Overall fit of the frame is important as well. How do the bikes compare seattube/toptube/stem?

Bob, if the Lotus has 1-1/8 tires then I assume your bike has 27” wheels. An easy upgrade would be to put some 27x1-1/4” Continental Ultrasport tires on there. 1-1/4”=31.75mm. Run them less than rock hard and they should be quite comfortable.

As far as saddles are concerned: could you share with us what kind of saddle is on there now? Also, could you tell us a little about you as a rider? What distance rides will you be doing? How many hills? What is your current fitness and what are your fitness or cycling goals? How you answer allows us armchair coaches to be of more assistance to you.

one important bit of cycling wisdom I have learned over the years involves “contact points on the bike” - your butt, your hands and your feet. Your butt is just 1/3 of this triad. Good handlebar tape, good gloves, and conducive “cockpit” (bars, stem of correct width, stem length and drops that you can make effective use of in addition to comfortable hoods) - these will optimize the hand part of the triad.

2nd - optimize the “feet” part of the triad. Even though your bike is “vintage”, I would suggest running modern clipless pedals if you are not already - this makes a HUGE difference in efficiency and comfort. You can run mountain (SPD) or road pedals (Shimano/Look/Time/Speedplay are all good) - your choice. When your butt gets sore alternate your pressure points like a yogi on your bike. Stand on your pedals with the cranks at 3 o’clock and 9 o’clock and coast, clamping your saddle between your thighs but not sitting on it. Then sit down. Utilize your rigid shoes/clipless pedals to their fullest by using all your gears through changes in terrain and wind. Pedal lightly, and do drills where you practice pulling up as opposed to mashing. This makes you hamstring dominant when needed.

Last part of the triad is the saddle. You say yours is “hard”. We really do need more info here. A picture would help. Soft saddles are rarely the solution for longer rides, saddles that fit properly are. Everybody has their favorite and they generally stick with what works for them. I ride a Selle Italia Turbomatic Team. It is both hard (dense padding) and somewhat soft (elastomers between the shell and saddle rails mute road bumps somewhat). A microadjusting seat post is really a necessary upgrade to fine tune just the right amount of upward (or slight downward) tilt. Playing around with leg extension by raising the saddle higher in very small increments as your fitness improves can extract more power out of your stroke and increase comfort - a double win if this applies to you. Yoga or stretching to get more flat can relieve pressure on the butt because you are rotating your pelvis forward and no longer sitting so much as perched on the saddle. I’m 56, have been 265 pounds and had back surgery but I have found this more racer type setup is more comfortbable, not less.

Lastly, To me Lotus bikes are more classic and a bit dated usually in how the bike shop fitted them. Often the frames were too big. You might find that the critical frame dimensions are much different than your modern steed. I’d suggest you take some notes, using a metric measuring tape of your modern bike’s top tube length (virtual), headtube length, saddle height, set back, etc... and compare to the lotus. You might find (for example) that you need a “zero setback” seatpost to push the saddle forward a bit to replicate your golden measurement from your modern reference bike. The same goes for the bars and stem. The ones on your Lotus may just be wrong for your personal needs.

I’ll be curious to hear more details from you as you seek to make your Lotus comfortable for you.