Back pain on longer rides

[bkelly13]

I have been riding short rides for many years, lunchtime rides while working, 10-15 miles, 20 on weekend. Just joined a group that rides about 30 miles and much faster than my solo rides. About halfway through my back becomes very painful. Looked up some back muscles and I cannot tell if is it Trapezius or Levator scapulae muscle. Or maybe something else.
I get some relief by consciously pulling my shoulders down while riding. But I cannot seem to keep them down for long before forgetting about that. I use aerobars but with the group probably less than half the time.
Is this a known problem or maybe unique to me.
70 years old, 6'2", 170 lbs, near the front of our pack.

 

[Mr. Beanz]

I would guess your stem is too long. Or the handlebars too far down for your current limberness at the moment.

I am surprised you are using aerobars on a group ride. They usually don't care for them as your hands are away from the brakes in that position.

 

[bkelly13]

I would guess your stem is too long. Or the handlebars too far down for your current limberness at the moment.

I am surprised you are using aerobars on a group ride. They usually don't care for them as your hands are away from the brakes in that position.

I am 6'2". The stem is 9.5 Cm long center to center. From seat post to the handlebars is 63.5 CM, center to center. When selecting the bike at the only nearby bicycle store, it was selected then adjusted with the help of the sales staff. They made multiple measurements.
Maybe I should raise the bars some and see if that helps?

 

[Mr. Beanz]

I am 6'2". The stem is 9.5 Cm long center to center. From seat post to the handlebars is 63.5 CM, center to center. When selecting the bike at the only nearby bicycle store, it was selected then adjusted with the help of the sales staff. They made multiple measurements.
Maybe I should raise the bars some and see if that helps?

I would try something if you are feelings some discomfort. I think there may be some staff that get it right but I'm betting there is plenty of staff (various bike shops) who don't. I set up my bikes and the only way I could get comfy was to do long rides and adjust accordingly. I don't think one set up will work for all. 2 guys same height same dimensions could both be set up the same according to stats and one not be comfortable. I am no pro fitter but I am thinking just as saddle choices, not everyone with the same stats would pick the same saddle.

Just my thoughts being really comfortable on my fleet of bikes.