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Opinion on sizing

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Opinion on sizing

Old 06-24-20, 12:41 PM
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Pactin
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Opinion on sizing

Howdy, looking for opinions on what size bike I should be looking at, given the size of my (previous) bike fit below.
Me: Height 5'6" , inseam about 30" , average flexibility
Bike: Nominal 48cm (XS), Stack: 513, Reach: 370
Spacers: 10mm dust cap spacer + 5mm spacer
Stem: 100mm length at -7*

I am pretty comfortable on this fit/size bike, but wondering if I can do better. Just reading a few internet resources, for my height I *should* be on a nominal 52cm.
Am I actually too big for bikes of this sizing? Am I sacrificing anything being on a smaller frame?

Thanks

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Old 06-25-20, 10:49 PM
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Looks too small to me. I'm the same height as you, proportioned about the same. I ride 52-54 cm frames, my 52 probably fits me best.

Sacrificing? That would depend on what you want to do on the bike. In general people are more comfortable and can ride a little further and a little faster on a properly sized and fitted bike.

Keeping this bike, you might do a little better with a 120mm -17° slammed stem. Cheap and worth a try.
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Old 06-26-20, 03:17 PM
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Originally Posted by Carbonfiberboy View Post
Looks too small to me. I'm the same height as you, proportioned about the same. I ride 52-54 cm frames, my 52 probably fits me best.
Thanks for the response! It definitely helps to get input from someone of similar build. I figured it was small, but strangely I don't believe I feel any negative effects.

Sacrificing? That would depend on what you want to do on the bike. In general people are more comfortable and can ride a little further and a little faster on a properly sized and fitted bike.
General purpose road riding and some very rare hard pack dirt roads. Majority of my rides are 20-40mi, and less than 2k feet of climbing. With this setup I feel no pains or abnormal muscle fatigue, but I'm wondering if there is power or aero to be gained in a larger frame.

On occasion I will do climbs with 4k feet ascents, so I guess additional comfort and proper positioning on descents would benefit me there.

Keeping this bike, you might do a little better with a 120mm -17° slammed stem. Cheap and worth a try.
Never thought about this. Wouldn't this place a lot more weight on the front wheel?
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Old 06-26-20, 04:51 PM
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If you're comfortable on it for the rides you like going on you're not sacrificing anything.

Fit is dependent both on proportions and flexibility. If you feel like you need to be more stretched out in time you can get a longer stem. Did you buy that bike used, asking because it has no steerer tube left.
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Old 06-26-20, 05:50 PM
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Originally Posted by Pactin View Post
Thanks for the response! It definitely helps to get input from someone of similar build. I figured it was small, but strangely I don't believe I feel any negative effects.


General purpose road riding and some very rare hard pack dirt roads. Majority of my rides are 20-40mi, and less than 2k feet of climbing. With this setup I feel no pains or abnormal muscle fatigue, but I'm wondering if there is power or aero to be gained in a larger frame.

On occasion I will do climbs with 4k feet ascents, so I guess additional comfort and proper positioning on descents would benefit me there.


Never thought about this. Wouldn't this place a lot more weight on the front wheel?
Maybe, depends on your current balance. You would move the saddle back, probably also a good idea to get more reach. What you're shooting for w/r to reach is for your upper arms to make a 90° angle with your straight torso. Dropping your bars a little and moving them forward will have a positive effect on your aero position..
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Old 06-27-20, 12:13 AM
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Originally Posted by ridethecliche View Post
If you're comfortable on it for the rides you like going on you're not sacrificing anything.

Fit is dependent both on proportions and flexibility. If you feel like you need to be more stretched out in time you can get a longer stem. Did you buy that bike used, asking because it has no steerer tube left.
Good to hear. I only had the query when researching the fit of a new bike, not necessarily from feeling the need to stretch out more. With regards to how I got it, I built it. I slowly started chopping the steerer tube when I felt I could go lower and lower.

Originally Posted by Carbonfiberboy View Post
Maybe, depends on your current balance. You would move the saddle back, probably also a good idea to get more reach. What you're shooting for w/r to reach is for your upper arms to make a 90° angle with your straight torso. Dropping your bars a little and moving them forward will have a positive effect on your aero position..
So if I understand correctly if I lengthened the stem I should compensate balance by moving saddle rearwards - both of which would increase reach?
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Old 06-27-20, 10:35 AM
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Originally Posted by Pactin View Post
Good to hear. I only had the query when researching the fit of a new bike, not necessarily from feeling the need to stretch out more. With regards to how I got it, I built it. I slowly started chopping the steerer tube when I felt I could go lower and lower.


So if I understand correctly if I lengthened the stem I should compensate balance by moving saddle rearwards - both of which would increase reach?
Read and apply: How can I fitting my bike
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Old 06-28-20, 10:33 PM
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You position a saddle with regard to KOPS or however you feel that setup best suits your body. Everything else, stem length etc, is secondary to that.

The first part of bike fit is getting your saddle position set up with regard to your cranks (and also deciding crank length during that process). The reach is the second part of that equation. If one is going shorter and shorter on stem length to the point where it's 80 or 90 on a road bike... it's likely to small. 90 is acceptable but for most road riding something like 80 is way too short and means that the frame is too big. On the other end, it is easier to make a smaller frame fit larger if you can tolerate the drop. Going up to a 130 or even 140 stem length isn't totally ridiculous though I think 140 really indicates that you're on too small of a frame unless you have really long arms and really short legs in which case going to a larger frame could be problematic.

I usually ride a 56 frame, but I'm currently on a 'medium' frame with an ETT of 545 which fits more like a 54-55. The geometry of the frameset is slightly more relaxed overall and given the angles and the steerer tube length, I'm able to ride it pretty comfortably with a 120 stem without too much drop with the caveat that there's no way I'm cutting the steerer. I'm okay with that, but again it's a different kind of compromise.

In general I've found that I prefer to be slightly more stretched out instead of having a lot more drop. You come to find what you like over time.

TLDR: If you're comfortable keep working on your position making small changes and don't overthink it! If you're not having issues on rides that you're doing as you've started going out longer then you're in an acceptable range.
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Old 06-29-20, 10:28 AM
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I'll disagree about the need for keeping your knee over the pedal. There are more important things that need to take precedent over any such requirement. So my recommendation will be to try any other changes and see what they do for you even if they put your knee outside KOPS.

https://www.sheldonbrown.com/kops.ht...dal%20spindle.
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Old 06-30-20, 10:40 PM
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I wouldn't go by sheldon brown when it comes to fit advice these days.

Also, I didn't say that KOPS was the only way to do things. More and more endurance riders are moving their cleats back as far as they'll go to take the gastroc out of the equation as that's most prone to fatigue the earliest. There's a range of what works.
I also said "You position a saddle with regard to KOPS or however you feel that setup best suits your body." So you may want to read completely before commenting!

Regardless, reach to bars is secondary to where your ass is going to end up and how high up that will be.

Are you suggesting that reach takes precedence over where your knees end up? That makes zero sense to me.

KOPS is an artifact in that it's a holdover from old pedal interfaces. Just because KOPS isn't the solution doesn't mean you don't need to start by figuring out where your knees should end up.
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Old 07-01-20, 08:47 AM
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Yes, reach adjustments do take precedent over any consideration for where your knee is over the pedal, IMO. Where your knee is over the pedal just has no bearing on anything.

So I know it makes zero sense to you. Likely if it works for you, then you are one that has the perfect physical dimensions that KOPs needs to keep people spouting the non-sense of KOPs.

Knee placement is not going to solve any of the issues of fitting a person to a bike. All of this is in my opinion. You are permitted to have your own opinion.
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Old 07-01-20, 10:43 AM
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A slightly amusing relationship in the world of bike fitting: it happens that when my balance on my bike is correct, the bony protuberance below my knee cap is exactly above my pedal spindle on my came-one-the-bike 170mm cranks. Weird, huh? Certainly doesn't work for everyone, but doesn't seem unreasonable to use it as a place to start. That said, I did have to put on a 30mm setback post to get the clamp in the middle of my saddle rails. Maybe I have long femurs. Everyone's different, the reason that bike fitting is so much fun.
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Old 07-01-20, 01:21 PM
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Amusing relationships abound everywhere. Doesn't make them important. To me this is just like 3 out of every 4 people in the world make up 75 percent of the population. Or that 100 percent of those born will likely die.

My plumb bob hangs three or so inches in front of the spindle when the pedal is forward and horizontal to the ground. Not certain though where KOP's comes from. The front of the knee? middle?

Don't know, don't care. It's just a mythical relationship that I admit can be used to get a person in a starting point to begin adjusting various things. However when people say that you must stay in KOP's over all else. Or, refuse to try a position because it takes you outside KOP's, then I have a gripe.

Balance depends on a lot of things. And balance where? On the seat, while not moving and in a fairly upright position? No, that's not me. Balance is a dynamic changing thing from power you are putting out, your airspeed (not ground speed) as you move, your bodies core strength and its natural tendency to only bend so far before it leverages some of your weight out of the seat.

For me I can only do that with a saddle forward and a fairly aero position. Balance is more my power balance around the BB, not on the seat. With my saddle back, I have to have a more upright position to be comfortable. And that means using more watts on long rides that I don't want to give away. If I was more disposed to leisurely riding, then maybe KOPs would work. But only because it's a coincidence, not a must do this above anything else.
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Old 07-02-20, 08:10 PM
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Originally Posted by Iride01 View Post
Amusing relationships abound everywhere. Doesn't make them important. To me this is just like 3 out of every 4 people in the world make up 75 percent of the population. Or that 100 percent of those born will likely die.

My plumb bob hangs three or so inches in front of the spindle when the pedal is forward and horizontal to the ground. Not certain though where KOP's comes from. The front of the knee? middle?

Don't know, don't care. It's just a mythical relationship that I admit can be used to get a person in a starting point to begin adjusting various things. However when people say that you must stay in KOP's over all else. Or, refuse to try a position because it takes you outside KOP's, then I have a gripe.

Balance depends on a lot of things. And balance where? On the seat, while not moving and in a fairly upright position? No, that's not me. Balance is a dynamic changing thing from power you are putting out, your airspeed (not ground speed) as you move, your bodies core strength and its natural tendency to only bend so far before it leverages some of your weight out of the seat.

For me I can only do that with a saddle forward and a fairly aero position. Balance is more my power balance around the BB, not on the seat. With my saddle back, I have to have a more upright position to be comfortable. And that means using more watts on long rides that I don't want to give away. If I was more disposed to leisurely riding, then maybe KOPs would work. But only because it's a coincidence, not a must do this above anything else.
The "official" KOPS measurement point is from that bony protrusion just below the kneecap, on the front of the lower leg.

For sure moving the saddle forward opens the hip angle and allows a more comfortable aero position. Works really well with aero bars or on a tri or TT bike. UCI rules say the saddle tip must be at least 4 cm behind the BB, which is a very weird rule since saddles come with different nose lengths and riders come with different femur lengths. Mine's 8 cm back. I have to have it near there or my arms get tired after about 4 hours. I see a lot of riders shaking out their arms. And yes, my thighs almost hit my lower ribs when I'm all the way down. With a -17° slammed stem they do hit.

Like you say, balance is something every rider has to determine for themselves.
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