This nice old Lejeune came to me as a bare frame and I built it up in a more or less period-correct fashion as a pandemic project. The black seatpost still bugs me, but it was all I could get at the time. Not sure when the frame was built, but I'd guess 1971 or thereabouts. (Sorry about the non-drive side image, but it's a cropped snapshot from a recent tour.)

I had not ridden the finished bike much until this spring, though, and now that I've put some significant miles on it I've come to realize that I'm not happy with the way it handles. Simply put, it has a tendency to wander from a straight line. Even when I concentrate on holding a straight course, it often feels like it's "slaloming" a little--as if it's describing a series of long, very shallow s-curves. I doubt that it would be evident to an onlooker, but I can feel it clearly.

What gives? Frame geometry is not something I know much about, but the frame angles don't strike me as steep. They seem very similar to other French frames I've had, and though I haven't compared them side by side, I'd say it's perhaps a little more relaxed than my Gitane TdF. Although I didn't do a string check of the frame alignment before building it up, I did look it over closely and saw no signs of crash damage or other obvious issues. The headset is perhaps a tiny bit tight, because that's what it took to eliminate any play. Could that have anything to do with it?

I really like the way this bike looks, and would like to love the way it handles. Help me out, somebody!

EDIT: A quick check with a string from one dropout and around the head tube to the other dropout seems to show that the rear triangle, at least is pretty true. Seat tube to string is 32mm on one side and 34 on the other. I can't imagine that moving the triangle 1mm to the left could make a difference. Dropout spacing is spot on at 120m. The fork is obviously harder to check, but there's no misalignment visible to the naked eye--at least not mine.

I'd start with the string test. I have had frames that "looked fine" then when I checked I found them way out of whack. One frame had both rear dropouts shifted in the same direction. SO doing a DO alignment and checking spacing was not enough.

I had a trek that did that. I couldn’t get the headset adjusted properly and it would pull to the side a bit when I rode it. Ended up being the fork was slightly bent to the side. Not sure how that happened, they’re usually bent forward or backwards. Maybe try putting a different fork on it to at least eliminate a bent fork.

Perhaps a ride to see Frank the Welder is in order?

Good idea--Frank has done some great work for me in the past, but it's been so long that he didn't immediately come to mind.

I own one of these in visual vintage- 1972.
transfers, chrome, separation stripes all match.
Sold it off in 1975, repurchased in 1983.
was that good.

As this came to you used, I also suggest starting from scratch regarding alignment.

Frank should have the necessary measurement tools. My thought is 1mm at the seat tube extends to 1.5-1.6mm off at the axle.
might need to be partially torn down to check twist between the head tube and seat tube or BB axle.

fork too can be a culprit.

I have a later and earlier bike in addition. My approx ‘74 is less of a favorite, slightly steeper in the head angle. Thinking, I have four total!
different sizes slightly.

Visually, I think these are great graphic representations of a 70’s race bike.

I'm skeptical that misalignment can cause the stated symptom. If the bike pulled consistently to one side, especially when riding no-hands, then it'd be alignment for sure. But how can alignment cause "slaloming"?

That was kind of my feeling, but I know so little about frame alignment that didn't mention it, figuring that maybe it was on of those things that everyone but me already knew about. God knows there are enough things like that.

My '83 Nishiki International did that. I took the headset apart, got rid of the caged bearings, cleaned everything up, put in 'the right number' of Grade 25 loose-balls, added good quality fresh grease, and reassembled.

Fixed it. Not just 'improved:' fixed.

Why? I'm really not sure. My approach was a hunch after verifying my frameset was intact/straight/aligned.

Good luck!

This really sounds like a headset that doesn't turn as effortlessly and smoothly as it needs to in order to allow proper self-centering of the front wheel.

Note that this could be the result of some sort of localized alignment issue from one cup's mounting to another, or from a bent steerer, or from a crown race seat in need of proper finish machining.

And also note that even if a headset turns effortlessly without a stem installed, tightening the stem quill bolt bulges the steer tube elastically which causes the steerer to shorten slightly.
This results in the headset adjustment tightening up perceptibly.

Perhaps also, the bearing races may have become slightly dented from riding on a tightly adjusted headset, which will make future adjustments somewhat of a compromise between too loose and too tight (just as with any of the aforementioned alignment issues).

An "indexed" steering race can cause this symptom.

Bikes *never* travel in a perfectly straight line; they oscillate right and left in (depending on how good the rider is) long or very long S-curves.
With an indexed headset, the oscillation pauses at the index point before continuing on the other half-curve.
The sensation is that the bike is suddenly preferring the other side.

I had this exact symptom with a hairline crack in the bottom bracket. Just enough to make it sway.

I had a Superbe headset that was hard to adjust. I took one loose ball out of each race and it worked as intended. I would put my money on the headset.

Yeah, I think a headset overhaul in order. I'll dig into it and report back.

I can report from experience that LeJeune skipped serious headtube dressing - I would remove the headset and attend to that to set the internal diameter and squareness. Mark the pressed in parts to reference.

A laterally bent fork will pull consistently to one side, not the "S-curves" Jon describes. I suspect that the problem is elsewhere. I'd start with the headset. Make sure that it is not fretted ("indexed steering"), not fully seated, or simply maladjusted.