Frame with 72deg seat tube angle and short stack/reach

Discuss light weight issues concerning road bikes & parts.
zefs
Posts: 436
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

Anyone aware of road bike frames (carbon,steel,ti) with 72deg STA ~580 stack ~390 (max) reach?
Lightweight is important but can't find carbon frames with that kind of geometry.
Van Nicholas Boreas in XL/Bianchi Intrepida have similar specs with 72 STA but looking for more options.
Happy Holidays!

MarcFaFo
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Joined: Fri Sep 14, 2018 4:58 pm

by MarcFaFo

Colnago is almost there

by Weenie


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Calnago
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by Calnago

Unless there is some morphological or aesthetic reason you specfically need a 72 degree seat angle, what you really should be concerned with is whether or not you can get your saddle in the right place in space with the given seat tube angle you have to work with through both moving the saddle fore and aft along the existing rails of the seat post, or consider a different post with a different offset (seatpost offset and saddle setback are two different things by the way). Given that you're looking for a 72 degree seat angle, I'm going to assume you're fairly tall. I'm 6'1" (184cm) for example, and I've found that the perfect seat tube angle for me (road bike) is between 72.75 and 73 degrees with a seatpost offset of 20-25mm. That will ensure that the clamp is pretty much centered on the rails, which is good for both functional support of the saddle and just plain looks a lot better than having the saddle clamped at either extreme of the rails. TT positions or very aero road bike postiions would have me more forward, thus steeper seat tube angles on tt bikes, and maybe even a road bike if you ride that way all the time. Those numbers I threw out there are just for my situation and yours may be quite different but the concept’s the same. 72 degrees would not be inappropriate for someone taller. The trouble with going much slacker is that at some point it starts interfering with tire clearance if you’re building a road bike with fairly tight geometry. So a really tall guy with a super slack seat tube angle (for fit) may run into clearance issues especially if really short chainstays are thrown into the mix. But as the weight moves further and further back, as it would with a tall fellow and decent saddle setback, hopefully the chainstays will also be lengthened a bit (it doesn’t take much) in proportion to the change in weight distribution for handling’s sake.

As for the reach and stack, that has nothing to do with seat tube angle, since reach is measured from a vertical line through the center of the bottom brakcet. You could have any seat tube angle and reach will not be affected.
Last edited by Calnago on Fri Dec 28, 2018 8:24 pm, edited 1 time in total.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

zefs
Posts: 436
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

Reason is long inseam for my height, basically a 73sta with 25mm offset and the saddle all the way back isn't enough to keep me balanced and not slide forward when applying power (saddle is level and saddle drop is small). But I think it could be balanced with longer cranks and moving the cleats a bit further back, as well as a longer stem. The longer stem does not fix the saddle setback (since that's about leg length) but it will atleast let my upper body go where it needs when sliding forward does happen, and unload the shoulders otherwise the body is always tensioned.

Etienne
Posts: 182
Joined: Tue Aug 23, 2005 11:41 am
Location: France

by Etienne

Hi,

I don't know exactly why sliding forward on your saddle leads you to the conclusion that you saddle setback is not large enough ... but I would firstly look around saddle height because in my experience, sliding forward (considering cockpit length is adequate) is often linked to the need to reduce the distance between your pelvis and the pedals.

If the meaning of "balanced" is "weight balance", my personal experience as a long legged guy is that saddle setback should not be to pronounced as it put too much weight on the rear wheel, affecting confort and handling.

My different bikes have 73° with no setback to 73.5° with 15mm setback seatposts ... so nothing too fancy here.

E

zefs
Posts: 436
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

I think it's the opposite, sliding forward means the pelvis is not far back in comparison to the pedals. If I sit on the widest part of the saddle I am stable but I don't think that's the correct spot to sit, unless I've gotten that part wrong.
I will try a longer stem and see how it goes.

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wheelsONfire
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Location: NorthEU

by wheelsONfire

Ax Lightness Vial EVO Race size 56/ Large
Stack 578mm, reach 380mm (head tube 73 degree / fork rake 46mm)
TT 561mm = setback 181mm (seat tube angle = 72.6 degree)

Got this myself. Previous bike was Large Vial EVO D.
Reach 394, seatback 171mm. Both angles 73.5 degree on this frameset.
Slightly higher stack (5mm) due to longer fork.

Incl with EVO Race, a headset dust cover at 5.3mm expander, top cap and screw 18 grams.
New design seat tube clamp, 12mm height, with a stopper so it doesn't slide under seat mast tube top edge.
Instead of even thickness, it's just a bit thicker at top and bottom.
All hardware and screws black.

The frame is really gorgeous in gloss with black decals.
Fork is matched (ofcourse).
This new 2018 model, is redesigned for higher stiffness.
Weight of frame, BB, headset and seat tube clamp, 940-950 frams.
Fork 306 grams uncut.
UCI approved. Decals under clear coat.

Good clearance for 25mm tubulars. I think for tubulars, you could use 28mm on the rear. Front tire could be a bit too close due to height of tires (28mm).
Bikes:

Ax Lightness Vial EVO Race (2018.12.21)
viewtopic.php?f=10&t=156137
Paduano Racing Fidia (kind of shelved)
Open *UP* (2016.04.14)


Ex bike; Vial EVO D

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wheelsONfire
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Location: NorthEU

by wheelsONfire

Btw, i don't agree a slacker seat tube angle is affecting anything regarding chainstays lenght.
If you run a 73-73.5 degree seat tube and a setback seatpost, or if you run a slacker seat mast tube of 72 degree and a 0 setback seatpost, may give same position over BB.
Rather look at the reach of the frame pending on if you run a long reach frame and short stem. Or short reach frame and longer stem.
If a bike has short trail aka fast steering, a longer stem helps the bike to be more stable. Not to mention you may get a better weight balance (in my case atleast)
There's IMO, far to few options of a shorter reach frame these days. If you look for that, you're looking at Colnago, Trek Domane or Specialized Roubaix.
These bikes also give you a too high stack.
Bikes:

Ax Lightness Vial EVO Race (2018.12.21)
viewtopic.php?f=10&t=156137
Paduano Racing Fidia (kind of shelved)
Open *UP* (2016.04.14)


Ex bike; Vial EVO D

zefs
Posts: 436
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

Yeah the reach is short since it's endurance geometry, but I also need more setback that's my understanding. This frame doesn't allow a different seatpost thanks to Giant as it only accepts the D-fuse seatpost which is not round. The clamp mechanism is weird too, it only allows the angle to be set by increments of ~2 degrees which is not ideal.

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wheelsONfire
Posts: 2794
Joined: Mon Jul 07, 2014 8:15 am
Location: NorthEU

by wheelsONfire

Which frame do you talk of now?
A Giant?
I prefer these classical bikes like Ax. Lots of seatpost options, no need for idiotic side clamp posts or being forced to one standard.
Integrated bikes might look sleek, but i am not for it when it comes down to what i would actually buy.
Bikes:

Ax Lightness Vial EVO Race (2018.12.21)
viewtopic.php?f=10&t=156137
Paduano Racing Fidia (kind of shelved)
Open *UP* (2016.04.14)


Ex bike; Vial EVO D

Mr.Gib
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Joined: Fri Mar 18, 2005 4:12 pm
Location: eh?

by Mr.Gib

@zefs, sounds like there is some confusion. I'd sort out your position and your thoughts on how you should be positioned before shopping for a frame. If you are sliding off the front of your saddle, like Etienne noted, it is likely your saddle is too high or too far back, not the other way 'round.

And definitely give some thought to cleat position. If you have big feet, with some shoe and pedal combinations the furthest back cleat postition just barely gets the pedal in the correct position. Eg, with my SWorks size 45 and Shimano pedals, I can just barely get the spindle of the pedal under the ball of my foot with the cleat slammed all the way back.

Unfortunately the era of slack seat tubes seems to be over. Outside of the huge sizes, 73 degrees is pretty much it, with more frame moving to 73.5.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

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Calnago
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by Calnago

So you're sliding off the front of your saddle and think that both more saddle setback AND a longer stem might be the solution? I agree there may be some confusion here, and I'm leaving it at that.
wheelsONfire wrote:
Sat Dec 29, 2018 3:29 pm
Btw, i don't agree a slacker seat tube angle is affecting anything regarding chainstays lenght.
If you run a 73-73.5 degree seat tube and a setback seatpost, or if you run a slacker seat mast tube of 72 degree and a 0 setback seatpost, may give same position over BB.
Regarding the chainstays, for sure they have nothing to do at all with where you end up in relation to the BB, you can get there in several ways as you point out. But the chainstay lengths have a lot to do with overall weight distribution and overall handling. Take an extreme example, which I often like to do just to demonstrate the idea... As you sit further and further back and higher (as you would being a taller person) the weight distribution also moves further over the rear wheel. If you were a giant among cyclists and men in general and say 8' tall or something, by the time you were seated on the bike, without lengthening the chainstays you could very easily find yourself flipping backwards (at least getting started for a wheelie might even make Sagan jealous). And conversely if you're really short... as short as chainstays as possilbe might be preferrable here but then you have the constraints of the rear wheel clearnace etc. Back to normal ranges for a road race bike, the difference between a shortish 405mm and longish 415mm chainstays (typical road race geo) is quite large. I argue that I can absolutely feel the difference between two bikes with that being the difference. So, not related to fit at all, but certainly a part of the equation when talking about weight distriubtion between the wheels, as the OP seems to be concerned with as well.

To the OP... as a good very general guideline as to your balance on the bike... can you ride comfortably with no hands, sitting up, without sliding forward? Is your saddle the right tilt, preferably pretty level so that you don’t have to push back with your legs just to keep from sliding off? That can make a big difference. Then, when you're say on the hoods riding, can you just sort of hover over the hoods with your hands just above them but not touching without immediately falling back onto the hoods. That's also a good sign of being nicely balanced on the bike. Doesn't apply to TT positions etc, with weight really far forward, but for general road riding it's a good check.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

Etienne
Posts: 182
Joined: Tue Aug 23, 2005 11:41 am
Location: France

by Etienne

zefs wrote:
Sat Dec 29, 2018 2:23 pm
I think it's the opposite, sliding forward means the pelvis is not far back in comparison to the pedals. If I sit on the widest part of the saddle I am stable but I don't think that's the correct spot to sit, unless I've gotten that part wrong.
I will try a longer stem and see how it goes.
Well, let's sum up the problem : sliding forward AND not stable unless you sit on the back of the saddle ... and you end up concluding that you need more setback and a longer stem :shock:

I think you should read carefully Gib's and Calnago's advices !

zefs
Posts: 436
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

I didn't say I need both, but when I slide forward I need more reach to be able to relax my upper body/shoulders. The longer stem would be 14cm on a 56 frame which seems a lot (although I have long arms), unless I needed a 58 size. If I place my sit bones on the wings of the saddle (widest part) I am quite stable and can rotate the pelvis forward which straightens the spine and I can breathe easier, but probably not the correct place to sit on since I feel hip movement restriction and get irritation on left side only. That is what led me to think I could use more setback, on current stem reach.

Saddle height is correct, I am using the heel method with no hip drop.

Unless it's a saddle width issue/where I sit on the saddle, which is a flat Arione R3 open large (142mm) for 120mm sit bone measurement (although I had the same issue with all the saddles I tried which are 143mm+, I try to sit further back and get irritation left side).
Maybe if I use the 132mm saddle I would be able to sit on the widest part without getting the irritation I mentioned.

Here's a picture to explain it better (green is where I want to sit to be stable, red is where I end up, the difference is around 3-5cm):
Image

by Weenie


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wheelsONfire
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by wheelsONfire

If i sit where my body rest well enough to bike with no hands on the bar, i feel less ok when i am pedaling. I somehow need to be more forward for comfort when pedaling and holding the bar. Weird, but that's how it goes. I feel better when i am on a wide nose saddle, more balanced.
I hate when the tail have even a small tail up/ rise. Which IMO, almost all saddles have to some degree.
Saddles with cut out, more often than seldom dip/ sag between rear and nose, which again (since dipping), makes the tail/ rear become unpleasant.
Padded bib shorts (which all are) makes things even worse. Since they're always thicker under sit bones.
I'd rather have a thin padded chamois just hindering friction. No padding in terms on padding that build up.
No saddle is designed with bib shorts chamois. Chamois add material, therefor also altering the shape of the saddle.

I have just ordered SQ Labs One12 bib shorts. These are radically different and only 4mm thick, as thickest.
Bikes:

Ax Lightness Vial EVO Race (2018.12.21)
viewtopic.php?f=10&t=156137
Paduano Racing Fidia (kind of shelved)
Open *UP* (2016.04.14)


Ex bike; Vial EVO D

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