Hi,

I rebuilt an old loose ball BB bike. It rides really well very smooth when pedaling, but when I try to back pedal (i.e. turn the cranks backwards) its quite stiff and not easy to turn at all.

Any suggestions why? As I mentioned moving the cranks the right way is very smooth. These are geared bikes with 8 speed freewheels.

First, derailuer bikes aren't designed to be pedaled backwards. The RD is designed to feed the chain onto a cog when pedaling forward. There is nothing but the FD to guide the chain onto the cogs when pedaling backwards. That being said, remove the chain and see if pedaling backwards is smooth. Then check if the freewheel spins smoothly backwards. Assuming these check OK, you are fine.

Are you talking about with the chain removed from the cranks so only the crank elements (BB) are in action? If not then I suspect the freewheel/freehub, pulley wheels, chain links are stiff. Andy.

The first test which gives plenty of information is to pedal to get the rear wheel spinning in the air, then stop pedaling and let it coast. Watch the top of the chain to see if the top loop sags, or if the spinning wheel pushes the pedals around. A gentle pushing is fairly common, but a sagging top loop or positive pushing force means the freehub is sticking.

OTOH- stiff backpedaling, not coming from the BB, and no freewheel resistance, means the source of friction is in the lower loop, usually within the chain itself from poor or dried lube, or rust, or sticky RD pulleys.

Should have been clearer. The chain is removef and back pedaling is stiff. Forward pedaling is smooth.

Any help?

The crankset, with chain removed, is stiff backwards, and better forwards ? Very odd.

You probably didn't get help because your problem as described defies analysis.

Once the chain is off, the crank is turning on bearings, and there's no logical reason for the drag to be different backward vs forward. Possibly (barely) there's some kind of wear pattern on a seal that may prefer one direction, but I can't see it causing a material difference.

So, your option is to first decide that there is a difference, and it's not just your imagination. Then decide if it's meaningful, and not some minor idiosyncrasy. If it clears those hurdles, tear down and overhaul your BB. If it doesn't clear those hurdles put it out of your mind and ride your bike.

I wish I had the bike in front of me in the stand. All I can think of is to take apart the BB again and look for any damage to the cups and the cones. Also maybe back down on the tension just a tad.

Did the think spin freely in both directions before you rebuilt it?

Saying "I am facing the same problem" implies that there is a problem. This is equivalent to someone on a car forum saying "Whenever I get up to speed driving forward and then try to shift straight into reverse, I get a grinding feel."

There is not a problem. As the responder in post no. 2 said, derailleur-equipped bikes are not designed to allow backpedaling.

Don't backpedal. "Problem" solved.

Depending on the bottom bracket type, my guess would be either the lock nut ( 1 piece crank) or lockring (square taper 3 piece crank) are not locked down causing the bottom bracket to "tighten up" the adjustment setting when rotated backwards.

The portion of your post that I put in bold above is an opinion that does not give us good information. What is needed is your observation of what happens when you follow FD's suggestion in post 4. The test you did does not isolate the problem (if there is one) as any reduction in tension on the chain will make it run easier.

The drivetrain on my wife's bike will spin backwards for about 3 full crank revolutions. The drivetrain on my CX bike will do about 3/4 of a revolution. Rear derailleur, 100%. She's got a 105, I've got a clutched Rival 1 with a whole lot more spring tension. If the cassette spins freely and the cranks spin freely, you know there's nothing mechanically wrong. It is something easy to get hung up on though, I think.

Most bikes can tolerate backpedaling if the chain happens to be on a chainring/sprocket combination reasonably close to being in the same plane. Some bikes with long chainstays can tolerate moderately offset chainring/sprocket combinations. So what? Why anyone cares about backpedaling defeats me.

Yes, of course. And not just friction systems. But anyone knowledgeable enough to make such a diagnosis would be asking about aligning the derailleur rather calling the mere fact of backpedaling resistance in some gear combination a "problem."