How can I tell if my MT bike frame is too big for me?

[DoubleJ]

I'm 1.78m tall. I have a large (19inch, 50mm stem) KTM carbon 29er that's an extremely comfortable bike to ride. When you're on it it literally feels like you can sit on it all day long.

 

I have had comments that the bike feels a bit slack and not nearly as nimble as a trailbike or a decent XC race bike, which is fine for me as I dont do many trails.

 

I very rarely have many aches and pains getting off the bike after a big ride (up to about 100km). The reason I ask is that last weekend I got on a mate of mines medium frame bike and jislaaik it felt small, nimble and very quick.....so, how can I tell if my frame is too big? Should I go medium frame, or just be happy that I am pain/problem free?

[Captain Fastbastard Mayhem]

May be down to the different geometry between the bikes. 

 

What was your mate's bike, and which KTM do you have?

[DoubleJ]

May be down to the different geometry between the bikes. 

 

What was your mate's bike, and which KTM do you have?

KTM Myroon Master - Large

 

He's got a medium Canondale Rocketship with NOS (29er).

[Eldron]

Eldron's really non scientific rule of frame sizes:

 

If you can get away with a 350mm seat post your bike is too big for you. 400mm all the way*

 

 

*disclaimer: I have loooong legs and a short upper body so the rule above works for me.

 

 

For normal people I'd say the 350mm seat pillar needs to be quite near to "Min Insert" line.

[Captain Fastbastard Mayhem]

KTM Myroon Master - Large

 

He's got a medium Canondale Rocketship with NOS (29er).

Cannondale Rocketship? Don't you mean Flash or Scalpel?

[DoubleJ]

Cannondale Rocketship? Don't you mean Flash or Scalpel?

Hardtail

[DoubleJ]

Cannondale Rocketship? Don't you mean Flash or Scalpel?

Must be a Flash... It's kakfast with only half a fork.

[Captain Fastbastard Mayhem]

Okay, well. If it's the FSI (new flash) For starters - the chainstays on the 'dale are far shorter than on the KTM. As in 11mm shorter, which for a chainstay is a lot. This means it'll be a lot more nimble and you'll be able to get it on to the back wheel a little easier. Should also be a snappier handler. Then the head angle is 2 degrees slacker, so it'll be far more stable at speed than the KTM and will inspire a lot more confidence. Wheelbase on the medium 'dale and large KTM is the same, but overall the 'dale is just the better bike, IMO. 

 

You are the right height for a large. Just that the Dale is more of a speed machine, also lighter (which definitely helps things) and probably stiffer as well.

[raptor-22]

at 1.78m a large with a 50mm stem is more a trail/endure type of set up.

 

A medium would certainly be more nippy up hill with a slightly less stable feel on the descents, but overall likely faster

[Captain Fastbastard Mayhem]

If it's the Flash, then the numbers are a bit different. Dale is 0.5 deg slacker (71 vs 71.5) but also has longer chainstays (442mm vs 440mm) 

 

2 completely different bikes betweent he flash & FSI. 

 

Agreed that the Medium whatever it is will be more whippy / nippy etc, but at the expense of technical stability on the way down. And also potentially discomfort due to the much shorter reach, depending on the bike he has (flash vs FSi)

 

IMO you should rather go for the larger frame unless weight is your primary concern. 

[Rick Sanchez]

I am 6ft tall, wonder how a medium would suit me.

Probably nippy as hell, with a lot more "gooi"-ability into those tight corners

[Captain Fastbastard Mayhem]

I am 6ft tall, wonder how a mdeium would suit me.

Probably nippy as hell, with a lot more "gooi"-ability into those tight corners

Dude. Don't go near a medium. Seriously. Unless it's one of Canyon's RACE bikes, which have very long measurements for the frame size. 

[DoubleJ]

I very rarely see tight corners so I'm not phazed about nippy handling...do mostly gravel roads (K2C type stuff) so I cant really say that I need a bike that handles better than what I currently have. 

 

I was just worried that I'm doing my body a disservice in the long run if my frame is too big.

[raptor-22]

I am 6ft tall, wonder how a medium would suit me.

Probably nippy as hell, with a lot more "gooi"-ability into those tight corners

 

 

need to look at the whole package and your build (body structure to understand if this can work for you.

!,78m is the upper limit for a medium size frame generally.

[raptor-22]

I very rarely see tight corners so I'm not phazed about nippy handling...do mostly gravel roads (K2C type stuff) so I cant really say that I need a bike that handles better than what I currently have. 

 

I was just worried that I'm doing my body a disservice in the long run if my frame is too big.

 

 

if its working for you then don't change it.

If you want to start riding up steeper hills you may be wanting to consider  a more forward position on the large KTm which means a longer stem

[Rick Sanchez]

I very rarely see tight corners so I'm not phazed about nippy handling...do mostly gravel roads (K2C type stuff) so I cant really say that I need a bike that handles better than what I currently have. 

 

I was just worried that I'm doing my body a disservice in the long run if my frame is too big.

Your frame won't be too big. Reach can be adjusted with shorter or longer stems and the larger frame will just have a longer seat tube. So, you could probably fit on a Medium, but if you don't feel any discomfort or pain, then you are fine IMO.