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tri v. road bike sizing
CREATED: 01/26/10 by silvercannonca REPLIES: 9
silvercannonca    JOINED: 2/28/09    POSTS: 41
tri v. road bike sizing
POSTED: 1/26/10 2:11 PM

this isn't the same old, tri v. road bike q, rather, the q is specific to sizing. i have a road bike that has been wonderful - a 54cm. i'm looking to get a tri bike as well (doing the Ironman plunge this year). one bike shop told me I should be riding a 52cm. another says, I could ride a 56cm. both shops are local tri shops and both have some good some bad reviews so I don't know what to believe. same bike, same model, one store says go up a size, another says on a tri bike you drop down a size.

any input? those of you who have both, are are tri and road bikes the same size or do you go up or down a size? I'm now very leary of getting a tri bike at all because several k is a lot to plop down for a bike that isn't going to fit -- be it too big or too small.

thoughts?

garydean's ravatar garydean    JOINED: 2/28/09    POSTS: 47
RE: tri v. road bike sizing
POSTED: 1/26/10 3:42 PM

Alas, since this is naturally reoccurring question/issue, it too has addressed, at some length and with some vigor, in previous threads. To forestall fireworks, Sheldon Brown's comprehensive and clear discussion of the topic is recommended: http://www.sheldonbrown.com/frame-sizing.html
Take Aways:
1. These days the most important standardized measurement is top tube size -- but even then comparing two frames mainly in terms of top-tube length is only valid if both have similar seat tube angles While the still in use seat tube measurement (52, 54, etc.) provides a general idea of whether a bike would fit you, it alone is not dispositive. I.e., a 52 of one make or model could fit you as well as a 54 or 56 of another make or model.
2. Before purchasing one should try out the specific frame with the specific stem.

Good luck,
Gary

vatriathlete    JOINED: 2/28/09    POSTS: 682
RE: tri v. road bike sizing
POSTED: 1/26/10 3:42 PM

that is a tough one.

for me personally i was lucky, i fit bascially the same "marked size" on both my road and tri bike, coincidently the toptube lengths on both of my bikes are within 1 cm of each other too.. go figure.

so takeing that into account since you are riding a 54 road going up or down to the next size, which isnt that much "could" be done with each size with some tweaking of the stems and handlebars on each. i'm surprised neither shop recommended the same size tri bike as your road bike.

personally i'm not a big believer in tweaking the stem and handlebars to make a bike fit a person, the correct frame size should get you 99% of the way there and then the stem size should only be there for optimal fine tuning at most, ie slightly change steering feel, small ergo adjustments, etc. but hey that is just my opinion.

you are right 1k or more on a bike is a lot of money to be spending on a bicycle that may not fit correctly.

silvercannonca    JOINED: 2/28/09    POSTS: 41
RE: tri v. road bike sizing
POSTED: 1/26/10 4:06 PM

thanks VAtri, that is helpful. as i mentioned, I was looking at the exact same bike, exact same model, two different stores, and they recommended two very different sizes so the difference between the 52 and 56 recommendation is not solved by difference in bikes -- it's the same bike. i'm with you in not being a tweaking fan. i've tried the 'tweaking' to make the wrong size frame fit once before with disappointing results, and riding a bit down the road and back didn't help detect the problem. a good solid ride, long ride told a different story than a 15 min spin near the bike shop

seems my best bet is to try a third shop and compare the info they give me to the first two - hopefully there is some consensus between two. thanks again

JustinNunez    JOINED: 12/30/09    POSTS: 26
RE: tri v. road bike sizing
POSTED: 1/26/10 5:00 PM

Just got into a similar dilemna myself this past weekend. One shop was sizing me up to be a 54 and the other said 51/52. I expected to be a 54 because I was riding a 56cm road bike but after a few test rides on a 51 and 54, and some professional help on fit adjustments on both, it was decided that I fit much much much better on the 51. Granted, we could have very different types that would make all this meaningless, but I'd suspect that you fit better on the 52 than the 56.

philotri's ravatar philotri    JOINED: 2/28/09    POSTS: 253
RE: tri v. road bike sizing
POSTED: 1/26/10 5:47 PM

No suggestion as to which is right for you although I do suggest riding all the sizes and seeing what feels best.

But, I just saw this article and thought that it might help you a little.

http://www.slowtwitch.com/Bike_Fit/General_Fit_Articles/In_between_bike_sizes__1173.html

BTW, the bike shop should let you take longer than a 15 minute ride so that you can make the right decision. One shop even let my husband bring bikes home overnight. Bring everything you need to make that test ride as similar as you can to your everyday riding - your shoes, pedals, etc.

merlinkim's ravatar merlinkim    JOINED: 2/28/09    POSTS: 294
RE: tri v. road bike sizing
POSTED: 1/26/10 10:11 PM

Remember, as you get more comfortable on the tri bike, you may want to lower your bars. Head tubes on smaller bikes are usually shorter, making a lower position possible than on a larger bike. If this is your first tri bike and you're already bottoming out the stem on the frame (or think you will), then the bike is too big. Don't forget standover height -- if the bike is too big, it can make getting on and off . . . uncomfortable.

silvercannonca    JOINED: 2/28/09    POSTS: 41
RE: tri v. road bike sizing
POSTED: 1/27/10 2:13 PM

Txs Philo,
Spot on article/info.

vatriathlete    JOINED: 2/28/09    POSTS: 682
RE: tri v. road bike sizing
POSTED: 1/28/10 10:26 AM

funny but good article on bicycle fitting

http://xtri.com/features_display.aspx?riIDReport=6206&CAT=3&xref=xx

also good posting on the article that talks about inbetween sizes. funny how that article is saying that length (ie, top tube) is more important than height. lol

bad ford's ravatar bad ford    JOINED: 2/28/09    POSTS: 184
RE: tri v. road bike sizing
POSTED: 1/28/10 2:59 PM

Bottom line is that bigger bikes are faster. My evidence is only anectdotal, but it's worth mentioning that I ride a small bike, and a LOT of people pass me.

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