Inbetween Sizes

[JACTHECAT]

Hi all

Went to Halfords today to get sized for my first mountain bike, looking at the Carrera Valour or Vengeance.

I am about 5' 11"

On the 18" bike I felt that when I was taking a corner my knees were right up around the gears/bars - Is this normal on a mountain bike?

On the 20" bike when I was stood straight my crotch was just touching the top bar - Read that this is a sign that the bike is to big?

Is it picking a better of two evils, any advice is welcome!?

 

[MikeW-71]

20" is too big if you don't have at least a couple of inches clearance on standover. I'm 5' 10" and went for 18".

 

[sreten]

Hi,

Go for the smaller size and adjust to suit. You want plenty of standover on a MTB.
According to some 3" on a MTB, 2" on a hybrid and 1" on a road bike *.
That's assuming average proportions and a bike sized to suit.
Unusual proportions and average bikes may need some comphromise.

rgds, sreten.

* Whist they seem different the typical frame angles make them near the same.
My road bike has 1" and a sloping top tube, but for my size the front tube is very
tall and the stem very short compared to an old school road bike level top tube,
so the top tube is near normal near the seat but higher towards the front.
Standover is how much you have to squat for the toptube to take your weight,
it isn't just your crotch being aware of the top tube. 2" minimum for MTB.

 

[jazzkat]

I'm 5' 11" and I've an 18" Mtb. I was told that is is better to go smaller for controllability too. If you don't have the stand over on the 20" what happens when you go to put your feet down and the ground is lower either side of the bike?

By the sounds of it the saddle could have been too low as well, if your knees were bent enough to catch the bars?

 

[MrGrumpy]

I`m an inch taller than you and my Carerra Fury is an 18", guy in Halfords reckoned I should of been on a 20" but took my own advice, easier to make a smaller bike larger than the other way. Anyway for MTBs I would want it smaller to chuck it around more

 

[JACTHECAT]

Thanks for the advice so far.

For the riders on 18" frames have you noticed your knees a bit close to the gears/frames when turning?

 

[vickster]

Perhaps a bike with a different geometry would suit you better?

 

[MrGrumpy]

Thanks for the advice so far.

For the riders on 18" frames have you noticed your knees a bit close to the gears/frames when turning?

Nope not me but as said geometry can also make a difference.

 

[Pale Rider]

If 18" is too small and 20" is too big, the obvious answer is try a 19" of which there are many.

 

[cyberknight]

What do you mean your knee is close to the gears /frame when turning ?

 

[JACTHECAT]

When my knee is at its highest point of the cycle and I'm turning at a 45 degree angle, it seems to be knocking my hand just below the thumb.

 

[MrGrumpy]

Is this you

 

[screenman]

You would fall off before you turned the bars that far whilst moving, other than very slowly. Very you can very easily fit a longer stem.

I would buy the 18 and tweak it, rather than buy a bigger one.

 

[JACTHECAT]

It feels that way mrgrumpy :-)

I'm really new to all this - what will the longer stem do for me?

 

[vickster]

I'm really new to all this - what will the longer stem do for me?

It'll put more space between the saddle and the handlebars, give you more space on the bike. Do you have to buy from Halfords? I'd be looking for a bike that fits better rather than trying to make one fit assuming you are free to look elesewhere