Stems and Reach Calculations

[MacB]

Folks, shameless plug for my 'wanted' thread here:-

http://www.cyclechat.co.uk/forums/showthread.php?t=50136

also I wanted to know how you work out reach and prospective stems, ie how much does angle impact it etc, my head can't seem to work out the maths today.

 

[Garz]

Nothing wrong with asking for help mac!

Whilst your asking I shall double check my setup, I did check last time by using your elbow on edge of seat and the finger tip just touches the stem.

 

[Joe]

http://alex.phred.org/stemchart/Default.aspx

 

[MacB]

http://alex.phred.org/stemchart/Default.aspx

thanks Joe, I'll work at getting my head round that, will need to understand how to work out the angles of what I have first I've got my eye on a selection of short riser bars on e-bay as well.

This is a picture of the new butterfly incarnation, more work to be done but am awaiting some new tubular grips. As you'll see the main hand/controls position have moved from rear flats and sides, to forward flat/corners and sides. Plus I've wangled inboard bar ends for a truly aero option. Taking some measurements I have:-

nose of saddle to centre stem clamp = 460mm
nose of saddle to flat part of bar to side of clamp area = 55cm
nose of saddle to control mounting area and main hand positions = 67cm

I was thinking of having the bars less tilted as well, my only concerns are, if I bring bars too far back will the rear of them interfere with my knees. I suppose I could always cut off the flat part of the bars at the back, but want to keep them for the truly sit up and beg moments. I've also considered using a cable doubler on the front brake so that I can have a secondary lever on the flat parts as well.

 

[jimboalee]

Nose of saddle has nothing to do with it. Remember there are many different saddles.

To calc your 'Reach' which is Centre Seat tube at its top; to Centre of handlebars at stem clamp.

1/ Measure your Height. H
2/ Measure your 'Seated height'. S
3/ Measure the height of your Sturnal Notch. T
4/ Measure your Arm Length. A

LL = H - S
B = T - LL
C = B + A

Reach = C x 0.52

 

[GrahamG]

I take it that's meant as a rough guide seeing as frame geometry and bar height are both going to have a bearing?

 

[jimboalee]

I take it that's meant as a rough guide seeing as frame geometry and bar height are both going to have a bearing?

Nope, that's how it's worked out.

Say, for example the 'Reach' works out to 617.5mm ( mine ).
Raising the bars vertically by 20mm is going to make V little effect to 'Reach'. It might round 'Reach' off to 618mm.

I can't be bothered to do the maths cus it makes next to sod all difference. The bar height is determined by the angle of the Lumbar vertebrae to the road surface.

Incidentally, I have a Spesh SWorks 54cm size with a Toptube L of 548mm. Add on 100mm for stem length and 25mm off for the head tube angle ‘setback’ and it is 623mm.
I’m not going to grumble about 5mm too long. In fact, I have 5mm extra padding on the handlebars just where I hold them which makes them the correct distance AND more comfortable.

Tricks of the trade eh?

 

[MacB]

Nose of saddle has nothing to do with it. Remember there are many different saddles.

To calc your 'Reach' which is Centre Seat tube at its top; to Centre of handlebars at stem clamp.

1/ Measure your Height. H
2/ Measure your 'Seated height'. S
3/ Measure the height of your Sturnal Notch. T
4/ Measure your Arm Length. A

LL = H - S
B = T - LL
C = B + A

Reach = C x 0.52

Nose of saddle does matter, that's how I measure the setback, plus your reach formula presumes drops or flats