Compact cranksets
 

Has anyone used or is using a compact cranset on their tandem?

I do, as noted in the 110-74 bolt circle thread below. I started using T.A. stuff to get the wide variety of crankarm lengths, and most of my tandems now have rear ends that are T.A. Zephyr on both sides, with the drive side being a 110-74 triple crankset.

Where I live, you have to have the 130 gear inch high gear to ride with groups, so the bolt circles carry the regular road gearing of 53-39-28. The equipment shifts just fine with STI.

The road Compact or the MTB version?

I use the Non compact MTB version offroad with 48/36/24. The compact version will now carry 44/34/22. Not much difference in teeth but the extra 2 lower can mean that you can use 8 speed with an 11/28 cassette- wheras with the non compact 24, I use 9 speed 11/32. Those extra teeth on the top end do make a difference though and 48/11 does give me a higher speed than 44/11.

Let me go out on a limb here and ponder if Artmo isn't trying to ascertain if there are any tandem teams running "compact cranks" as in 50/36 doubles (or a similar two-ring configuration) vs. triple chain rings, without respect to the bolt circle diameter of the cranks.

You got it, Tandem Geek!
I don't follow the bolt daimeter, 110/?? discussion. I'm too old!!

A compact double would be fine most of the time but we sometimes do some hill-climbing that really requires a small granny gear. (4 middle-aged legs).

That would be my impression, tho' I've only tried a compact on one of my solos. (4 old legs)

While I like my one solo bike's 50/36 + 12x25t 10 speed combo for climbing vs. a set of triple cranks with a smaller cogset, I'm not sure I'd want to mess with a similar configuration on our tandem. Mind you, you can't ride more than 100 yards without changing elevation where we live and ride and it's rather easy to accumulate 2,500' of climbing in 30 miles without any serious climbs: there are just a lot of moderate hills that have you climbing a fair amount of the time.

That said, and getting back to my single bike with the 50/36, on a long ride that's not climbing intensive there are many times where I find myself crossed up trying to avoid doing a double shift when I change from big to small or small to big chain ring, i.e., upshift front chain ring and then downshifting the rear cogset to compensate for the 16t jump. Now, I suspect that if I was running a wider range rear cassette, such as a 13x29t, it wouldn't be as pronounced. I'd expect that this condition would be even more pronounced on the tandem if only because Debbie would be asking "what are you doing up there" as I worked through any odd gear combintations.

However, even still, given that one of the big "attractions" to the compact drive configuration is eliminating the need for a triple crankset & 3rd chainring for weight savings, I'm just not sure the "juice is worth the squeeze" for the average tandem team's needs unless they rode on dead-flat terrain and had no plans for riding far from home where those really low gears can come in handy.

As it is, I find much greater utility in switching rear cogsets to conform to our riding needs, using a 12x27 with our 54/44/32 ringset for most of our riding. When we head for the mountains I change it out for a 12x32t. If we were heading somewhere devoid of any serious hills I'd likely throw on a 12x25t with a shorter chain and just ignore the freeloading alpine chainring.

Finally, if I didn't find that we were often times cranking along in our 54t chainring using the 12t & 13t cogs I'd probably consider going to 52/42/32 configuration. Moreover, if we lived in the flatlands even a 50/40/30 or simply a 50/40 might seem attractive. But, so long as our travels would take us to where we might encounter climbs, as sport/recreation cyclists I wouldn't bother removing the alpine ring.

Anyway, just some thoughts on your question as it didn't seem to be getting any traction on this long holiday weekend.

I have a 50/34 compact crank on one of my road bikes and what I have noticed is that there is much less gear 'overlap' between the big ring and the little ring compared with the traditional 53/39 crank. Instead of shifting only the front chain ring I now have to shift both to maintain cadence, sometimes shifting multiple cogs on the rear cassette before I feel comfortable again. Whereas with the 53/39 crank I usually find shifting from the big-to-little (or vice-versa) maintains my cadence or is very close. I also notice more cross chaining with the compact system. Seems like I am rarely in the middle gears with the compact while the middle gears on my 53/39 see the most use. That being said the compact crank will let you run a tighter rear cassette for equivalent gear inches-maybe even getting you a slightly bigger spread.

Then there is the compact crank-front drailure issue as most are designed to work with the bigger 53/39 rings and don't work quite as well with the smaller 50/34's or 36's. I actually didn't notice any problems here but I did reposition it per Sheldon Brown's axiom-'the closer the better'. There are a few front derailures designed specifically for use with compact cranks on the market now. Seems like set-up is more critical on the tandem too. Shifting problems are amplified for some reason.

I don't know if I would like a compact crank set-up on the tandem. The extra shifting to maintain cadence, the chain line issues (although I tend to cross chain pretty bad on the tandem-it's so far back there!) and front derailure concerns don't seem worth it. I am no fan of the triple front chain ring but on the tandem it seems to work pretty good. I rarely use the 'granny' ring but it sure nice to have and gives a huge gear inch spread I don't think you will get with any compact setup. But if you don't need all those gears then maybe it would be worth it. But my preference would be the standard 53/39 with the rear cluster of your choice if I was going to go with a two-ring setup. Rear cassettes are easy to change and relatively cheap.

Thanks Tandem Geek for your, as always, detailed analysis. I was not planning to change to compact on our tandem, but was merely curious.

I find the same as redpath and you on my solo in that there is much more front changing and resultant rear changing to maintain cadence. When I come to the only "hill" around here, a bridge, in fact, I always make sure I'm on the small front ring before I start the climb, so as to avoid "double clanging" as we used to call it years ago in the UK. Thanks.

If you put a shorter chain on to go from 12-27 to 12-25, do you also put on a longer chain to go from 12-27 to 12-32?

How many links do you add/ subtract for each?

12-27 is right for 95% of our rides and that's how our new bike will be set up.

Both bike mechanics that I've trusted before advocated changing chain and cassette together when either showed signs of wear.

I'm making more significant steps towards becoming my own mechanic and appreciate the advice offered here.

I've learned how to change a cassette pretty quick. And I got more of a lesson about chains than I expected in the last couple of weeks that may make a separate post if I get time for it.

Is it easier / better to have a ready made chain sized to go along with big cassette, or a short length of chain set-up with PowerLinks to splice in when we need to put on the climbing gears?

Regomatic
<< Both bike mechanics that I've trusted before advocated changing chain and cassette together when either showed signs of wear. >>

I think this is overkill. Normally a cassette will need to be changed once in every 2-3 chain replacements, but it will depend upon individual circumstances.
I think your mechanic is bit like car dealers who tell you you need to change your oil every 3000 miles, when modern oils will easily last 6000 - 10000 miles:)

The newer "mechanic" now provides mostly very learned advice only, and most of it free of charge, and only does the work that I'm not 100% comfortable doing myself until I know that I can do it in a manner that will be safe and reliable.

So your new 2nd bike has a fresher cassette than you need. Anything else you want to b!tch about ;) ?

Just kidding, but I told you it was well maintained!

Going to a 12x25t was a hypothetical as we try to avoid riding in places that are completely flat and devoid of hills. As it is, we have one tandem that is always set up with 54/44/32t chainrings and a 12x27t cassette all the time that runs a 56" (112 link) chain, which is also the right length chain on our tandem for a 12x25t cassette.

Our S&S travel tandem also has 54/44/32t chainrings and is more or less our "climbing tandem" fitted with a rear disc and a 12x32t cassette that runs a 58" (116 link) chain. About 1/2 of the time I'll go ahead a switch the 58" chain for a 56" chain when I change cassettes but if I don't the shifting isn't as crisp but perfectly adequate: running a 25t on a 58" chain would definitely be marginal, hence the comment about changing to a 56" chain.


Rule of thumb noting that most 700c road tandems use ~17.5" rear stays...

If you're running a 53t - 55t or large chainring...

32t - 34t rear sprocket = 58" (116 link chain)
28t - 30t rear sprocket = 57" (114 link chain)
25t - 27t rear sprocket = 56" (112 link chain)
21t - 23t rear sprocket = 55" (110 link chain)

If you're running a 50t - 52t, subtract an 1" (2 links)

If I worked at a bike shop and was incentivized to sell parts and services I'd advocate changing the chain and cassette at the same time too. However, following your mechanic friend's logic, why wouldn't you also change out the chainrings? After all, if you've let the chain wear out to the point where it can wear down the sprocket teeth and change the pitch of the cassette cogs you use the most, it will have also done the same thing to the chainring(s) you use the most.

Seriously, if you make a habit of changing out your chains before they "stretch" too far beyond 3/32" you can extend the life out of your cassette and chainrings by quite a bit. Instead, what I'd recommend is reading up chain and sprocket wear at Sheldon Brown's Website and then make a point of inspecting your cassette sprockets and chainrings whenever you install a new chain and only consider changing the cassette and chainrings when they no longer mesh well with the new chain of if your shifting begins to degrade. Now, to be fair to your mechanic friends, changing out the cassettes and chains will ensure your shifting performance remains as crisp as it can be, but as Artmo noted, it's overkill for anyone but pros where big bucks, sponsorships, and rankings are resting in the balance.

I don't recommend splicing new sections of chain into partially worn-out chains except when making a field repair to a broken chain to get yourself (or another stranded cyclist) back home.

Do some leg presses instead.

Perhaps in other parts of the country it is different... but here [Central Maine] [I have been a bicycle mechanic for the past 25 years]. I have NEVER replaced anything that was not needed, and have never been pressured by bosses to do anything other than what was needed.... nore have I witnessed it.. by others that I have worked with.

We find most riders don't have a clue about their bikes... and by the time their chain needs to be replaced... the cass. is worn enough that it needs to be... or at the least should be replaced.

If you replace the chain often enough... you can get several chains out of a single cass.

I have found that generally cass. wear way before chainrings. My assumption is because there is much more chain wrap on a chainring.. and less pressure on each tooth.

All too often I see people wear their chains out enough.. that the chainrings are in need of replacement also. they just ride and ride and ride.. not cleaing their chains.. and just adding more oil. Everything just gradually wears.. and they do not notice the decreasing "performance". Even the jockey wheels will have their teeth worn to sharp little points.

If I was running several different cass. [of different sizes] on the same bike. I would have different chains. with each cass. sized to that cass.

glenn

I don't doubt that for the small-town bike shops this is the norm and I wholeheartedly agree that for the vast majority of bike owners, there is no such thing as preventative maintenance. They ride 'em until things stop working or fall apart.

Frankly, I'm not sure I can tell you how many miles I get out of a given chain or cassette since they get moved around and/or rotated on and off bikes. However, regular chain maintenance and replacement before it pegs the "replace now" indicator on my chain checker does seem to yield about a 4:1 to 5:1 ratio on chain life to cassette and chainring life. With this in mind, and as I've mentioned before, I tend to look at chains as consumable items and buy "good ones" but not the best ones when they're on sale for about $18 - $22. I've also been tempted to just go ahead a buy a spool of chain -- basically a life-time supply -- but have not done so as there are now too many different chains in use on our bikes to be practical, e.g., meaty left-over 8 speed and 9 speed timing chains, Shimano 9 speed drive-side chains, a few 10 speed chains (although Shimano 9 speed work on our Campy 10 speed gear) and 1/8" chain for the fixed gear / track bike.

Getting back to drivetrain wear, I look for visual or performance clues to signal when the cassettes or chainrings are nearing the end of their useful, trouble-free life. In addition to seeing a poor fit between a good chain and a sprocket, well-worn cassettes tend to skip, cause "chain chatter" and ghost shift. On worn-out middle or alpine chainrings, a sure sign that they are about "done" is a chain slip under heavy drivetrain loads, i.e., the chain doesn't seat properly and "jumps" or slips on the chainrings when you start out or find yourself climbing in a gear that's a bit too big. For the big chain ring, I know it needs replacement when it becomes a source of chain noise and/or when the chain starts getting pulled off the big ring and down to the middle when I've got the chain crossed-up in larger 27t - 32t rear sprockets on a short climb where I opted not to shift into the middle ring. The latter usually happens as we begin to ease up and regain a higher cadence near the top of the climb.

<< So your new 2nd bike has a fresher cassette than you need. Anything else you want to b!tch about ?>>

Haha! I hope my advice will save you money in the future:)

Different people have different standards of how they want things to work. Some also have different awarenesses. The first example that comes to mind.. I had a friend, a racer, come in with his bike for some shifting issue.. I take the bike for a test ride... and the headset is so worn out I can barely ride the bike... it is locked straight ahead.. it was the worst case of "indexed steering" I had ever seen. He was not even aware of it.

I have some customers that are not at all handy... and do not want to come back to the shop after their "spring tune up" so if I do not think their tire will make the season.. they want it replaced now[their idea not mine]. While others... will ride it until it is sufficiently worn out... some of course go way beyond that.

I myself can feel very subtle differences..and I want my stuff to work. to me a worn chain feels like crap.

yet I do not "push" my standards onto my customers.. We are a small enough shop so that we get to develope a relationship with most of them... and get to know what they want.. and generally the mech gets to personally talk with the customer of the bike he is working on.

To me ideally you do not mix chains and cass. of differing wear. Let's pick a weird example.. lets say you have a bike with a few thousand miles on it...and someone steals the chain. [yeah I know weird scenario] . The cass. is still good but has some wear. In this case I am of course "OK" with just putting a new chain on it. but this new chain will wear out quicker.. because it is on a used cass.

chains and cass. wear together.

I, as most people here use a chain until it is gone.. and replace the chain and the cass at the same time. when this is done on time.... chain rings last a VERY long time.

One of my co-workers.. will take a cass. use chain #1 for a certain amount of miles.. then put on chain#2 then chain #3.. then go back to #1 again. all with the same cass. It does works really well, but it seems like a lot of work to me.

He also has one main road bike... and I have many.. using his method would be a chore for me.

To me if a chain jumps or slips or comes off.. [because of wear] it is well beyond it's useful life. In this condition.. chain breakage is not out of the question... imagine hammering a hill and having a chain snap.
With what most of us are paying for tandems the price of new chains and cassettes are relatively cheap.

I do not have different sized cass.. for the same bike. {I may start that this year} If I did I would keep a seperate chain with each cass.. so that each had the same wear on them.

glenn

That's pretty much how it was explained to me.

Since we've gotten a little off topic here, and I still have more questions about chains and fewer about compact cranks I'll address them on a new thread and others can get this one back on track.

OK lemme chime in on the drive-train wear.

Let me first state that I am a large man, ride a lot of miles and occasionally ride in wet weather or when snow has melted leaving salt water on the road. On my single bike I get two chains out of each cassette. However, I replace the chain at about the 50% worn mark on the Park chain gauge. This is what I have found:

When one replaces just the chain when it is worn to 50%, the new chain will not skip on the cassette, but will wear to mach the cassette (50%) within a very short period of time - maybe a week or two. During the period that the chain is wearing in to match the cassette, it will rumble on the big chain ring. Once worn in this stops. Now the new chain is at 50% worn and will stay that way for a long time - many months depending on conditions. When it gets around 60-70% worn it will shift poorly and then it's done. I will replace both chain and cassette. I usually go through 3-4 chains and 2 cassettes a year. The problem is if you let the chain get 60-70% worn and now the chain-rings are worn too. I have to replace the small ring every year.

This year I am going to have to replace both chain rings, chain and cassette and I am going to try something different - replacing the chain at 25% worn and see if I can save the chain rings a little longer as Campy Record rings are 90$ a piece!!!!

They do, but that's because even a worn chainring will readily accept a new chain and perform well. Where chainring wear "reveals" itself is when a worn chain is put on a new chainring and can't properly mesh with the elongated pitch of the chainring's sprockets. As you'd expect, an old chain with elongated pitch on a new chainring will slip as the chain tries to engage sprockets that now have a shorter/correct pitch.

Thankfully, most folks (or shops) will put on a new chain when new chainrings are installed, for much the same reason that you put a new chain on with a new cassette (which I do agree with, as opposed to putting on a new cassette with every new chain).

The one place that you can also learn to appreciate how chains and chainrings wear is on the timing rings of your tandem; however, that's a dirt road for another day (or you can simply check the archives).

Keeping drivetrain clean/lubed will extend the life. However, most folks can't be bothered with that.
Even wiping a chain down occasionally wil help. Dirt is the enemy!