Stem/bar length these days?

[ishaw]

My son has outgrown his current bike and I'm thinking a medium pinnacle iroko I built for me but was too small might just be his size now (he's a tall soon to be 13 year old).

When I built it up I went with a short stem (70 or 80mm iirc) and wide 720mm bar. Personally I found it to be pretty sketchy but that might have been down to me being used to more narrow bars and a longer stem. Cosmetically I think the short stem looks a bit pants but it is what it is.

So, leading on to my actual question, what is considered a good stem and bar length? I know a lot depends on personal preference and human dimensions but l
I'm looking to modify the bike to suit someone smaller than I am and how I set it up, and hoping there is some guidance or general rules to get it about right off the bat, or it could get expensive.

Thanks

 

[bignick]

Hmm…

Quite a question/query…

I’ve just built a cotic Solaris max and cotic recommend a 35mm stem but I’ve settled on something a little longer.

The longest I see on modern bikes in the mags/reviews seem to be 40-50mm.

Bars seemed to have settled on 780mm with xc bikes a little narrower.

This is quite a can of worms to open.

Lots to consider - rider height, shoulder width, arm length, frame size, reach, general geometry etc…..

I’m tall so just go wide bar and then fiddle with stem length.

Not sure if that actually helps….

 

[eshew]

Yep no perfect answer. Really just depends. Modern stems 40-60mm, modern bars 700-800. With bars just start wide and move the grips in to test widths. Cut at your favorite.

 

[Imlach]

Moving from narrow to wide bars, I found it pretty sketchy as well. Short stems are great IMHO, so I'd stick with that. More importantly I would just make sure that he feels that his hand/arm positioning feels natural and adjust accordingly. You can always play with bars with more backsweep etc, if needed.

Basically what eshew said

 

[M_Chavez]

I've spent many hours dialling in the road bike position until is suddenly "clicked" into something that works better than anything I've tried before.

Are there any general guidelines for a comfortable retro mtb position? This will determine the stem length and bar width.

 

[mk one]

Whatever happened to the "you will grow into it" approach?

I would just sit him on your bike and you should be able to judge how shorter the stem and narrower the bars need to be quite easily for him to be sat in a reasonable position.

 

[clubby]

Main starting point for stem length would be what the manufacturer fitted. Current bikes are getting longer and slacker and designed to handle better with proper short stems ie 35-45mm. Go above that and handling just feels weird.
For bikes designed with long (by today’s standards) stems ie over 60mm, then going down 10-20mm is usually ok. Any less and steering starts to flop.

Bar width is more related to body shape and preference, but long stems and wide bars don’t mix well.
I like wide bars, and don’t feel good on narrow these days. Xc bike has 760mm but on a 90mm stem. Plus bike has 780mm on 35mm stem. Enduro bike is 800mm on 42.5mm stem. Ebike is 800mm on 35mm stem. If the 800mm bars weren’t carbon, I’d probably cut them to 780mm but it’s not a big enough difference to bother.

Luckily your boy won’t have any preconceived ideas of what things “should be” but should be able to tell what’s comfy. Good thing about lock on grips is you can adjust the grip width and let him try things out before cutting anything down.

 

[rwm1962]

Is the elbow against the saddle nose & longest finger half way between steerer & bar centre a reasonable guide for stem length?

 

[eshew]

Only if it's before July 1st. After that I typically do ankle to knee with the width of my head.

Or you can just ride the bike and adjust length and rise for preference.

I tried the arm and finger trick and the finger tip was only about 15mm-25mm beyond the stem topcap bolt on the old and new bikes.

I either have short arms or long top tubes. Or you have the opposite problem

 

[Imlach]

I touch my nose and if it smells funny, I go shorter, if it smells funky I go longer. If it smells just right, well then my setup is airtight

New moons unfortunately interfere, the reception is often poor during that time. So best wait til morning.