Compact Crank......Crosschaining ??
 

I've been lurking here for some time, enjoying the wit, information, points of view, humor, and common sense. I'm 62 and returning to cycling after a long time away. I'm 6 weeks into building a base-- my goal is a comfortable rolling hill metric in a few months. Here's my question:

I'm building up an old frame with a (new concept to me) compact crank. Given that some people could care less about radical chain lines, and others are more finicky.....how many cogs on my 10spd cassette will mechanically be available to me? A gear chart shows me there will be lots of redundancy, but how much front shifting will I have to do to avoid serious crosschaining?

Thanks.....and nice to be here!

I have a compact on one of my bikes. Cross chaining is really not an issue - the full cassett is available on each chain ring although a tweek to the front DR may be needed. Now with that said, what I find with my compact is that if I am climbing and in big rolling terrain I use the small CR, if I am on the flats or small rollers I stay in the big CR. I really don't switch back and forth too much as each CR has a lot of range. I do a lot more shifting of chain rings with my triple than with my compact. In the areas I ride in I would not survive on a conventional 54/39 without a wide range cassett and that would not allow me to stay in the cadence range that works best for me.

^^ What CF said.

You might even consider a 46t & 36t combination with a 12-27 cassette. You should be able to stay on the big ring 2/3 of the time.

46t & 17 on the rear cog provides about 18 mph at a 85 cadence. The 17 cog is in the middle of the cassette, so the chain line should in-line. Most bikes are over geared.

Michael

If my experience is typical, you should be able to use about 8 of 10 cogs on the 34 ring. The ninth starts to rub against the big chainring. It's about the same on the 50 ring. I am not constantly using the FD when riding.

"Cross-chaining" per sey won't be the problem...as there should be enough 'trim' on the front derailleur to trim out any chain rub on the front derailleur when on the small ring.

What can be sort of a problem will be the chain itself rubbing on the big ring if you are on the small chain ring on the front and the smallest (12 tooth?) cog on the back.

I have a 36 tooth small ring on a compact setup and I get some 'dinging' at times if I leave it on the small ring on the front and the smallest cog on the back....not bad, but just enough to be aggravating, as it does make some noise. I tried moving the whole crankset to the right 1mm using a spacer ring on the right side, but it really didn't help, so I put it back to 'normal'.

I ~think~ that it could be worse if the small front ring is a 34, as the interference by the big ring is going to be greater.

I built up a bike with 36 x 50 front rings as the shifting between a 36 x 50 is supposed to be better than a 34 x 50. So far, I'm happy with the front shifting, and compensated some for the slightly bigger front ring by using a 12x27 rear cassette. But I don't take that bike on really long hilly rides...I take a triple.

As far as redundancy goes....If I'm making good speed on the flats and am on the small ring on the front, and any of the top 3 on the rear, when I shift up to the big ring, I usually do a 'double-shift' on the rear....full sweep of the front shifter for 3 steps on the rear, and then 1 more shift to see how it feels. Sometimes I just stop at the 3 cogs down. That's one of the biggest complaints I read about on a compact setup....have to do double down-shifts, or just ride as much as possilbe on the big ring if you have the power...I don't, I'm a little guy, so I'm in the 36 ring most of the time unless I'm drafting somebody, or have a tailwind.

I use a compact on two of the bikes I have and I use 50/34 rings. Cross chaining is a problem as The chain line does get excessive if using the Big chain ring and the two or three largest rings on the cassette- or the small chain ring and the two smallest rings on the cassette. I don't get any noise of derailler rub- but one look at the chain and I can see that the chain is being pulled to almost strain point. cross chaining could eventually cause a couple of problems- Premature chain wear and excessive wear on a few of the Cassette rings

And saying that- I do cross chain occasionally as I try to keep my eyes on the road and not on the back wheel.:innocent:

Cross chaining while possible will wear your components much faster. Everybody does it once in a while but it's probably best you don't make a habit of doing it.

Per Shimano cross chaining on a double does not hurt anything, but then if you do wear out your chain prematurely they will be happy to sell you a new one. I try to never cross chain completey but if I am one gear away I don't really worry about it. As far as shifting the front more often, one of my bikes has a 38/46 and I shift the front when I stop. When I take off as soon as I get up to speed I then shift back to the big ring. I don't know if it is because they are so close but the front shifts very smoothly on that bike. My other bike has a 34/48 on it and I like that range better. It gives you just a little more going up hill and you don't spin out so fast going down hill.

I have a 50/34 on a couple bikes and use either a 12/27 or a 11/32 cassette. The only thing I avoid is big-big. I've done a lot of climbing on the 50 and used the next to the easiest gear on both setups and never had problems with chainwear, cog wear or chain rub (just trim the FD as needed). Normally when I'm in that gearing it's because I'm in a group trying to avoid multiple shifts and the hills aren't terribly long. I usually do not spend much time in the 11-14 along with the 34 and admit to having a little chain rub if I'd go to a 34/11 or 12 but that's why the 50 is there-so I'll usually just shift up to the larger chainring. There is a lot of trim available that helps to adjust the FD to keep from having too much chain rub.

Once you get your FD setup and adjusted correctly I'd not give the cross chaining issue too much worry........but that's just me. I know there are a lot of folks that think differently and that's okay.

Can one really trim the front derailleur with a Shimano brifter system?

On a 2x9 setup, I would be inclined to use the 7 inner cogs with the inner chainring and the outer 7 cogs with the outer chainring.

Don't know about the various other types but I have 105 brifters. Specified them on Boreas as I did not know if I could cope with a double- and the 105 LH brifter is for a double or triple crank. I could convert to a triple later if required. BUT- it does give me 4 clicks for full movement- or as jppe put it- 4 half clicks. By setting the cable correct- I can trim the front derailler by one half click- or a full change by 2 half clicks. Ideal for elimintaing front derrailler rub when crosschaining. (Except I don't do that- Do I:innocent:)

Not sure about all Shimano brifters but definitely yes with Dura Ace. :thumb:

Thanks to all above who've shared info and points of view. After I'd ridden for a week, I knew I was back to stay, so I bought a pair of used Open Pro's (can't seem to find MA40's anymore...lol) and thumbspread the 126 spacing on my old Allez frame to accept the 9spd hub. The next week I upgraded to some used Centaur brifters because they fit my small hands better than Shimano. I gently stored away my old Mavic retrofriction dt shifters. I discovered the J-tek adaptor-- a very handy gizmo to make this patch-together puppy work.

Having found a used Litespeed frame (going straight to carbon would make this newly reborn oldtimer wince), I'm now tring to decide on either a Rival or Centaur group.....I'd appreciate any opinions on either group.

Thanks again!

Sora is the only Shimano line of road stuff with no trim function for the front der. That I am aware of anyway. Ultegra, 105, and Dura Ace all have a trim function. The new Sram Red, Force do not have a trim function which makes for a lot of tweaking and cross chaining is more an issue.

My Sora shifters have a trim function at least the 2008 shifters do.

Why not use the dt shifters? Lightweight, don't require much adjusting and last forever. They are also easy to use when trimming and need no "patching" together to make them work.

rck........agree with all of your above post not to mention the dt's are bombproof, classy, and shift sweetly through 9 cogs. But, guess I sorta want to see and use what you "modern" riders are doing. I also like the brifter ability to shift out of the saddle from the hoods. Once I get this new bike set up, I may re-install the dt's on the old. There is something satisfying about being in total control of the shift....not to mention the intuitive art of the overshift. Then again, bouncing around some bumpy county road downhill with both hands on the bar is nice, too.

But right now, my main concern is getting my 62 year old body back to some level of fitness.

Don't worry about that. It will come but you do have to work at it.

That's my solution. I also like non-indexed barcons, which permit me to keep both hands on the bars at all times.

In my parts chest, I have a pair of SunTour ratcheting barcons....well-used, but good for another 10 years. Also non-ratcheting Campy NR's. But, returning to cycling after many years away, all this new, trick stuff seems very intriguing. I may discover modernity promises or seems more than it satisfyingly delivers; but I do like my Campy brifters. I suspect I'll return my old bike to its original pristine status and have a new frame set up with current stuff. Just have to see which one I end up riding more.