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Strange sounds on the converted single speed . . . .
OK,
A long time ago we converted our scale 40 to a single speed. Now running 44/16 with slicks as the commute bike.
I kept hearing a strange sound that I thought was the BB going - and also noticed - as I looked down,that the front ring seemed to be doing the pretzel thing - I could see it moving side to side as I spun the cranks (maybe 5 - 7 mm) - so thinking maybe I had warped the ring (what with powerful legs 
) last night I took the ring of and laid it down - it's as flat a pancake - no warp what so ever - so I spun the cranks and can see that they appear to be slightly warped - so to speak - of the four "Spokes" where the ring attaches - two seem "off". - Oh the BB is nice and tight and no signs of going.
Questions:
(1) Is the "warp" of the cranks just normal for a three ring set up (Something to do with getting the chain to change)? - I doubt VERY much that I have bent this LOL.
(2) Could the BB be going and I'm just not getting any noise when I spin it on the stand?
Any other ideas?
thanks
Yarg
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i broke 2 crank sets before i figured this little gem out.
Essentially i found that the other 2 chainrings that would normally be attached to a 3 chainring crankset do serve a structural function. Removing them weakens the spider (spokes) a little (not a great deal i must say). If you are a big rider, or put out a heap of wattage on hills then over time, the spider will be under greater strain.
I bought a cheap bash guard for where the big chainring should be, and made sure that there were chainring bolts in place where the small chainring should be. Havn't had the problem since.
The other thing to consider is that the crank spider is placed under heaps of stress anyway. If it is an older crankset, then it could simply be a normal use fatigue that has weakoned it.
Could also be that you just didn't have all the chainring bolts tightened at equal tension.
I'm sure there are possible reasons.
I've been riding strictly single speed for about 5 years now. The one thing i have learned is that there is nothing simple about single speed bike building. Particularly on a non single speed frame. It can be very fiddly and precise
Have you checked that the downtube / seat tube / bottom bracket frame isn't cracked and "flexing" under load?
Hi Yarg. I haven't run an outer ring ss but I have run a 34 16 offload set up. I liked the purity but as the last guy says it's not quite as simple as you'd imagine but IMHO once set it's very reliable & low maintainence. I also believe that true hardcore single speeders run the lstronger BMX chains & sprockets.
I wonder if what you have is a combination of high load on a weakened crank (due to you running the outer only),
I would try knocking the ring mounts back into shape then moving the ring to the middle position or grind the teeth off of an old middle ring & fitting it as a reinforcement.
Possibly crude but makes sense (to me).
Regs T
Firstly,
Good feedback folks - plenty to think about.
the words "Powerful" and "Yarg" are not generally used in a sentence unless there is a negative between them . . . however that said:
The frame shows no signs of cracks etc.
One "spoke" of the spider is definitely out of wac. In the short term I might try to tweek that back - and I'll see if I can find an old ring or two to fit.
Now I'm looking at SS crank options - I haven't spoken to the department of war and finance yet
It probably means a new BB as well . . . see how we go.
Yarg
Many "single speed" cranks are just the standard crank without the triple rings and still have the granny bosses etc (i.e. raceface). The other option is to use a Surly chainring in stainless which are super strong and so make up for the removed rings. I have seen a SS mate turn a standard chainring into a knot which destroyed the cranks due to chainring bolts not being super tight, one to watch for
Truvative Stylo SS cranks can be had quite reasonably on eBay and the like. Bullet proof cranks in my experience, and nice and light too. The standard SS unit usually comes with a bash ring in Alu, but I just run a Blackspire or Renthal SS chainring. My last set up cost less than a C$note with new parts.
I came across Cycle Underground based in sydney and make custom chain rings and bookmarked there web-page. I have yet to do business or contact them. Last news post on the main page was in 2008, if they are still in business there custom chain rings look pretty good for single speed. If anyone gets in contact would love to know if they are still in business.
Also, in regards to the funny sound. I had a funny sound not so long ago and found it to be my rear hub free body was cracked.
A while back I posted asking thoughts on an unusual loud crack that seemed to eminate from my cranks every so often under take up load. I greased everything, made sure that everything was tight and even changed the middle ring but it was still happening.
I lived with it until today when reading this thread gave me an idea that it might be the freehub, a 4 year old Hope Pro2.
I stripped the said hub today & found 3 of the 4 pawl springs broken. I've just ordered new ones, $12 inc post. I'll have to wait a couple of weeks but luckily I've spare wheels/bikes.
Cheers, T
I striped of the cranks over the weekend - and had a good look at the BB (in situ) and I swear the crank side is slightly off centre - so i put the crank back on - and am still sure its slightly of centre. . . . . . .
I think it's time to go pro . . . .
Yarg