Why do so many ss bikes have slack chains?

[silva]

Holy thread resurrection batman! If that's the case how come I can take most of the slack spots out by reseating the chainring on the spider? Currently I'm running 46 X 18 and usually run 44 X 18

Some phenomenons have more causes, the one I gave was mine.
Never had chainring out of centers. Or at least not in a degree that I noticed consequences of it.
My 48/16 resulted in a 3 cm up/down tension difference. At the moment, I "workaround" it by moving the chain over the chainring regularly / whenever I hear ticks, by 12 links.
I'm now exhausting my drive train, chain and rear cog are very worn, and when something breaks, I'm gonna replace all, a 47T chainring, a new 16T cog, and a new (same chain).
It should also solve a tensioning problem, being that with 48T a new chain requires the eccentric in the bottom bracket to be close to its front position, causing the need to start with 108 links to shortly after take off 2 to 106 links, with the 47T I should be able to mount 106 links, with the eccenter close to rear position.

But about your chainring cause, out of interest, if you reseat it, does it again shift offcenter later on?

My chain is abit special, it's over 500 grammes, a 1/8" with 3/16" sideplates, UK brand Gusset, model "Tank", a bmx chain, too short for my bike, had to add some links from a second.
Very happy about it, at the moment it lasted 15 months, at 50-60 km/day, and most of that period with a 5 mm wrong chainline, on top of aboves problem. My first chain on the bike, a KMC Z1RB 1/8", lasted just 1 month. The wrong chainline caused the chain to be tilted to nearly 45° on 2 sections. Since I corrected the chainline, it gradually leveled again, but it's still visible in a degree.

 

[Deleted member 1258]

Some phenomenons have more causes, the one I gave was mine.
Never had chainring out of centers. Or at least not in a degree that I noticed consequences of it.
My 48/16 resulted in a 3 cm up/down tension difference. At the moment, I "workaround" it by moving the chain over the chainring regularly / whenever I hear ticks, by 12 links.
I'm now exhausting my drive train, chain and rear cog are very worn, and when something breaks, I'm gonna replace all, a 47T chainring, a new 16T cog, and a new (same chain).
It should also solve a tensioning problem, being that with 48T a new chain requires the eccentric in the bottom bracket to be close to its front position, causing the need to start with 108 links to shortly after take off 2 to 106 links, with the 47T I should be able to mount 106 links, with the eccenter close to rear position.

But about your chainring cause, out of interest, if you reseat it, does it again shift offcenter later on?

My chain is abit special, it's over 500 grammes, a 1/8" with 3/16" sideplates, UK brand Gusset, model "Tank", a bmx chain, too short for my bike, had to add some links from a second.
Very happy about it, at the moment it lasted 15 months, at 50-60 km/day, and most of that period with a 5 mm wrong chainline, on top of aboves problem. My first chain on the bike, a KMC Z1RB 1/8", lasted just 1 month. The wrong chainline caused the chain to be tilted to nearly 45° on 2 sections. Since I corrected the chainline, it gradually leveled again, but it's still visible in a degree.

Yes eventually it moves again and needs recentering. It sounds like you have vertical drop out on your bike, my Genisis has track ends.Have you used the Sheldon Brown website?

 

[Deleted member 1258]

Some phenomenons have more causes, the one I gave was mine.
Never had chainring out of centers. Or at least not in a degree that I noticed consequences of it.
My 48/16 resulted in a 3 cm up/down tension difference. At the moment, I "workaround" it by moving the chain over the chainring regularly / whenever I hear ticks, by 12 links.
I'm now exhausting my drive train, chain and rear cog are very worn, and when something breaks, I'm gonna replace all, a 47T chainring, a new 16T cog, and a new (same chain).
It should also solve a tensioning problem, being that with 48T a new chain requires the eccentric in the bottom bracket to be close to its front position, causing the need to start with 108 links to shortly after take off 2 to 106 links, with the 47T I should be able to mount 106 links, with the eccenter close to rear position.

But about your chainring cause, out of interest, if you reseat it, does it again shift offcenter later on?

My chain is abit special, it's over 500 grammes, a 1/8" with 3/16" sideplates, UK brand Gusset, model "Tank", a bmx chain, too short for my bike, had to add some links from a second.
Very happy about it, at the moment it lasted 15 months, at 50-60 km/day, and most of that period with a 5 mm wrong chainline, on top of aboves problem. My first chain on the bike, a KMC Z1RB 1/8", lasted just 1 month. The wrong chainline caused the chain to be tilted to nearly 45° on 2 sections. Since I corrected the chainline, it gradually leveled again, but it's still visible in a degree.

Found it, towards the bottom of this page is the article on chainring centreing.

https://www.sheldonbrown.com/no-derailers.html

 

[silva]

I know the Sheldon Brown information source.
An offcenter chainring is clearly not the cause of the tension variation that I experience, when swapping the chain for another, the tension variation is gone with the chain.
The tension variation in my case gets "build up" by concentrated wear, due to same links engaging around peak force, and other same links around min force.

 

[rogerzilla]

Prime number-toothed chainrings let you pick any rear sprocket size without the concentrated wear problem (usually more of a problem for the sprocket than the chain). Or you can just choose chainrings and sprockets where chainring teeth/sprocket teeth is a sufficiently messy fraction.

If you've got a 48T ring and don't want to change it, 17T or 18T is good enough to spread the wear, as is 15T if you're a masher. 16T is just uniquely bad, especially if your chain also has 96 links, which is quite common on off-the-shelf fixies. You're hitting the same sprocket teeth with every power stroke and the chain is also hitting the same ring and sprocket teeth all the time.

 

[silva]

To reduce wear I opt for as big sprockets as possible, and to be able to push in all condition, I opt for a low gear.
My previous bikes had 52/16 but the new frame didn't have clearance for > 48T, so I was given 48 as max.
Only that I wasn't told that this concentrates wear.
Lower than 16T at the back would give away the wear benefit and in my case also has a problem being the cog is bolted on a disc brake flange, lower than 15 isn't possible and 15 only by using special countersunk bolts in order to prevent the bolts voiding the chain, which I consider awkward.

The solution that I intend is a 47T front 16T back and 106 links.
Current is 48T 16T 108(new)>106links(shortly after)

 

[silva]

By the way, shouldn't a good chainring mount not prevent movement of the chainring?
How comes it can?
Are the holes for the bolts drilled with too much tolerance?
Is the chainring not supported enough on the cranksets spider?
Both?

 

[Deleted member 1258]

By the way, shouldn't a good chainring mount not prevent movement of the chainring?
How comes it can?
Are the holes for the bolts drilled with too much tolerance?
Is the chainring not supported enough on the cranksets spider?
Both?

Manufacturing tollerences, most are not exactly round, most have a little free play in them, I find it difficult to tighten the bolts up tight enough to stop movement without breaking something, I'll have to investigate torque settings at some point and get the torque wrench out.

 

[rogerzilla]

47 x 16 is pretty high for a road fixie. I'm running 47 x 18 on the track bike for road use (52 x 17 for the short Calshot track).

 

[fossala]

47 x 16 is pretty high for a road fixie. I'm running 47 x 18 on the track bike for road use (52 x 17 for the short Calshot track).

I don't know if it is. I run 45x16 down Cornwall, Belgium is quite flat.

 

[Ian H]

I'm down to 43x18 most of the time now, which is fewer inches than my years on the planet.

 

[rogerzilla]

It depends on your preferred cadence. 47 x 18 gives me 21mph at 100rpm, which is about right for an 18mph cruising speed with a bit of headroom for descents; 30mph is still under 150rpm, so not too crazy, and 35mph is ok in short bursts.

 

[Ian H]

I'm happy spinning, so evens is comfortable. I'd have to work out the cadence for that.

 

[rogerzilla]

Really good roller riders can spin at 250rpm under "no load" conditions. They could descend at 50mph on my 70" gear. I can only dream of such stuff! Some trackies can do 200rpm and put power down at the same time.

 

[fossala]

I'm down to 43x18 most of the time now, which is fewer inches than my years on the planet.

How do you get down the hills in Devon, drag a brake? I'm spinning out on 45x16 at 32mph-ish spinning up to 160rpm.