# Why do so many ss bikes have slack chains?



## mustang1 (12 Oct 2018)

... I thought one of the advantages of ss bikes was lack of maintenance, but judging by how many slack-chained ss bikes I see, I think the riders may confuse _lower maintenance _with _no maintenance_.


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## dave r (12 Oct 2018)

I ride fixed, one of the little problems I've come accros is uneven chain wear, so when I'm setting the chain tension I have to check where the tight and slack parts of the chain are so I can adjust it at a tight spot.


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## rogerzilla (12 Oct 2018)

A slack chain on a SS isn't especially dangerous. It can be on a fixie; the worst-case scenario is that the chain jumps off and gets caught up on the pedal spindle, which causes the bike to fold up as the rear triangle is pulled over.


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## Threevok (12 Oct 2018)

Most of the problems with my chain becoming slack is the inability to tighten the QR up enough to stop the wheel slipping forward. 

I have (DMR) chain tugs that are designed for the bike, but they do not have enough range of movement to accommodate the larger sprockets I use, even after modification.

I purchased a slimmer (Genentic) set with more range of movement, but both these and the DMR ones are so wide, that there is very little thread protruding - to safely do the QR up - even when running just the drive side tug.

I have converted the rear hub from QR to 10mm with a thru axle, in the hope that I can torque this up sufficiently to prevent slippage. If not, then it looks like a bolt up conversion may be the only option for me.

So when I see SS with slack chains, I feel their pain


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## rogerzilla (12 Oct 2018)

I run an old straight-lever Campag QR on the back of my SS bike (which happens to be a fixie right now) and have had no slippage, even up steep climbs. No need for tugs. Do you have chrome ends? These are more challenging as they're so hard and slippy. Otherwise, get a proper enclosed-cam QR from Campag or Shimano with steel teeth on the acorn nut and QR body, oil the cam and it will clamp as firmly as axle nuts, if not more so.


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## Drago (12 Oct 2018)

Lube them with viagra, that'll tighten them up nicely.


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## tyred (12 Oct 2018)

You will also find that some chainsets aren't that accurately made and the chainwheel isn't centred.


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## dave r (13 Oct 2018)

tyred said:


> You will also find that some chainsets aren't that accurately made and the chainwheel isn't centred.



I know, there's fun to be had in trying to centre your chainring.


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## Illaveago (13 Oct 2018)

I was wondering if a bit of chain rotation would help with chain wear ?


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## dave r (13 Oct 2018)

https://www.sheldonbrown.com/chain-wear.html


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## Smokin Joe (13 Oct 2018)

Sheldon's bike -


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## mangid (13 Oct 2018)

I think tight spots are inevitable, it really does take much movement in my experience for it to go from too tight to 'slack'. 

I know the tight spot, and always walk the wheel back just before that spot. Tight spot is RHS crank at 25 past, so tighten with it at 15 past. I then spin it a couple of times, reassuring myself that I got the tight spot right (there will be a slight binding). Then just loosen one nut with the crank at the binding point (25 past) and let the tightness take care of itself.

I used to be pretty paranoid about slack chains, and did run tugs for a few years. But time and experience have convinced me that even a fair bit of movement when at it's loosest isn't an issue. 

I've thrown a chain 3 times, once chain was too loose, 2nd time sprocket came undone, third time was down to damaged stays flexing. 

Currently the tightest spot has maybe 5mm travel, and the loosest has ~15mm travel. Chain is approaching EOL at 9K miles.


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## silva (7 Jan 2019)

dave r said:


> I ride fixed, one of the little problems I've come accros is uneven chain wear, so when I'm setting the chain tension I have to check where the tight and slack parts of the chain are so I can adjust it at a tight spot.


The cause of that is a gear ratio that is an integer, ex 48/16.
Same chain links re-engage at the moments of putting force (crank arm locations).
There is no rotation of the most stressed links throughout the chain.
So your chains wear concentrates on two series links, no spreading.

Another potential problem is a non straight chain line.
Then wear concentrates on one side of the chain, causing the chain to become tilted.


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## dave r (7 Jan 2019)

silva said:


> The cause of that is a gear ratio that is an integer, ex 48/16.
> Same chain links re-engage at the moments of putting force (crank arm locations).
> There is no rotation of the most stressed links throughout the chain.
> So your chains wear concentrates on two series links, no spreading.
> ...



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


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## rogerzilla (8 Jan 2019)

You also get slack and tight spots with brand new components. The usual culprit is the chainring being less than perfectly round and/or not being perfectly centred on the spider. Sometimes the spider isn't great for concentricity, either. You have to pay a lot for the best and roundest track kit.

A workaround is to use bigger cogs, since these are less fussy about concentricity errors.


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## silva (8 Jan 2019)

dave r said:


> 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.


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## dave r (8 Jan 2019)

silva said:


> 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).
> ...



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?


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## dave r (8 Jan 2019)

silva said:


> 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).
> ...



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

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


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## silva (9 Jan 2019)

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.


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## rogerzilla (9 Jan 2019)

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.


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## silva (10 Jan 2019)

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)


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## silva (10 Jan 2019)

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?


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## dave r (10 Jan 2019)

silva said:


> 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.


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## rogerzilla (11 Jan 2019)

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).


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## fossala (11 Jan 2019)

rogerzilla said:


> 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.


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## Ian H (11 Jan 2019)

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


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## rogerzilla (11 Jan 2019)

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.


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## Ian H (11 Jan 2019)

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


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## rogerzilla (11 Jan 2019)

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.


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## fossala (11 Jan 2019)

Ian H said:


> 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.


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## Ian H (11 Jan 2019)

fossala said:


> 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.



I have a 17t on the other side. Some years ago I clocked 42mph downhill on that. I think I worked it out to 212rpm. Couldn't get that high nowadays.


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## silva (11 Jan 2019)

It's still hard to imagine how a chainrings mount can go so offcenter that it results in a noticable chain tension variation.
Any idea about what kinda bias this is about?
Take for ex a 5 bolts mount, tolerances tend to be random, so that they all together cause a net offset in a particular direction, appears rather unlikely to me.


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## rogerzilla (12 Jan 2019)

If you loosen the bolts, you'll find the chainring can usually move quite a bit in any direction you want. Some are much tighter but it is a fitting that generally has a lot of tolerance built in. Rarely, you will find a chainring that won't fit onto a spider (Andel track cranks are rather "tight" in this respect and not all 144BCD rings actually fit), and the manufacturers want to avoid that.


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## dave r (12 Jan 2019)

silva said:


> It's still hard to imagine how a chainrings mount can go so offcenter that it results in a noticable chain tension variation.
> Any idea about what kinda bias this is about?
> Take for ex a 5 bolts mount, tolerances tend to be random, so that they all together cause a net offset in a particular direction, appears rather unlikely to me.



With a single speed/fixed transmission it doesn't have to be much to produce slack/tight spots in the chain, a chaining can be within manufacturing tolerances but still not be exactly round, the same with the spider, it may be within manufacturing tolerances but not be exactly the shape its supposed to be, a couple of mm out here and there is all it takes. When a chainring is attatched to a spider there is usually room for a small amount of movement.


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## silva (12 Jan 2019)

I'm riding since about a decade singlespeed and later fixed gear, 3 different bicycles, had to tension my chain numerous times over that period, and never noticed any tension variation noticable to me and no I'm not blind heh.
It's only since my latest fixed gear, but as explained, it's certainly not the chainring mount that is the (by far) main reason, it's the 48/16.
Maybe a remaining question: my plan is thus to change to 47, so that there is a rotation of chain links engaging teeth at peak force moments - I wonder is there any way to quantify the wear spreading. For ex my 48/16 could be quantified as a zero spreading / worst case scenario.
Because, it's an annoyant problem, you feel it when pedaling and I'm forced to tension abit too much on the least loose point, without my chain hangs way too lose on the most loose point, risking falling off.

Adding another question about chainrings offcenter, don't they "recenter" too?
Because, if forces cause them to move abit on their mount, then forces can bring them back, at least in the case of fixed gear, when one can put force in the opposite direction.
This is also something that you may feel underway.


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## rogerzilla (14 Jan 2019)

I don't think a chainring will move once the bolts are tightened, at least not unless your chain has such a tight spot that it also wrecks your rear hub bearings.


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## silva (9 Feb 2019)

When the bolts are in place (so already before actual tightening), the position of the chainring is already fixed by reeds on the spider arms, with quite small tolerance, certainly not more than 1 mm (on my bikes its with bare sight metal on metal).
Question now is how much tolerance translates to chain tension variation. A mathematical question that is.


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## rogerzilla (11 Feb 2019)

You'd need to use catenary equations for that, but 1mm less distance between chainring and sprocket is a fair bit of sag. If you run a chain until it has the maximum recommended 1/16" of elongation per foot, it will be in danger of falling off the chainring, and that's only about 2mm over a typical chainstay length.


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## Ajax Bay (6 May 2019)

silva said:


> the chain tensioning problem is due to no derailer/tensioner (springbased), a singlespeed can have one but a fixed gear not, reason being ability to resist pedals in order to slowdown which would wreck the tensioners mount due to force direction being opposite. I wonder if there really is no solution for this.


This has been posted in the mechanical thread. But people here will be able to comment with more understanding.
Is (satisfactory for operation) chain tension a significant problem and why is there "really no solution"?


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## Waterwheel (2 Aug 2019)

rogerzilla said:


> A slack chain on a SS isn't especially dangerous. It can be on a fixie; the worst-case scenario is that the chain jumps off and gets caught up on the pedal spindle, which causes the bike to fold up as the rear triangle is pulled over.


I had that problem loads of time on a fixed gear bike. By the way some single speed bikes come with a chain tensioner similar to a derailleur. I think that is a great idea as then the chain is not too tight or too slack. An over tight chain will wear out too quickly and a slack chain risks coming off the chain wheel and causing an accident. Incidentally I found that single speed bike chains last far long than derailleur bike chains. A hell of a lot longer. For example I have just replace my derailleur bike chain after just two months. With a single speed bike I used to get up to 8 months wear out of it.


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