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

Discuss light weight issues concerning road bikes & parts.
zefs
Posts: 387
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

Yeah, it's weird...about the pedalling motion, I think it's related to hip angle since it's closing as you sit further back (that is why you also need to go up as you go back). Another reason that makes me think I need more setback is hamstrings/glutes are not working unless I sit on the position I mentioned (3-5cm back) and only quads get soar but that kind of setback would require custom geometry since it's ~1cm of setback per degree.

reedplayer
Posts: 460
Joined: Sat Nov 14, 2015 10:10 am

by reedplayer

ridley helium L, 575 stack, 390 reach, sa 73°

by Weenie


none
Posts: 117
Joined: Mon Dec 17, 2018 11:29 pm

by none

AFAIK, the further setback you have from B/B, the lower the seat height.
Maybe you slide forward because your seat height is too long?
Maybe try tilting the saddle nose up to prevent sliding forward, it may not look pleasant, but it would function properly, and much easier adjustment than having a custom frame built with 72 sa.

jih
Posts: 243
Joined: Fri Jan 29, 2016 12:54 pm

by jih

Why not get a seatpost with the most setback that you can find? That’ll give you the same position as a really slack seattube angle, but for much cheaper to try it out until you know exactly what position you need.

Velo Orange do a seatpost with a ton of setback. Probably there are others too.

mattr
Posts: 4600
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Why not get a proper fit?

Zakalwe
Posts: 549
Joined: Sun Jun 17, 2012 3:15 pm

by Zakalwe

zefs wrote:
Sun Dec 30, 2018 11:31 am
I think it's related to hip angle since it's closing as you sit further back (that is why you also need to go up as you go back)
Yeah, that’s not right. No one does this.

bikeboy1tr
Posts: 361
Joined: Thu Mar 21, 2013 3:19 am
Location: Southern Ontario Canada

by bikeboy1tr

mattr wrote:Why not get a proper fit?
Oh oh not one of many bike fit threads again. I was trying to search out the title of one thread, think it was, Not wasting more money on a another bike fit. Lots of great information there.

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"Life is like riding a bicycle. To keep your balance you must keep moving"-Albert Einstein
2018 Colnago V2R Rim Brake
2014 Norco Threshold Disc Brake
2012 Time RXRS Ulteam Rim Brake
2008 Time VXR Rim Brake
2006 Ridley Crosswind Rim Brake

mattr
Posts: 4600
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Yeah. It gets painful after the 25th time.

https://weightweenies.starbike.com/foru ... 3&t=154329

That the most recent bike fit thread.

zefs
Posts: 387
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

Where do you guys place the sit bones in the saddle based on the image I posted? And do you move from that spot when doing intervals for example?
Last edited by zefs on Sun Dec 30, 2018 4:46 pm, edited 1 time in total.

bikeboy1tr
Posts: 361
Joined: Thu Mar 21, 2013 3:19 am
Location: Southern Ontario Canada

by bikeboy1tr

That's the thread @ mattr I got educated on a couple things there.

Sent from my STH100-1 using Tapatalk



"Life is like riding a bicycle. To keep your balance you must keep moving"-Albert Einstein
2018 Colnago V2R Rim Brake
2014 Norco Threshold Disc Brake
2012 Time RXRS Ulteam Rim Brake
2008 Time VXR Rim Brake
2006 Ridley Crosswind Rim Brake

zefs
Posts: 387
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

Not a big deal, will test the new stem as well as saddle width and come to a conclusion.
Have a great new year everyone! :beerchug:

jlok
Posts: 970
Joined: Tue Jun 30, 2015 3:30 am

by jlok

I was attracted to this thread by the 72 degree sta.

First, I agree with Calnago. Riding no hands comfortably / hovering around handlebar without touching it is a good check on balance, which has something (or much) to do with saddle position.

Long story: I was convinced that slamming the stem was the right thing. In order to do that I pushed forward the saddle to compensate for / keep the saddle tip to hood reach (ard 690, drop was around 100). Effective STA was increased as a result. I couldn't ride handsfree. That was a Giant Propel Disc Size M (STA 73, eTT 550, stack 545).

I changed to T1sl Disc Size M (STA 73.5 eTT 540 Stack 545) without bike fit 'cos I thought I had been doing the right things (by comparing only Reach/Stack, pretty stupid). Yet, I got a chance to visit a bike fit and got convinced that the geometry that suits me is (STA 72, TT 540, saddle to bar drop 60, combining with the suggested cockpit the resultant saddle tip to hood is around 700).

I have a 25mm setback seatpost and used up all the rail on my Pro Stealth to push back the saddle. The STA is simply too steep for my femurs at 73.5. But I already felt what Calnago says. I can now ride handsfree easier. Control felt more confident due to the more sorted position. And I realize I'm not that flexible to accomodate big handlebar drop...

Setting a STA 73.5 bike with effective STA at 72 means the eTT is increased by 1.5 cm (let's just assume 1 degree STA worths very roughly 1cm of fore/aft adjustment). So cockpit reach (stem + handlebar) has to be reconsidered. The best for me is to get a bike with 72 STA and zero degree WW seatpost. That's why I'm here. Guess I have to go custom to get the perfect bike for me.
Litespeed T1sl Disc / BMC TM02 < Giant Propel Advanced SL Disc 1 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

zefs
Posts: 387
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

I've done the same, with a 35mm offset Canyon seatpost and had to switch to a 10cm stem from 12cm.
The problem is the whole geometry plays a role, even if you swift the body weight to the back of the bike there are parameters like wheelbase/chainstay length and fork trail that don't change but it doesn't apply to everyone since someone with smaller proportions/ better flexibility/lower weight could get away with it.

Then as you mention if you want to use a specific saddle you might get out of rails adjustment if you are in a similar situation. For me the issue was that I needed a 56 endurance geometry for the type of riding I do and got a 54 racing geometry.

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wheelsONfire
Posts: 2739
Joined: Mon Jul 07, 2014 8:15 am
Location: NorthEU

by wheelsONfire

Oops, double post
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

by Weenie


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hfx
Posts: 8
Joined: Mon Mar 27, 2017 1:03 pm

by hfx

Take a look at the Lapierre Xelius, I would say the numbers are quite close to what you're looking..
Image

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