Choosing between small and medium frame size

alxb

Hi all!

I am the not-so-happy owner of a new road bike. Why not so happy? Because I have doubts that I have brought the right size and I am considering changing it for a smaller one.

On the merchant's site, Decathlon Belgium , there is conflicting information related to sizing.

I am at 168 cm and one sizing table from their site suggested a small ( size 48) for height between 165 and 173 and medium (50) for height 173-182. In another table from the decathlon shop it was suggested medium for my height.

Finally I have bought the medium, size 50, based on the fact that on the small it was unconfortable for my upper back (the handlebar felt close and low ). Also on their site was a remark that when being in between sizes one should choose the upper size for more comfort.

The medium felt ok when riding in the shop, but now after riding for more than 10 minutes I fell that I am stretching for the handlebar. Since it is my first road bike, having ridden mostly mountain bike and city bike until now, I don't know how should a road bike feel.

I have reversed the 100mm stem to point up, also moved the seat forward, it is better but still I feel too stretched.

I am thinking about keeping the medium and trying an adjustable 90mm stem, and/or a steering tube extender.

The other choice would be to try to change to the small bike, if they agree, to move the saddle slightly back and to buy a longer stem and/or a steering extender.

I found some shops with Retul bike fit around Brussels, the price is close to half of the value of the bike, so I am hesitating.

Would be useful to hear if you had similar experience with your first road bike.

Since it seems that both the small and the medium need some adjustment, which one would you choose ? Also what is the reason behind the remark to choose bigger frame for comfort?

Any advice would be appreciated!

mariamartinez

my advice....is to send the fastfitnesstips guys your dimensions and they will send you ideal bike geometry and fit, at least they did for me, and I know they have a clever calculator on sizing. However if you bought a slightly large bike and your bars are too far, then just buy a shorter stem and take out some spacers to lower it. If the bike is much too big, then yes you run into problems with the stack height and the effective top tube. This is why its better to go one half size smaller than one half size bigger.

StillGoing

The advice of going for the larger size flies in the face of almost everyone else. Size down and fit a longer stem if necessary. You can make the smaller frame fit with a longer stem and setback, but you'll struggle to make a too large frame fit. Shortening the stem length could have an effect on the handling.

https://youtu.be/B69I_uayeMA

lesfirth

I have found that moving your saddle forward to reduce reach does not work. I feel it puts more weight on your hands. Try fitting a shorter stem. I have not found that it makes your bike "twitchy" as has been suggested on this forum. Building up core strength is of great benefit.

keef66

Which bike? I'm 168 cm too and looking at for example their Triban range I'd be choosing the small. I have longer legs and a shorter torso, and I know from experience I need a top tube of 540 or less otherwise I feel too stretched out.

The downside is on a smaller frame I need more seatpost showing, so the saddle to bar drop can be an issue, usually addressed with spacers and a flipped stem.

Matthewfalle

lesfirth wrote:

I have found that moving your saddle forward to reduce reach does not work. I feel it puts more weight on your hands. Try fitting a shorter stem. I have not found that it makes your bike "twitchy" as has been suggested on this forum. Building up core strength is of great benefit.

agree.

saddle backwrds and forwards only affects positioning of knee over b/b

shorter stem should bring it all in, try and keep things level as raised/lowered stems increase reach.

i would go back, explain, try the small for a decent ride and get it set up for you - longer stem, high seat post. if you look at the pictures of my bikes on on the "your bikes" thread they all have high seat post, normal stem

#tightposition

webboo

When sat in the saddle with your hands on the brakehoods when you look down do the handlebars stop you seeing your front hub.
If so it’s the right size. Behind the hub stem is too long, in front too short.
However if it is several cm’s either way then the frame may be the wrong size.

smudgerii

I have to Btwin 540 in small and at 172cm the small is the perfect size for me

diamonddog

You bought the wrong size, take it back and change it for the Small.

alxb

Thank you all for the advice!

Also after reading about stack size in your comments I took a closer look on this and I think I need a bigger stack size for more confort (less neck pain). The small and medium sized frames have the same reach, but the stack size is smaller on the medium, so I will focus on the medium and raise the handlebar somehow.

I will go today to a shop to have a bike sizing . It seems to be cheaper than a bike fit. Maybe they will tell me how much and how can I safely rise the handlebar. I am thinking about extending the steering tube with 5 cm.

pilot_pete

AlxB wrote:

The small and medium sized frames have the same reach, but the stack size is smaller on the medium, so I will focus on the medium and raise the handlebar somehow.... I am thinking about extending the steering tube with 5 cm.

That doesn’t make sense to me. A medium frame has a smaller stack than a small frame in the same model? And how are you going to extend the steerer tube? Are you sure it will be safe to clamp your bars around an extender with so many spacers below? Have you already cut the steerer down on the fork?

PP

alxb

My bad, the smaller frame has the small stack.
I will not add an extender anymore, for safety reasons.

After going to the bike shop I mentioned it turned out that the position I have on the medium is less sporty but correct otherwise. Since I have flipped the stem up and the frame is designed to provide a raised position I was told that it is as confortable as a road bike can be. I kept the bike and I will take the time to get used to it.

What do you mean by cutting the steerer down on the fork?

Pilot Pete wrote:

AlxB wrote:

The small and medium sized frames have the same reach, but the stack size is smaller on the medium, so I will focus on the medium and raise the handlebar somehow.... I am thinking about extending the steering tube with 5 cm.

That doesn’t make sense to me. A medium frame has a smaller stack than a small frame in the same model? And how are you going to extend the steerer tube? Are you sure it will be safe to clamp your bars around an extender with so many spacers below? Have you already cut the steerer down on the fork?

PP

pilot_pete

This is an uncut steerer, the fork steerer tube is supplied uncut, the bike shop or the first owner would tend to get the bike fitted and the stem/ bars at the right height and then cut off any excess steerer.



A slammed stem is where it is put as low as possible, I.e. as low down the steerer tube as possible and then any excess cut off. Obviously there is no going back once you’ve cut off the excess so you need to make sure you haven’t got the bars too low as options for raising them will then be limited to stem angles.

PP

hadoken

I bought a Triban 520 in size small as my first road bike and it was fine, I am 166-67cm tall if that helps. The guy in the shop tried to get me to by a medium!