1

I'm looking at getting a new bike, but struggling with the most suitable one given the different geometries.

Given a particular torso angle, is there an optimal stack & reach? A large S&R would see the arms stretched out further in front, while a smaller S&R would see the arms pointing more down toward the ground. If too small, the knees would hit the elbows and if too large, one would struggle to take weight on the hands, but is there a parameter that would dictate the "correct" sizing?

I'll try to add an image soon to help clarify if needed.

Cheers!

  • Handle bar width also affects the riding position. – mattnz Dec 23 '18 at 19:25
  • 2
    What kind of bike are you thinking of getting? Hybrid, drop bar road, mountain? – Argenti Apparatus Dec 23 '18 at 19:32
  • 5
    Go try some different bikes and see what you like; if you don't like it, it isnt right. – Batman Dec 23 '18 at 19:38
  • @mattnz fixed HB width (roughly shoulder width) as for road bike. – chriszerog Dec 23 '18 at 20:45
  • @Argenti see above – chriszerog Dec 23 '18 at 20:48
1

I think what you are getting at in your question is: is there and optimum bike geometry for any given rider and riding position or style? Yes, there is, but stack and reach are not the measurements used to specify bike fit per se and they are not the only frame geometry parameters that affect bike fit. Seat tube angle is also important as it affects where the seat is located.

The basic measurements used in bike fit deal with the three contact points on the bike: feet, butt and hands:

  • Saddle height above bottom bracket
  • Saddle horizontal set back aft of bottom bracket
  • Horizontal saddle to bars distance
  • Saddle to bars vertical drop

If you know what those are for a rider you can pick a frame with stack, reach and seat tube angle that will allow seat, seatpost, stem and handlebars to be positioned and adjusted to get that fit.

Of course, that is not the whole story. The steering geometry that is influenced by wheelbase, chain-stay length, head-tube angle and fork trail are big factors in bike selection as well as cockpit geometry.

I think because stack and reach, along with other frame geometry parameters are published by bike manufacturers people thing they need to find 'their' preferred or optimum stack and reach. I would not pick a bike that way. The best advice is to test ride an array of bikes at a number of different stores and let bike store staff give you some advice on sizing and fit. See what feels best for you.

  • The saddle to bars distance depends on frame, seatpost setup and stem. The saddle to bars drop depends on frame, seatpost setup and stem. Reach and stack are frame measurements, and they limit how the full system can be set up. – ojs Dec 24 '18 at 7:51
  • I downvoted the answer because I disagree with " Yes, there obviously is. That is what professional bike fitting services are for." statement. – Klaster_1 Dec 24 '18 at 10:46
  • @ojs yep, that's exactly what I am trying to say with my third paragraph – Argenti Apparatus Dec 24 '18 at 12:56
  • @Klaster_1 Yeah, I'll admit that sounds a bit snarky – Argenti Apparatus Dec 24 '18 at 13:10
0

Stack and reach are the ways of measuring a bicycle's fit - and yes, there are optimal measures of stack and reach for each cyclist.

Test ride a few bikes, find one that fits you well/best. Measure stack and reach of that particular bicycle. Those are your prefered stack and reach measurements. Then, when choosing a new bike, measure the stack and reach of that bike.

P.S. Common mistake people make is setting saddle to bar distance by altering saddle position. Saddle position should be set relative to the bottom bracket (pedals). Bars position is set after that. Fit basics explained in more detail.

Frame geometry (in terms of fork trail, seat tube angle, chainstay length etc. - the things apart from the stack and reach) is not something that a customer need worry about too much (as long as they get the stack and reach that fits them), especially if going for a "known brand" bicycle frame. It's usually designed to suit the frame's intended use - whether it's touring, gravel, road, MTB... As long as you pick the frame marketed for your intended use, you're fine. Or as good as it gets, considering modern frame design trends.

  • 1
    Thanks, but don't agree with the final paragraph. I'm the same height as a friend, but would need to raise the saddle on his (known brand) road bike about 6" for it to work for me, resulting in a very big saddle to bar drop. It's the "correct" size for me according to the sizing chart, but wouldn't work for me at all. I'm sure it would work fine if my proportions were "normal". – chriszerog Dec 25 '18 at 19:29
  • It is subjective. That's why, like I've explained, it is best to test and find your prefered stack and reach. By "frame geometry" I meant the other characteristics like fork trail, seat tube angle etc. – Relja Novović Dec 25 '18 at 19:35
  • 1
    Please stop linking off to other websites - its almost clickbaity. Best is to put the main points into your answer on SE so that if/when the remote website changes or vanishes, at least this answer will remain useful and not a pointer to nowhere. – Criggie Dec 26 '18 at 4:52
  • See no PM option so will write here. The links are in the "read more into that if you want" manner - the answer stands without any of them working in my opinion. I find it a lot easier and less time consuming, than writing it all over and over again - for most of the frequently asked questions. For me, some 20 years ago, reading the answer I gave would have been helpful, but that's me. If it's a problem, feel free to edit/delete however you think is best. If it's against the rules I'd make sure not to do it again. – Relja Novović Dec 26 '18 at 7:29
  • The aim of stackexchange is to provide a permanent collection of answers, so the idea is to answer here instead of collecting links to external sites. The fact that it's your own blog also makes the entire answer look like spam even if some of the information is correct. – ojs Dec 26 '18 at 7:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.