Knocking Noise when Pedaling
 

Hi there,

I have a steel framed bike outfitted with a Sturmey Archer 3 speed fixed hub with a White Industries freewheel attached. The bike is just over a year old and has horizontal dropouts. Lately I have noticed a sort of regular knocking sound when I am riding. It doesn't happen when I am not pedaling. I am worried that there is something wrong inside the hub, but I'm not sure. I checked my crank bolts and they seem tight. Can they be too tight?

I recently took the bike into a shop to see if they could figure it out where the sound was coming from. When I picked it up they had taken a coupl links out of the chain and the sound was worse. I am going to take it back to them (they warranty their work) but I am hoping someone might be able to give me some insight before I do.

Any thoughts?

Thanks in advance,

Andy

Hey Andy,

Id say first thing is how familiar is the bikeshop with single/fixed gears since that is a rather unique hub set up. Iv ran into a similar problem with my fixed before. One thing id suggest is check you gear ratio. High ratios and tentions create alot of torque. On my bike i found that the high torque created a similar noise to come from my chain and spokes and actually contributed to a broken spoke. Is your ratio higher then 3? Also when does it happen when your riding, all the time whether your on the flat, decending, and climbing? If it only happens when your climbing or trying to accel on the flat id say it could most likely be a ratio related tention problem.

Firstly, it IS possible to have the crank bolts too tight, but on a square taper crank, I've been told that "too tight" is when the crank splits at the hole for the spindle. I've never tried to find out, that may be complete rubbish.

Now the knocking. How often do you get the sound? Once per revolution of the cranks? Of the wheel? If neither of those, is it regular, and does it vary with your speed?

Check your cranks and rear wheel bearings for play. The rear wheel may have slight play in it because some SA hubs are designed to (the classic AW did, not sure about the S3X, that's more closely related to the 5-speed than the regular 3-speed)

Also, check the adjustment of the gear cable. I'd assume that a fixed-wheel hub would make noises under coasting as well if it was misadjusted, but it's under a lot less load when it's just driving the freewheel round, so it could be that.

Thanks for the comments!

As for the regularity, its seems to conincide with crank revolutions, but the knocking sound is paired with a vibration that feels like it is coming from somewhere in the rear.

When I turn the cranks without adding much pressure or when I am coasting I don't get the noise, and I also don't get it when I stand on the pedals when going up a hill. Anywhere between those extremes it happens though.

My rear wheels does have some play in the hub, but my cranks do not.

Hmmm, that sounds like it could be the hub. Is it particularly bad in any of the gears? SA don't seem to have an exploded diagram of the S3X on their website like they do with most of their hubs, so all I know about its innards is gleaned from my imperfect knowledge of the 5-speed it's apparently similar to. As such, I won't make any judgements just yet.

How much play is there in the rear wheel?

Pkshields may be onto something, high gears tend to lead to a lot of standing on the pedals, which puts cyclical stresses on the drivetrain and rear wheel, as opposed to the more constant stress from staying seated and spinning. What size sprockets are you using front and rear?

Also, is there any slack in your chain? SA hubs can have issues if the chain is too tight.

There doesn't seem to be a difference in the noise depending on the gear. I'm not sure what size sprockets I have on there. I think I am running 42 on the front and an 18 on the back.

I have had the problem both with a slack chain and a tighter chain. The problem is worse with a tighter chain.

Again, thank you for your comments!

maybe an inherent sound of the pawls in one of the gears not engaged
clicking.

AW3 speeds do that in high, the low gear pawls click as they pass.

S3X is the lower 3/5th of their 5 speed 1:1, .75 and .63,

I plan to take it in later today. Thanks again for your comments I will bring them with me as suggestions for the mechanic.

Cheers,

If I remember correctly, an 18 tooth is the equivalent of (roughly) a 29-tooth rear sprocket in first gear. (about 60% of direct drive, or roughly 1.6xsprocket size)

As such, you probably aren't thrashing the hub enough to have damaged it too badly, and even if you had, I'd expect the issue to be at its most severe when you did stand, which you've said it isn't.

What crankset are you running? Possibly more importantly, what chainring? When I had a singlespeed setup with a chainring designed for use with a front derailleur, it began making a noticeable noise on every rotation of the cranks. I suspect it was the slightly different profiling of some of the teeth (they do it to improve shifting, I assume) that was causing the sound. It went away when I got a proper singlespeed chainring.

The S3X doesn't have any pawls, if it did it would have to freewheel in at least one of the gears.

At least I assume it doesn't, the ASC certainly doesn't.

Take it back , sound is just a 5 letter word in text,



what do you expect from blind deaf guesses..

maybe airburst has pulled one apart, I have now idea how all 3 ratios
could be hooked up to turn the hub shell at the same rate.
direct .. does,

and then there are 2 planetaria options, that turn, internally
faster than the hub shell .. the nature of a reduction gear.
you tell me ..

Never dismantled one, only seen the diagrams for the ASC, and an article on how to convert an old 3-speed into a 2-speed fixed. Basically, the planet cage gets anchored to the hub shell, and all the pawls get removed. Then you can either drive the planet pins directly, for direct drive (cable completely slack, what used to be overdrive gear), or drive the gear ring, which drives the planet cage, but it works just like first gear normally does in that the planet pinions provide a reduction gear.

The 3-speed fixed combines that mechanism with the double sun gear/double planet gear system from the 5-speed, to get "super low", "low" and "neutral" or "direct". That may not be how the S3X does it, but what I do know is that it's possible to perform the same conversion as above on one of the old 4-speed hubs to produce a frankenhub 3-speed fixed-wheel that does work like that.