I'm getting some tingling and numbness in my left leg after about 40 minutes.
I have a selle anatomica saddle and I notice that the left side of the saddle is lower than the right.
It's as if I'm putting more pressure on that side. I am very conscious of my posture and pedaling pressure.
Seems odd to me. Any thoughts on this?

That's common with a leg length discrepancy - either actual or effective from an imbalance. An experienced and knowledgable fitter can help. Ideally they use Retul which also measures power output separately in each pedal. Over time one leg can end up doing as much as 50% more work than the other in extreme cases

My first thought was a seat issue. Maybe too wide a seat or nose too high. Or perhaps you would do better with the seat pointed slightly to one side. (I ride with all my saddles pointed slightly to the left. I am also finding as I get older, I am becoming less and less symmetrical.

I'd try a ride with the wrenches to adjust the seat pin and clamp and experiment. (And if you find that helps, be prepared to do a few more rides to dial in "perfect". Settling for less than perfect when it comes to seats is settling for a lot less!)

Ben

I have the same problem. I'm pretty sure it's due to slight scoleosis that is getting worse as I get older. Anyhow, over the years I've tried a number of things which have helped. Now numbness sets in after about twenty miles rather than five. I went from an old Avocet saddle to more modern ones. I have a Selle Italia SL Flow which I like very much and a Specialized Phenom on the other bike, which is also very comfortable. Having the right width is important for keeping the circulation going, and I find that a flatter saddle is less likely to cause numbness. Shoes: again for the sake of circulation I now wear slightly looser, more padded, less racy shoes (Bontrager Race; I think they're the bottom of the line, but they're comfortable). 79pmooney's suggestion of pointing the seat slightly to one side should also help, as would a thorough fitting, of course.

Could be sciatica, that is what causes my left leg numbness.

Left leg numbness is one of the signs of a bulging disk in the lower lumbar area. Just a heads up, after you get everything as far as fitting is concerned, straightened out, if the numbness in the leg is down to the foot, be sure to tell your physician about this. Not trying to be an alarmist, something I learned the hard way when I had a spinal compression at 2 lumbar levels and lost use of one leg completely for several years.

Bill

^ this as bulged lower disk or herniated lower disk is prime cause of Sciatic pain I mentioned.

I have some arthritis in my back. I've ruptured discs on several occasions so that could be the root of the problem. So then this is something I'm going to have live with?
I"m not getting back surgery for this. I have an MD appt. wednesday, I'll see what he says. I was hoping others with this problem might have made some saddle adjustments etc. that help.

+1 . I learned a painful lesson last summer where my left leg was in pain and numb all summer . I finally went to the my family doctor in May and 2 MRI later confirmed the bulged lower disk . I am feeling much better now but who knows what is going to happen next year once I am on the bike again .

I had an interesting conversation with the fitting specialist at Selle Anatomica. He asked me a few questions and then made some suggestions. He seemed genuinely interested and invited me to call him again to let me know how it works out. Excellent customer service. I'll be seeing my doc tomorrow just to check on any structural issues. I did ride today for a little over an hour. I got some tingling in my leg, but stood up a few times and flattened my back. It was a pleasant ride.

Sounds like a good way to run a saddle business to me. I hope that some adjustments to your fitting can help you and the back issues, surgery is serious enough and the spine isn't a place to experiment. I put off any surgery to my lumbar vertebra for several reasons, much to my detriment in the long run.

Do what you find works for your issues, but include the doctors and physical therapy people, if you do end up using them, what ever the level of help you might need to get out of the pain, or numbness, in your leg. Best of luck on the adjustments and on getting sorted out. P.M. me if you need to talk about anything related to my injury, the surgeries I had, and what I have found from the experiences I had.

Bill

A couple of things, from experience. I have a similar condition.

Check out your legs to see if one is longer than the other. It is more common than you would think.

Your saddle may be adjusted up and down, and back and forth to obtain the most comfortable position. I am sensitive to front and back.

The angle of the seat can also be adjusted. If it is pointed down, move to level.

Put the saddle in a more neutral position, as the left tilt will shift more weight to the left side.

Sometimes the stem length and height is an issue. I see that you indicated a Cannondale Adventure 2, try raising or lowering the handelbars. With road bikes, longer stems are available and different angles can be used to obtain the optimum fit. It is a bit easier with road bikes as you can move your hands to different riding positions.

Some people have a dominate leg, especially if they have had a back issue.

Try pedaling with slightly more pressure on the right leg, and use the left leg as secondary.

Look at your foot position during pedaling. Is one foot pitched versus the others or square on the pedals. You did not mention if you use clip or platform pedals. If you don't use clip pedals, you can try them. Pedals can be also adjusted for pitch in and out, front and back.

Pedal through it, if one side is stronger than the other, over time your butt and back muscles will strengthen and it will be less noticeable. That has actually helped my back over time.

Don't use the discomfort as an excuse to stop riding.

Would changing the dynamics of pedaling work? Instead of the standard diamond frame road bike, how about a recumbent?

I have occasional numbness in my right leg that no doubt stems from the bulging disks diagnosed 8 years ago. At that point, I had so much leg pain that I could hardly walk or stand. A regimen of PT and exercise provided great relief until last year when I started having occasional numbness. The interesting thing is that unlike the OP, it never occurs when I am cycling. In fact cycling seems to relieve it.