Technical FAQ: More options for adjusting bike fit dimensions

Have a question for Lennard? Please email him at veloqna@comcast.net to be included in Technical FAQ.

Dear Lennard,
With regard to your most recent article about bike fit and age and the challenge of maintaining a “pro-looking” bike, there is one option that I think a lot of people overlook. Handlebars have a lot of variance in their reach measurement which has the same fit effect as stem length. In the last few years, a lot of bars with really short reach have been introduced. So, if someone has an older handlebar that may very well have a reach of 90mm or more, changing to a bar with 70mm of reach might solve their issue while being in line with their appearance (or vanity) goals.
— Scott

Dear Lennard,
Regarding bike fitting aging cyclists, one adjustment available that may be available but would only help for when the hands are on the hoods or drops, is to swap handlebars for a short reach bend handlebars.

They may only shorten things by 1cm and would not help at all when you are on the tops of the bars.
— Tim

Dear Scott and Tim,
Thanks for pointing that out. Changing the bar can be a useful way to bring the levers back toward the saddle.
― Lennard

Dear Lennard,
Eight years ago, I purchased my first drop-bar adventure touring bike — a Salsa Fargo Ti. The high head tube of the Fargo enabled me to stay with a drop bar until now. I’m 66 now and descending with that bike produces a lot of neck pain whether on gravel, or tarmac. I am considering converting it to an upright handlebar. I know there will be some trade-offs, but I want to keep this bike if I can. I always felt very much in control on technical single track with this bike and expect I might give some of that up. Actually, it is used mostly for bikepacking trips and touring. I’m not too concerned if I give up some climbing efficiency. I would like to make the right choice when I make changes to this bike.
— Michael

Dear Michael,
Guessing that you’re asking for my advice on switching bars on your Fargo Ti, I think that putting a riser bar on it sounds like a good idea. It of course involves replacing at least your brake levers and shifters with MTB-style ones. The bar will get you higher than your drop bar, which sounds like is warranted. Since the bar has no forward reach, you effectively shorten your reach relative to the hoods and drops positions with your drop bar.

You can try a low-rise bar at first, and as time passes and you want more rise, you can switch to bars with more rise; the shifters, brake levers, and grips will transfer over, as long as you left the cables, cable housings, and/or hoses long enough with the first bar. Rotating a riser bar allows fore-aft reach adjustment as well.
― Lennard

Dear Lennard,
I read with interest your recent article answering questions about how you reduced the reach and increased the stack of your road frame in order to compensate for reduced flexibility and height as a result of normal degenerative changes to the spine.

This is the one reason I have put off buying a lightweight carbon frame that has a relatively short chainstay, and I have stuck with my custom steel endurance build. Most endurance geometries and gravel bikes come with chainstays that are 420mm or longer. If I want something closer to 405, so that it will climb more aggressively, I’m limited to race geometries with low stack and long reach. However, I noted that some women’s specific geometry bikes have a shorter reach and slightly higher stack. Can these be a good alternative for even older male riders? Or is the frame adjusted in other ways to account for the lower body weight of a female rider.
— Marc

Dear Marc,
There is no reason for you not to get a women’s-specific bike. I’d say that’s a great solution to what you’re looking for. Shorter chainstays, shorter reach, and higher stack work just as well for males as for females.
― Lennard

Dear Lennard,
Recently I am considering building a gravel frame with a similar reach and stack as I did on my current endurance bike. I’m having toe clearance issues when mudguards are installed, and it seemed a trend for a few years now, I would like to try quite progressive geometry (~60mm stem, instead of 110mm now) on the new build. So, my question is, do these handling changes (slack steer tube angle, long reach paired with a short stem, etc.) alter my preferred reach/stack dimensions? Or should I just keep my original reach stack dimensions? My other question is: What is the effect of seat tube angle on a bike? In addition to changing the “real” distance from saddle to handlebar, is there any noticeable handling difference between different seat tube angles?
— David

Dear David,
To do what I think you’re trying to do, you certainly need to increase the reach of your frame at the same time you shorten your stem. If you like the position on your existing bike, then increase your frame reach by 50mm when you shorten your stem by 50mm. There is no reason to change your frame stack measurement since you like your bike position on your old bike.

Changing your seat angle by just moving the seat tube/top tube junction back doesn’t change your frame stack and reach, since the bottom bracket is the origin of the x-y coordinate system that is frame stack and reach. The actual top tube length increases, but, as you seem to suggest, you don’t change the “real” distance from saddle to handlebar if the saddle maintains its own stack and reach (its x-y coordinates relative to the bottom bracket). In other words, leaving the down tube and head tube the same as they were and decreasing the seat angle just ends up with the same position on the bike even though the top tube is longer. The saddle gets pushed further forward on the seatpost and maintains the same seat height and fore-aft position. If the bike has short chainstays and minimal clearance between the rear tire and the seat tube, then decreasing the seat angle mandates longer chainstays so the tire won’t hit the seat tube. This increases the wheelbase and hence the bike’s turning radius as well as adds a bit more lateral flex in the rear end. The shallower seat angle does slightly increase the flex of the seatpost and seat tube as you roll over bumps with your weight on the saddle. The differences will be subtle, and you may not notice them.
― Lennard

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Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.” He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn on Twitter.