Bumpy new seat roller

[lazy_rower]

I have an odd problem. I bought a set of new (white plastic) seat rollers for my Model C. The new front roller is bumpy. If I reinstall the old (grey plastic) roller, the bumpiness goes away. The bearings on the new roller spin freely, and the roller doesn't appear obviously out-of-round in any way.

Any ideas what's going on?

Maybe I should have just bought new bearings for the old rollers. Maybe I should just steal the bearings from the new rollers and put them in the old rollers. (The old back roller's bearings are shot.)

[lazy_rower]

I made the discovery that the puller on a roller skate bearing press works really well for the bearings on the concept2 rollers, and experimented swapping bearings and rollers around.

1. The old grey top rollers are louder, especially installed in back.
2. The smoothest rolling combination was a grey roller in front, and a white roller in back.
3. The top rollers do not have equal depth bearing hubs on each side, so you need to be careful about the exact seat alignment when you install.
4. The bottom roller hardware has almost 0 clearance from the rail, which is a big problem combined with item #3. Judging by the scrapes on my unit, this has been a problem for a while.
5. You may get the unit adjusted smooth once, but reassembling the same configuration will be loud, bumpy, or out of alignment.

All in all, replacing the seat rollers was unsatisfying. The rolling is quieter, the bearings are smoother, but I feel more non-bearing bumps while it rolls.

[lazy_rower]

After thinking about it, I wonder if my seat has warped over time. It is just particleboard. All of these troubles stink of misaligned parts.

[Tsnor]

Bumps. Not out of round, or grinding.

Look for particles on the wheels. New wheels lose bits** faster than old ones. The bits get stuck on the track and embedded into the wheels. Your hand should be able to feel any bits that got stuck in the wheel.

** bits .... the residue on the monorail composed of dirt, perspiration, molydisulfide (the lubricant from the plastic rollers), and a very small amount of the nylon plastic worn off the rollers. Might also be some manufacturing residue.

[Ombrax]

All in all, replacing the seat rollers was unsatisfying.

That's unfortunate. To give you one additional data point (that probably won't help you a whole lot), I replaced the upper seat rollers & bearings on the Model E at my gym at work and didn't have any complications. (the original rollers were bumpy due to dents in the white material)

One thing I did notice is that the replacement rollers C2 sent me had a significantly narrower "rolling section" that touched the rail top compared to the previous rollers. (I would guess that they were around 60%-75% the width of the old ones.) Eventually over time this became obvious on the rail top, with the old wider path visible, and the newer narrower path at the outboard edge of the first path. As best I could tell that didn't cause any problems.

Bottom line, in my experience roller replacement on a heavily used gym Model E wasn't a big deal.

[lazy_rower]

** bits .... the residue on the monorail composed of dirt, perspiration, molydisulfide (the lubricant from the plastic rollers), and a very small amount of the nylon plastic worn off the rollers. Might also be some manufacturing residue.

I wish! Re-cleaning the rollers and slides was the first thing I checked. The bumping is rhythmic, so it's definitely roller and not slide related. But everything is clean.