oberwl

Just curious: What's your take?
Posted my old road bike for sale. Haven't ridden it in around 6-9 months. It may be a bit dusty, but after airing up the tires and going around the block it seemed fine.
So the buyer arrives. Says he's not familiar with SRAM Double Tap. I show him how it works.

He goes off on test ride. Comes back says the rear derailleur not shifting down. I notice he Cross chained big to big 50-28.
So I try to shift it down, jump on the bike to see what's going on. Yep not working.

I remove the chain & pull off the rear derailleur. The internal spring that pulls the jockey wheels into the body is broken. One side of the spring has come disengaged.

So Question, Is this a rider error, or Worn Part?

I know that the bike should be able to cross chain in the stand, but kind of expected that something is going to go wrong when ridden with force.
BTW: I live on a slight grade, so going up there would be more force than just on even pavement

dsaul

A properly set up drivetrain should be able to use the big/big combo without causing damage to the derailleur. I have used that combo many times on my SRAM equipped bikes with no problem. If the derailleur broke from shifting into that combo, under load or not, the chain was too short. "Cross Chaining" is not ideal, but its not the "end of the world" that people preach on these forums and shouldn't cause anything more than some additional drag and noise.

SurferRosa

I've sold a lot of bikes and had a couple mechanicals during a customer's test ride. But I've never seen them shift into the big/big to cause an issue. I do sometimes tell them after the sale to avoid the big/big and small/small. My old bikes aren't intended for that.

I wouldn't worry too much about fault. Just fix it and move on.

Phil_gretz

Most failures that occur during the test ride will be your responsibility to repair. Even if the rider crashes the bike, unless you can prove that the rider behaved negligently or dangerously.

Like SurferRosa said, I've sold many bikes that have had mechanical issues even after I had thoroughly rebuilt them and test ridden them. That's why I've learned to do several stressing test rides to see if I can force a failure before a buyer sees the bike. The most common piece out of adjustment will be bottom bracket bearings. Sometimes it takes a few iterations for the bearing compression to be "just right". Second most common might be headset bearing adjustment.

Like the OP, I have had a derailleur return spring fail during a test ride. I replaced the derailleur on the spot to complete the sale, but that was made possible by having a box of spares that would be suitable. Not easy in the OP's case. I also had a buyer discover a small sidewall cut in a Panaracer Pasela gumwall that I had ridden maybe 200 miles. Ugh. I replaced that tire on the spot for him. Stuff happens.

msu2001la

I would definitely run a 2x drivetrain through all possible gear combos on a test ride. Cross-chaining causes increased wear, but it shouldn't cause parts in the drivetrain to immediately fail.

ClydeClydeson

If big-big X-chaining causes damage, that's assembly error.