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I am going to buy a road bike. I am considering a Trek 1.2.

I used the Competitive Cyclist Fit Calculator to find the size of bike that fits me.

Inseam:             80.5  
Trunk:              59.5  
Forearm:            36  
Arm:                67.2  
Thigh:              57.4  
Lower Leg:          53.7  
Sternal Notch:     138.1  
Total Body Height: 171

All the measurements are in cm.

The ranges that are given in the results are these:

Seat tube range c-c:   52.1 - 52.6 for competitive fit.  
Seat tube range c-c:   53.3 - 53.8 for eddy fit. 

The purpose of my bike is going to be able to do long distance mainly. I cannot afford another bike for racing but I will most probably be doing Ironman from next year using the same bike. But I personally think that riding 180 km in 8 hr is endurance and not year.

Now which size should I go for? 52 or 54?
Should I just check the standover height of the bike? Or I should I look into something more than that?

I am asking this because in India not many shops deal with Trek road bikes. The Trek 1.2 is only available at one shop. That fellow says he won't allow me to test ride the bike. So I am in a bad situation. I want to buy this bike but the right size. The whole geometry is available in the site I have given. Ask for more information, if needed.

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Generally questions about bike fit generate lots of conflicting advice and personal opinions. There are very good questions with practical answers out there, but all of them will recommend you ride the bike with help from a LBS. Additionally, take any and all advice about bike fit with a grain of salt. –  WTHarper May 28 '13 at 16:30
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Unfortunately, I don't believe this question is a good fit for our site and I'm closing it. First, bike fit depends on your flexibility and type of riding, so there's not enough info to answer this. Second, there's much disagreement about bike fit details so this is likely to get into opinions, debate and/or argument. Third, this is unlikely to ever help anybody else. Fourth, really you should go down to a bike shop and try out both bikes in both sizes. If you can think of a way to edit that fixes those problems, go for it and flag for a re-open. –  freiheit May 28 '13 at 17:43
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@Freakyuser: I think your changes help quite a bit, especially spelling out why you can't do a test ride... –  freiheit May 29 '13 at 16:42
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That's up to you. Basically, a shop that won't give a test ride is unlikely to be there if there's something wrong with the bike later on. –  Daniel R Hicks May 30 '13 at 11:11
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I think this question needs more work and cannot be answered in more than a general way without it. It says you want a Road bike and your calculator gives you two options Competitive and Eddy fit. What are you going to use your bike for? Competition, Touring, Commuting? How much experience do you have? What kind of bicycle have you been riding and for how long. The point being do you need to be fit onto a bike that will be competitive but not comfortable, or comfortable but not competitive? –  Joe May 30 '13 at 13:57

6 Answers 6

up vote 3 down vote accepted
+50

I think you could ride either size comfortably. You may need to change the stem to accommodate your longer reach, but the range of adjustment for the seat is what you want to look at, not so much the seat tube length. When you look at sizing, the reach is as important as the height. But good fit can be achieved within a range of values; I think it is better to think of proper fit as a range of values rather than a point estimate.

measurement diagram

You can obviously change the reach by changing the stem.

I faced a similar problem as you. My current main ride was an eBay purchase. It has the same sloping top-tube (TT) design as the one you are looking at. The nominal size is very different than my other road bike, so I used the CC Fit Computer to help me decide if the bike would fit, and 5,400 miles later I can tell you it fits very well.

The geometry of the Trek 1.2 is here; the geometry of my bike is here.

Just for the sake of comparison, my CC Fit measurements/results are:

Measurements

Inseam: 85.1
Trunk: 67.3
Forearm: 33
Arm: 61.6
Thigh: 59.7
Lower Leg: 57.8
Sternal Notch: 143.5
Total Body Height: 175.3

The Competitive Fit (cm)

Seat tube range c-c: 55.1 - 55.6
Seat tube range c-t: 56.8 - 57.3
Top tube length: 54.6 - 55.0
Stem Length: 11.2 - 11.8
BB-Saddle Position: 80.6 - 82.6
Saddle-Handlebar: 52.4 - 53.0
Saddle Setback: 4.0 - 4.4

The Eddy Fit (cm)

Seat tube range c-c: 56.3 - 56.8
Seat tube range c-t: 58.0 - 58.5
Top tube length: 54.6 - 55.0
Stem Length: 10.1 - 10.7
BB-Saddle Position: 79.8 - 81.8
Saddle-Handlebar: 53.2 - 53.8
Saddle Setback: 5.2 - 5.6

The French Fit (cm)

Seat tube range c-c: 58.0 - 58.5
Seat tube range c-t: 59.7 - 60.2
Top tube length: 55.8 - 56.2
Stem Length: 10.3 - 10.9
BB-Saddle Position: 78.1 - 80.1
Saddle-Handlebar: 54.9 - 55.5
Saddle Setback: 4.7 - 5.1

Your measurements show that you have a longer reach than I have, but shorter legs.

My bike is a nominal 53 cm (refer to the sizing chart) but the virtual frame size (the size if the TT was level) is a 56. I have it set up right now with the saddle at 70cm above the center of the BB and the reach set at 62 cm.

As for you, because your arms are longer, I think you would probably like the 54 better, but I do believe you could ride the 52 comfortably, perhaps with a slightly longer stem. My guess would be that the stock stem is 100mm.

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That was a very useful answer. I want to chat with you. Any possibility? I am Raghul Trekker in fb. –  Freakyuser Jun 1 '13 at 6:05
    
Glad to help, please consider chatting here so that others may benefit if they stumble on this thread in the future. –  Zippy The Pinhead Jun 1 '13 at 16:57
    
I thought of chatting about bikes specific to brands, which the community won't welcome. –  Freakyuser Jun 1 '13 at 17:06
    
BTW, do you have a compelling rationale for going with Trek? I have nothing against Trek-- I ride a Trek on dirt-- but are there not other brands you can explore? How do the Trek prices compare with other brands/manufacturers? My main road bike has a frame by Dodsun (made in Taiwain), and it is an excellent bike, and a much better value than Trek. A couple of friends are riding a Trek Domane and they really like them, but I still beat them on value. –  Zippy The Pinhead Jun 1 '13 at 17:06
    
The trek I am looking for is 1.2 (2012) which comes at a cost 42 k with Sora components and carbon fork. All other brand come with the same specs at 45 k minimum. Moreover the brand name pulls me with the less cost. –  Freakyuser Jun 1 '13 at 17:16

I remember one of the old Discovery Channel team mechanics, said the difference between Trek sizes isn't that big (2 cm) so their riders could use 1 size smaller or bigger. Other than fit, there's also personal preference, like going smaller to get a lighter frame, and pros do this.

So, don't sweat about it too much. If you have a pretty good guess about your perfect size, than 1 size smaller or bigger wouldn't matter much. Even if you did a test ride, I doubt that it will help much if you didn't have a good idea of what to expect. Even if you could get a perfect size (53 cm), because it's only based on seat tube length, it might not give you the perfect fit still because the top tube length could be shorter/longer for you.

You can adjust differences in seat tube length by adjusting seat post and switch stems to accommodate top tube length. I used to ride 52 and now riding 50 madone because the 52 was sold out and that 50 was heavily discounted. The shop shown me that even with smaller frame the measurements are still the same as the old bike.

That said, if you're thinking about ironman, I think you should go with the 54 because the the wheelbase is longer and will give more stability. Usually TT bikes have longer wheelbase.

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I guess that's one advantage of going with a big name like Trek. They do enough volume that they can afford to make very small size increments in their sizes, and still sell lots of each. Compare that to a smaller manufacturer, like the one I bought my last bike from, and the difference between the one I bought, and one size smaller was very noticeable, even after only 1 minute of riding. I could see how some riders would fall in between the 2 sizes and wouldn't be comfortable on either size. –  Kibbee Jun 4 '13 at 13:59
    
@Kibbee It could also depend on the geometry. Giant, for example, only have 6 sizes for their top model and you probably would fit size M which could probably be size 52-56 on Trek, and minus the headache. When correctly set up, you shouldn't notice any difference, it's just that there's a limit how you can setup up one frame size for a rider. I think you're within those range and the biggest difference between the sizes are weight and wheelbase. –  imel96 Jun 5 '13 at 2:27

The simplest correct answer is that without a test ride, you can't guarantee the correct fit. That is why test rides exist.

Either bike may be within the correct range, but you dont know which is better, until you ride them, and no one can tell you which is better, when you are looking at 2 bikes that are both in the right range.

It is a subjective decision, based on how the bikes feel to you.

Denying you a test ride is denying you the ability to get the right bike, guaranteed.

I know you want a different answer, but you need to look at a shop which will let you ride the bikes, even if it means going with a different brand or model.

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Buying a bike without riding it is a terrible idea. Similarly terrible ideas would include ordering a mattress without laying on it, laying down cash for a guitar without playing it, and purchasing bike shorts without trying them on. And I agree that any shop that won't let you test ride a bike is pretty suspicious. I'd try to take my business elsewhere.

That said, we live in a non-ideal world. Sometimes the perfect deal comes along, or you just plain need something and have to take a chance and buy it sight-unseen. In this answer, I'm assuming that you've tried to find other ways of riding the bike (asked friends, looked for other shops, etc.) and have failed to get that test ride.

There are ways to make an imperfect frame fit, if the sizing isn't too far off. Extra-long stems and seatposts, barends, saddle rail extenders... all of these are gadgets that you can buy to help get yourself on an ill-fitting bike. If you make some good guesses, yu can avoid using any of these contraptions.

What can you do to mitigate the risks?

First off, I'd read up on bike fit as much as possible. This way, you can make guesses that are informed guesses.

With any frame, even a custom-built one, you'll end up adjusting saddle-to-pedal distance, reach, handlebar height, and frame size. It sounds like you've narrowed things down to a couple of sizes; that's great, as it makes your job much easier.

A DIY true

Narrowing it down

In the two sizes you've chosen, which one will allow you more latitude when dialing in your fit?

If, for example, the smaller frame barely has enough standover height, that's a point in favor of avoiding the larger one. If the smaller frame would need an extraordinarily long stem to get a good reach (that's the saddle-to-handlebar dimension), that's a point in favor of the larger frame.

And so on. Tally up all of these factors and see which frame makes the most sense.

Can this possibly work?

Speaking as someone who owns a built-to-order road bike, who put money down before the thing was even built: It's possible to do this if you know what you want and know what's important to you.

An awful lot can go wrong. You've made a lot of guesses, based on your experience with other bikes, reading spec sheets, and just plain hoping your gut feelings are right. If you can't afford to los the money you'd spend on this bike, I'd think twice before ordering.

If it's possible to wait a while and test-ride a bike then (maybe you're going on vacation later this year and can hit some shops then?) (is a road tide coming to town? Put out a classified ad) I'd do that.

But if not, try to ride some other road bikes and get a good idea what's important to you in road bike fit. Remember that you're gambling a bit with your money, make the best guesses you can, and hope. The worst-case here is that you end up selling the bike and taking a loss.

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1  
This is a great and very complete answer. –  amcnabb May 31 '13 at 17:59
    
Getting a custom built frame is probably a little different in the sense that I assume that the builder does their best effort to ensure the bike will fit will, based on measurements of the rider and other bikes that the rider feels comfortable on. Whereas the builder of a manufactured bike has no idea who will be riding it. I guess you could do the opposite, by comparing the measurements of the bike you are planning to buy, and a bike you are comfortable with, and try to figure out if they are somewhat similar. Or find a bike with similar measurements, and take that for a test ride. –  Kibbee May 31 '13 at 19:39
    
Of course it's different, I'm just using this as a logical extreme to make my point. With enough care, you can theoretically know what will fit by just using measurements. –  Neil Fein May 31 '13 at 19:41

It seems odd that somebody wanting to sell a bike to you wouldn't allow a test ride. Most places encourage you to take the bike for a test ride, at least around the parking lot or around the block, and usually with a bike store employee following closely behind. If they can't offer you a test ride, perhaps you could persuade them to mount the bike onto a trainer. That would at least give you some sense of how the bike fits, although doesn't tell you much about how it handles. Another option is to find a bike rental service that has the same model bike that you are planning to buy (some rental services even sell their old bikes). This can give you the opportunity to try out the bike for an extended period. If you still can't get a test ride, I'd opt for a different bike from a different shop that does allow test rides. There's nothing particularly special about the Trek 1.2 that you can't find in 100 other bike models, which are available in lots of different stores. I wouldn't recommend buying a bike without actually riding it first.

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+1 for giving me some stern opinion. –  Freakyuser May 30 '13 at 11:49

I would advice to visit your Local Bike Shop (LBS) and try out ideally both bikes in both sizes. But at least try a bike in each size; and/or discuss with the LBS and have him measure your inseam and see what he says.

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what is LBS? Every bike has different frame size. So I thought people would know the frame size for trek bikes. –  Freakyuser May 28 '13 at 15:49
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LBS = Local Bike Shop. –  sevargdcg May 28 '13 at 16:14
    
Local bike shops don't have trek road bikes at all. I am buying this from a neighboring state (within India) and he is not allowing me for a test ride. I have edited the question with the help of 2 other people. –  Freakyuser May 30 '13 at 10:02
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Does it have to be this Trek? Find a dealer who'll let you have a test ride, you'll be in for better service in the long run. –  alex May 30 '13 at 10:44

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