Help with frame size
 

Hello everyone !
Umm, I don't really know how to start this. I am actually new here and I don't know all the rules so I am asking for pardon if I broke any rules. Thank you for considering :)
I currently have hard-tail mountain bike but road biking fascinates more so I want to start road biking. I’m planning on buying a bike from online shop. I went up on the internet to know my suitable frame size but the thing is, different sites are suggesting different bike sizes suitable for me. In some of them according to my height I should get a S(48-51cm) bike in some M((52-53cm). Now I’m really confused.

Basically my question is, what is the perfect frame size for me?
Stand-over height: 5’4”
Inseam length : 27” (inch)
Preferred riding style: Sportive

Thank you very very much :D
PS: I know the best solution is to go to a bike shop. But there’s some reason I can’t go to one. If you wanna know why you can ask me.

What is your price range and do you do all of your own work already? If it breaks, who fixes it?

From what I've seen, a lot of the bikes that you will buy online will be inferior to better known brands. If it is cheap online, it will be a cheap bike. Better off going to a big box store and buy one of their offerings. I know that Canyon is direct to consumer now and some other places sell name brand bikes but they are really screwing the LBS. Check local cycling clubs or craigslist too.

The reason to say this is that even though the size sounds right, you often don't know without actually putting hands on one. you can get close and that usually works, but to stand over one and feel comfortable is the key factor IMHO.

Not sure why you can't go to a LBS. We have a few LBS around us but my favorite closed its doors a couple of years back. It was like losing a friend. Great people. Great customers. A place to spend a Friday evening over a few cold beers putting parts on a new frame. If it's a distance thing, that's fine.

Go to a local bike store. Different manufacturers have different ways they measure size and you can only discover this by talking to someone who knows what they are selling. For example I just bought a new BMC in size 58. I also tried a Pinarello...the shop knew that they are sized different and I needed a 56 in a Pinarello. It felt the same as the 58 BMC. Some manufacturers like Giant don't use numerical sizes at all but use S, M, L etc instead. Get in there and have a professional sizing done to know what you need.

What size mountain bike do you have? You will generally have to get the saddle the same distance from the pedals on a road bike as on a mountain bike... in the same ballpark, anyways. Measure the distance from the centre of the bottom bracket to the top of your saddle, and the horizontal distance from the seat post to the top of the frame's head tube, and compare these numbers to published geometry of bikes you are considering.

In general, a 5'4" person would fit on a 'small' size bike, but all manufacturers and bodies are different.

Please do not go to your local bike shop, waste their time, get their expertise (?), then go buy online.

Figure it out yourself. Or borrow someone's road bike for comparison. Cheap and online means you take your chances, return it if wrong.

Get a professional fit if necessary, as suggested above.

stand over height is the height of the top tube from the ground, plus about two fingers of room (between the top tube & your crotch). so I think if your inseam is 27" your stand over height should be 29"

but bike sizing isn't only based on stand over height. if I remember correctly REI makes a good effort at explaining bike sizing

https://www.rei.com/learn/expert-advice/bike-fit.html

from what I've read you can get a good bike on-line but it would be very good to have a shop assemble it. or a least check it after you assemble it. so it helps to have a cpl shops you can visit, but not absolutely necessary. test riding used bikes or renting bikes can be helpful if possible. if you find a cpl used road bikes in your area that you feel comfortable on you can take some measurements & compare with REI's advice above

This is solid advice. I have 6 bikes and I have those critical dimensions the same on all them of them. It isn't easy, at least in these parts, to find high quality small bikes, most being made for riders between 5'7" and 6 '. I would take the time to read online on this subject and compare the descriptions of the components of bikes at different price points to get a sense of what components a quality bike is likely to have. In the interim, I would buy some light weight, road-type tires for the bike you have to replace the wide, heavy knobbies mtn bikes are usually sold with. You can also add bar ends to your handlebars to get closer to a roadbike feel. There are even bar ends that provide the same appearance and function as drop bars so you can see if you like that.

I would like to thank everyone for commenting. Your help is really appreciated.

I can't go to a LBS because I don't have one :( . I don't live in the UK. In my country (Bangladesh) road biking isn't very famous. A few years back, cycling wasn't famous either. We created a club sorta thing called BDCyclists and we also created a Guinness world record of longest single line bicycle parade (though recently broken). After that cycling got a boost but for some reason people were more interested in mtb/ hardtrail even for commuting. Naturally the shops started selling this type of bikes. Though some of them still import road bikes. Here comes the second reason why I can't go to them, my budget is really low. I'm a student studying in the 10th grade. As I don't earn yet I don't have a big budget. With some savings from my pocket money and my parent's help I managed to gather about 280 pounds (around 30K of my currency). With this small amount of money I found it difficult to get a brand new entry level bike. So I decided to buy one used from ebay. I have some relatives in UK who agreed to buy and bring it to Bangladesh for me.

Well now you have my whole story :D Any suggestions?

My bikes size in 18"
That is actually a really good idea. Never thought of it like that. Thank you very much :)

Have you looked at used - especially vintage? While the sizing is a little different for level top tube bikes, quill stems allowed for s lot more adjustment. Ride that for a while, move the handlebars and seat around, and you'll get an idea of the stack you want - with threadless, the handlebar height is not enormously adjustable, so that'll drive your frame size to the greatest extent.

My budget is only 280 pounds. maximum 300.. No I don't do all works by myself though I try to. There are some repairing shop.

I am looking at the used bike on ebay. That's why I asked for my frame size because in some site recommended was S size in some M size.
Thanks for your reply

Stand over it, ... pull it up underneath you, 1 hand on bars, other on saddle .. how much air under the tires ?

Given your height and inseam, go smaller. 53cm is too large. (I am 5'9" with a 32" inseam, barefoot, and 53cm fits me well.)

What online sources are you considering?

Try to find a bike with solid componentry that hasn't been ridden much (low miles).

I like this method. I'd never heard it put that way.

methinks your math is backwards. a 27" inseam with a 29" standover height would result in 2" if "interference" between the top tube and the spot between the legs... Standover should always be LESS than inseam.

[MENTION=493676]shahriar[/MENTION], I'd say spend a bit of time and try the Competitive Cyclist Fit Calculator. It will involve all sorts of both length measurements, and has its limitations, but should give you a fair idea of what's the right size range for a bike. Top tube length (or effective top tube on newer frames), stem length, saddle-bar reach, etc have been fairly close for me. Their "Eddy fit" is probably a good place to start for a beginning roadie.

Are there many used road bikes in your area? Honestly, a decent quality used bike is probably the best place to start given your finances. Even if it's got down tube shifters and such, it will get you riding and that's more important!

I'll give advice based on standover. If you can't standover the the bike, it's too big for you

I wanted to use the Competitive Cyclist Fit Calculator but it had too many measurements and I didn't have someone to help me. I thought I would do it later but forgot :P . Thanks for reminding !

There's aren't many used road bike in my area.Though I tried on some road bikes like the merida reacto 500 and Bianchi nirone 7 etc. That's why I'm looking on to ebay. but sadly all the bikes that I like or fit me just goes above my budget during auction.

Thank you very much for the help.

Thanks for your advice.
I saw the M suggestion on 2-3 sites. One of the link is given below and another one was evans cycle if I remember correctly. And I got the S suggestion from bike size calculator.
(oops I can't post URLS. the sites name was bicycle-guider. If you search on google with bike sizing it comes up almost at the top)

I'm trying to find a bike with solid components. I don't need and want anything fancy like ultegra or sram red. But sadly, even the bikes with 105, tiagra etc that looks to be in good condition (in the photos at least) goes above my budget during the auction :( My low budget is making it really hard. Thanks for your suggestion tho :)

oh, haha thanks

I'm your height and the magic number for me seems to be 52cm, but not many brands have that size.

It all depends on you proportions. I feel crammed on many 50cm frames. I had a frame built up as a townie bike and it was a 54cm bike. The fit was good, save I had the seat at the lowest possible spot.

Is there something similar to Craigslist of Facebook Marketplace locally? I've noticed that eBay bike prices usually run higher because of more shoppers. Being able to test ride the bike beforehand is a huge benefit, especially since you're new to this.

Are there any cycling clubs anywhere near you? It might be worth looking on Facebook, Strava, etc and see if there is anyone local who can at least give you a bit of advice (and possibly a deal on some secondhand parts)

So, your max budget translates to $390 US, start looking older on the bikes. Honestly, when I was in 10th grade, my bike was 8 years old. My Dad and I had upgraded it from 6sp friction shifters to 7sp indexed. Of course, this was in the era of 8spand 9sp ergo shifters that I wanted badly but that wasn't happening. Look at some older bikes with 10, 9 or even 8 speed. Get something with decent SRAM/Campy/Shimano equipment that hasn't been trashed. The name brand parts hold up and will still shift like new maybe with a bit of cleaning and new cables. I've got bikes from 7sp to 11sp now and can tell you that while new bikes are better, the rider is still the most important part.
Good luck!