Frame size, new bike fitting, questions

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TobinHatesYou
Posts: 13009
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

tourniquet wrote:
Mon Mar 27, 2023 11:11 am
Hey, I need a new bike frame and I was wondering if you have some ideas.

Background:
In 2018 I bought a Hongfu FM008 in Size 50 and built my first real road bike. I'm 170cm tall (short, lol) and have 81cm inseam (relatively long legs for being short).
In order to look cool I cut the steerer (too) short and now the geometry is just too agressive for my body dimensions. Can't really ride in the drops.

Yes, the FM008 is sometimes marketed as an Endurance frame, but in the small sizes the headtube is rather short... maybe the linear scaling of stack and reach throughout the sizes is not that good... but that's another topic.

long story short: Either I buy handlebars with +2cm rise (meh) or I swap the frame.

Any recommendations for a small rim brake frame with relaxed geometry that doesn't look super ugly?
  • I am open to open mold as well as western brands.
  • 28mm tire clearance would be cool (the FM008 even struggles with 25mm)
  • Standard 27mm seatpost would be cool (because I need 0 offset)
Geometry-wise the Emonda ALR with H2 geometry seems like something that could suit me, but it's alloy, relatively expensive, the sloping in small sizes looks extreme, and requires Direct Mount Brakes.

The 2018 Emonda SLR H2 rim-brake frame may still be available, but it is costly.

https://www.trekbikes.com/us/en_US/bike ... t/p/28103/

Looks like they may finally be running out of blanks in common sizes too.

by Weenie


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inertianinja
Posts: 296
Joined: Wed Jan 26, 2011 3:14 pm

by inertianinja

I'm considering getting an Aethos this year, would love some help confirming the size.

Previously I was on an FM-066, size 56, with a 110mm stem, one 5mm spacer, and bars with 70mm reach. It was low but i felt comfortable on it.
Now I'm on an Ostro size 56, slammed, 110mm stem, bars with 80mm reach, and it's a touch long for me.

I put the Ostro and FM-066 up against the Aethos 56 and 54:

Image

It seems like the 56 is right in terms of stack/reach, but I'm confused by the longer effective TT length - what effect will that actually have?

Does this just mean that the front-center is smaller? I'd end up with a saddle more forward than on the other bikes?

kafreeman
Posts: 173
Joined: Thu Jul 23, 2015 8:46 pm

by kafreeman

It's the higher stack height increasing the effective top tube length.

Top tube length should be equal to the reach plus the distance from the bb to the centerline of the seat post at the stack height.

The FM-066 and Aethos appear to have the same seatpost angle, so bb to seatpost are going to be the same for a given bb to saddle measurement. The Aethos will have a greater bb to post measurement because of the higher stack.

You can take the tangent( 90-seapost angle ) * stack height

tan((90−73.5))×557.5=165.14

tan((90−73.5))×565=167.36

Sent from my SM-G998U using Tapatalk



Weber
Posts: 125
Joined: Sat May 15, 2021 11:21 am

by Weber

Can someone enlight me because i found contradictory information about anteversion and retroversion of pelvis in road cycling. Which one is more desirable?

TobinHatesYou
Posts: 13009
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Weber wrote:
Sat Apr 29, 2023 10:11 pm
Can someone enlight me because i found contradictory information about anteversion and retroversion of pelvis in road cycling. Which one is more desirable?

You want anterior pelvic rotation to minimize arching in the spine. It also gets you in a far lower position and gives you a longer effective reach.

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godspeed
Posts: 19
Joined: Sun Nov 20, 2022 2:33 pm
Location: Lamia , Greece
Contact:

by godspeed

Hello there !

Iam about to pull the trigger on Oltre '12 49 size. It will be 3 sizes smaller than normal.( Iam 172cm - 79inseam ) Iam thinking to put longer stem to fix that top tube difference. What else problems will i have? It is right to use this size? Post your similar expiriences !

DaveS
Posts: 3939
Joined: Fri Mar 24, 2006 1:26 pm
Location: Loveland Colorado

by DaveS

Effective TT length has no bearing on the fit. To compare the reach properly, you have to reduce the reach of the frame with the shorter stack by 3mm for each 10mm of stack height difference. That assume that spcers will be used on the smaller stack frame to make it identical to the frame with the larger stack. Sometimes, stem angle can be used instead of spacers to bring up the bar height of a small frame.

steveadore
Posts: 399
Joined: Wed Mar 04, 2020 10:01 am

by steveadore

Hello,
I'm 179 cm tall, with shorter legs (saddle height of 714mm on 170mm cranks), longer torso, short arms (negative ape index: 175 cm wingspan) and rather average flexibility for my 48 years (I'm fit, lean, and ride regularly, but my saddle to bar drop is only around 3 cm, due to my short arms and short legs). I've been riding a 2013 Specialized Roubaix SL3 in size 56 with 90mm negative 12 degree stem for years and (having been professionally fitted) this bike just feels great to me. I can easily do a century and still feel fresh at the end.

Now I've been tempted to pick up a new old stock Specialized Tarmac SL6 rim brake bike (the last of its kind) at a very good price, so I'm having difficulties trying to make a rational decision. The problem is the following: the Tarmac is also a size 56, like the Roubaix, but it has an 8mm longer reach and 25mm lower stack. Since I would use 18-20 mm more spacers on the Tarmac, I could decrease the effective reach difference to only 3 mm, but the stack would still stay lower by 1-2 mm too. This is probably still manageable, especially as I plan to use the same bars on both (and also the same saddle & saddle setback, as the seat tube angle difference is almost negligible: 0.25 degree steeper on the SL6).

BUT, and this is main concern, I would also need to use a 90mm stem on the Tarmac (actually 85mm would be ideal, but that's far too short and not readily available anyway), on top of 30mm spacers, to achieve this (i.e. the 3mm longer reach and 1-2 mm lower stack compared to my Roubaix). AND the head tube angle on the Roubaix is 1 degree slacker (72.5 degrees) than on the Tarmac (73.5 degrees). Both the Roubaix and the Tarmac came with 100mm stock stems in size 56, but on the Roubaix I went down to 90m after my Retul fit many years ago, and on the Tarmac the seller fitted a 90mm (negative 6 degrees) stem for me.

What really bugs me is whether the inherent twitchiness of the SL6 geometry (especially in larger sizes, such as the 56) much worse. As I said, 90mm is the max stem length I could use on this long bike, and while the 90mm stem on my slacker, endurance-geometry Roubaix feels perfect to me, I wonder if this could be a major issue on the Tarmac? I would use the Tarmac for the same purpose as the Roubaix (no racing, just all around rides for fun and fitness).

The fork trail figures between the two bikes are otherwise very similar (Tarmac 55m, Roubaix 56mm, according to Spesh charts, though I suspect the actual trail on the Tarmac might be a bit less than 55mm), but there's the problem of short stem + tall stack of spacers + steepish head tube angle. Do you think this combination is less than ideal? I've only been able to take the SL6 for a very short spin (15 minute test ride), set up according to my Retul fit numbers, with the 90mm stem, and it felt good, with balanced weight distribution, though I definitely noticed the somewhat more nervous steering compared to my Roubaix. It also felt just a little too long (tension in my lower back), even though the effective reach at the handlebar should be ~3mm longer and 2mm lower only according to my calculations).
I don't bomb downhills at high speed (50 km/h max, and then I pull the brakes), but I'm still wondering whether the SL6 in this size and with this setup is a good choice for me. I am aware that endurance bikes fit me better, but there's not much choice for a modern carbon bike with rim brakes and warranty (since the SL6 is new old stock) these days.
Here are some Bikegeo pictures too:
Screenshot 2023-05-16 at 19-39-08 Bike Geometry Calculator.png
Screenshot 2023-05-16 at 19-37-52 Bike Geometry Calculator.png
Screenshot 2023-05-16 at 19-37-20 Bike Geometry Calculator.png

TobinHatesYou
Posts: 13009
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

steveadore wrote:
Tue May 16, 2023 6:42 pm

though I suspect the actual trail on the Tarmac might be a bit less than 55mm

Why do you suspect that? Trail is a function of HTA, fork offset and wheel+tire dimensions. That 55mm trail figure is based on a 25mm tire size. If you ride a 28mm tire, the trail becomes 56mm.

The Tarmac might be twitchier for a number of obvious reasons. If it has narrower tires inflated to higher pressures for example...

Your short legs (less saddle setback) and long torso mean your center-of-mass is more forward than others. You would benefit from a bike with a longer front-center, but moderate-to-short reach. This means a bike with a slack HTA and a shorter stem in all likelihood. So yeah, an endurance bike makes the most sense. In your shoes I would choose a disc-brake bike that fits rather than a rim-brake bike that doesn't fit and by self-admission "feels nervous."

steveadore
Posts: 399
Joined: Wed Mar 04, 2020 10:01 am

by steveadore

TobinHatesYou wrote:
Tue May 16, 2023 11:26 pm
steveadore wrote:
Tue May 16, 2023 6:42 pm

though I suspect the actual trail on the Tarmac might be a bit less than 55mm

Why do you suspect that? Trail is a function of HTA, fork offset and wheel+tire dimensions. That 55mm trail figure is based on a 25mm tire size. If you ride a 28mm tire, the trail becomes 56mm.

The Tarmac might be twitchier for a number of obvious reasons. If it has narrower tires inflated to higher pressures for example...

Your short legs (less saddle setback) and long torso mean your center-of-mass is more forward than others. You would benefit from a bike with a longer front-center, but moderate-to-short reach. This means a bike with a slack HTA and a shorter stem in all likelihood. So yeah, an endurance bike makes the most sense. In your shoes I would choose a disc-brake bike that fits rather than a rim-brake bike that doesn't fit and by self-admission "feels nervous."
I'm sorry, 55mm trail for the SL6 was given in the Spesh geo charts, but the bikegeocalc gave me a bit less. In any case, I would use 28mm tires. But my short test ride was with the stock 24mm Spesh tires inflated to 100 psi.
Interesting what you say about slack HTA, long front center and short stem. The SL6 has 2 of those, but definitely not the slack HTA. And of course the shorter stem is not ideal for it. Just to clarify, the nervousness was not bad and it felt stable (and nimble). I just tried to sit up (place my weight rearward) and relax my hands on the bars, that's when I felt the steering to be more direct and quicker than on my Roubaix.
(I already have disc-brake bikes, I just need a backup rim brake one as a companion for the rim brake Roubaix, and the SL6 is the last of the mohicans, so to speak :) )

llpatrick
Posts: 27
Joined: Thu Apr 12, 2007 6:21 pm
Location: Singapore/Malaysia

by llpatrick

Hi All

I'm in search of a carbon disc Frameset that's light and with geometry close to a SworksVenge.

Disc Wheelset done at 1125gms with Light bicycle rims and I9 Torch

Anyone have any introduction to a Small frame that close to the size 49cm SworksVenge?

Bike build will be for a Taiwan Wuling ride. Maybe the KOM challenge later on.

With limited budget, can't go for the lightest of groupset
Mechanical shifting and Hydraulic brakes are the choice for easy flight arrangements.
I have the following components planned.
Sram
Force 2x 11 mechanical HRD with Ratio 12s mod
Rival 22 FD
Force 22 RD
Rival Quarq 48/35 2x 12 crank 170mm
Red Flat mount calipers
Red 12 chain/KMC X12
XPLR 10-44 Cassette 12s

Weber
Posts: 125
Joined: Sat May 15, 2021 11:21 am

by Weber

Hi, I m currently using a PRO LT Handlebar with a drop of 125 and a reach of 70, but I need to create more space in the front end of my bike. I'm considering two options: either increasing the reach to 80 or adding an additional centimeter to the stem by going from 110 to 120.

Any thoughts or recommendations regarding this matter?

Kubackjeee
Posts: 65
Joined: Mon Jul 11, 2022 9:43 am

by Kubackjeee

:)
Weber wrote:
Sat Jun 17, 2023 6:42 pm
Hi, I m currently using a PRO LT Handlebar with a drop of 125 and a reach of 70, but I need to create more space in the front end of my bike. I'm considering two options: either increasing the reach to 80 or adding an additional centimeter to the stem by going from 110 to 120.

Any thoughts or recommendations regarding this matter?
Longer stem would be cheaper and better option IMO if you find those handlebar and transition from bars to hoods comfortable.
Scott addict rc
Specialized Diverge e5 comp 2019

panuelos
Posts: 12
Joined: Wed Nov 10, 2021 6:20 pm

by panuelos

Hello, so i am not opening new thread i am wondering if anyone with BMC teammachine slr01 has fitted fizik antares adaptive 3d saddle with 7x10 rails successfuly or have you had to buy any new saddle clamps or default ones works ?

Thank you

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



wozzo
Posts: 107
Joined: Mon May 09, 2022 1:43 am

by wozzo

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Last edited by wozzo on Fri Jul 21, 2023 12:33 am, edited 1 time in total.

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