Triathlon - Tribike size compared to Road bike size
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01-03-10, 08:41 PM
Hi, I'm getting ready to buy a triathlon bike, or a road bike and convert it to a triathlon bike. I have some questions about sizing. I'm 183cm tall, and I have measured my inseam, myself and at a bike shop here in Taiwan. I have been fitted for a large frame road bike, which makes sense, but I have read and heard that tri bikes can be smaller than road bikes.
There are tons of bikes here in Taiwan that are Medium frame and I could pick and choose from many at a good price. However large are much harder to find. If I need a large, I will just shell out and search harder, however, I often see tri riders on TV and youtube, who are riding a frame that looks smaller than I look when riding the large frame. I have long arms BTW. Any advice?
Should I just try a med frame in the store, and see if it feels comfortable? Is there any other way to be sure about the measurements?
Again here are my measurements
height = 181cm
arm length = 65cm
ground to torso = 150cm
01-03-10, 09:29 PM
Given the same bike manufacturer - it's very common for your tri bike size to be smaller than your road bike size. By size however, I'm talking about the difference between say a 58cm road bike and say a 56 or 54cm tri bike. You also have to take into account that different bike builders measure their bikes differently. As a "for instance," my road bike is a 60cm and a perfect fit from maker "A." I built up a 58 cm frame from maker "B" that was too large, and my triathlon bike is a 56cm and a great fit. If you fit a large frame, but are at the top of that range, your tri and road fit could conceivably overlap within that generic frame size.
In short, if I were you I would certainly be willing to try out medium frames. As you are just shy of 6'-0", a medium tri frame would not be unusual. For what it's worth, I'm 6'-1" and ride a 56, which would likely fall in the medium range. I have a friend who rides a 56cm road bike I believe, but a 51cm tri bike. It really all depends on the frame and how you fit on the bike. Also, whether or not you are buying a bicycle with true triathlon geometry or a road bike that you plan to convert will make a difference. If you are looking at frames that come small, medium, large make sure you know what the actual dimensions are. That will help you narrow the search.
Are any of the shops you are visiting able to properly fit you? If not, there is a pretty good online fit calculator on the Competitive Cyclist web site. Perhaps that could help you narrow the field as well. Hope that helps.
i agree with what he said. i ride a 56 road bike, and around a 53 tri bike
I think that there is somewhat of a confusion on the exact nature of road to tri sizing. Many companies have now adapted size naming so that a person who rides a 54cm road bike will also ride a 54cm tri bike, however, the top tube of the two bikes will be different, the road bike being longer.
For instance Cervelo 54cm:
P2(tri) at 78* = 53cm top tube
S2(road) at 73* = 54.5 cm top tube
B2(tri) at 78* = 52.8 cm top tube
F3(road) at 74.5* = 54.5cm top tube
So in effect your top tube will be shorter on your tri bike, but in many cases the size name will be the same. Obviously if your proportions are different than most people or your riding style is different than your bike selection may be different. One clear example is that if you are riding in UCI time trials, then you may need to size down a frame size because your seat will be farther back then if you're riding triathlons.
At ~6' you could probably be anywhere from a 54-58cm depending on the company and their fit characteristics.
01-04-10, 06:58 PM
Triguy points out some good issues. Similar to, "what size(s) is a medium?" it all depends on the bike manufacturer. Numbers, as Triguy points out, may mean different things between bikes as well as manufacturers. I would say that short of getting a professional fit, your next best option would be to determine the best geometry and dimensions for you based on your measurements and fit coordinates, then find a bike that matches those as closely as possible and test ride it.
01-04-10, 07:22 PM
OK Thanks. I will summarize my understanding first: The tribikes have steeper angles than road bikes and therefore may have shorter top tubes. Different companies have different dimensions. I can also adjust a M size frame big, or a L size frame small. Here are my specific measurements and prospective bike dimensions. What are your opinions about where I fit?
01-05-10, 09:03 PM
Quick question, will this bike be used only (or at least primarily) for triathlon, or are you looking for something to do double duty?
01-06-10, 10:24 PM
I will use this bike for commute and for triathlon training and race.
01-07-10, 07:49 AM
I'm sure there are lot's of different opinions on this, so I'll be happy to throw mine into the mix. If it will also be used for commuting (and I assume riding in traffic) I would opt for a road bike with clip-ons. I ran a road-to-tri conversion for a couple of seasons and it went well. I might suggest starting your search based on your road fit. Personally, I have slightly different tastes for my road versus tri setup. I like a long top tube on a road bike, but for my tri bike I wasn't trying to maximize the top tube length. Based on the measurements you have given, and the chart above, I would start trying out large frames first (I think that is what you said a shop previously recommended).
If you really want to crunch the numbers, go to the fit calculator again and run it for a triathlon/TT scenario to get your Aero fit - then compare those numbers to the road bike fit. In your case, you'll be looking to see what type of overlap you can get - perhpas with the help of a forward facing seatpost.
01-07-10, 09:19 AM
Thanks for your cents. I will def use clip-on aerobars, and take them off for the commute. I am considering one particular M sized bike, so I can post the measurements and dimensions and see if that sparks any thoughts. According to the road fit calculator, I would be __ short for the M bike I'm considering, but I would like to try and make that up with a longer flipped stem and just maxing out the bike. It's my first road bike, and maybe I'm doing a bit too much thinking before I really know. Time to go to the store and ride a few more. :D:D They have the bike I am considering at the bike shop, but I don't think they want to haul it down and let me try it on the stationary rollers, because I won't buy it from them.... although I wish they would because even though I will buy the frame from someone else, I will need other accessories I would buy from them. I'll go in and ask them nicely :D:D ;)
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