Understanding Stack & Reach

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  • timothyw
    timothyw Posts: 2,482
    tomisitt wrote:
    Flexibility is the key here. If you’re a bendy 20 year-old then an STR ratio of 1.35 may be fine, but if you’re a 50 year-old with a bad back, you may need an STR ratio of 1.55 or higher. If you currently have a bike that fits you well and you can work out the STR ratio, you can use that ratio to find other frames that will fit your combination of size and flexibility. I know, for example, that I can fit comfortably on anything with an STR ratio of 1.40 or higher, but anything lower will be (literally) a stretch.
    While this is a good way to establish that a frame of your size conforms to the type of geometry that you like, it's not a very good way to confirm that a bike is the correct size for you.

    Someone might, for example, have built a frame for a 7ft basketball player with the ratio of stack to reach that suits you, but that doesn't mean that you'd be able to ride it (or even stand over it!)

    The good thing about stack to reach measurements is that they allow you to more directly compare the size of two different frames - supposing you have a bike now with 400 reach and 600 stack, and you've spotted another bike that you like the look of - it quotes at reach of 390 and a stack of 600. Assuming that the handlebars are similar, you will be able to create a near identical fit on the second bike by fitting a stem 10mm longer than that on your other bike.

    With the combination of stack and reach measurements, and a stem calculator (such as this one - http://yojimg.net/bike/web_tools/stem.php) you have the tools to recreate fit across bikes without any trial and error.

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