Stack and Reach: Why It's Your Best Friends

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  • I reckon it's worth talking about the Stack and Reach measurement that'll be very invaluable when it come to figuring out what size bicycle you need.

    The Stack and Reach measurement is a fairly new way of measuring the frame size, the horizontal distance from the bottom bracket to the top centre of the head tube is always consisted (Reach), so the measurement is the most accurate way of measuring the frame;

    I'm going to talk about the Reach as this is the most important part.

    The big problem with uncommon frame sizes is that they're never always what they claim to be in term of sizing, I'll put down an example;

    Specialized Amira;

    Let look at two different size, the 51cm (S) and 54cm (M), the 51cm should have a shorter reach than the 54cm, especially with the top tube being 1.8cm shorter on the 51cm, sound about right doesn't it?

    51cm - 51.8cm top tube.
    54cm - 53.7cm top tube

    Except it doesn't, they both have exactly the same reach, if you look at the Stack and Reach measurement, this is what you get;

    51cm -
    Stack: 52.8cm
    Reach: 37.8cm

    54cm -
    Stack: 54.7cm
    Reach: 37.8cm

    It starting to get confusing, how did the reach stay the same, when the top tube is 1.8cm shorter?

    The main reason is due to the seat tube angle, the 54cm have a 74 degrees seat angle (standard is 73), however the 51cm have a staggering 75.5 degree seat angle, the steeper seat tube shorten the top tube making it felt a lots longer than it claim to be.

    When you slacken the seat angle from 74 to 73 degree, you add an approx 1cm in length from 54cm to 55cm, this is how I figure out the correct fit for customer's bicycle before I heard of the Stack and Reach measurement which made light work of fitting people properly.

    the 51cm Specialized is 1.5 degrees steeper, so approx 1.5cm shorter, which is why the geometry said that the top tube is 1.8cm shorter.

    This is very important, as when it come to fitting, you'd need to ensure that your saddle to bottom bracket is set at an idea distance that you find comfortable;

    With a steeper seat tube, you end up setting the saddle further back to get the idea distance from the bottom bracket that you find comfortable, worse, you may have to invest in a new seatpost that have enough setback to fix this (Velo Orange is the cheapest you can get), Vesalius found out the hard way when his new bike have a 76 degrees seat angle, he end up buying not only a new seatpost that have a big layback, but also a new saddle that have a longer rail to allow it to be set further back, you can see that the saddle is set far back as possible so he'll be able to comfortably sit on the saddle without putting too much weight on the handlebar, very important in audax ride where you spend all days, even a week on a bicycle as shown below.

    If this sound confusing, please let me know, so I can edit to my heart content to make it clearer.


    3 Attachments

    • setback.jpg
    • stack-and-reach-diagram.jpg
    • specialized-amira-c2-2014-women-s-road-bike-satin-carbon-white-w-purple-tint-EV193855-7000-1.jpg
  • I'm sure this'll get merged but great info; sadly out of rep for scoble

  • It's in the ladies forum, common frame sizes are easy to fit, but the smaller sizing are much more complex and could potentially help make it easier to select a new bicycles.

  • Cervelo demonstrated how the geometry of many manufacturers frames move the headtube relative to the BB in a completely inconsistent way as frame sizes change.

    Some frames have the reach actually increasing as you get into small sizes and stack reduces.

    Check Specialized vs. Cervelo geo which is why Mark Cavendish can switch from 52cm to 49cm Venge frames and probably not even change his stem.

  • Some frames have the reach actually increasing as you get into small sizes and stack reduces.

    e.g Fuji

  • What does stack change? How is it adjusted? Saddle height? spacers?

    #iamthick

  • What does stack change? How is it adjusted? Saddle height? spacers?

    #iamthick

    The problem with the headtube length is that it varied too much, bottom bracket and fork length are two of the main reason why it's not easy to measure your fit based on the headtube length on it's own, a lower BB on a 140mm headtube will feel quite high, whether a higher BB make the same headtube felt quite low.

    A really long fork will required a shorter head tube to have an idea Stack for the frame size, that's why CX bicycle appear to have smaller head tube than the road bike for example.

  • Head tube length plus spacers essentially.

    I have two frames with near identical reach but diff stack because one has a 15.5cm HT and the other 14.0cm HT.

    I have stem slammed on both so no spacers but the higher stack on the 15.5cm HT I can compensate for by using a -17 deg stem whilst the shorter HT means I'm using a normal -6deg stem.

  • ^ the different stem angles then produce a variance in reach for two stems of the same length (assuming the same head tube angle on both frames). I had a spreadsheet for calculating all this across each bike I've owned, but I can't find it now.

    For instances where the manufacturer doesn't publish stack and reach on the geo chart, does anyone have a link to a calculator that estimates off other available measurements?

  • I literally just had a test ride on Roadlite AL (small/53) with 20mm spacers and 90mm stem* and it felt extremely upright compared to mine; i.e. more stack (?) When I put in my measurements in Canyon calculator it spits up the same size for me. Of course its not the perfect/right tool. I have my fit tomorrow I just wanted to see how this bike feels like knowing stack and reach. I guess I can do with a bit more of both which is good news.

    *belongs to a mate with same height but diff body measurements plus he is not as flexible.

  • The Roadlite have a very big stack for the size.

  • Stack and reach calculator via Weight Weenies
    http://bb2stem.blogspot.co.uk/, feed the info in and you get a measurement. The only problem is it's not easy to find fork rake angles, especially on older bikes

  • ^^ True; just compared geo charts plus he has spacers and a small-ish stem. My ideal frame would have stack of about 535 to 545 and reach of about 365 to 375.

  • Is there a reason why this is in the ladies forum? Surely it has a gender neutral audience.

  • It's more of an issues to women than the mens, average sized bicycles tend to fit the averages men very well without any adjustment apart from the saddle height.

  • Agreed, especially for the vertically challenged, I wouldn't have had to spend hours trawling WW, Cervelo forum etc if I'd known it was here all along. Link please

  • Agreeing with CB ^^

  • For an issue that predominantly affects women, there sure are a lot of men and no women in this here thread.

    #actualwimmin #quiteshort #somehowmanagestocope

  • LOL - Can't have the 'short' men feeling left out, can we?

    Err, Boffs you ain't "quite short". That's mine, so back off :-).

    I did read the above and tried to absorb but failed. Most of my bikes are kids bikes due to reach 'issues' so I take them to Scherrit for a once-over.

  • LOL - Can't have the 'short' men feeling left out, can we?

    morgan hasnt posted has he?

  • Err, Boffs you ain't "quite short". That's mine, so back off :-)

    You're not allowed to be in charge of "short" AND "quite short". That's not fair.

  • Short it out, you two.

  • I did read the above and tried to absorb but failed. Most of my bikes are kids bikes due to reach 'issues' so I take them to Scherrit for a once-over.

    TL:DR - bike size said top tube is short, turn out you sit too far forward, by the time you move your saddle back enough to be comfortable, the reach felt too long now.

  • @ Boffs - OK. OK. You have 'short' and I'll have 'quite short'. How's that?

    Oliver, as a tall person you have no say in this. Out! :-)

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Stack and Reach: Why It's Your Best Friends

Posted by Avatar for edscoble @edscoble

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