After reading over the “Tour de Bike Fit” i’m left with a few questions, Most of which are centered around how to choose a bike to begin with.
I think I understand the concept of stack and reach, and I think I understand how to pick a road bike frame (inseam length, but i’m sure that torso and arm legth go into this somehow seeing as not only do you sit on the thing you also reach for the controls.). But how do you caculate stack and reach for a tri bike if you do not have a fit bike or access to one? I know that thier are variables in the proccess (such as hip angle) that can only be figured out while on the bike, but their must be some way to calculate stack and reach for a rider just by body size?
I agree. With a complete measurement of all the body parts (well, not ALL the parts…he he) it would seem as though a stack/reach could be calculated. But the amount of work to do that would be more than just scribbling something on a napkin. So far I don’t know that anyone has done the geometry calculations.
Also keep in mind that there isn’t one ideal fit for every person because you will have other factors at play than purely aerodynamics…such as belly girth, flexibility, back problems, neck problems…Going through a professional fit process should take all of that in to account…which is why any automagic calculations like you are asking for would only be a starting point anyway…an estimate really.
Most of which are centered around how to choose a bike to begin with.
That's exactly my question. How are first time tri bike buyers supposed to know what bike to get? I've seen one store stress that you should get fit before purchasing a bike. That makes sence to me, but I haven't seen anyone else say it. If it was the general concensus, you would think more stores would say it.
Its tough to calculate because it can depend a lot on individual flexibility. The Cobb “A” and “B” backs make a difference in what bike will work for a given rider even if two riders have identical measurements.
If you have a road bike set up with shorty aerobars you can estimate the Tri bike setup assuming rotation forward around the bottom bracket.
Good point. However i am looking for that starting point. I’m having a little confusion because in many of Dan’s articles he mentions some “formulas” that work in certain instances with certain assumptions, ( i.e. for a fit and trim individual with normally boy proportions cockpit length will be roughly equal to seat height). While these formulas or phenomenon may not be the rule in every instance (such as a nomally proportioned but terribly out of shape person, or a long torsoed short legged person) they work most of the time. The reason i’m looking for these formulas is that while I like my LBS I hate going into anything unprepared, so if I know my stack and reach “area” I can be some what knowlegable about what bike I may want to purchase, where as if I don’t i’m at the mercy of what ever bike fitter I run into for better or worse.
I figured you wanted to mail order something sight unseen. If you have the luxury of going in to a shop and trying out the bikes they’ve got in stock then you can simply use the 90 degree angles as your guide. Not low enough? try a smaller bike. arm rests too far out? either you need adjustable rests that can be moved back (bar swap perhaps) or you need a frame with a shorter top-tube relative to height.
If the shop sells and stocks timetrial bikes then they probably know a bit about the proper fit. If you don’t want to put all your trust in the bike shop employee have them fit you to a bike, have them snap a shot with your digital camera while you are on a trainer aboard the bike, then tell them you need a few days to think about it…come back here and post a ‘critique my fit’ thread. We can’t replace a skilled bike fitter, but we can tell you if you are close.
You might check the local gym or spin class for a spin bike. you can play around on that for a while and try different seat heights and angles, reach, bar drop. do it while spinning at cadence and see how that feels. That should help give you a starting point. If you are proportioned close to the norm then you can probably go with any major brand, you just have to get the right size and equip it properly. you might also consider getting and adjustable stem like the ergostem to begin with. this will allow you to experiment with different positions until you dial in the one that is best. good luck
I think almost every reputable bicycle shop that specializes in high-end bicycles would suggest having a fit done before purchasing a bicycle. That’s how we do it, and we can therefore find an athlete’s optimal fit without being constrained by an existing bicycle. Then we can compare existing bicycles to the athlete’s fit coordinates and figure out which bicycle will suit the athlete best. This is what Dan advocates for as well. There are a number of other shops just in Boulder that operate this way (Pro Peloton was just featured in the latest Velonews), and BCSM and Retul are not shops but have systems in place to accomplish the fit before searching for bicycle options.
Most of which are centered around how to choose a bike to begin with.
That’s exactly my question. How are first time tri bike buyers supposed to know what bike to get? I’ve seen one store stress that you should get fit before purchasing a bike. That makes sence to me, but I haven’t seen anyone else say it. If it was the general concensus, you would think more stores would say it.
that’s easy: because bikes have seat posts that go up and down, stems come in different lengths and angles, aerobars are adjustable, and the differences among different brands of bikes really isn’t that big. This business of ‘having to fit you to the bike’ is more marketing than anything else, IMO.
Thank you. Just goes to show how easly we overthink bike fit.
I’ll make it even easier: once you get your saddle height set, bend over and stick your arms out. Really, that will get you 95% of the way there.
Let me ask this: If I go to a shop to get fit (marketing be damned), and it’s apparent I fit better on a make of bike that particular store doesn’t sell, how willing are bike shops to let you walk out the door with your measurements and hit up another shop for purchase of the bike that *does *fit?
While I can’t speak for other shops when it comes to this subject, we at CMS are happy to help an athlete figure out if a given make and model of bicycle will fit them, even if we don’t carry the brand. We look at our fitting more as a service than a direct sales tool. We hope that through displaying our expertise during a fit, an athlete will want to work with us more and will buy a bicycle from us. But there have been countless times that I have done a fit for an athlete looking to get a new bicycle and they have chosen, with my assistance, a bicycle from a brand we don’t carry. Additionally, as part of our fitting services they are entitled and encouraged to return with their bicycle (purchased from us or elsewhere) for a delivery fit to help them get dialed in. The way we encourage people to purchase bicycles from us is to credit back fit costs towards bicycle purchases.
We feel that this overall fitting and sales strategy allows us to remain impartial when it comes to bicycle selection.