Road bike sizing

[Chadvdw67]

Hey guys, hoping you guys can help me, I am considering getting a "new" road bike, but the sizing on them confuses me a little, I know that I would need something between 54 and 56, but would I size smaller for a more comfortable ride, or bigger? I prefer a more upright riding position, I spend 90% of my time riding on the hoods, I very seldom get down into the drops, only when "supertucking" on a downhill 🤣 and for corners, also mainly when going downhill, but I am not really sure what size bike I should be looking at?

 

For reference, I am 183cm tall (6.0' for you imperialists) and 100kg, riding a Large MTB....

[MongooseMan]

IANABF (I am not a bike fitter), but my experience has been size down, then add a longer stem.

That way the bike is less twitchy, plus you've got more room to play with.

Go too big and you're left with a 6mm stem, and not much to go from there.

I speak from experience, also ~182cm, currently have a 56cm, and my next bike will likely be a 54.

Edited October 15, 2022 by MongooseMan

[guidodg]

you most definitely need a 56cm unless you have relatively short legs and arms for your height

I am 178cm with an 87cm inseam and ride a 56...cannot imagine riding anything smaller

[MongooseMan]

Let's also be very clear that a simple "56cm" measurement has almost no meaning anymore across various bike brands. You're really struggling to compare like with like when using only that metric.

A good resource for comparing across multiple metrics: https://geometrygeeks.bike/

Edited October 15, 2022 by MongooseMan

[Thomo]

Most would suggest that the key measurement is the top tube ... so +-56cm there irrespective of whether the brand calls it S,M or L.

That said, the other measurements and angles all play a role and can influence recommended size.

[Sandro]

What's your inseam measurement, that's more of an important question? I'm 1.85m and ride a 56cm frame. Agree with Mongooseman and also prefer slightly smaller as opposed to big.  

[100Tours]

I ride anything between a 53cm Pinarello and a 56cm classic frame. So it depends a little on the bike you're looking at (not helpful I know).

Personally the most important dimension (for me) is reach - which for purposes of my analysis you can take as the distance from your elbow to your fingertip.

if you place your elbow at a right angle against the tip of the saddle then your fingertips should reach to the middle of the stem (forearm horizontal) on a road bike. You can adjust the saddle position and the stem length to make this work, but if the saddle is reasonably centered and the stem is between 80 and 120mm you'll be about right. Longer stems are also possible, but if you're new then start with something in the middle of the range.

The larger frame will have a higher front/longer head tube, which supports a more upright position. Also the longer (large) bike will be more stable. The smaller frame conversely will be more responsive, and stiffer, and lower.

 

Edited October 16, 2022 by 100Tours

[Dappere]

On 10/15/2022 at 12:16 PM, Chadvdw67 said:

Hey guys, hoping you guys can help me, I am considering getting a "new" road bike, but the sizing on them confuses me a little, I know that I would need something between 54 and 56, but would I size smaller for a more comfortable ride, or bigger? I prefer a more upright riding position, I spend 90% of my time riding on the hoods, I very seldom get down into the drops, only when "supertucking" on a downhill 🤣 and for corners, also mainly when going downhill, but I am not really sure what size bike I should be looking at?

 

For reference, I am 183cm tall (6.0' for you imperialists) and 100kg, riding a Large MTB....

@Chadvdw67 A lot of us have been here, while the advise received by fellow hubbers are valuable. Save yourself a lot of disappointment and money and go to see a bike fitter. 

They will be able to help you select the correct size, based on your goals and anatomy. Some bike shops might have a fitter in-store that could also assist, just be cautious of the brand bias. 

There are too many variables to consider, height alone can't guarantee a good fit.  

[EddieV]

57 minutes ago, Dappere said:

@Chadvdw67 A lot of us have been here, while the advise received by fellow hubbers are valuable. Save yourself a lot of disappointment and money and go to see a bike fitter. 

They will be able to help you select the correct size, based on your goals and anatomy. Some bike shops might have a fitter in-store that could also assist, just be cautious of the brand bias. 

There are too many variables to consider, height alone can't guarantee a good fit.  

 

Bike fitting might seem like a "grudge payment", but from personal experience I would also recommend it. I have long limbs and a short torso, and bike fitting never use to be an issue until compact frames with their non-standard geometry and specs came around.

Luckily, according to the bike-fitter, I'm somewhat flexible and with the addition of a setback seatpost and slightly shorter stem could make me fit comfortably on that purchase. (a decade ago) 

I have all the measurements saved ie. angle and distance from BB to seat, and distance from seat to handlebar, reach, height/drops etc. for whenever I build up new (old) bikes. 

At 1.79 my perfect framesize seem to be a 55cm old school steel frame, with a longer seatpost 😁

 

 

 

[Thomo]

2 hours ago, Dappere said:

...  just be cautious of the brand bias.  

... and stock availability.

Some will try to convince you that whatever is on the floor is your size. 🙈

[Bub Marley]

Bike fitting is great when you need to dial in your dimensions to the tee. OP is just looking for advice on frame sizing and generally speaking most people fill in between 2 sizes. My 2c here is, if you want a more aggressive position, pick the smaller option of the 2. If you go for the smaller size, you’ll generally compensate with a longer stem etc. If you want a more upright/endurance position, go for the larger frame. 

 

[Dappere]

1 hour ago, Bub Marley said:

Bike fitting is great when you need to dial in your dimensions to the tee. OP is just looking for advice on frame sizing and generally speaking most people fill in between 2 sizes. My 2c here is, if you want a more aggressive position, pick the smaller option of the 2. If you go for the smaller size, you’ll generally compensate with a longer stem etc. If you want a more upright/endurance position, go for the larger frame. 

 

Sure, let's say the OP went with that logic. Aggressive = smaller frame, Endurance/upright = larger frame. 

OP goes for aggressive setup (smaller frame), gets a bike setup and the stack of the bike is too small to get them into the correct position, OR,  OP goes for an endurance/upright setup (larger frame) and has to run a 70mm stem to get into the correct position. 

In order to make decisions on frame size, you need certain guides, guides that a bike fitter could provide, and can save you the hassle of having to sell a bike you just bought. 

[lechatnoir]

4 hours ago, EddieV said:

 

Bike fitting might seem like a "grudge payment", but from personal experience I would also recommend it. I have long limbs and a short torso, and bike fitting never use to be an issue until compact frames with their non-standard geometry and specs came around.

Luckily, according to the bike-fitter, I'm somewhat flexible and with the addition of a setback seatpost and slightly shorter stem could make me fit comfortably on that purchase. (a decade ago) 

I have all the measurements saved ie. angle and distance from BB to seat, and distance from seat to handlebar, reach, height/drops etc. for whenever I build up new (old) bikes. 

At 1.79 my perfect framesize seem to be a 55cm old school steel frame, with a longer seatpost 😁

 

 

 

Best money I've ever spent on my bike. A decent fit might end with me spending money on contact points and stem/seatpost, but it means more comfort on the bike, I'm all for it. It also means more power, or in my case, a LITTLE more power, so the end result is further, faster in more comfort. I can't understand why more people with more than a passing fancy in cycling don't get a proper bike fit

On bike sizing, my bike fit showed that I ideally needed an XL mtb (spez chisel) over the L i'm on currently, but my 54 roadbike is 100s (i'm 179, but shrinking).... it's down to the bike geo I was told

Edited October 17, 2022 by lechatnoir

[Jewbacca]

I'm 1.74cm short and ride a size small ladies road bike (I think it's a 50) with a 120mm stem.

The bike is gold. 

I can adjust my stack height beautifully, play with position using stem length and spacers as well as get my weight nice and far forward over the front wheel for traction, out the saddle efforts etc...

In no world would I ever ride a road bike that was too big for me. Zero

[Eldron]

Frame sizing, height and inseam are enough to buy a new bike around 40% of the time in my experience.

The other 60% have atypical bodies and need a body measurement to get the right size and geometry bike (inseam, arm length, torso length and flexibility minimum).

As an example - if you have a long torso and short legs then aero/sprint bikes are great for you. If you have a short torso and long legs then more endurance style geometry is best for you.

Most fitters will offer a measuring service if they're decent.

Frame sizing is also a mine field - measuring the seat tube gives you very little idea on how big a bike is.

Unless you know your ideal Stack and Reach chances are you won't end up on the right geometry or size.

Most fitters should offer a dual fitting - the first appointment is body measurement and assessment - this will yield enough info to find the right geometry&size. Part 2 will be fitting you to the right bike.

 

 

[Eldron]

2 hours ago, Dappere said:

Sure, let's say the OP went with that logic. Aggressive = smaller frame, Endurance/upright = larger frame. 

OP goes for aggressive setup (smaller frame), gets a bike setup and the stack of the bike is too small to get them into the correct position, OR,  OP goes for an endurance/upright setup (larger frame) and has to run a 70mm stem to get into the correct position. 

In order to make decisions on frame size, you need certain guides, guides that a bike fitter could provide, and can save you the hassle of having to sell a bike you just bought. 

100%

Small = aggressive/Large = endurance is a myth.

A bike with a long Reach and low Stack is aggressive. A bike with a short Reach and high Stack is endurance. A bike with more aggressive geometry will be "aggressive". A bike with relaxed geometry will be more comfortable/endurance.

The smaller sized bike will be a tad stiffer and handle a but more directly. Larger sized bike will be a little bit more comfy and a little slower to react to changes in direction.

 

I really don't understand the reluctance to get fitted. It costs a fraction of the price of a new bike (probably around the same as a new part for your bike) but has a MASSIVE effect on your long term comfort, efficiency and injury prevention.