Correct Stem Length

[Rowber]

Hi I need some advice please.

 

Had a bike fitment done according to which I need to use a 420mm (centre to centre) handlebar with my Mtb. This measurement is based on shoulder width I assume. It reccomends a 120mm stem. Now for my problem. I cant change the bar width on the programme. I have read that if you go wider you need to shorten the stem. How can I work this out? There must be a mathematical equation one can use. Unfortunately maths is not my strong point in life!!! I know I'm going to be told to try different stem lengths till I find a good match but unfortunately that is not really an option for me. I am looking at getting a 700mm flat bar. What length stem do you reckon I should be looking at? Thanks, would really appreciate some advice.

[GoLefty!!]

420mm flat bar???!!!! yikes what bike fit programme is that? Stay away!!!

 

 

but vback to the crux of the matter.

what type of riding do you prefer?

Which bike do you have? and year model?

How flexible are you? ie.e can you touch your toes and have you seen them in recent years?

[rock]

first,  politely ask for a refund for your 'bike fit'

[Rowber]

2014 Giant Xtc composite hatdtail.Yes I can see my toes and touch them (haha) although only recently again. I will mainly be riding gravel roads, jeep tracks etc. Very little single track.

[GoLefty!!]

ok then a 700mm wide flat bar should be ok. What is the drop from saddle to the centre of the bars currently?

 

The trick is to try and get your positin of your back and arms to make about a 90 degree bend at the shoulders..

 

Would help if you post a side on pic of you on the bike.

 

Alternatively, take the measurement the fit programme spat out. Its giving you a reach either to bar tops for a road bike or brake hoods.

 

draw a line on a page that represent your top tube.

 

now draw two parallel lines that correspond with your shoulder width.

 

Add the effective top tube length of your bike to the 120mm stem length and draw a perpendicular line that intersects with the other three lines.

 

Where the perpendicular line crosses with the shoulder length lines, draw an arc using a compass. These lines will represent where your hands can be placed in space.

 

You now need to find bar and stem dimensions that intersect with the arc.

 

Remember that a bar has different sweep angles and this is measured from the bars mid length.

 

So on the top tube line try different length "stems. Then project lines from that centre point till they intersect with the arc your hands should fit onto. with  a bit of playing around you should find a decent stem, bar sweep and width combo that will place your hands on the arcs.

 

 

no maths required...

 

 

 

but it might be easier to just get a professional bike fit done

[Rowber]

Thanks will give it a bash

[Frosty]

Hi I need some advice please.

 

Had a bike fitment done according to which I need to use a 420mm (centre to centre) handlebar with my Mtb. This measurement is based on shoulder width I assume. It reccomends a 120mm stem. Now for my problem. I cant change the bar width on the programme. I have read that if you go wider you need to shorten the stem. How can I work this out? There must be a mathematical equation one can use. Unfortunately maths is not my strong point in life!!! I know I'm going to be told to try different stem lengths till I find a good match but unfortunately that is not really an option for me. I am looking at getting a 700mm flat bar. What length stem do you reckon I should be looking at? Thanks, would really appreciate some advice.

If you need a 120mm stem, I have one that's up for sale.

 

Ritchey WCS, 4-axis

[Hairy]

Find a bike shop with a good selection of stems. Make an arrangement to meet in store during their slow business time of the day in order for you to try out the various stem lengths on your 700mm bars.

 

If you don't have the bars yet then also buy this from the lbs At the same time.

 

420mm bars on a 120mm stem...You must have seriously narrow shoulders with exceptionally long arms and torso

[s14phoenix]

It almost sounds like a road bike fit....

 

how tall are you?

What size frame is your bike?

What kind of riding do you do?

 

the measurements of that narrow bar with that long stem does not seem right at all...

 

I have a 6ft3 friend riding a XL XTC.

He is upper body tall and rides with a 740mm bar and 90mm stem.

He changed from a 120mm and 680mm bars.

 

And all this was also done after some weird bike fit measurements. However there is all sorts of setups for different people - it is a very personal thing and you will more than likely need to take a couple of trail and error iterations.

 

I would personally say a 80/90mm stem on a 700mm bar for XC use sounds ok. but there is no way to tell until you try and see - 10mm could be the difference between comfortable and not at all.