JochenRindt

When riding my Puch, I've been experiencing a "slip" while pedaling. I took it into the shop and they were not able to reproduce the slip, but they did rule out the bottom bracket as a cause. The chain and cassette are new. The mechanic thought it was possible the freehub was worn, specifically the paws, but as that is not serviceable, it can't be disassembled to see. After I got the bike back, I rode it about 17 miles and could feel no slip. Now, I'm wondering if perhaps the crank arm bolts were loose and that was the cause of the slip. So I returned to the shop and asked if he could check them. He said that as a matter of routine, that was one of the first things they would check. But he checked them again while I watched and they were tight. So I'm wondering- would loose crank arms cause that slip?

wheelreason

No.

FBinNY 

Loose crank arms on square taper manifest with more of a click than slip.

IME the most common cause for a slip or skip is a stiff link. Possibly the mechanic lube the chain as he was checking things out.

soyabean

Grease can seep into a freehub, or worse if grease was deliberately used to rebuild a freehub, can cake up over age and certainly gum up the pawls by solidifying.

If the pawls can be barely heard, time to replace or rebuild the fh.

Crankycrank

We need to know if you have a freewheel or freehub/cassette setup. I noticed most of your bikes listed were older freewheel models and Puch's were certainly more popular in the 70's-80's.

dedhed

Depends. My Ultegra FH is virtually silent

zandoval 

Pawls barely heard could mean its caked up grease and dirt. As soyabean can atest, remove the Freewheel and soak it in gasoline to clean it out. Then use light weight oil to lube it up.

Or after cleaning with gasoline then soak it in diesel for a lube.

Oh... And lets start a gasoline is too dangerous to use as a cleaner thread... AGAIN!

grumpus

It is, and it's not more effective for cleaning bike parts than kerosene or diesel, which will not turn you into the human torch or destroy your house.

Andrew R Stewart 

First- Crank arms can and do move about on the BB axle if they are mot tight. By the OP's description ,but not actual stated fact, I assume they have a cotterless crank. When these arms become loose and are ridden for a length of time the interface between arm and axle can and does get damaged. But a loose arm is very easy to check for, one pushing and pully, works back and forth, the arms and feels for or watches for the arm to move about independent of the axle or frame. I doubt this is happening as it's real obvious and generally gets a lot worse fairly quickly. If the crank is a cottered design (and I doubt this) the arms can become loose as the cotter pin loosens or becomes deformed from the very high levered forces.

Ratchet pawls, be they in a freehub body or freewheel, generally have their own distinctive manor of skipping. A sudden release of the pedal resistance, the crank arm moves forward (rotationally) an amount that is usually the gap/degrees to the next ratchet tooth and the pawl reengages and the crank arms go back to the normal feel. Often there's a noise like a clunk (not a click) when this happens. Allowed to happen enough and the pawls can become damaged and the problem becomes more frequent and feels worse as the pawls start to skip over more than one ratchet tooth at a time.

However there are other parts that can come loose or sometimes feel like something's "slipping". Pedals could be loose in the crank arm, could have loose/worn bearings/bushings, could be made of more than one piece of material and these pieces could move about (pedal platforms being peened to the body is a common example). Chains can be so worn that they no longer mesh fully with teeth (front or rear) and like a worn out pawl the links will slide up and over the teeth to try again to reengage. Suspension pivots can be so sloppy that the "wondering about" of the rear end feels like slipping. Seat and posts can also be loose/worn and contribute their movements to the situation. I've even seen fork issues be a cause of what some might say is slipping.

It sounds like the OP did the right thing and sought professional help. If the slipping feel returns, having that shop test ride the bike before doing any corrective work can help narrow down causes before any servicing hides it. (Note I said "hides", just because a bolt was loose then retightened might not have fixed the cause, just fixed the symptom. Like taking a pain killer for a broken bone. you might not feel the pain (good) but not have treated the fracture (bad). Andy

oldbobcat

If it was loose crank arms, the shop mechanic would have figured it out and fixed it right away. You'd think.

How old is this Puch, and how many cogs does it have on the rear cluster?

wheelreason

Do we?...

Crankycrank

^^^Might help to recommend a way to clean/lube each one if needed. Not the same for freewheel or freehub.

Duragrouch

Assuming it was a smooth-slip and not a clunk-slip, I'm gonna guess not chain, chainring, or cog related. Above comments rule most things out. So I'm gonna guess a slight rear tire slip due to rolling over something wet or slippery on the ground, especially if standing on the pedals, especially if it was just barely starting to rain, when the water forms an emulsion with road dust that is more slippery than after it really rains and rinses things clean.

bboy314

A more detailed description of the “slip” would be helpful for diagnosis, and more details about the bike and its components. Did the shop check for drivetrain wear? Could it have just needed a slight shifting adjustment (assuming indexed shifting)? Either way, sounds like maybe it’s been fixed?

Iride01 

Has anything been changed on the bike recently? A new chain can slip briefly on worn front or rear sprockets when there is a lot of power being put into the pedals.

I'd think the bike shop would know if a crankarm was loose for most all crank types. However if this is a cottered crankarm, then can imagine it might slip but still seem tight on the spindle when examined with no loads. But I can't imagine that the crank arms will still be 180º apart after than happened.

Messed up freewheel that disengages I've had plenty of times before with my kids bikes when left out in the rain to rust. But liberally spraying a light lube, WD-40 or some penetrating oil into the crack between the freewheel cogs and body usually will eventually fix that. But maybe only temporarily.

JochenRindt

It is a freewheel with an 8 speed cassette. Shimano 600 hub.

FBinNY 

You can't fix what ain't broke.

You now know it's not a loose crank, both because the signs are wrong, and the mechanic checked it in front of you.

It might have been any of a number of things, but regardless, it's OK now.

Take the win, and move on until/unless it acts up again, at which point you'll have something to work with.

smd4

This is an oxymoron.

JohnDThompson 

Do you mean "freewheel with an 8-sprocket cluster?" "Freewheel" and "cassette" are mutually exclusive possibilities. One or the other; not both.

Can you post a close-up picture of the rear cluster, preferably with the wheel out of the frame, so we can visualize which of the two possibilites apply?

JochenRindt

Sorry, I was at work when posting and got distracted. What I meant to say: an 8 speed cassette on a free hub.