My brain hurts...a geometry conundrum
#1
Senior Member
Thread Starter
My brain hurts...a geometry conundrum
For the life of me, I cannot figure out why the fit on my two bikes do not match.
The two bikes in question are:
Cervelo R5: Stack: 548mm, plus 10mm top cap, 10mm spacer, 100mm -6 stem. The frame reach is 380mm. HT angle is 73
Orbea Terra: Stack: 560mm, plus 15mm top cap, 0mm spacer, 100mm -12 stem. The frame reach is 378mm. HT angle is 71
I'm using the same bars (77mm reach), saddle, saddle height, and saddle setback (laser measured) on both bikes.
Based on stem comparison tools (and mental math) the two bike should be, near-as-makes-no-difference, the same. Yet, my Terra has 1.5cm less saddle-to-bar drop and 1cm short reach (saddle nose to hoods)...anyone know what's going on? I've been struggling to get comfortable on the Terra since the day I got it (back in January), and I'm to the point that I'm ready to replace it.
The two bikes in question are:
Cervelo R5: Stack: 548mm, plus 10mm top cap, 10mm spacer, 100mm -6 stem. The frame reach is 380mm. HT angle is 73
Orbea Terra: Stack: 560mm, plus 15mm top cap, 0mm spacer, 100mm -12 stem. The frame reach is 378mm. HT angle is 71
I'm using the same bars (77mm reach), saddle, saddle height, and saddle setback (laser measured) on both bikes.
Based on stem comparison tools (and mental math) the two bike should be, near-as-makes-no-difference, the same. Yet, my Terra has 1.5cm less saddle-to-bar drop and 1cm short reach (saddle nose to hoods)...anyone know what's going on? I've been struggling to get comfortable on the Terra since the day I got it (back in January), and I'm to the point that I'm ready to replace it.
#2
Senior Member
Join Date: Jul 2006
Location: Lebanon (Liberty Hill), CT
Posts: 8,473
Bikes: CAAD 12, MASI Gran Criterium S, Colnago World Cup CX & Guru steel
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 1743 Post(s)
Liked 1,281 Times
in
740 Posts
Have you ever measured your inseam and the frame size of the bikes? By that I mean using a virtual TT to measure frame size. Just curious.
#3
Senior Member
Thread Starter
I've been fitted before, and the R5 is spot on.
There is only a 5mm difference in the EFF of the two bikes (548 vs 543), due to the slightly steeper ST angle of the Terra, and is account for with saddle setback.
There is only a 5mm difference in the EFF of the two bikes (548 vs 543), due to the slightly steeper ST angle of the Terra, and is account for with saddle setback.
#4
I'm good to go!
Join Date: Jul 2017
Location: Mississippi
Posts: 14,992
Bikes: Tarmac Disc Comp Di2 - 2020
Mentioned: 51 Post(s)
Tagged: 0 Thread(s)
Quoted: 6195 Post(s)
Liked 4,810 Times
in
3,318 Posts
BB drop. Maybe?
#5
Senior Member
Join Date: Apr 2012
Location: Nor Cal
Posts: 6,016
Mentioned: 17 Post(s)
Tagged: 0 Thread(s)
Quoted: 1814 Post(s)
Likes: 0
Liked 923 Times
in
569 Posts
It's a different bike for a different purpose- why do you want the exact same fit?
Beyond that, wouldn't it be easier to get a longer stem than to replace the bike?
Beyond that, wouldn't it be easier to get a longer stem than to replace the bike?
#6
Senior Member
Thread Starter
The BB drop is actually less on the Terra (70mm vs 72mm).
Plus, since all measurements are taken from BB center, it shouldn't have any effect...or does it?
Plus, since all measurements are taken from BB center, it shouldn't have any effect...or does it?
#7
Senior Member
Thread Starter
Yes, I could throw on a -17, 110mm stem on, but based on the geometry of the two bikes, that should not be need...thus the point of this thread
#8
Senior Member
Join Date: Apr 2012
Location: Nor Cal
Posts: 6,016
Mentioned: 17 Post(s)
Tagged: 0 Thread(s)
Quoted: 1814 Post(s)
Likes: 0
Liked 923 Times
in
569 Posts
A more upright "gravel" position doesn't work for me...my road fit is what is comfortable to me. Plus, I'm not doing anything super technical so there is no/need benefit to altering my position. I ride my gravel bike, like I do my road bike, so why should the fit be different?
Yes, I could throw on a -17, 110mm stem on, but based on the geometry of the two bikes, that should not be need...thus the point of this thread
Yes, I could throw on a -17, 110mm stem on, but based on the geometry of the two bikes, that should not be need...thus the point of this thread
Seems like the longer wheelbase would make a difference.
Have you tried lining them up side-by-side?
#9
Senior Member
Join Date: May 2012
Location: Point Reyes Station, California
Posts: 4,528
Bikes: Indeed!
Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 1507 Post(s)
Liked 3,478 Times
in
1,132 Posts
The stem top cap does not enter into the equation because it is above the stem not under it. Therefor it has no effect on handlebar height.
The difference in handlebar reach may be accounted for by a difference in seat tube angle unless you measured your saddle setback from the vertical centerline of the bottom bracket.
Brent
The difference in handlebar reach may be accounted for by a difference in seat tube angle unless you measured your saddle setback from the vertical centerline of the bottom bracket.
Brent
#10
Senior Member
Thread Starter
The stem top cap does not enter into the equation because it is above the stem not under it. Therefor it has no effect on handlebar height.
The difference in handlebar reach may be accounted for by a difference in seat tube angle unless you measured your saddle setback from the vertical centerline of the bottom bracket.
Brent
The difference in handlebar reach may be accounted for by a difference in seat tube angle unless you measured your saddle setback from the vertical centerline of the bottom bracket.
Brent
Maybe it does have something to do with the longer wheelbase/fork length(cervelo doesn't list it)/HT angle...but since everything is measured from BB centerline, it really shouldn't affect the overall stack/reach.
#11
Senior Member
The reach difference has to be due to the saddle position, relative to the BB. Use a plumb Bob to check the nose of the saddle, relative to the BB.
Carefully check the saddle height on both bikes, from the center of the BB.
I measure the saddle to bar drop, vertically from the floor. If one is less than the other, just remove spacers to make them the same. Stems lengths can be measured differently and the angle also affects the horizontal length.
There could also be a mistake in the bike geometry charts.
Start with the saddle fore/aft and height and go from there.
Carefully check the saddle height on both bikes, from the center of the BB.
I measure the saddle to bar drop, vertically from the floor. If one is less than the other, just remove spacers to make them the same. Stems lengths can be measured differently and the angle also affects the horizontal length.
There could also be a mistake in the bike geometry charts.
Start with the saddle fore/aft and height and go from there.
#13
Senior Member
Join Date: Jul 2007
Posts: 7,570
Mentioned: 54 Post(s)
Tagged: 0 Thread(s)
Quoted: 1851 Post(s)
Liked 679 Times
in
430 Posts
Have you tried any of the online caclulators?
Bikegeo.net is a good place to start.
And Stem Comparison Tool | yojimg.net is a great stem comparison tool.
Bikegeo.net is a good place to start.
And Stem Comparison Tool | yojimg.net is a great stem comparison tool.
#14
Senior Member
Thread Starter
The reach difference has to be due to the saddle position, relative to the BB. Use a plumb Bob to check the nose of the saddle, relative to the BB.
Carefully check the saddle height on both bikes, from the center of the BB.
I measure the saddle to bar drop, vertically from the floor. If one is less than the other, just remove spacers to make them the same. Stems lengths can be measured differently and the angle also affects the horizontal length.
There could also be a mistake in the bike geometry charts.
Start with the saddle fore/aft and height and go from there.
Carefully check the saddle height on both bikes, from the center of the BB.
I measure the saddle to bar drop, vertically from the floor. If one is less than the other, just remove spacers to make them the same. Stems lengths can be measured differently and the angle also affects the horizontal length.
There could also be a mistake in the bike geometry charts.
Start with the saddle fore/aft and height and go from there.
Then I've measured saddle-to-bar drop from the floor, along with a laser level along the handlebar plane...I keep getting the same number, as well. Stems were also measured, and both are 100mm. Technically speaking, the -12 stem should have a slightly longer reach, yet that is the bike that is coming up short.
I've run out of spacers to remove, and, as mentioned above, I'm more concerned with WHY the numbers aren't lining up, when the math says that they should...I shouldn't have to run a -17 stem, and a low-stack top cap to account for a 12mm difference in frame stack.
I'm going to have to assume that something is off with the geometry chart, as well
Same exact saddle on both bikes, so measuring from the nose works
#15
Senior Member
Thread Starter
Have you tried any of the online caclulators?
Bikegeo.net is a good place to start.
And Stem Comparison Tool | yojimg.net is a great stem comparison tool.
Bikegeo.net is a good place to start.
And Stem Comparison Tool | yojimg.net is a great stem comparison tool.
Then, I just ran the two bikes through Bikegeo, and this is what it gave me...
#16
Occam's Rotor
Join Date: Jul 2013
Posts: 7,248
Mentioned: 61 Post(s)
Tagged: 0 Thread(s)
Quoted: 2366 Post(s)
Liked 2,331 Times
in
1,164 Posts
For the life of me, I cannot figure out why the fit on my two bikes do not match.
The two bikes in question are:
Cervelo R5: Stack: 548mm, plus 10mm top cap, 10mm spacer, 100mm -6 stem. The frame reach is 380mm. HT angle is 73
Orbea Terra: Stack: 560mm, plus 15mm top cap, 0mm spacer, 100mm -12 stem. The frame reach is 378mm. HT angle is 71
I'm using the same bars (77mm reach), saddle, saddle height, and saddle setback (laser measured) on both bikes.
Based on stem comparison tools (and mental math) the two bike should be, near-as-makes-no-difference, the same. Yet, my Terra has 1.5cm less saddle-to-bar drop and 1cm short reach (saddle nose to hoods)...anyone know what's going on? I've been struggling to get comfortable on the Terra since the day I got it (back in January), and I'm to the point that I'm ready to replace it.
The two bikes in question are:
Cervelo R5: Stack: 548mm, plus 10mm top cap, 10mm spacer, 100mm -6 stem. The frame reach is 380mm. HT angle is 73
Orbea Terra: Stack: 560mm, plus 15mm top cap, 0mm spacer, 100mm -12 stem. The frame reach is 378mm. HT angle is 71
I'm using the same bars (77mm reach), saddle, saddle height, and saddle setback (laser measured) on both bikes.
Based on stem comparison tools (and mental math) the two bike should be, near-as-makes-no-difference, the same. Yet, my Terra has 1.5cm less saddle-to-bar drop and 1cm short reach (saddle nose to hoods)...anyone know what's going on? I've been struggling to get comfortable on the Terra since the day I got it (back in January), and I'm to the point that I'm ready to replace it.
https://geometrygeeks.bike/compare/c...-terra-2018-s/
#17
Senior Member
Join Date: Jul 2007
Posts: 7,570
Mentioned: 54 Post(s)
Tagged: 0 Thread(s)
Quoted: 1851 Post(s)
Liked 679 Times
in
430 Posts
I plugged the numbers into BikeGeo too. Fork length was not listed for Cervelo and Offset was not listed for the Orbea. I adjusted those numbers (386 and 52) until the tool gave me almost the exact mfg. listed stack, reach and wheelbase for the R5 and was 1 mm off on the stack/reach for the Terra.
When I did that. the stem reach was 473 and 471 and stack was 586 and 588 - which are essentially rounding errors. So, yeah, your math should be right and the fit should be the same for the two bikes.
Are you sure you have a -6 and -12 stems?
When I did that. the stem reach was 473 and 471 and stack was 586 and 588 - which are essentially rounding errors. So, yeah, your math should be right and the fit should be the same for the two bikes.
Are you sure you have a -6 and -12 stems?
#18
Senior Member
Why not pick the bike that you think has the best fit, then adjust the other to match it. I still say you can't trust geometry charts. If you're sure that saddle heights and setbacks, from the BB center, are the same, then do whatever is practical to make one bike about the same as the other. Since stems mostly come in 10mm increments and angle changes the horizontal reach, you may not be able to get them the same.
I had a Colnago and LOOK with that problem, I made the reach from the saddle to the bars the same, but one had a little more saddle setback than the other. It wasn't a big deal.
From what you've posted, a 110mm -17 stem would fix most of the issues. I know that someone makes a stem that's around -21.
I had a Colnago and LOOK with that problem, I made the reach from the saddle to the bars the same, but one had a little more saddle setback than the other. It wasn't a big deal.
From what you've posted, a 110mm -17 stem would fix most of the issues. I know that someone makes a stem that's around -21.
Last edited by DaveSSS; 06-26-20 at 02:45 PM.
#20
Senior Member
Thread Starter
I plugged the numbers into BikeGeo too. Fork length was not listed for Cervelo and Offset was not listed for the Orbea. I adjusted those numbers (386 and 52) until the tool gave me almost the exact mfg. listed stack, reach and wheelbase for the R5 and was 1 mm off on the stack/reach for the Terra.
When I did that. the stem reach was 473 and 471 and stack was 586 and 588 - which are essentially rounding errors. So, yeah, your math should be right and the fit should be the same for the two bikes.
Are you sure you have a -6 and -12 stems?
When I did that. the stem reach was 473 and 471 and stack was 586 and 588 - which are essentially rounding errors. So, yeah, your math should be right and the fit should be the same for the two bikes.
Are you sure you have a -6 and -12 stems?
Why not pick the bike that you think has the best fit, then adjust the other to match it. I still say you can't trust geometry charts. If you're sure that saddle heights and setbacks, from the BB center, are the same, then do whatever is practical to make one bike about the same as the other. Since stems mostly come in 10mm increments and angle changes the horizontal reach, you may not be able to get them the same.
I had a Colnago and LOOK with that problem, I made the reach from the saddle to the bars the same, but one had a little more saddle setback than the other. It wasn't a big deal.
I had a Colnago and LOOK with that problem, I made the reach from the saddle to the bars the same, but one had a little more saddle setback than the other. It wasn't a big deal.
I'm not trying to be hard headed about bike set-up, it's just that I know what works for me and what doesn't. An extra 10mm here or there, really screws with me.
#21
Batüwü Creakcreak
Join Date: Jan 2007
Location: The illadelph
Posts: 20,791
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 229 Post(s)
Liked 288 Times
in
160 Posts
Any issues with the saddle on the bike that doesn't fit as well? Are you sure it's pointed dead straight?
What exactly feels off with the fit? Just the drop is different?
What exactly feels off with the fit? Just the drop is different?
Last edited by ridethecliche; 06-26-20 at 03:29 PM.
#22
Senior Member
Thread Starter
No issues with the saddle.
It's just the stack and reach...too high and too short, which leads to me hunching over, which leads to extra stain on my shoulders and lower back.
It's just the stack and reach...too high and too short, which leads to me hunching over, which leads to extra stain on my shoulders and lower back.
Last edited by melikebikey35; 06-26-20 at 04:13 PM.
#23
Batüwü Creakcreak
Join Date: Jan 2007
Location: The illadelph
Posts: 20,791
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 229 Post(s)
Liked 288 Times
in
160 Posts
Throw another spacer or two under the stem of the terra and see how it shakes out. Silly reason to give up on a bike if it's too low and you have no spacers...
#24
Senior Member
Thread Starter
There are other things about the bike that I'm not super fond of, but if it was at least comfortable, I could live with it.
#25
Batüwü Creakcreak
Join Date: Jan 2007
Location: The illadelph
Posts: 20,791
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 229 Post(s)
Liked 288 Times
in
160 Posts
The Terra is the bike that is too high and too short...and I'm out of spacers to remove. I'll try to source a lower headset cover in order to get me another ~5mm of drop, and see if that helps.
There are other things about the bike that I'm not super fond of, but if it was at least comfortable, I could live with it.
There are other things about the bike that I'm not super fond of, but if it was at least comfortable, I could live with it.
If neither of those two simple things don't work then I'd just sell it and get something you like better.
Any more than that and you're just spending time trying to make something work that you're not happy with when you're better off just riding what does work or getting something that *actually* works.
You could also try bars with slightly more drop and/or reach to see if that makes things better.