MTB Frame Size

[Aggies]

Everyone has different views on frame sizes and I have seen a lot of people that is clearly on the wrong size. Mostly the frame is too small. Let's build a database on MTB rider sizes and everyone can then refer to this topic for advice. The two most critical items is your inseam to determine frame size and top tube length, but the latter can be changed with differnt lengths of stem.

 

State the following (if you know all):

Length = 1.88m

Inseam = 92.5cm

Saddle Height = 81.5cm (Centre BB to top of Saddle)

Frame = L 20"

Bike = Merida 96 Dual Suss

Comment = Feels to small as seat post is very high

 

No road sizes please.

[AndreZA]

Length = 1.80m

Inseam = 85.5cm

Saddle Height = 77cm (Centre BB to top of Saddle)

Frame = M 19"

Bike = BeOne Karma

Comment = Perfect fit. Had setting the same on a L 20" Santa Cruz Superlight as top tube was almost the same.

[MyGT]

please help here,

 

do i only need to use my inseam measurement to determine what size bike i ride or what about the upper body length from my hip to my shoulder? and then my arm length and what about how far forward or upright i should be seated on my seat so that i am comfortable and still in an aggresive cycle position?

 

i seriously considering changing the my mtb frame (ride a large gt zaskar) to a medium. but not sure.

[covie]

Everyone has different views on frame sizes and I have seen a lot of people that is clearly on the wrong size. Mostly the frame is too small. Let's build a database on MTB rider sizes and everyone can then refer to this topic for advice. The two most critical items is your inseam to determine frame size and top tube length, but the latter can be changed with differnt lengths of stem.

 

State the following (if you know all):

Length = 1.88m

Inseam = 92.5cm

Saddle Height = 81.5cm (Centre BB to top of Saddle)

Frame = L 20"

Bike = Merida 96 Dual Suss

Comment = Feels to small as seat post is very high

 

No road sizes please.

 

I find that people are totally obsessed in using the 20" measurment as your alpha and omega in fitting your bike. I am 187 so pretty much the same height as you and my giant anthem 20.5" is perfect.

 

However I had another 20.5bike and it felt too cramped. Reason being we all ingore teh effecive top tube length. On my previous bike it was a couple centimeters shorter than on my current Anthem, the top tube being a bit longer made the world of difference to me. So your 20" frame sizing is spot on i would say, but I would look for a frame with a longer effective top tube.

[covie]

please help here,

 

do i only need to use my inseam measurement to determine what size bike i ride or what about the upper body length from my hip to my shoulder? and then my arm length and what about how far forward or upright i should be seated on my seat so that i am comfortable and still in an aggresive cycle position?

 

i seriously considering changing the my mtb frame (ride a large gt zaskar) to a medium. but not sure.

 

 

Give your length, inseam details etc. But first option if you feel the bike is too large is get a shorter stem. Its only a couple hundred bucks and that will give you a definitive answer.

[Aggies]

I find that people are totally obsessed in using the 20" measurment as your alpha and omega in fitting your bike. I am 187 so pretty much the same height as you and my giant anthem 20.5" is perfect.

 

However I had another 20.5bike and it felt too cramped. Reason being we all ingore teh effecive top tube length. On my previous bike it was a couple centimeters shorter than on my current Anthem, the top tube being a bit longer made the world of difference to me. So your 20" frame sizing is spot on i would say, but I would look for a frame with a longer effective top tube.

 

 

That is exactly why I have started this topic. How do you get the best advice? It is from seeing what worked for who.

 

Every person is different and the same frame will not work the same for everyone. What is the two most important measures?

1. Inseam as it determines the saddle height and to a point the frame size (let's settle for seat tube length)

2. Effective top tube length, but length does not have must to do with it.

 

Most important is to fit the frame size to your inseam measure. If not you end up with a seat post way to long for the frame. Fact is that you cannot change the "frame size".

 

Overall reach is however very easily adjusted by using differnt stem lengths. Example: the effective top tube on a L can be 600 and on a XL 620, this is a difference of only 20. You do however get stems ranging from 60 to 160 giving you 100mm to play with.

 

Step 1: Match frame size to inseam.

Step 2: Match reach with stem length.

 

As mentioned, I am 1.88 with 92.5cm inseam. My one friend is 1.88 with 87cm. This indicates that I have relative longer legs and he have relative longer torso.

 

I will need a bigger frame with a shorter stem. He will need a smaller frame with a longer frame.

 

And we have not even looked at the difference in arm length.

 

If we have this complete database, you can map your measures to people with similar measures and see if they liked the fit or not, giving you a much better idea than any scientific formula would.

[Stig]

Go to the"competitive cyclist" website in the US and do a scientific fitment calibration.

[covie]

Aggies its a total oxymoron if you ask me.

 

There are about 50 different techniques to do a bike fit and they all claim to work. Though do you research and it works for about 3 out of 5 people.

 

Then its the comfort vs riding style, some people like a more relaxed style to spend time on the bike and others like a more confined feel for a more agressive riding style. (MTB)

 

And the tough one is very few bike shops will lend you a bike for week to see if it works for you.

[gummibear]

Length = 1.80m

Inseam = 85.5cm

Saddle Height = 77cm (Centre BB to top of Saddle)

Frame = M 19"

Bike = BeOne Karma

Comment = Perfect fit. Had setting the same on a L 20" Santa Cruz Superlight as top tube was almost the same.

 

What's your stem length?

[Velouria]

Reason being we all ingore teh effecive top tube length.

Couldn't be more right - this is the number that means the most, and is the most difficult to correct once you've bought a frame. There is only so much you can adjust the stem and seat tube by...