stem degrees

[gillan]

I have a thomson 80 degree job on my road bike....with a 73 degree head angle does this mean my steam rises from the horizontal by 7 degrees??

If so if I want to lower the handlebar height do I want to get myself a 73 degree stem which will leave the stem horizontal i.e. parallel to the ground??

yours mathematically challenged

PS anybody recommend any decent aheads that come in 73 degrees if that is an fact what I'm after

 

[skwerl]

First-off you shouldn't adjust handle-bar height using stem angle, you need to remove spacers from the steerer tube.
Changing the angle will change the bar height and the reach.
A 73 stem will drop the angle 7 degrees below your current stem.
The angle is not measured against the horizontal. It's measured against the right-angle formed between stem and head-tube. A 90 degree stem will form a perfect right-anlge with your head-tube, ie it will be a few degrees above horizontal
73/17 degrees is pretty severe. Race bikes tend to have an 84/6 which, combined with a steepish head-tube, will put the stem pretty much at horizontal to the road.
I'd look at removing spacers first

edit - what bike do you have? If your current 80 degree stem doesn't leave the stem parallel with the ground you must have something with fairly relaxed geometry.

 

[gillan]

yup

colnago

it has a longer head tube (for its size) than I'd anticipated.

Its actually quite comfy with the higher position but would like to put some tri bars on for a tt so a lower height would get me lower on the tri bars

and also

as I'm used to it being lower on other bikes I can check out the position with a more horizontal stem

how does this 84/6 thing work...would that still leave me 11 degrees above horizontal??

 

[skwerl]

yup

colnago

it has a longer head tube (for its size) than I'd anticipated.

Its actually quite comfy with the higher position but would like to put some tri bars on for a tt so a lower height would get me lower on the tri bars

and also

as I'm used to it being lower on other bikes I can check out the position with a more horizontal stem

how does this 84/6 thing work...would that still leave me 11 degrees above horizontal??

84/6 is just two ways of saying the same thing. Either 84 degrees between stem and head tube or 6 degrees of the right-angle formed off the head-tube.
If your current stem is an 80 degree and it's not horizontal to the ground then you'll need something in the 70s
I take it there's no scope for removing spacers from the steerer tube?

 

[gillan]

yeah

no spacers below stem to achieve lower height

I have seen a stem at 73 degrees so maybe I'll buy a cheap one and see how I get on with it

cheers

 

[andy_wrx]

Why not buy one of the adjustable stems cheap on eBay ?
(Look ErgoStem type things)

You can then try it at various angles and work-out what you prefer and then buy a proper stem that angle, plus you also have the option to start-out with one setting and then lower further as you get happier on the aerobars.