|
|
|
Forum Member
 
Group: Forum Members
Last Login: 17th May 2009 00:58
Posts: 36,
Visits: 117
|
|
Chain came off at the weekend. Both sprockets look hooked.
Can I just flip them over the other way, so they're running the other direction? If not, why not?
|
|
|
|
|
Supreme Being
Group: Forum Members
Last Login: 23rd August 2010 20:19
Posts: 1,002,
Visits: 1,795
|
|
Yes you can, but only as a desperate, get-you-home, 'it's the weekend and all the shops are shut' measure  The hooks on the teeth will be facing in the wrong direction and will chew the chain up pretty quickly (if it turns at all), and then you will be left with no teeth at all and possibly a damaged chain. Think of the damage a flailing chain could do to the back of your leg (they don't put chain guards on bikes for nothing) and then spring for a new chain and sprox. Chain and sprocket sets are a consumable, like brake pads. You wouldn't consider whipping out a worn brake pad and turning it round to get some more wear out of it, would you? Don't answer that!
Are you sure the chain was adjusted correctly? I can't see how a chain could just fly off, even if the teeth were worn right down, unless it was very loose. New parts, check tension and lube weekly, adjust when necessary, and they'll last for years.
--
2003 ST1300 Pan Euro
1995 Yam XT600E
http://goingfastgettingnowhere.blogspot.com/
|
|
|
|
|
Supreme Being
Group: Forum Members
Last Login: 23rd August 2010 20:19
Posts: 1,002,
Visits: 1,795
|
|
Just thought -
Also, your rear sprocket might turn round OK, but the front one is likely to have a boss on one side, and you'd never get the chain line right with it on backwards.
Generally speaking, a chain and a pair of sprockets tend to 'wear into' each other after a while, which is why renewing just one of the components is rarely successful unless the set is almost new.
--
2003 ST1300 Pan Euro
1995 Yam XT600E
http://goingfastgettingnowhere.blogspot.com/
|
|
|
|
|
Supreme Being
Group: Forum Members
Last Login: 16th May 2010 15:09
Posts: 637,
Visits: 1,168
|
|
| All true. Sprocket wear is directional and it'll gouge the chain to pieces pretty quickly. In fact, put a new chain on correctly-mounted old sprockets and it'll be shot in no time. It's false economy not to replace the whole lot when it needs doing - on the bright side, the sprockets are, at least, the cheap part of the replacement. I've never seen a chain come off as a result of sprocket wear alone: it's always been mainly down to maladjustment. Or, in one case, the most phenomenal tight spot that left a ridiculous amount of slack elsewhere in the chain run. You do see it sometimes at racetracks like Cadwell, on the mountain section - landing a flat-out jump on a superbike can compress the rear suspension enough to do it, but I suspect you'd know if you'd done something like that...! If it were me, I'd be tempted to replace the chain at this point even if it looks superficially okay. They tend to last ages without much adjustment, then hit the elastic limit and start to wear out quite quickly. It sounds like yours might be getting to that point and, in any case, could well have been fatigued by being spat off. It's no fun when they snap - even if it misses your leg, you've got a good chance of picking up a holed crankcase or having it flail into the rear wheel. I wouldn't have thought a CG125 chain and sprocket set would come in at much over £20, better safe than sorry.
>> ex silens nox noctis <<
|
|
|
|
|
Supreme Being
Group: Forum Members
Last Login: 23rd August 2010 20:19
Posts: 1,002,
Visits: 1,795
|
|
Just to add a comment which seems slightly relevant:
Lots of people talk about 'chain stretch' but they don't. They wear. Each roller in its little casing wears a tiny fraction of an inch over time, allowing the links to sit slightly further apart, and taken together over 100 links or so the chain gets longer. But the metal itself doesn't stretch.
This is why the teeth on the sprockets go hook-shaped. The links are designed to sit very snugly in the gaps of the teeth, but as the chain lengthens through wear, the links start to 'climb' up the face of the next tooth along, as the spacing between rollers is slightly longer than it should be. This wears a hollow on the driven face of each tooth, which gets longer as the chain wears, until eventually some rollers are bearing on the very top of the tooth they are supposed to be driving. When the sprocket wear reaches that point, the tooth looks 'hooked'. This is the reason for the chain and sprox 'wearing together'. The wear in the chain is matched by wear on the teeth, and the thing continues to do an effective job at transmitting power, until the rollers start to bear on thin air rather than metal, at which point the whole set is scrap. As Endo says, it is pointless replacing one and not the other, as you have broken the cycle of matching wear between teeth and chain. The only time I would replace a chain or sprocket rather than a whole set would be if one or the other was accidentally damaged very early in its life - like the first 1000 miles.
The same logic applies to a lot of parts which wear together, such as valves and valve seats. It doesn't apply to brake discs and pads, as the pads are supposed to take nearly all the wear and are much softer material than the discs. New pads will bed into the old disc quickly, even if it is quite badly worn.
Just a thought (or 'thort', as Molesworth would have riten).
--
2003 ST1300 Pan Euro
1995 Yam XT600E
http://goingfastgettingnowhere.blogspot.com/
|
|
|
|
|
Forum Member
Group: Forum Members
Last Login: 17th May 2009 00:58
Posts: 36,
Visits: 117
|
|
Scratch that idea then!
Currently the old sprockets are holding on just fine, so I guess I'll leave it until the chain finally breaks loose, slicing through metal, flesh and bone on it's final flight into the scenery, before I shell out £40 for a new set.
What's the difference between "normal" and "heavy" duty chain? Is it just marketing ********?
|
|
|
|
|
Supreme Being
Group: Forum Members
Last Login: 16th May 2010 15:09
Posts: 637,
Visits: 1,168
|
|
| A lot of the time, yes. There are various types of supposedly-superior chains, from heavy-duty to X-ring. To be honest, I've never found enough advantage to them to justify the extra cost. As BD so eloquently explained, chain "stretch" basically isn't...it's grinding friction. A lot of that is environmental, as whatever you use for lube attracts grit and so on, turning it into a fine grinding paste. Add to that the effects of moisture and so on and you've got a reasonable but fairly consistently finite life span. Keeping it regularly cleaned, re-lubed and well-adjusted is a far more significant factor in prolonging that span than shelling out extra on high-performance brands. Speaking of performance, that's the other claim usually made: a heavier chain theoretically suffers from less transmission lash and hence loses less power from the crank. Whether that's offset by having more weight to turn or not, I can't say I've ever noticed any real difference out on the road. Standard O-ring from a reputable company will pretty much do the business every time.
>> ex silens nox noctis <<
|
|
|
|
|
Supreme Being
Group: Forum Members
Last Login: 23rd August 2010 20:19
Posts: 1,002,
Visits: 1,795
|
|
Just had a thought (hey, steady on there). I have just changed the chain and sprockets on my XT and was doing a bit of Googling (as you do) and came across an article about chains and such like. The writer claimed to use the rule of two chains to one set of sprockets - as long as you change the chain before any significant wear has started on the sprockets, the sprox will easily outlast two chains. I think he has a point, provided that you change the chain early enough. So I retract my comments earlier in this thread about 'always' changing them together. With a bit of good planning, this may not be necessary. No use to Roop, I guess, as his were comprehensively shagged, and of course Endo is right when he says that the sprox are the cheapest bit of the set anyway. But food for thought, perhaps.
Here's the article: http://www.canyonchasers.net/shop/generic/chain-rplc.php
--
2003 ST1300 Pan Euro
1995 Yam XT600E
http://goingfastgettingnowhere.blogspot.com/
|
|
|
|