CrowSeph

This may sound stupid...
On my old bike i had the exactly same lumbar pain, i solved by using a short reach handlebar (70mm) instead of the classic (90mm) and also i put the levers more upright. On my old bike my stem lenght was 80mm.
On my currently bike i have almost the same problem, the saddle have less seatback than the old one (1,5 instead 2,5 cm) but this bike have a stem longer 100mm, i moved a bit the levers on the top and the pain became less. Maybe i'll solve with a shorter stem but by talking with a team member he said: "Is not the bike geomtry, is how your body stay on the bike". Today when riding i noticed that i stay too relaxed on the bike, loading the weight on my lumbar area, feels natural.... But i i try to keep more load on my shoulder i can feel relief on my lumbar area.
At this point is just me still learning how to stay on the bike or the biomechanical setup is still wrong?

Also there is the "old rule" telling to take a look at your front hub. If your handlebar will hide it = your stem lenght is probably fine.
ps. the saddle seatback i think is correct because i used a straight line from my knee to the ipothetical foot metatalsars's line.

terrymorse 

Do you do any core strength exercises? Or stretching?

CrowSeph

nope

Maelochs

Knee to pedal spindle is a general, not a specific measurement. In the same way, having the stem block the view to the hub is just a rule of thumb. It doesn't really work in every situation. It is a guideline, not a rule,

If you find the optimal saddle/spindle distance, whatever it is, you should probably duplicate it on every bike.

The relationship between the pedals and the saddle is really the key .... because you are using your whole body to spin the pedals, putting out all your power through your legs, from saddle to pedals. If you get this right---for Your body and fitness/flexibility---then the rest lines up pretty simple, in my experience.

If you found a riding position which works for you on one bike, set up all your bikes that way .... is how I understand it.

I may be wrong.

DaveSSS 

I place my saddle further back than KOP would indicate. Most frames in my size have 74-74.5 degree STA, so I use 25-32mm of seatpost setback. A too far forward position can put too much weight on your hands. I have no such problem, even with an 11.5cm saddle to bar drop.

Mojo31

Bingo.

CrowSeph

Honestly i don't think that's the solution because I had the same issue even when I was goings 3/7 days at the gym, working on my full body.

terrymorse 

Well, it couldn't hurt to try them for a week or two.

Here are some stretches that can help cyclists.

Trainright also has some good recommendations for back exercises.

Also, posting a photo from the side on your bike might help us see where you may be having difficulty.

79pmooney

Forget the "rules" (hub through handlebars, knee over pedal). You could spend the bucks for a bike fit. Might well be worthwhile. But in the meantime, you have a bike that works and one that doesn't. Set up bike B (the one that doesn't work) like bike A.

Now, forget about stem lengths. Do the basic measurements. Bring bike A indoors and set it close to vertical along a hall. (Indoors for the level-flat floor, something a lot of garages and basements don't have.) Hang a string from the toptube with a weight tied to the bottom. (A plumb bob is perfect but not required.) Move it until it hangs directly over the bottom bracket.

Measure horizontally from the half way point of the seat (I mark it with tape) to the extension of the plumb bob line. Do the same with the center of the handlebar tops. Measure floor to bottom bracket. Floor to handlebar top center. Floor to top of seat at your mark. Subtract the bottom bracket height from both the seat height and the handlebar height. You now have all you need to define where your hips and hands are relative to the bottom bracket. Do the same with bike B.

If your seats and handlebar/brake lever configurations are similar on the two bikes and those dimensions don't match - well your body has to make up the difference. (If those "contact points" are different, you could mark the seat below your hip socket. Handlebars where you rest your hands. Do these measurements again on both bikes.)

Just matching say stem lengths rarely works because bikes typically have different seat tube angles and top tube lengths so the point at which you place that stem might be in a substantially different place relative to the bottom bracket. (And that bottom bracket - think of it as an engine's crankshaft. Everything on the human engine revolves around it.)

Edit: Maelochs gets it. I'm just laying out the steps to be taken.

CrowSeph

What you said is very accurate but i can't since I don't own anymore the old bike. Today I'll post an image of myself on the saddle if that will help.

eduskator

But were you stretching? Flexibility greatly helps.

genejockey 

Alternatively, stand your bike on a pretty much flat, pretty much level floor, with the back wheel touching the wall behind it. Make sure the bike's standing vertical by checking that the handlebars are level side-to-side. Measure the distance from the center of the bottom bracket to the wall, and to the floor. Do all your measurements to the wall and the floor, and subtract the BB-wall and BB-floor distance. This is especially easy if you know how to work in Excel - you can set up the formulas, and just enter the measurements and have the dimensions calculated for you.

genejockey 

Well, if you don't have the old bike anymore, and don't have the measurements from it, you MIGHT be able to look up a few basic dimensions in an old catalog, or maybe geometrygeeks.com.

Or, forget the other bike and just get a good bike fit on this one. You CAN try a number of things yourself, but you also may end up chasing phantoms - I once got a new bike (purchased online during the early Pandemic) and the first ride was terrible. My hands kept going numb. For many folks, the first thought would be that the bars were too low so I would put too much weight on them. BUT the bars were an inch HIGHER than my other bikes where I had no numbness problems. So I lowered the bars an inch and the numbness went away. So, unless you're experienced with self-fitting OR have a bike that really fits well to compare, I'd seek a professional.

79pmooney

Drawback - tire marks on the wall. Otherwise, yea.

genejockey 

Never could get the hang (haha) of working with a plumb line.

CrowSeph

heres how i fit on actual setup. https://drive.google.com/file/d/1nsM...4l2DKQNUi/view

terrymorse Maelochs genejockey

Maelochs

I have probably said this so often people are bored, but ....


I set my bike by the washer-dryer, with a milk crate on the other side. I can sit on the bike with one pedal wherever I want it and use the other foot on the milk crate .... with my hip on the washer-dryer if I need the stability. I slide back and forth on the saddle and spin the pedals .... using a hand on the washer-dryer to stay upright. At some point I found the place where the stroke felt best, where I felt that I was getting good extension and comfort---which involved raising and lowering a little----a lot of fiddly effort, but worth it----I started actually moving the saddle front to back until it supported me at the height and with my knees and hips where the felt best. I do fine saddle-angle adjustments after I get the bar height.

I have a tiny torso and long limbs, particularly below the knee, and my hips are wide.. Some guy with legs just a tiny bit shorter, thigh and calf, with narrower hips i----and more or less flexibility---is going to find his optimal saddle position nowhere near where mine is----and no one can tell by looking. You have to adjust it, ride it, adjust it, ride it. But at some point you Should find where your body wants the saddle to be, so that you can pedal a full stroke and stay stable and never feel cramped or stretched.

Once I get the saddle, i go back to the washer/dryer, prop myself up with one pedal high and the other side on the milk crate, and I lean forward until I feel balanced and not overstressed. Then I swing my arm forward with a little bend in the elbow, and see where it falls .... that is where I want my normal riding position, be it on bar tops, hoods, hooks, whatever ..... if I cannot hold that position without my arms, then when I get tired i will lean too hard on the bars and hurt my elbows, wrists, or hands. I need a stem and bar combo---reach and drop, length and angle---which puts the hoods, flat, and drops somewhere I can reach them as much as I need to (depending on which I use most.)

I ignore "nose of saddle to stem" because every saddle has a different nose, but do whatever works for you. I measure "extension of the seat post to saddle top" and from there to hoods, bar tops, stem at bars, and top cap ... usually just to top cap, and then a figure what stem i need, and to base of hoods, where I rest my hands, to get bar reach.

I have used the Competitive Cyclist site (https://www.competitivecyclist.com/S...latorBike.jsp?) which gives good measurements, and have drawn on graph paper models of my body and my bikes so i can put a picture of me on any frame and know what stem/bars i will need---it has proved to be surprisingly accurate---once I know where the saddle needs to be.

Getting the saddle right is essential, and it cannot be adjusted by anyone but the person who rides (IMO.) No one else can feels that "Aha" when you get tit and you feel more power through your stroke, less dead spots, no stretching or discomfort .... KOPS is a great starting point but "saddle where it belongs" is the goal.

genejockey 

When I think about getting my bike fit right, there are a couple questions I ask myself.
Just riding along on the hoods - in a safe situation, obviously, not a group ride! - can I lift both hands off the bars without falling forward? Probably best to do this on a trainer, obviously. If you can't, your saddle's too far forward.
Do I find myself constantly sliding back or forward on the saddle? Do I feel like I'm being thrown at the bars, or alternatively like I have to reach out for them? Or do I feel planted and stable in the right place? That's saddle angle.
Can I spin a fast cadence smoothly, something like 120-130, without feeling like my legs are just flailing? Do I feel like I'm reaching with my toes at the bottom of the stroke, or alternatively like I'm "flat footed"?
That's all getting the saddle right.

For the bars, when I get on the bike, do my hands just naturally fall onto the hoods? Can I ride on the hoods for mile after mile without my hands, arms, shoulders, neck, or back bothering me? Can I ride a couple miles in the drops, putting out power the whole time, without crushing my plumbing, without hunching my shoulders so that keeping my head up is difficult? If I do a longer ride, like > 3 hours, do I have any back or neck problems in the next few days? Do I feel like I need to turn the bars up to reach the hoods, rather than keeping the ramps and hoods level?

The difference between "close" and "dialed" is surprisingly obvious. I have way too many bikes. They all feel really good - because I set them all up as close to the same as I possibly could. But there's one, my most recent acquisition, that feels PERFECT. All the others, I feel completely at home within a mile of riding, but that one bike, it's perfect as soon as I'm in the saddle.

genejockey 

My first observation is that your arms are locked straight out, with the elbows turned to the outside. Do you feel like you have to keep your arms totally straight? Like you're pushing yourself off the bars, versus resting your hands on them?

If you had or could borrow a trainer, you could spin on that for a few minutes, so you feel like you're in your usual riding position, then take the picture (I presume you had assistance).

CrowSeph

Nope, arms feels good. In the picture I tend to leave them straight because I was trying not to fall 😆

genejockey 

See the first question in my long post about falling forward if you don't have you hands on the bars.

CrowSeph

Is interesting that if you take a closer look at the lower back, you can see an arch. That's were my pain came from. May i should play a bit and find what can influence that arch and try to lower it...

genejockey 

I don't know. It depends on your flexibility. I'm really inflexible, always have been Even in high school, stretching before track meets trying to touch my toes. I could never get closer than mid calf. Other guys could touch their easily, even put both hands flat on the ground. Not me! So, FOR ME, I need to roll my pelvis forward and ride with a pretty much straight back, rather than bending at the waist. This means I need a "wave" saddle, rather than flat.

But that's me. If you're more flexible, you can curve the whole back. Cam Nicholls has a series of bike fitting videos, I think on the Road Cycling Academy YouTube channel. You might find them helpful.

Or confusing.

terrymorse 

OK. First, the saddle height:



Protractor says the knee flex is 40 degrees, which is at the upper range of recommendations. But your toe is pointed, so your actual knee flex is less. Verdict: saddle height looks OK.

Second, the torso angle:


Protractor says torso angle is about 44 degrees. That's kind of high, as the recommended range for a road bike is usually 30-40 degrees.

Third, shoulder angle:


Angle appears to be 83 degrees, which is within the recommended range of 80-95 degrees.

What the angles don't show is a rounded (arched) lower back and straight elbows. The rounded back suggests you have inflexibility at the hips. The ideal is an almost flat back. The combination of high torso angle, rounded lower back, and straight elbows is the smoking gun here. It's no wonder you have lower back pain.

I don't know a change to bike fit can fix this. But if anything, moving the bars higher and farther forwards could induce you into a more stretched out upper torso position. More importantly, stretching and more stretching to loosen those hips.

For reference, here's a photo of the upper body within the recommended angle ranges.



Source: bikedynamics.co.uk

genejockey 

I somewhat discounted the knee angle because his foot is at Bottom Dead Center, rather than full extension (in line with seat tube). Toe pointing seems severe to me, though. I'd want to watch from behind to see if he's rocking his hips. THAT could give you low back pain, too, because you're working those muscles. I saw a guy a few months ago - I thought he was riding out of the saddle, but no, he was seated and just rocking his hips like nobody's business!