Using retul bike fit to help decide on frame size and model selection

Discuss light weight issues concerning road bikes & parts.
rynogee
Posts: 63
Joined: Sun Sep 05, 2010 2:11 am
Location: DK

by rynogee

Has anyone previously had a retul bike fit done in order to inform their view of an optimum frame model and size? (i.e. on the retul bike, not taking your own bike in for a fitting)

I'm often slightly between sizes, and seem to have slightly odd reach to leg length proportions, but I'm not convinced of the need to go custom (yet) just whether to go down a size, and which model/brand is closest to optimal fit in this context.

Ive seen a sample retul output and it focuses on stack and reach 9for frame measurements) but also gives a seat post angle measurement. I'm not sure if this is enough or not (doesn't have top tube length).

Has anyone invested in this for this purpose (it's certainly not cheap, but possibly not a huge impost given the cost of the new bike).

alcatraz
Posts: 929
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

I'm long legged with a short torso. I found that going with smaller frames fit me well. The seat looks funny a bit high but it's ok.

Had I not been a bit flexible it would have been hard to find a small frame (low reach) with a tall enough heag tube to allow for long legged people and short reach.

May I ask what is your issue?

BMC tt frames exist in long and short versions. I think that is pretty cool although to expensive for me.

/a

Antoine
Posts: 455
Joined: Tue May 03, 2011 6:36 pm
Location: France

by Antoine

Riders from Direct energie have had a bikefit recently, it seems good :
https://www.matosvelo.fr/index.php?post ... ct-energie
https://www.bikefitting.com/

3Pio
Posts: 866
Joined: Wed Mar 09, 2016 7:13 pm

by 3Pio

rynogee wrote:
Thu Feb 15, 2018 6:50 am
Has anyone previously had a retul bike fit done in order to inform their view of an optimum frame model and size? (i.e. on the retul bike, not taking your own bike in for a fitting)

I'm often slightly between sizes, and seem to have slightly odd reach to leg length proportions, but I'm not convinced of the need to go custom (yet) just whether to go down a size, and which model/brand is closest to optimal fit in this context.

Ive seen a sample retul output and it focuses on stack and reach 9for frame measurements) but also gives a seat post angle measurement. I'm not sure if this is enough or not (doesn't have top tube length).

Has anyone invested in this for this purpose (it's certainly not cheap, but possibly not a huge impost given the cost of the new bike).
I done that before purchasing my bike, and also had help from the fitter about what geometry suit me best from the bikes i choosed.. Helped me a lot to understund what size im, and where to begin as starting bike position..

Also im longer legs then torso.. Another small thing to keep in mind, ur body is not the same all the time.. Since i done the test, i lost few kgs, and become more flexible (but when are doing Rettul fit, i guess u have some plans about riding, so u'll know which way to go.. More conservative, or more agressive regarding ur future plans about riding..) , so maybe i can fit now on a bit smaller frame (i'll test ride this days one size smaller bike).

Still, worth investment...Do it..

TobinHatesYou
Posts: 1212
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

For the most part seattube angle is not that important. Most individuals will be able to achieve the appropriate amount of saddle setback on a frame in the correct size range.

There are only 3 sets of contact points: saddle, pedal platforms, bars (subsets: tops, drops, hoods)

Saddle position and effective pedal platform distance are inherently linked. Depending on your hip flexibility, your ideal saddle position is basically dependent on your component leg lengths.

Reach and stack determine how aggressive or relaxed your final body position will be. Frame reach and stack are by far the two most important values from a fit standpoint. They need to be within an acceptable range that can be reasonably augmented by stem angle, stem length, spacer stack, bar reach and bar drop.

Retul is probably the best widely used computer-aided fit system, but whether you get a proper fit still requires the human element to know what he/she is doing. Make sure you do proper research before deciding on who to go to. Don't just pick the closest Retul fitter the local Specialized dealer.

rynogee
Posts: 63
Joined: Sun Sep 05, 2010 2:11 am
Location: DK

by rynogee

thanks all, my main issue is that I am certain i need to go down a size from my current frame, but I'm not sure how much smaller is optimal. I'm looking at lots of brands but often the sizes seem like they might be too small (or too close to my current frame). I'm on a canyon cf slx (2014) size M which is nearly 55cm effective top tube. I feel like I need around 54 or slightly less based on not wanting to run a super short stem (currently 110), and the fact than my saddle nose is about level with BB centre currently (on a zero setback post). So my problem is really reach, not stack. Don't want to compromise handling and other things (overlap perhaps) in going too small as well, so trying to find out what's optimal. I've been looking at BMC, trek, and maybe specialized in size smalls mostly or whatever is close to 547 TT.

TobinHatesYou
Posts: 1212
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

110mm is not a short stem. It's not a look-at-me dick-wagging stem, but it's not short.

It sounds like you have made the basic rookie mistake of positioning your saddle forward to overcome reach issues. This should never be done. It throws your dynamic leg angles completely out optimal range. With a saddle slammed forward on a zero-setback post you are really closing up your hips at the top of the pedal stroke and bending your knees too much... Or you have overcompensated with too high of a saddle position and are likely overextending your knees and pedaling toes down.

In reality your saddle position is a fixed coordinate based on certain criteria. If you can't reach the bars comfortably with that saddle position, the fix occurs in this order: shorter reach bars, raising the stem with more spacers, changing the stem for something shorter and/or with more rise.

c60rider
Posts: 276
Joined: Mon Feb 27, 2017 11:12 pm

by c60rider

Everything I've ever come across in years of bike riding and still seems to be the general consensus is to buy the smallest frame you can get away with. So if you're in between two sizes get the smaller one. Seat posts are huge these days, stems can be long and a small spacer can compensate. There's not a huge difference from one size up and down typically 10mm here and there on most measurements.

AJS914
Posts: 2005
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

It seems like Retul would be overkill for simply determining your optimal reach and stack. Figure out what stack/reach you need and then look at frames from that point of view. It doesn't matter if they call it a Small or Medium.

If you aren't sure of your fit then maybe start with a pro fit on your current bike.

Looking at the geometry chart for the Canyon CF SLX, there is only a 6mm difference between the Small and Medium sizes. The biggest difference is the stack which is a 20mm difference.

If you want less reach than you have now, a 10cm stem is not shameful, just not "pro" looking. You can also go for bars with less reach. Whether you could ride a small depends on whether you could deal with 20mm of less stack. Spacers are not shameful either - again, just not "pro" looking.

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silvalis
Posts: 376
Joined: Mon Sep 07, 2015 1:02 am
Location: Aus

by silvalis

TobinHatesYou wrote:
Fri Feb 16, 2018 12:13 am
With a saddle slammed forward on a zero-setback post you are really closing up your hips at the top of the pedal stroke and bending your knees too much...
Could you elaborate on this because I'm having trouble visualising your words.

Assuming the upper body angle to horizontal is staying the same (eg the bars are moving equivalent with the saddle) and assuming the cleat position isn't changing as well, then moving the saddle/hips forward relative to the bb in an arc will open up the hip at the top of the pedal stroke, not close it...

TobinHatesYou
Posts: 1212
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

silvalis wrote:
Fri Feb 16, 2018 1:42 am
TobinHatesYou wrote:
Fri Feb 16, 2018 12:13 am
With a saddle slammed forward on a zero-setback post you are really closing up your hips at the top of the pedal stroke and bending your knees too much...
Could you elaborate on this because I'm having trouble visualising your words.

Assuming the upper body angle to horizontal is staying the same (eg the bars are moving equivalent with the saddle) and assuming the cleat position isn't changing as well, then moving the saddle/hips forward relative to the bb in an arc will open up the hip at the top of the pedal stroke, not close it...
Two reasons:

1) Because when you move your hips closer to the BB along the horizontal axis, you are turning the full extension of your leg closer to a straight vertical line instead of a more natural diagonal. Think "|" vs "\" ... With more setback your pedaling involves less knee flexion, and as a result of that less hip flexion.

2) Because the OP is presumably trying to stick to a long and low stem/bar position up front because it looks "pro." He should move his saddle back to a normal position (lower and farther back) and use a shorter/higher stem/spacer/bar combo.

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silvalis
Posts: 376
Joined: Mon Sep 07, 2015 1:02 am
Location: Aus

by silvalis

Isn't the definition of "opening up the hip angle" when you increase the angle between your upper body (or even horizontal at the hip) and your upper leg?

/ ... / (torso)
\ vs | (leg)

TobinHatesYou
Posts: 1212
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

silvalis wrote:
Fri Feb 16, 2018 7:52 am
Isn't the definition of "opening up the hip angle" when you increase the angle between your upper body (or even horizontal at the hip) and your upper leg?

/ ... / (torso)
\ vs | (leg)
That's the fully extended angle (not important.) With increased setback, you bend your knee less at the top of the pedal stroke when you begin your power phase. All of your angles flatten out slightly.

And like I mentioned in the second part of the reply, if you slide the saddle forward, you also have to raise it. If you don't also slide forward and raise the bars, you will be at a much more aggressive back angle. Since the OP is moving the saddle forward as reach compensation, he is most definitely closing his hips even more.

Another adjustment people make when they use more setback, is they tend to rotate their pelvis/hips forward more and straight their backs.

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TonyM
Posts: 2179
Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

I used a Retül bike to determine the right frame size for my F10 disk (47, 50 or 51.5).

We change the Retül bike according to the 3 different size and also with different stem length etc....

That was very useful!

I did not pay for for it but I would have paid if necessary - considering the price for the frame/ bike and the importance to get the right frame size/ stem length etc....


rynogee
Posts: 63
Joined: Sun Sep 05, 2010 2:11 am
Location: DK

by rynogee

TonyM wrote:
Sat Feb 17, 2018 4:32 pm
I used a Retül bike to determine the right frame size for my F10 disk (47, 50 or 51.5).

We change the Retül bike according to the 3 different size and also with different stem length etc....

That was very useful!

I did not pay for for it but I would have paid if necessary - considering the price for the frame/ bike and the importance to get the right frame size/ stem length etc....

thanks, I hadn't thought of putting in the geometry of the frames I'm considering to try them.

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