Frame size

[Bazmo]

Hi guys.

I am 1.78m tall, inner thigh lenght 83cm. What size frame should I get?

[Boktiet82]

I used the below website, but I would suggest go to the shop and feel what bike fits best...just my 2c

https://www.bicycle-guider.com/bike-articles/bike-size-chart/

[Steady Spin]

Lots of factors come into play but from my personal experience 1.78 puts you on the border between medium and large. 

You don't mention what your preferred discipline is?

[Eldron]

Go and get measured up. Height and inseam alone cannot determine frame size or correct frame geometry (it can if all your dimensions are average but chances are they're not).

Average inseam for 1780mm is 870mm - double check your inseam - it is common to undermeasure when you're doing it yourself.

 

 

[Dexter-morgan]

I am 1.79 m Tall with a 84cm inseam, as another person mentioned bang in the middle of Medium and Large on Mountain bikes, I am on a 56cm Road bike, If you gonna do longer distances, go large, if you gonna do lots of technical twisty stuff go for the Medium, just my 2c.

[Bazmo]

I used to have a medium frame road (road bike) didn’t have issues. I want to cycle again, the bike shop suggested a large. 

[ChrisF]

40 minutes ago, Bazmo said:

Hi guys.

I am 1.78m tall, inner thigh lenght 83cm. What size frame should I get?

 

A friend is also 1,78m

 

He had a Scott in Large.  So ordered his new Scott in Large .... OOPS !!!  Dropper post is barely 2mm above the lowest setting !!

 

First long ride he noted that he is more stretched out, and having slight neck pain of "looking up" from the stretched position.

 

He may well have to get a new handlebar to get to a better position ....

 

 

Sad part is the Medium may well be a bit cramped .... at 1,76m I somtimes wish for a size between a M and L ....

[NickGM]

52 minutes ago, Bazmo said:

Hi guys.

I am 1.78m tall, inner thigh lenght 83cm. What size frame should I get?

It's very likely that you can make both a medium and a large work. There is a lot of leeway with moving saddles back and forth, changing stem length and angle (etc). But there is no substitute for a test ride and as @Eldron said, people often under-measure inseam. I've used this as a resource before:

https://www.rivbike.com/pages/pubic-bone-height-how-to-measure-your-pbh

Although if you spend enough time online you'll find people who disagree with Rivendell's sizing advice (that's the internet for you).

From my own experience, I'm between 56 and 58 but have long legs, so I've found 58 works nicely because on a 56 the saddle was a long way up and I got back pain reaching down to my bars. My Fiance is between a 52 and 54 but has shorter legs (proportionally) and a 52 has worked nicely for her. I don't know if leg length is the deciding factor if you are between sizes, that's how it played out in our house.

 

[Eldron]

The other problem with this discussion is frame sizing. Many people will say "I'm an xxcm frame". This was mostly true when frames had horizontal top tubes.

The invention of sloping frame technology made frame sizing impossible by the traditional method (center to top). A 56 Trek Madone and Giant TCR are quite different sizes.

Stack and Reach is the my favourite method. Unfortunately you'll have to spend some money to find your ideal Stack and Reach but it seems silly to me to spend a heapload of cash on a new bike that you're going to spend many, many hours on and not ensure you're getting the right frame.

Don't get me started on Geometry 🙂

[dave303e]

Inseam, ape index, inseam to height index etc are all part of the choice before you even start on geometry.

Personally I will always go smaller on the frame. I am 177cm so also on the med large barrier.

I have stupidly long arms and legs( ape index +6cm) but with a shorter torso the smaller frame works for me, usually with a longer seat post and really wide bars. Smaller frame feels bit more nimble and is usually a few grams lighter.

[Eldron]

23 minutes ago, dave303e said:

Inseam, ape index, inseam to height index etc are all part of the choice before you even start on geometry.

Personally I will always go smaller on the frame. I am 177cm so also on the med large barrier.

I have stupidly long arms and legs( ape index +6cm) but with a shorter torso the smaller frame works for me, usually with a longer seat post and really wide bars. Smaller frame feels bit more nimble and is usually a few grams lighter.

This raises another issue in frame sizing - what you want to do with the bike.

Two people with exactly the same body measurements might well use different size frames. Usually if you want a racy/fast 100km machine then smaller as Dave above - the problem is that Shorter also means Lower and that wouldn't suit someone looking for a more comfortable Gran Fondo/touring/fun 100km bike (lower Stack equals bigger drop equals lower back angle equals earlier onset of back pain).

It is an area that is growing really well in the store - the number of people coming to me BEFORE they buy a bike for measurement and advice is increasing. That is the right way to buy a bike - you can make allowances for the wrong size frame with stems, set back, hood angle etc but getting the right size frame from the start is always better.

 

[guidodg]

2 hours ago, Eldron said:

Go and get measured up. Height and inseam alone cannot determine frame size or correct frame geometry (it can if all your dimensions are average but chances are they're not).

Average inseam for 1780mm is 870mm - double check your inseam - it is common to undermeasure when you're doing it yourself.

 

 

that doesn't sound right...average inseam for a 1,78cm person is probably around 84cm

[Jakkals.]

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Edited February 2, 2022 by Jakkals.

[Jakkals.]

Sorry, let me try again...your torso is on the longer side of the equation...I would recommend a 56ctc top tube or 55ctc. based on the information you've given.

[Eldron]

2 hours ago, guidodg said:

that doesn't sound right...average inseam for a 1,78cm person is probably around 84cm

My thumb suck was a little out - here is a grab from bikefitting.com software - the averages are from around 5,000,000 real world measurements on our global database. Average inseam for 178cm man is 85.9cm.

[figjam_sa]

Id you are looking at a mtb, Trek has a size M/L that would work