Stack and Reach measurements

JesseD

Anyone know if there is a simple way to calculate stack and reach measurements for a frame set from a simple geometry chart of the frame?

I am probably going to buy a frameset/bike on line however some bike geometry charts don't list stack and reach figures and going off top tube and head tube length is a bit hit and miss.

Thanks

the_chief15

Stack and reach calculator

http://bikegeo.muha.cc

mfin

It's not hit and miss not knowing stack and reach. If you know your current frame geometry and setup and you have the geometry of the new one it's often relatively easy. You need to look at ETT/Head Tube/BB-Drop and Seat Angle mainly. (Also assuming you want the new bike to fit like your existing one, as people who know they are fitted right do).

Have you got the two geom tables for the two bikes and the sizes you have/are looking at? Can you post them?

Also, whether you currently run a setback seatpost, how much setback, saddle position roughly on the rails and how high... these rough things will come into things too.

JesseD

the_chief15 wrote:

Stack and reach calculator

http://bikegeo.muha.cc

Tried the calculator against the geometry chart for my existing bike and the stack and reach figs don't match the manufacturers figures?

Felt Figs - Stack 580mm / Reach 386mm
Calc Figs - Stack 543.6mm / Reach 359.5mm

Mfin - I ride a 56cm with a 110mm stem +/- 6 degree stem, I have no spacers under the stem and also feel I could comfortably go down another 10mm on the stack figures over the next 6 months as I have lost weight and become fitter and more flexible since I bought it a year ago, the reach is spot on though.

HT Angle - 72.5
ST Angle - 73.5
Top Tube - 560mm
Head Tube - 180mm
BB Drop - 70mm
Stack - 580mm
Reach - 386mm
Stem - 110 -/+6 degree
Bar Reach - 80mm
Spacers - 0mm

The frame I am looking at is as follows

HT Angle - 72.5
ST Angle - 73.5
Top Tube - 548.6mm
Head Tube - 145.5mm
BB Drop - 70mm

Battaglin Hyper Geo - http://www.battaglinroadbikes.com/hyper
Felt Z75 Geo - http://www.wiggle.co.uk/felt-z75-disc-2016/ (mine not the disc but geo is the same)

letap73

I have used the excel - stack and reach calculator below before:
http://bb2stem.co.uk/

Looking at the geometry figures from above - at a guess - based on the head tube length - the stack is likely to be in 545 region so you may need spacers under the stem. The larger frame may also be suitable. I would not want to guess at the reach figures for the bike you are looking at.

JesseD

Decided to email the manufacturer directly to see if they can assist me, have also emailed Planet X who are selling the frameset to see if they can source the stack and reach measurements, will have to wait and see what they say.

Gutted really as I had decided on a Canyon Ultimate CF SL Aero in a medium which was actually perfect for me, however they have now sold out and are not going to be getting anymore in that spec and at that price as the new models will be released in October.

Hey ho, thanks all

darkhairedlord

looks like a lot smaller. the bb drop is the same as are the seat tube and head tube angles so the only diffrence is the top-tube and headtube. Both are smaller. By the time you've added some spacers to bring the stem to the same height the reach will be even smaller. To get the stack this would need about 40mm of spacers and would pull the reach back by about 20mm compared to the Felt. if you want similar geo to the felt you might be better off looking at the next size up, unless you were after a lower front end in which case shove a longer stem on it.

JesseD

darkhairedlord wrote:

looks like a lot smaller. the bb drop is the same as are the seat tube and head tube angles so the only diffrence is the top-tube and headtube. Both are smaller. By the time you've added some spacers to bring the stem to the same height the reach will be even smaller. To get the stack this would need about 40mm of spacers and would pull the reach back by about 20mm compared to the Felt. if you want similar geo to the felt you might be better off looking at the next size up, unless you were after a lower front end in which case shove a longer stem on it.

Ok thanks, was concerned that because of the 9mm longer TT that the reach would be too long on the larger frame.

The dimensions of the larger one are

Top Tube - 569mm
Head Tube - 170mm
BB Drop - 70mm
HT Angle - 73°
ST Angle - 73°

I know this is all guess work at the moment but would this be a closer match if I kept a 110mm stem?

I can happily come down from the 580 stack of the Felt as I am slimmer and more flexible than when I bought it and I feel I can get a bit lower when in the drops and on the hoods, plan is to drop by 10mm by next season.

darkhairedlord

JesseD wrote:

darkhairedlord wrote:

looks like a lot smaller. the bb drop is the same as are the seat tube and head tube angles so the only diffrence is the top-tube and headtube. Both are smaller. By the time you've added some spacers to bring the stem to the same height the reach will be even smaller. To get the stack this would need about 40mm of spacers and would pull the reach back by about 20mm compared to the Felt. if you want similar geo to the felt you might be better off looking at the next size up, unless you were after a lower front end in which case shove a longer stem on it.

Ok thanks, was concerned that because of the 9mm longer TT that the reach would be too long on the larger frame.

The dimensions of the larger one are

Top Tube - 569mm
Head Tube - 170mm
BB Drop - 70mm
HT Angle - 73°
ST Angle - 73°

I know this is all guess work at the moment but would this be a closer match if I kept a 110mm stem?

I can happily come down from the 580 stack of the Felt as I am slimmer and more flexible than when I bought it and I feel I can get a bit lower when in the drops and on the hoods, plan is to drop by 10mm by next season.

the extra 10mm of spacers to get the same sstack will essentially push the reach back by about 3mm, making the TT "effectively" shorten to 565/566. Couple this with the 1/2 degree shallower seat tube angle (meaning the TT is measured slightly further back than the felt) and it wont be far off. A change of stem to 100 instead of 110 might still be in order but it will be there or there abouts.*

*Note, this is only opinion, you will need to do your own calculations as it's your money!

mfin

Above post is about right, all the logic is there, this Large is the closer sized to your current bike.

OP, in your original post you said you'd likely wanna come down 10mm on the front, so you'll still be good.

So, I agree with darkhairedlord's assessment.

The other one you listed was too small and low, this large one looks about right (in fact it's pretty damn good).

Bear in mind your saddle will be further forward on the rails if the seatpost was identical, as in same layback. That will position you correct fore-aft again in relation to the BB. So, assess the layback of your current seatpost vs the one on the new bike, or perhaps you will be using the same one?

(Note if you already run a seatpost forward on the rails it can be worth moving to one with less layback on that 73 half a degree slacker seat tube angle of the new frame in large).

JesseD

mfin wrote:

Above post is about right, all the logic is there, this Large is the closer sized to your current bike.

OP, in your original post you said you'd likely wanna come down 10mm on the front, so you'll still be good.

So, I agree with darkhairedlord's assessment.

The other one you listed was too small and low, this large one looks about right (in fact it's pretty damn good).

Bear in mind your saddle will be further forward on the rails if the seatpost was identical, as in same layback. That will position you correct fore-aft again in relation to the BB. So, assess the layback of your current seatpost vs the one on the new bike, or perhaps you will be using the same one?

(Note if you already run a seatpost forward on the rails it can be worth moving to one with less layback on that 73 half a degree slacker seat tube angle of the new frame in large).

Thanks both,

Mfin - yes i reckon 10mm is doable in 6 months.

With regards to seatpost, i have a 25mm layback on at the moment however should really have an inline one, saddle is pretty forward.