

https://b2b.retul.com/frame-finder/stac ... ch-tables/

Based on the video, I think that's the database from which you get an output of frames that match your measurements. What the customer gets (at least in 2015) from a fitting is bonkers, right down to the stack height of the headset. I can assure you that (a) ett is on the geometry chart you end up with and (b) I wasn't asked what stack and reach I currently have.

We aren't going to agree. But I am betting the emphasis it is given at the moment is a fad and that ultimately people will still want to see pretty much the whole geometry table.

Do you remember when sloping top tubes first came in? Geometry tables showed the actual tt length and it was impossible to compare frames from different manufacturers. They all did it, but it didn't make it any more sensible and it didn't last long.

If you watch cycling trends for long enough, you learn a bit of healthy scepticism about where the herd are currently headed.

First.Aspect

DeVlaeminck wrote:

That actually makes as much sense as all your replies on this thread - f all!!

It would be good if you can tell me why I'm wrong. Honestly, I do find this sort of stuff interesting - occupational hazard - but the school playground stuff not so much.

First.Aspect

How do you chose the appropriate frame size here?

https://salsacycles.com/bikes/vaya/2017_vaya_claris - I need a reach of about 370, so the 52 and 57 could fit, but the 54 and 55 would be too small.

What about this one? http://www.somafab.com/archives/product ... cross-disc - I guess I'd need to buy the 42 cm size, right? I'm 5ft 10 by the way.

Any smartass fancy a go at either of these? Remember, no peeking at the ett measurement because that's totally useless.

joey54321

First Aspect wrote:

How do you chose the appropriate frame size here?

https://salsacycles.com/bikes/vaya/2017_vaya_claris - I need a reach of about 370, so the 52 and 57 could fit, but the 54 and 55 would be too small.

What about this one? http://www.somafab.com/archives/product ... cross-disc - I guess I'd need to buy the 42 cm size, right? I'm 5ft 10 by the way.

Any smartass fancy a go at either of these? Remember, no peeking at the ett measurement because that's totally useless.

These links perfectly illustrate the need for stack and reach. Take the first link. The ETT is 2cm different between the 52 and the 54 sized frames. From this you might think "ah, that means I need a 2cm longer stem" but that isn't the case. The saddle rail and seat back will be positioned so the saddle is the same place compared to the bottom bracket (for good biomechanics) so now the difference between the saddle and the bit where the stem attaches is only 3mm different, not 2cm!

First.Aspect

joey54321 wrote:

First Aspect wrote:

How do you chose the appropriate frame size here?

https://salsacycles.com/bikes/vaya/2017_vaya_claris - I need a reach of about 370, so the 52 and 57 could fit, but the 54 and 55 would be too small.

What about this one? http://www.somafab.com/archives/product ... cross-disc - I guess I'd need to buy the 42 cm size, right? I'm 5ft 10 by the way.

Any smartass fancy a go at either of these? Remember, no peeking at the ett measurement because that's totally useless.

These links perfectly illustrate the need for stack and reach. Take the first link. The ETT is 2cm different between the 52 and the 54 sized frames. From this you might think "ah, that means I need a 2cm longer stem" but that isn't the case. The saddle rail and seat back will be positioned so the saddle is the same place compared to the bottom bracket (for good biomechanics) so now the difference between the saddle and the bit where the stem attaches is only 3mm different, not 2cm!

Now who is using technobabble to support an argument?

The need or potential use for stack and reach at some stage of a bike fit is not the question. I asked you to tell me what size frame I need, based on stack and reach (but lets ignore stack because lets face it these are silly bikes). You've ridiculed use of ett which took me about 10 seconds. Please show your working.

I forgot to mention, I have a 20mm setback seatpost just now and I'm struggling to find one with a 50mm setback. I know I can turn it around so it is 20mm forward as well put people would point and laugh when they see it like that. I also really like my short nosed saddle with its short little rails. Please help, because I'm about to shell out £2000 and I'll be really angry if you get it wrong.

What about the second one? Should I buy a 42cm frame? Seems a bit small. If I size up, the reach is the same for the next four sizes, so I guess any of them would do. That *must* be right, mustn't it?

joey54321

I had suspicions before but now i'm fairly sure you are just a troll so I'll stop here.

Stack and reach are useful but not the only thing to determine a bike fit. The point was always that they are a step closer to determining if a bike fit will work for you. Stack shows you if the height will fit. Reach shows you if the length will fit. Seat post angle shows you if the saddle will fit. And I know what you're going to troll (say), that if you are looking at seat post angle you may as well look at ETT. The difference is a bunch of trigonometry is already done for you, why bother doing it yourself.

First.Aspect

joey54321 wrote:

I had suspicions before but now i'm fairly sure you are just a troll so I'll stop here.

Stack and reach are useful but not the only thing to determine a bike fit. The point was always that they are a step closer to determining if a bike fit will work for you. Stack shows you if the height will fit. Reach shows you if the length will fit. Seat post angle shows you if the saddle will fit. And I know what you're going to troll (say), that if you are looking at seat post angle you may as well look at ETT. The difference is a bunch of trigonometry is already done for you, why bother doing it yourself.

So, are you telling me you can't tell what size frame I need?

I'm not trolling you (any more than you deserve), but you have clearly been evangelizing about the wrong thing. The truth is, reach is worse than useless in these two cases as a starting point.

If you read into this subject, you will find the origins of these numbers were to address how to compare full suspension mtb geometries with each other, and those for extreme tube shapes on tri-bikes, and the like, where the conventional reference points were hard to determine. Every bike has a bb and every bike has a headset, so you can always use those - hence stack and reach.

They *are* useful but they can also be utterly misleading - depending on what you are trying to use them for. You don't need them to figure out whether a manufacturer's 54 or 55 cm bike is the one for you.

timothyw

First Aspect wrote:

joey54321 wrote:

I had suspicions before but now i'm fairly sure you are just a troll so I'll stop here.

Stack and reach are useful but not the only thing to determine a bike fit. The point was always that they are a step closer to determining if a bike fit will work for you. Stack shows you if the height will fit. Reach shows you if the length will fit. Seat post angle shows you if the saddle will fit. And I know what you're going to troll (say), that if you are looking at seat post angle you may as well look at ETT. The difference is a bunch of trigonometry is already done for you, why bother doing it yourself.

So, are you telling me you can't tell what size frame I need?

I'm not trolling you (any more than you deserve), but you have clearly been evangelizing about the wrong thing. The truth is, reach is worse than useless in these two cases as a starting point.

If you read into this subject, you will find the origins of these numbers were to address how to compare full suspension mtb geometries with each other, and those for extreme tube shapes on tri-bikes, and the like, where the conventional reference points were hard to determine. Every bike has a bb and every bike has a headset, so you can always use those - hence stack and reach.

They *are* useful but they can also be utterly misleading - depending on what you are trying to use them for. You don't need them to figure out whether a manufacturer's 54 or 55 cm bike is the one for you.

You are asking us to size you up for a bike, having told us what reach measurement you desire, but not what stack measurement you desire.

Fit is a function of both.

Still, I'll bite.

The guide height on the geometry chart puts you, at 5ft10, on the overlap between the 55 and the 57cm sizes.

You've said you want a reach around 370 - the 57cm bike has a reach of 372mm - so that one.

First.Aspect

No I'm sorry that frame is significantly too large. I would need the 54.

You need both to size a frame did you say? I needed ett.

I did check other factors, of course. It is true it's not completely fair because you don't know how high I like my bars. And this type of bike isn't supposed to have a size that mimics a roadies position. But even so if I were to equivocate between the 54 and 55 I'd check the seat angle and, yes, stack to decide between them.

But you started with my height which is a horribly crude guide to get you to one end, the other end or the middle bit of a geometry chart.

Even though you cant reach the low hanging fruit, I would like you to say something about the other chart though. You have a bit more info now. Pretend I'd like a stack of about 580 and a reach of 370.

timothyw

You want a stack around 580 and a reach of 370 on the soma bike?

In that case you'll want the stack 582 and reach 382 size 54, and a 1cm shorter stem than usual.... or a different bike.

I wouldn't recommend buying any size of bike without a test ride or the option to return it if you don't get on with the fit.

First.Aspect

TimothyW wrote:

You want a stack around 580 and a reach of 370 on the soma bike?

In that case you'll want the stack 582 and reach 382 size 54, and a 1cm shorter stem than usual.... or a different bike.

I wouldn't recommend buying any size of bike without a test ride or the option to return it if you don't get on with the fit.

I'd opt for the size down actually. The 54 is too big and I'd need to pull the seat forward quite a bit. Might be okay with a shorter than normal stem you are right, but I like a normal stem thanks. Isn't that the point of getting the right size of frame?

Better than the last one though.

It's better to test ride yes. Not always possible these days.

timothyw

First Aspect wrote:

TimothyW wrote:

You want a stack around 580 and a reach of 370 on the soma bike?

In that case you'll want the stack 582 and reach 382 size 54, and a 1cm shorter stem than usual.... or a different bike.

I wouldn't recommend buying any size of bike without a test ride or the option to return it if you don't get on with the fit.

I'd opt for the size down actually. The 54 is too big and I'd need to pull the seat forward quite a bit. Might be okay with a shorter than normal stem you are right, but I like a normal stem thanks. Isn't that the point of getting the right size of frame?

Better than the last one though.

It's better to test ride yes. Not always possible these days.

If you want the same stem as you consider 'normal' then get a bike with the same stack and reach as 'normal'. This was covered where I said 'or a different bike'.

Pulling the saddle forward is considered a no-no because this would imply pulling it out of the optimal position, although I appreciate this is a bit of a fuzzy concept. Certainly my experience is that I was happier overall once I identified the bike which had the saddle position I liked most, and replicated it on my other bikes.

While sizing down is often the best option, you've mentioned in a previous post that you choose bikes based on looks - for a lot of people this means getting the frame size which allow you to 'slam" the stem even if it means a slightly shorter stem than usual.

In this case, the size down doesn't reduce the reach (so you'll still probably want the shorter stem) and you'll also need extra spacers under the stem.