Derailleur Question

[look 171]

From what you described, the chain needs to be tightened a bit. Chain stretch wouldn't normally cause it to jump off the chain ring. I imagent when you go over a bump, you foot is at 3 and 9 o'clock acting as shock absorber, meaning no force or turning on the pedals therefor chain bounces off the chain ring. Another place often over looked is the chain ring bolts. Tighten them up a bit. Maybe one or two had come loose.

[look 171]

before you lube the chain, check every link is free and not stiff.
That causes shifting issues and it may even be the cause of chain jumping off the ring.

[stevej37]

Originally Posted by look 171

From what you described, the chain needs to be tightened a bit. Chain stretch wouldn't normally cause it to jump off the chain ring. I imagent when you go over a bump, you foot is at 3 and 9 o'clock acting as shock absorber, meaning no force or turning on the pedals therefor chain bounces off the chain ring. Another place often over looked is the chain ring bolts. Tighten them up a bit. Maybe one or two had come loose.

Yes, my feet are at that position to give equal absorption of the bumps. I could try it at noon and six and see if that makes a diff. I'll be on the same route tomorrow.

I will check the chain before lubing it, and ring bolts....I don't notice any noise from the chain or sprockets when pedaling. (other than normal)

Thanks for the help.

[look 171]

Originally Posted by stevej37

Yes, my feet are at that position to give equal absorption of the bumps. I could try it at noon and six and see if that makes a diff. I'll be on the same route tomorrow.

I will check the chain before lubing it, and ring bolts....I don't notice any noise from the chain or sprockets when pedaling. (other than normal)

Thanks for the help.

No, don't do the 12/6 position. It isn't needed. 3/9 is the balance you need to stay on over bumps safely. The correct amount of links seems to be good from the pic. Give the derailleur hanger bolt, the silver piece, a tiny twist to make sure it isn't loose. Don't need much. They strip easy.

[stevej37]

^^^ I switched the seat post shortly after I bought the bike for a shock absorbing one.
Made a big difference for the expansion joints on the road. My back can't take sharp bumps, I had back surgery a year ago.

I'll check that hangar bolt.

[A930Rocket]

Originally Posted by stevej37

You are correct....I only have 7 gears....my bad.
So it happens mostly in 6 because I hardly ever use high (7) gear.
Same situ just one gear less.
.

6-7-8…. Whatever it takes.

[stevej37]

Originally Posted by A930Rocket

6-7-8…. Whatever it takes.

You'd think that having a decal on the side of the bike saying 7S...I would know there is no 8th speed. It must be dementia.

[look 171]

Originally Posted by stevej37

^^^ I switched the seat post shortly after I bought the bike for a shock absorbing one.
Made a big difference for the expansion joints on the road. My back can't take sharp bumps, I had back surgery a year ago.

I'll check that hangar bolt.

Remove 3-5 lbs off your tires. It makes a HUGE difference with the sharp jolts.

[john70t]

Originally Posted by herr_oberst

Alright. Looking at that drivetrain, I wouldn't be surprised if it's a combination of 2 things. Chain stretch, front cog wear..

The first stupid hack question would be to increase the chain tension by removing a link. Or two. It doesn't fix the problem.
(you DO carry carry a chain-splitter tool, air pump, patch kit, tools, just checking)

And there is a way to measure derailleur spring back-tension of course.

The next question would be check lateral run-out of gears. Warped disks.
They can tweek L/R but they should not. Not compared to knees.
Like a saw blade.

[LEAKYSEALS951]

Originally Posted by stevej37

^^^ Yours is in low gear though....I've never had it happen in any of the low gears.

What he's looking at is how "stretched" his derailleur is in the low gear. First- he isn't in low gear, but second to low, but that 's not the point- you want to make sure the spring tension on the derailleur isn't too loose- or pulled straight in your "1" low gear.

This video at about 2:30 shows what happens when a derailleur gets stretched too much. I was betting his chain was too long- this is a way to see if it is, and if you can get by with removing 2 links- when he simulated it, the deraulleur got pulled straight / overextended, so removing 2 links was not an option for him. I ff'd to the exact section:



Assuming you cannot remove 2 links in the largest cog - as simulated in the video(what you call "1"), then you are either looking at a stretched chain or a b adjustment as a fix, or a combo of both.

take a screwdriver on the next ride, find a pothole that jumps it, tighten the b screw 1/2 turn or two, remember what you did, see if that fixes the jump on the spot. If not, or the shifting stops working well- loosen b adjuster by same amount, go home and buy new chain.

This is all after you have:
Checked chain for kinks/ tight links
Checked front chainring for bent teeth (side to side)
Lubed Chain

That bike also has a lot of corrosion on it.
Make sure there is :
No slop/looseness in crank bearings
No slop/looseness in reab hub

[stevej37]

Raining today, might be afternoon or tomorrow before I take it out.
I'll check the tire pressure...I believe I have them at 60 psi now.

What you're seeing in the pic is dirt/mud...no corrosion. It's only a year old.
After I clean it and lube the chain, I'll take another pic.

[stevej37]

Checked the 5 crank bolts...all were tight

Set the tire pressure to 50psi. Tire sidewall calls for 50-75 psi.

Lubed the chain good....can hear nothing now when turning the crank on the bike stand!

I can see no slop/looseness in any of the drive parts.

When the roads dry, I'll take it out. Don't care for the wet skunk stripe up my back.

[stevej37]

Oops...forgot the pics after cleaning and lubing.

[LEAKYSEALS951]

Hey Steve- sorry to keep blowin up your thread, but what kind of bike/model (what year) is that? (For better or worse- I've got time to kill....)

The bike seems to be built to look like a single speed type esthetic with the rims and the front chainring, but usually on bikes like that, I think of chain guard ring protector stuff. That bike doesn't have one. Not necessarily bad, they might have left it off for the single speed "look"- but I'd expect to see a guard on something like that bike as stock. Something like this-



bike is looking good clean!

[LEAKYSEALS951]

Originally Posted by stevej37

Oops...forgot the pics after cleaning and lubing.

Looking good.
I swear that setup might just be able to subtract 2 links and work. Maybe.... Maybe not

Here's another video on determining chain length from scratch. I'd swear your chain looks longer than the cog to cog +2 method mentioned in this video:



I would guess if you ran the chain from large rear cog (what you call 1) to front chainring without the derailleur, like he does, you'd have at least 2-4 extra links

[stevej37]

Originally Posted by LEAKYSEALS951

Hey Steve- sorry to keep blowin up your thread, but what kind of bike/model (what year) is that? (For better or worse- I've got time to kill....)

The bike seems to be built to look like a single speed type esthetic with the rims and the front chainring, but usually on bikes like that, I think of chain guard ring protector stuff. That bike doesn't have one. Not necessarily bad, they might have left it off for the single speed "look"- but I'd expect to see a guard on something like that bike as stock. Something like this-



bike is looking good clean!

Hey...no problem, I love talking about bikes. I learn something new each time.
I have three bikes, this one is a Propella, pedal assist bike that I use mostly when I know I'm headed for hills or a windy day. It must be pedaled or it won't go anywhere.

My bike I use for rails to trails is an 8 speed (I think that's why I was mixed up last night) belt driven Vilano. Perfect bike for stopping and starting often. No need to downshift before stopping.....just thumb it down while stopped to 1st or 2nd and take off. There's a recent thread on here...I'll look for a link.

My third bike is a 24 speed Vilano road bike. I lent that out a few weeks back. I don't like riding that one so much because of my back.

The Propella in the pics is one year old...I had a duplicate that was two years old and it was stolen off of my Swagman bike rack last year.
I have the Garmin Varia on the Propella to make road riding safer. I was hit broad-side 7 years ago and had to have a titanium rod put in my broken femur.
Some reading if you want....https://forums.pelicanparts.com/off-topic-discussions/957058-anyone-else-have-done-their-leg.html

Be sure to read the linked article in my first post. That's exactly what they did.

.

[rwest]

They make a device that clamps to the seat post that won’t allow the chain to fall off. It’s called a chain keeper or catcher. Some of the pros even use them when using one chain ring to prevent chain drop. I think chain drop is somewhat common even on a well set up bike.

[stevej37]

^^^ Everytime it's happened to me, it's caught/wedged between the pedal arm and chain ring. (and the rear of the chain stays on the gear it was in)
Easy to slip back on and hand turn the crank to get it seated....just messy.

It's also never happened to me while normal riding....just when hitting big bumps.
That's something I'm going to need to avoid or slow down more around them.

[rwest]

Here you go Steve, keep those fingers clean by waxing your chain instead!

Waxing Bicycle Chains

I’m a couple years into doing it and I love it, I can run my hands over my chain and my hand stays clean. Bike doesn’t get covered in oily film and I never have to use degreaser on my bike.

[rwest]

Steve,

What about getting a cheap clamp n front derailleur that just stays in place so the chain can’t fall off either side? You might have to get creative on getting it locked down in the right spot- they have limit screws which might have enough range.