Felt IA10 Frame Sizing Help

May 26, 20 9:36

Post #1 of 26 (3346 views)

I need some help in deciding what size IA10 frame to buy. I'm stuck between two sizes: 48cm and 51cm.
Went to Pedro to get a sizing fit, and these are the numbers:

Quote:

Height: 5’5 / 1665
Shoulder width: 38
Crotch/inseam: 820
Trunk(measured from the pubic bone to the jugular notch/clavicle notch): 530
Arm: 634
Forearm: 634
Femur shaft: 522
Sit Bone measurements: 143
RETUL MEASUREMENTS ROAD/TT
Saddle height: 73 (bottom to the top/center of saddle)
Saddle height 2nd location: 89 (bottom of the crank-6 o’clock to the top/center of saddle)
Suggested crank length: 165
Seat Tube angle: 79.0 degrees
Head Tube angle: 71.5 degrees
Effective Top Tube : 48.6
Tip of saddle to center of handle bars or base bars(T.T.): 51.0
Tip of saddle to hoods or brakes of base bars(T.T.): 69.0
Stem Length: 90
Stem Angle: -6
Steer tube spacer: 20
Seat angle: -5
Name of saddle: ISM pn 2.1
Hoods/base bars degree angle: 11
DROP bars and height of saddle: 14
Aerobars bars degree angle: 7
Aero Bars pad height and saddle height: 90
Reach: 389
Stack: 501

Apparently I'm at the top end of the 48cm frame and at the lower end of the 51cm frame. Felt Support voted for 48cm based on my height and inseam measurements alone, though Pedro said either frame could work (both would need some adjustment). I'm not sure about the implications of going for one or the other. I would greatly appreciate any insight for swinging the vote one way or the other!

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 26, 20 10:04

Post #2 of 26 (3325 views)

The larger frame would probably reduce the risk of hitting your feet while turning.

The longer front center will probably render a more stable bike.

I’m 186cm (6’1) on a 58 IA10 with stock basbar and clamps using Wattshop 20 degree armrests and Zipp EVO110 aerobars. I have 10mm of spacing in total. I could have gone for a size 56 but reach is good and I won’t get more flexible so I won’t be able to go lower in stack.

Personal best:
Ironman 9:22:02
Ironman 70.3 4:20:00

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 26, 20 10:07

Post #3 of 26 (3322 views)

According to the Felt IA excel spreadsheet size calculator, none of them will work for you, possibly because of your low stack of 501. Is that a typo? That is a damn low stack height for someone with a 73cm saddle height.
Think you can download the spreadsheet here:

https://cdn.shopify.com/..._p.xlsx?v=1550114518

Last edited by: SBRcanuck: May 26, 20 10:08

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 26, 20 10:12

Post #4 of 26 (3312 views)

I'm not a fitter so I wont comment your measurements or give strong sizing reccomendation. The IA10 is a very nice bike If both sizes fit you can't really go wrong with either choice.

I was in the same position a few years ago fitting both a 51 and 54 IA. I ended up on the size 54 IA10.

If aerodynamics are a top priority for you a former felt employee said in the very long IA thread from a few years ago that the larger frame would be more aero.

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 26, 20 10:27

Post #5 of 26 (3297 views)

Thanks! The numbers are not a typo. I've reached out to Pedro to clarify those, but I'm suspecting that they might not referenced to the pads. I'm a bit more concerned about hitting the wheel than flexibility, as I have only one direction to go in from my current position (hopefully!)

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 26, 20 10:28

Post #6 of 26 (3295 views)

73cm saddle height seems really wrong.

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 26, 20 21:22

Post #7 of 26 (3239 views)

I am 5’5-5’6 have had 2 felts IA FRD and now AI3 I ride a 51....felts run small. When I bought my first one they thought I should be on a 48 but did a recheck and got the 51 they were right .

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 27, 20 1:43

Post #8 of 26 (3224 views)

conky2313 wrote:

I need some help in deciding what size IA10 frame to buy. I'm stuck between two sizes: 48cm and 51cm.
Went to Pedro to get a sizing fit, and these are the numbers:

Quote:

Height: 5’5 / 1665
Shoulder width: 38
Crotch/inseam: 820
Trunk(measured from the pubic bone to the jugular notch/clavicle notch): 530
Arm: 634
Forearm: 634
Femur shaft: 522
Sit Bone measurements: 143
RETUL MEASUREMENTS ROAD/TT
Saddle height: 73 (bottom to the top/center of saddle)
Saddle height 2nd location: 89 (bottom of the crank-6 o’clock to the top/center of saddle)
Suggested crank length: 165
Seat Tube angle: 79.0 degrees
Head Tube angle: 71.5 degrees
Effective Top Tube : 48.6
Tip of saddle to center of handle bars or base bars(T.T.): 51.0
Tip of saddle to hoods or brakes of base bars(T.T.): 69.0
Stem Length: 90
Stem Angle: -6
Steer tube spacer: 20
Seat angle: -5
Name of saddle: ISM pn 2.1
Hoods/base bars degree angle: 11
DROP bars and height of saddle: 14
Aerobars bars degree angle: 7
Aero Bars pad height and saddle height: 90
Reach: 389
Stack: 501

Apparently I'm at the top end of the 48cm frame and at the lower end of the 51cm frame. Felt Support voted for 48cm based on my height and inseam measurements alone, though Pedro said either frame could work (both would need some adjustment). I'm not sure about the implications of going for one or the other. I would greatly appreciate any insight for swinging the vote one way or the other!

There's a lot going on here.

1. Never pick a frame size by height.
1a. You're not between frames. Nobody is. There is an optimal size. Pick the longest frame that allows you to get low enough, and the lowest frame that allows you to get long enough.
2. By that framework, the Felt is a challenge because of the cockpit they choose to spec on it... it's too high stack and the stem is a positive angle stem, which is why you're at the "low end" of the 51.
3. That said, if you ditch the Felt pads and extensions and get the Profile Design Subsonic undermount you can get long and low on the right sized bike.
4. You do pick your cranks by height, among other things, however. 165mm is waaaaaaaaay long for you at 5' 5". 155 or less.

51cm Felt IA with Profile Design Subsonic mount and proper length cranks, 155mm or less. Ski bend extensions only.

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

Re: Felt IA10 Frame Sizing Help [ericMPro] [ In reply to ]

May 27, 20 6:11

Post #9 of 26 (3205 views)

ericMPro wrote:

conky2313 wrote:

I need some help in deciding what size IA10 frame to buy. I'm stuck between two sizes: 48cm and 51cm.
Went to Pedro to get a sizing fit, and these are the numbers:

Quote:

Height: 5’5 / 1665
Shoulder width: 38
Crotch/inseam: 820
Trunk(measured from the pubic bone to the jugular notch/clavicle notch): 530
Arm: 634
Forearm: 634
Femur shaft: 522
Sit Bone measurements: 143
RETUL MEASUREMENTS ROAD/TT
Saddle height: 73 (bottom to the top/center of saddle)
Saddle height 2nd location: 89 (bottom of the crank-6 o’clock to the top/center of saddle)
Suggested crank length: 165
Seat Tube angle: 79.0 degrees
Head Tube angle: 71.5 degrees
Effective Top Tube : 48.6
Tip of saddle to center of handle bars or base bars(T.T.): 51.0
Tip of saddle to hoods or brakes of base bars(T.T.): 69.0
Stem Length: 90
Stem Angle: -6
Steer tube spacer: 20
Seat angle: -5
Name of saddle: ISM pn 2.1
Hoods/base bars degree angle: 11
DROP bars and height of saddle: 14
Aerobars bars degree angle: 7
Aero Bars pad height and saddle height: 90
Reach: 389
Stack: 501

Apparently I'm at the top end of the 48cm frame and at the lower end of the 51cm frame. Felt Support voted for 48cm based on my height and inseam measurements alone, though Pedro said either frame could work (both would need some adjustment). I'm not sure about the implications of going for one or the other. I would greatly appreciate any insight for swinging the vote one way or the other!

There's a lot going on here.

1. Never pick a frame size by height.
1a. You're not between frames. Nobody is. There is an optimal size. Pick the longest frame that allows you to get low enough, and the lowest frame that allows you to get long enough.
2. By that framework, the Felt is a challenge because of the cockpit they choose to spec on it... it's too high stack and the stem is a positive angle stem, which is why you're at the "low end" of the 51.
3. That said, if you ditch the Felt pads and extensions and get the Profile Design Subsonic undermount you can get long and low on the right sized bike.
4. You do pick your cranks by height, among other things, however. 165mm is waaaaaaaaay long for you at 5' 5". 155 or less.

51cm Felt IA with Profile Design Subsonic mount and proper length cranks, 155mm or less. Ski bend extensions only.

I believe the Felt Bayonet 3 bars can also be underslung, though probably a less tidy solution than the Profile Design option.

Re: Felt IA10 Frame Sizing Help [ericMPro] [ In reply to ]

May 27, 20 9:55

Post #10 of 26 (3186 views)

I got the pad stack and pad reach numbers from Pedro -

Quote:

472-pad reach from bb
642-pad stack from bb
seat height-73

According to Felt's calculator they place me right on the 51cm frame. That said, Pedro had also configured the Retul for the 48cm frame and mentioned that it allowed me to go lower than the 51cm's position. I am not sure if I should be going that way for 112 miles, since I'm not really that flexible right now. Another thing that I forgot to mention - I'm building the bike from scratch while reusing some components from my previous bike, so I don't necessarily have to use Felt's default offerings.
I'm a bit late to the crank-length debate. Is crank length determined by height or inseam? According to my measurements, my legs seem to be longer than my torso. In that case do we still get crank length as <= 155? I checked the "Machine" method here: https://ridefar.info/...g-distance-cyclists/ and it seems to suggest 167.5 based on my inseam.

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 27, 20 10:04

Post #11 of 26 (3179 views)

The proper crank length is determined by bike fit, aerodynamics, and power output.

Re: Felt IA10 Frame Sizing Help [ericMPro] [ In reply to ]

May 28, 20 6:03

Post #12 of 26 (3133 views)

ericMPro wrote:

conky2313 wrote:

I need some help in deciding what size IA10 frame to buy. I'm stuck between two sizes: 48cm and 51cm.
Went to Pedro to get a sizing fit, and these are the numbers:

Quote:

Height: 5’5 / 1665
Shoulder width: 38
Crotch/inseam: 820
Trunk(measured from the pubic bone to the jugular notch/clavicle notch): 530
Arm: 634
Forearm: 634
Femur shaft: 522
Sit Bone measurements: 143
RETUL MEASUREMENTS ROAD/TT
Saddle height: 73 (bottom to the top/center of saddle)
Saddle height 2nd location: 89 (bottom of the crank-6 o’clock to the top/center of saddle)
Suggested crank length: 165
Seat Tube angle: 79.0 degrees
Head Tube angle: 71.5 degrees
Effective Top Tube : 48.6
Tip of saddle to center of handle bars or base bars(T.T.): 51.0
Tip of saddle to hoods or brakes of base bars(T.T.): 69.0
Stem Length: 90
Stem Angle: -6
Steer tube spacer: 20
Seat angle: -5
Name of saddle: ISM pn 2.1
Hoods/base bars degree angle: 11
DROP bars and height of saddle: 14
Aerobars bars degree angle: 7
Aero Bars pad height and saddle height: 90
Reach: 389
Stack: 501

Apparently I'm at the top end of the 48cm frame and at the lower end of the 51cm frame. Felt Support voted for 48cm based on my height and inseam measurements alone, though Pedro said either frame could work (both would need some adjustment). I'm not sure about the implications of going for one or the other. I would greatly appreciate any insight for swinging the vote one way or the other!

There's a lot going on here.

1. Never pick a frame size by height.
1a. You're not between frames. Nobody is. There is an optimal size. Pick the longest frame that allows you to get low enough, and the lowest frame that allows you to get long enough.
2. By that framework, the Felt is a challenge because of the cockpit they choose to spec on it... it's too high stack and the stem is a positive angle stem, which is why you're at the "low end" of the 51.
3. That said, if you ditch the Felt pads and extensions and get the Profile Design Subsonic undermount you can get long and low on the right sized bike.
4. You do pick your cranks by height, among other things, however. 165mm is waaaaaaaaay long for you at 5' 5". 155 or less.

51cm Felt IA with Profile Design Subsonic mount and proper length cranks, 155mm or less. Ski bend extensions only.

May you also help me fiding out is a IA Disc in size 54 is the right size for me?
Height 178cm, seat height 780mm (om my road bike which is a 56 Specialized Venge). thanks

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 29, 20 7:17

Post #13 of 26 (3109 views)

Go longer not lower

Edit: also, huge red flag, my radar is up... you don’t “configure” a Retul bike for “a 48” or whatever... you use the Retul bike to find the optimal position for the client and then translate that into fit coordinates and then use those to prescribe a bike.

You don’t use a bike to prescribe a position, unless you ride in the UCI...

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

Last edited by: ericMPro: May 29, 20 7:19

Re: Felt IA10 Frame Sizing Help [PaulGico] [ In reply to ]

May 29, 20 9:14

Post #14 of 26 (3098 views)

PaulGico wrote:

ericMPro wrote:

conky2313 wrote:

I need some help in deciding what size IA10 frame to buy. I'm stuck between two sizes: 48cm and 51cm.
Went to Pedro to get a sizing fit, and these are the numbers:

Quote:

Height: 5’5 / 1665
Shoulder width: 38
Crotch/inseam: 820
Trunk(measured from the pubic bone to the jugular notch/clavicle notch): 530
Arm: 634
Forearm: 634
Femur shaft: 522
Sit Bone measurements: 143
RETUL MEASUREMENTS ROAD/TT
Saddle height: 73 (bottom to the top/center of saddle)
Saddle height 2nd location: 89 (bottom of the crank-6 o’clock to the top/center of saddle)
Suggested crank length: 165
Seat Tube angle: 79.0 degrees
Head Tube angle: 71.5 degrees
Effective Top Tube : 48.6
Tip of saddle to center of handle bars or base bars(T.T.): 51.0
Tip of saddle to hoods or brakes of base bars(T.T.): 69.0
Stem Length: 90
Stem Angle: -6
Steer tube spacer: 20
Seat angle: -5
Name of saddle: ISM pn 2.1
Hoods/base bars degree angle: 11
DROP bars and height of saddle: 14
Aerobars bars degree angle: 7
Aero Bars pad height and saddle height: 90
Reach: 389
Stack: 501

Apparently I'm at the top end of the 48cm frame and at the lower end of the 51cm frame. Felt Support voted for 48cm based on my height and inseam measurements alone, though Pedro said either frame could work (both would need some adjustment). I'm not sure about the implications of going for one or the other. I would greatly appreciate any insight for swinging the vote one way or the other!

There's a lot going on here.

1. Never pick a frame size by height.
1a. You're not between frames. Nobody is. There is an optimal size. Pick the longest frame that allows you to get low enough, and the lowest frame that allows you to get long enough.
2. By that framework, the Felt is a challenge because of the cockpit they choose to spec on it... it's too high stack and the stem is a positive angle stem, which is why you're at the "low end" of the 51.
3. That said, if you ditch the Felt pads and extensions and get the Profile Design Subsonic undermount you can get long and low on the right sized bike.
4. You do pick your cranks by height, among other things, however. 165mm is waaaaaaaaay long for you at 5' 5". 155 or less.

51cm Felt IA with Profile Design Subsonic mount and proper length cranks, 155mm or less. Ski bend extensions only.

May you also help me fiding out is a IA Disc in size 54 is the right size for me?
Height 178cm, seat height 780mm (om my road bike which is a 56 Specialized Venge). thanks

Shoot me a PM

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

Re: Felt IA10 Frame Sizing Help [ericMPro] [ In reply to ]

May 30, 20 12:05

Post #15 of 26 (3050 views)

Thanks Eric. I'm going to talk with my coach and Pedro to figure this out. Tried reaching out to Felt Support again with my complete measurements and they repeated the previous suggestion of 48cm for an aggressive fit and 51cm for a comfort fit.

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 30, 20 14:11

Post #16 of 26 (3040 views)

The fact that Pedro is recommending 165mm cranks makes me not believe anything in his fit numbers.

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 30, 20 14:24

Post #17 of 26 (3035 views)

"Tried reaching out to Felt Support again with my complete measurements and they repeated the previous suggestion of 48cm for an aggressive fit and 51cm for a comfort fit."

Sounds like they don't know much about fit.

And I don't know why people say "aggressive".

Re: Felt IA10 Frame Sizing Help [jimatbeyond] [ In reply to ]

May 30, 20 15:11

Post #18 of 26 (3023 views)

jimatbeyond wrote:

The fact that Pedro is recommending 165mm cranks makes me not believe anything in his fit numbers.

Would you recommend crankarms <= 155mm as suggested by Eric above? Will I need to change out my chainring config to adjust to a smaller crank (cadence/power)? Currently I'm on a compact crankset on my roadie, and I'm pretty comfortable at my current cadence/power levels. I stuck with the stock 170mm cranks that my used road bike came with and haven't been uncomfortable yet, but I definitely didn't get a bike fit from a certified fitter.

Also regarding your earlier remark-

jimatbeyond wrote:

73cm saddle height seems really wrong.

I've never been fit for a Tri-bike before. What do you feel would be a good saddle height? The body size measurements I posted are accurate to within a few cm of what I measured by myself.

Looking at the plethora of advice to go for the larger frame, I'm heavily leaning to the 51cm, though I'm a teensy bit unsure because of the in-person sizing session.

Last edited by: conky2313: May 30, 20 15:18

Re: Felt IA10 Frame Sizing Help [jimatbeyond] [ In reply to ]

May 30, 20 15:29

Post #19 of 26 (3018 views)

jimatbeyond wrote:

"Tried reaching out to Felt Support again with my complete measurements and they repeated the previous suggestion of 48cm for an aggressive fit and 51cm for a comfort fit."

Sounds like they don't know much about fit.

And I don't know why people say "aggressive".

Yeah, I'm a bit skeptical about them too. For instance, here's the sizing chart on Felt's website: https://feltbicycles.com/.../bike-fit-calculator
If I'm 5'6" then I need the 51cm but if I'm 167.6cm (which is the same as 5'6") then I can make do with the 48cm too.

Last edited by: conky2313: May 30, 20 15:29

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 30, 20 15:31

Post #20 of 26 (3015 views)

You should be using 150mm or 155mm cranks.

How did Pedro determine the 73cm saddle height?

Re: Felt IA10 Frame Sizing Help [jimatbeyond] [ In reply to ]

May 30, 20 15:39

Post #21 of 26 (3012 views)

At the beginning he extracted different measurements (height, inseam, femur length, shoulder width, etc.) and then he put me up on a Retul bike with some presets, including saddle height. Then he changed the height of the saddle, adjusted my pad reach, changed the length of the stem, etc. to get me into an aero position. All of this was interspersed with me pedaling on the Retul and him stopping me to make adjustments.

Re: Felt IA10 Frame Sizing Help [jimatbeyond] [ In reply to ]

May 30, 20 15:40

Post #22 of 26 (3010 views)

"Yeah, I'm a bit skeptical about them too. For instance, here's the sizing chart on Felt's website: https://feltbicycles.com/.../bike-fit-calculator
If I'm 5'6" then I need the 51cm but if I'm 167.6cm (which is the same as 5'6") then I can make do with the 48cm too."

Sizing charts don't mean anything.

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 30, 20 15:42

Post #23 of 26 (3009 views)

conky2313 wrote:

At the beginning he extracted different measurements (height, inseam, femur length, shoulder width, etc.) and then he put me up on a Retul bike with some presets, including saddle height. Then he changed the height of the saddle, adjusted my pad reach, changed the length of the stem, etc. to get me into an aero position. All of this was interspersed with me pedaling on the Retul and him stopping me to make adjustments.

Was your power output measured at different saddle heights and other position changes?

What crank arm length was used during the fit? Were multiple crank lengths tried?

Last edited by: jimatbeyond: May 30, 20 15:48

Re: Felt IA10 Frame Sizing Help [jimatbeyond] [ In reply to ]

May 30, 20 15:48

Post #24 of 26 (3005 views)

There wasn't any display showing power in front of me. I don't know if he had any other wireless power meter or if it was transmitting to his laptop directly. I wasn't asked to push out more/less power during the sizing fit. I'm going to go out on a limb and say no to the power level measurement.

Also I don't think he changed the crank length from the preset 165 that he'd setup initially.

Last edited by: conky2313: May 30, 20 15:50

Re: Felt IA10 Frame Sizing Help [conky2313] [ In reply to ]

May 30, 20 15:58

Post #25 of 26 (2994 views)

conky2313 wrote:

There wasn't any display showing power in front of me. I don't know if he had any other wireless power meter or if it was transmitting to his laptop directly. I wasn't asked to push out more/less power during the sizing fit. I'm going to go out on a limb and say no to the power level measurement.

Also I don't think he changed the crank length from the preset 165 that he'd setup initially.

If he didn't change crank arm lengths and wasn't measuring power output, how can he know what your position on the bike should be?

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