sizes/spec for a new chainset

[MountainEm]

Hi all,

*disclaimer! not very experienced in bike maintenance, but I've tried to read a lot about it - friendly, helpful feedback greatly appreciated!*

I need to get a new chainset/chain/cassette as apparently I've worn out the chain on my bike after less than a year from purchasing it new. I suspect either my riding style is sub-optimal, or the original bike setup was not suited to how I use it... or both?

Anyway - the original spec is
Shimano FC-M191 crankset (48-38-28T)
on Shimano BB-UN26 bottom bracket (68-113mm width x length?)
with Shimano CS-HG30-81 11-30T cassette (8 speed)
and KMC HG40 chain

I've been searching for a new crankset to replace like-for-like in terms of number of teeth, and have found 2 options:

• Truvativ Isoflow 8/9 Speed Chainset - 48/38/28 - 170mm, apparently requires a 107mm Shimano bottom bracket
  

or

• Shimano Alivio M411 Square Taper Triple Chainset - 48/38/28T, apparently requires a 118mm spindle
  

Neither or which seem ideal for the bottom bracket currently fitted to my bike, which I understand would be too long for the Truvativ set, and too short for the Shimano set.
Is this really a problem? From my limited knowledge, I can see that the chainline may be 'wrong' if the crankset doesn't fit the bottom bracket well, and this would cause the new components to wear quickly....
What would the forum users advise?
Is there a better set of components available, that wouldn't be a great deal more expensive?
Thanks in anticipation of your help!

 

[Eichers]

Hi MountainEm

The 113mm is the right length for the Shimano FC-M191 crankset and frame. You need to check if the options you have specified will suit your frame. The 68mm is the length of the Bottom Bracket and is a fairly standard size. Iso and square taper have different crank arm connections ... perhaps your local bike mechanic can advise you re your options?

Chain maintenance and chain quality is important. You need to relate chain maintenance to where and how you ride ... riding in wet or muddy conditions requires more maintenance than riding in dry conditions, etc.

Is your frame a hard or soft tail?

 

[alfeng]

While you may have worn out your chain, unless your bike has been consistently caked with a sandy mud, the chainset, BB, and cassette probably do not need to be replaced ... at least, not yet.

• As far as I can tell, your current crankset has steel chainrings -- they should easily last for 16,000 Km of riding.

What indicator makes you feel as though the fore mentioned components need to be replaced?

Sight unseen, let me suggest that your bike's drivetrain may simply need to be cleaned & the current chain may simply need to be lubed with some light oil ([COLOR= #808080]e.g., 3-in-1/"household"-type oil[/COLOR]).

FWIW. If you are intent on changing your chainset, then I recommend you choose one which uses a Shimano Octalink BB.

 

[MountainEm]

Klabs, alfeng, thanks for your advice.

@ KLabs - it is a hardtail. I had't appreciated that this might make a difference to the way the chain wears. Is that what you're getting at?

@ Alfeng - I have cleaned it all quite thoroughly and re-lubed, but it doesn't get round the noise, that I think is coming from the chain. The chain is definitely well stretched. Friendly bike mechanic looked at the chainrings and said they looked worn - he could tell which one was my 'favourite'. I was under the impression from various sources that if replacing a worn chain, you should replace the cassette with it as they all wear together... And as the wear was obvious on the chainrings, I thought I might as well go the whole hog and replace those too, even though there's no way I've put 16000Km on them...I perhaps haven't maintained the whole well enough over the past 11 months, but riding conditions haven't been that nasty either.

Am I getting carried away wanting to replace it all?

Thanks for your time!

 

[Eichers]

Hi MountainEm, yes, and chains can be easily over cleaned.

For instance, my friend complained to me that his chain had stretched to the point that it needed to be replaced, after less than 700 kms. I asked him how he cleaned his chain and he said that he would soak it in a bottle of kerosene ... this was actually over cleaning his chain because it was removing all the lubrication between the pin and the link roller which wasn't completely being replaced when he re-oiled the chain.

Best way to clean is to simply let the chain run firmly through a dry cloth or a cloth damped with a mild solvent. This process simply removes muck from the chain and hopefully not the good oil.
Then liberally oil (Prolink, Rock N Roll, or equivalent oil) each pin and roller so that the oil reaches inside the roller to the pin. Allow the oil to run and dry then again run the chain through a dry cloth to remove excess oil. Removing the excess oil helps prevent the chain picking up sand, dirt or mud (which are highly abrasive) and also it is not required for the smooth performance of the chain.

In my friends case he only needed to replace the chain and change his maintenance habits. Note though that there are wet and dry oils. Wet oils are better for wet conditions because they resist washing away and allowing the water to reach the pin and link roller

 

[tafi]

To be honest I am surprised you got a year out of an MTB chain.

Of course it depends on conditions but I have seen some who have worn through a chain and cassette (and sometimes two pair of brake pads as well) over the course of one weekend. In these cases it is usually due to dusty conditions and an endurance race format, but these guys are not neccessarily soloists either, and they do know to relube regularly throughout the event.

In other words, chain wear like that is not uncommon or premature (I would even go so far as to say it is probably better than average).

There is nothing wrong with thoroughly cleaing the chain as long as the lube you have washed out is replaced. Kerosene is my favourite solvent for this

I'm not in favour of dry lubes like pro link as they have never removed the noise aspect of a dry chain, and they have never prevented the ingress of dirt under the rollers (where the wear takes place). Dry lubes also possess no physical property to keep them in place under the roller. A dry lube is, of course, a (dry) solid which can be pushed around by the roller but will not necessarily pull itself back into places where it was pushed out of.

My preference has always been for a wet lube (preferably a viscous one - 3in1 is a pretty good example of a general purpose wet lube). Being a viscous liquid, it has significant surface tension wich helps to trap it under the rollers, filling in the gaps where dust may ordinarily get in easily. Note that this doesn't prevent the ingress of dust, but significantly slows it down. Eventually, no matter what lube you use, dirt will get in and re-lubriation is necessary to flush the dirty lube out, or a degrease and relube may be called for.

The issue with collecting dirt on the outside is largely a cosmetic one. At least you know that once a dust particle is stuck to the outside of the chain, it isn't going to get up by itself and walk in under the rollers. Nevertheless dirt on the outside is unsightly and I always use a rag dampened with some solvent to wipe the excess lube off. Wiping down regularly (even when not lubing) helps with this.

If you prefer dry lube, use it by all means but it never has lasted as long or provided the quiet operation you get when wet lube is applied properly.

And yes you are getting carried away on replacing components...

I gather you need to change the chainset becasue the chainrings are riveted to the crank and cannot be replaced individually. The cheapest and technically easiest option for now would be to replace it with another FC-M191. It is true that, in the long run, it might be cheaper to have a crank with removable chainrings, but the up-front cost is probably equivalent to a couple of the FC-M191 anyway. You may also run into difficulties getting hold of replacement 8 speed chainrings.

When looking at quotes for service charges, always bear in mind what the whole bike cost you. Upgrades to fancier cranks could end up costing you a good proportion of the replacement cost of the whole bike. If you are about to spend more than half of the replacement cost of the bike, then think very carefully. I'm not saying you should think about buying another bike, but you should, at least, think about sticking with components which are in keeping with its original worth.

At this level you do not need to concern yourself with chainlines since this has next to no effect on wear. To extend the life of your componenets, think more about regular lubrication, reducing crosschaining (running small chainring to small sprocket or large chainring to large sprocket) to a minimum, and try to use the full range of gears available (ie spread the wear out over more chainrings/sprockets).