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Impact of a bike one-size too small

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Impact of a bike one-size too small

Old 05-25-13, 04:14 PM
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gsa103
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Impact of a bike one-size too small

I had been considering buying a new bike. There's some decent local deals.

A friend who I ride with offered to sell me his old (2009) CF Trek (its either a 3. or 4.) with full Ultegra group.
The frame quality and group would be a large step up and exactly what I'm looking for, at a very good price.

The catch is that its a 54cm frame. My current frame is a 56cm and based on some online fit calculators, I need a 56-57cm TT.

How bad a time will I have trying to get comfortable on a frame that's slightly too small? I've test ridden the bike, and it felt better than my current bike (which could use some fit improvements). I did notice that the frame felt more twitchy, but not excessively.
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Old 05-25-13, 04:18 PM
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I wouldn't buy a bike that's too small. The only way I'd buy that bike is for the parts gruppo (assuming it was priced accordingly) to use is as a donor bike for a frame I was building up.
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Old 05-25-13, 04:20 PM
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IMO, for comfort, you are better off with a proper size frame.
You may need a different seat post and a longer stem to cram yourself onto that frame. How tall are you?
At not quite 5'9" I find a 54cm fits me well. But my buddy of the same height with stumps for legs and t-rex arms needs a 52cm.
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Old 05-25-13, 04:29 PM
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A 54 to 56 is actually 2 sizes. If you can still get your saddle far enough back because of the seat tube probably being steeper, you may be able to get away with it with a longer stem.
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Old 05-25-13, 04:47 PM
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Originally Posted by ricohman View Post
IMO, for comfort, you are better off with a proper size frame.
You may need a different seat post and a longer stem to cram yourself onto that frame. How tall are you?
At not quite 5'9" I find a 54cm fits me well. But my buddy of the same height with stumps for legs and t-rex arms needs a 52cm.
I'm 5'11", with short arms/legs (30" pants inseam), and a long torso. The seat post doesn't seem to be an issue, since I've ridden the bike, and the seat goes plenty high enough.

Longer stem might would possibly be needed.

What's the best way to evaluate how a fit is needed?

As a side note, LBS has a 2012 Bianchi Infinito Ultegra for $3100...That bike is sexy...Very tempted but more than I want to spend given my casual riding profile. (~50/wk mostly hill climbing).
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Old 05-25-13, 04:59 PM
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Originally Posted by gsa103 View Post
The catch is that its a 54cm frame. My current frame is a 56cm and based on some online fit calculators, I need a 56-57cm TT.
.
But what size is the top tube?
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Old 05-25-13, 05:07 PM
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Ride it? Post some pics of yourself on the bike?
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Old 05-25-13, 05:08 PM
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Make a offer on the Bianchi,like 2500.00
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Old 05-25-13, 05:11 PM
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i disagree with the other advice in this thread.

i am 5'10 and ride a 52. this is after years on a 56 and never quite feelin right.

i think its a lot easier to make a small bike work w longer stem and more seatpost and spacers than the other way around. shortening the stem makes your ride twitchier, and longer just makes it smoother.

if it was a lot too small, it'd be more concerned but "slightly" as you put it, i wouldnt worry about it.

my two cents. racer, former messenger, all season 10k mile/year commuter and tourer, fwiw.
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Old 05-25-13, 06:14 PM
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Originally Posted by longbeachgary View Post
But what size is the top tube?
Sizes were effective TT measurements on the bikes.

Trek actually labels the effective top-tube as 53.8cm.
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Old 05-25-13, 06:16 PM
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Originally Posted by badhat View Post
i disagree with the other advice in this thread.

i am 5'10 and ride a 52. this is after years on a 56 and never quite feelin right.

i think its a lot easier to make a small bike work w longer stem and more seatpost and spacers than the other way around. shortening the stem makes your ride twitchier, and longer just makes it smoother.

if it was a lot too small, it'd be more concerned but "slightly" as you put it, i wouldnt worry about it.

my two cents. racer, former messenger, all season 10k mile/year commuter and tourer, fwiw.
tell me about it!
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Old 05-25-13, 06:19 PM
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Originally Posted by gsa103 View Post
Impact of a bike one-size too small
http://roadcycling.com/news-results/extreme-positioning
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Old 05-25-13, 06:25 PM
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At 6'1" I was sold a 58cm and some sales guys even tried to push a 61cm on me over the first 2 years of road cycling. One day, my dream bike was on some sort of extreme clearance sale, but it was a 56. I figured, what the heck, I'll give it a go and boy am I glad I did. I did end up putting a 120mm stem on it and I use a thomson setback seatpost, and after that it is my favorite of 5 bikes to ride now. So comfy, no pains anywhere, and just feels "right".

IMO it's easier to make a small bike fit than a bike that is too big, so if the bike feels ok on the test ride there's probably a good chance you can make it fit perfectly with a few part swaps.
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Old 05-25-13, 06:28 PM
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Originally Posted by gsa103 View Post
Sizes were effective TT measurements on the bikes.

Trek actually labels the effective top-tube as 53.8cm.
that's cause Treks, for many years, come out slightly undersized for their 'label' in comparison to many other brands...
the size label means very little, get actual measurements and compare to actual measurements of what you're riding or what measurements you ideally would like to set to. Then consider what adjustments you'll need to make in stem, rise and setback to reach what you want.
Then consider that the bike will ride not as nicely, as nicely or better than you hoped...
I have a very nice Felt frame, which by all measurements should be a great fit for me, I rode it for a few days, made some adjustments, but could not get to liking the ride... nothing you could hang the cause on... it is of course, the rider. that's why there are so many different bikes in the same sizes... no accounting for the rider... and that's the important thing...
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Old 05-25-13, 06:32 PM
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Originally Posted by gsa103 View Post
Sizes were effective TT measurements on the bikes.

Trek actually labels the effective top-tube as 53.8cm.
Oh that's too bad. IMO, you are better off on your bike that fits than on a better bike that doesn't.
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Old 05-25-13, 07:13 PM
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I'm currently riding a 44cm (49cm tt) bike as my race bike (particularly because it was cheap, durable, and I wouldn't mind crashing it too much). My previous bike was a 49cm (52cm tt).

I'm 5'5" with relatively long legs and arms, but a short torso. Most fit calculators would put me on a 50-52.

That being said, aside from the difference in the angles of a very small bike to a more standard size bike, the difference is miniscule. Just increase stem length and seat post length and/or setback.

Edit: A good guidline is to not go less than 80mm or more than 120mm on your stem. Also, using a stem-raiser is a no-no. You should be able to find a comfortable position on your bike with 0-20mm of spacers under your stem. Too small is better than too big pretty much always.

Last edited by EdIsMe; 05-25-13 at 07:16 PM.
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Old 05-25-13, 07:18 PM
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Originally Posted by EdIsMe View Post
I'm currently riding a 44cm (49cm tt) bike as my race bike (particularly because it was cheap, durable, and I wouldn't mind crashing it too much). My previous bike was a 49cm (52cm tt).

I'm 5'5" with relatively long legs and arms, but a short torso. Most fit calculators would put me on a 50-52.

That being said, aside from the difference in the angles of a very small bike to a more standard size bike, the difference is miniscule. Just increase stem length and seat post length and/or setback.

Edit: A good guidline is to not go less than 80mm or more than 120mm on your stem. Also, using a stem-raiser is a no-no. You should be able to find a comfortable position on your bike with 0-20mm of spacers under your stem. Too small is better than too big pretty much always.
A longer stem can change the handeling characteristics of the bike.
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Old 05-26-13, 12:42 AM
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Originally Posted by EdIsMe View Post

That being said, aside from the difference in the angles of a very small bike to a more standard size bike, the difference is miniscule. Just increase stem length and seat post length and/or setback.

Edit: A good guidline is to not go less than 80mm or more than 120mm on your stem. Also, using a stem-raiser is a no-no. You should be able to find a comfortable position on your bike with 0-20mm of spacers under your stem. Too small is better than too big pretty much always.
One should never use the saddle setback as sized adjustment. Saddle setback is critical to pedaling efficiency and knee well being. Going too far back or forward to fit on a bike can seriously f up your cycling. Switching stems is the key.
Also, too short a stem might be problem, but I notice no great difference in handling when comparing a 120mm and a 140mm stem. this af course is for a taller rider, but goes to say it's all proportionate. For a short rider a 120mm stem might be way too long.

A silly article with lots of assertions but absolutely no evidence. One might write an article about how modern bikes handle massively better than the older models from the 70's and it would be as right as that particular article.

But of course, don't cram yourself on a 52 frame if you normally ride a 56/58
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Old 05-26-13, 12:56 AM
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Originally Posted by gsa103 View Post
I'm 5'11", with short arms/legs (30" pants inseam), and a long torso. The seat post doesn't seem to be an issue, since I've ridden the bike, and the seat goes plenty high enough.

Longer stem might would possibly be needed.

What's the best way to evaluate how a fit is needed?

As a side note, LBS has a 2012 Bianchi Infinito Ultegra for $3100...That bike is sexy...Very tempted but more than I want to spend given my casual riding profile. (~50/wk mostly hill climbing).
Your leg length might suggest that you ride a smaller frame but your upper body and reach are what makes the 56-57 cm frame the right fit as the seatpost measurement is rather meaningless.

You would probably find a 52cm frame to be too cramped up top and would have to compensate with a very long stem which will throw off the handling... we'd be looking at a stem of 130-140mm to equalize the reach for a 56 cm frame.

At five foot nine and a bit I have a 33 inch leg and my range of fit is 52-55 and top tube measurements are key... my road bikes are 53 - 55.5 at the top tube (custom built frames) with small variances in the stem length (80-100mm) to make them fit properly.
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Old 05-26-13, 05:32 AM
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One size smaller generally works for people, but once you have to start looking for absurdly long stems and your seat post looks like a telephone pole then there might be problems.
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Old 05-26-13, 08:11 AM
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Honestly, we're talking about 2cm here, I'd say you'd be fine.

If it's a friends bike, see if you could ride it for a week before purchasing and if it's uncomfortable, don't buy it.
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Old 05-26-13, 08:18 AM
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He should swap with the guy who had a 56 CAAD and needs a 54.
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