spelger

I'm in need of new chain rings, mine are pretty beat up with well over 40K on them. I have a triple but when i rented a double on a trip to florida i liked that. i also don't want to deal with the seemingly inherent difficulty to adjust the FD to be quiet all the time.

so, been looking at doubles and some points noted for most of these recommend a 10 or 11 speed cassette. my ride is an 8 speed and although i am not opposed to "upgrading" the cassette doing so just adds more things that need changing. can anyone explain why a double would recommend a specific speed cassette? i can't think of a technical reason for this (but i can see a marketing reason). how would the cranks or chain rings know what is back there?

Iride01 

Because the spacing between the rings varies from one to the other. If you have an old 7 or 8 speed rear, you probably won't find new compatible 2X cranksets being made. Most new 2x will be for 10, 11 and now 12 speed rears.

You can in many instances get away with running a 11 speed rear with a 10 speed crankset. But whether you can do 7, 8 or 9 speed rears someone else will have to say. A 9 speed chain might be too wide for a crank made for 10 or 11 speed rears. Or if you use a chain suitable for the crank, it might be too narrow for decent shifting on the rear.

As well, changing our your rear speeds to match the new crank will mean new indexed shifters and a new wheel hub at the minimum and that's means more money.

It'd probably be better to just let new bike fever take hold of you. Go browse your LBS's.

spelger

Ahh, now that makes sense.

i did the research before i posted but did not find this particular answer. costing the other parts to go from 8 to 10 so far is not all that bad. i may need to modify the free hub or buy a spacer in order to get an 11 tooth cog on which i'd like to do. right now i have a 12 and there are a few places here where i do spin out.

thanks for your reply.

HillRider

If you fit a 10-speed crank you can use a 10-speed chain with an 8-speed cassette. I've done exactly that and it works just fine. With the new chain you may need a new cassette but it can be 8-speed.

Leisesturm

If all three rings of a triple are worn to the point of replacement, the entire crank-arm is a more cost effective purchase than 3 new rings. Going from a triple to 2x is not without some caveats. The missing granny will have to be locked out with the low limit screw. It is possible the front derrailleur will need to be changed? The rider woould have to learn a new shifting sequence. No more cross chaining with abandon. Going to 10 speeds from 8 is probably a non-starter. Everything will need changing.

base2 

Sometimes running a 10 or 11 speed chain on an old 6 or 7 speed crankset might work, maybe. IME the chain drops between the rings, skates, then squeezes in, & jams solid. Super not recommended, even if it seems like it might maybe shift ok in the work stand.

As noted above an 8 speed crankset that was truly designed as an 8 speed crankset, you may get lucky depending of shift pins on the prospective rings/crankset. A 9 speed chain will would be the candidate to shift better & be quieter throughout the whole 8 speed drive train than any 10 or 11 speed chain could offer.

Going the other way (10 or 11 speed crankset with 8 speed chain) the chain will too wide & there is not a gear combination that the chain doesn't rub or try to catch itself on the shifting ramps/pins/pickups. Irritating, but will get you home in a pinch. A 9 speed would be less likely to present problems. Don't cross chain & you might just get away with it.

TL;DR
9 speed double rings with a 9 speed chain mated to your existing 8 speed cogs & shifters ought to work well.

Leisesturm

Even if true, how is that an improvement? Unless a truly huge step between the two rings, the double plus 8sp (11 - 32?) won't come close to a cheap triple plus the 11 - 32. At least the 10sp might go to 36T for a reasonable granny.

base2 

He didn't ask how it was an improvement. He stated he liked not needing to trim the double he experienced while on a trip to Florida.

He asked:

The answer is: they wouldn't. What they know is chain width. The only chain width that plays with his 8 speed cassette & shifters is a 9 speed chain.

If he wants double rings, as he states he does in the original post, then those got to play along too with what he's got. I don't know of any 8 speed doubles, do you? So 9 speed specific rings it is. Other speeds will rub or risk falling between.

Simple, No?

Racing Dan

If you want a double I suggest simply getting a new Sora or Claris crank. Not expensive. However, assuming its a road bike with integrated shifting in the brake lever you need a 2x left shifter too and likely a new FD.

You dont need or want a new cassette. If you change it to a different number of gears, you will need a right hand shifter as well with the same number of gears.

dedhed

Just a note - Florida is flat

HillRider

Running a 10-speed chain on a 6 or 7-speed crank is going to have shifting problems as you predict due to the wide chainring spacing. Not recommended.

As I noted above, a 10-speed crank with a 10-speed chain works just fine with an 8-speed cassette. My comment about needing a new cassette is due to used cassettes skipping with a new chain, not a mismatch between an 8-speed cassette and 10-speed chain.

spelger

It was not my intention to run an 8 speed cassette with the 2x crank that recommended 10 or 11 speed. i just did not understand why the crank was recommended with the 10/11 cassette. I'm looking at a 2x now and will likely go 11 speed in the back. i understand this means a new shifter, in fact, both left and right since i have a triple. i need to see if my existing RD will work, relatively new. i have a square taper BB so that needs to be replaced. learned that its replacement is not the horror story i thought it might be. so, yes, lots of new parts. finding them is not as tough as i thought it might be. it is exhausting doing the research, each little thing potentially is something to research again. for example, i learned a bit about going to 10 or 11 speed with an 11 cog from 8 speed and the hub either needs to be replaced, shimmed, or modified to accept the smaller cog.

and you're right, FL is flat, glad i don't live there, i did not enjoy the riding there as much as i do here in NV.

thanks for the help.

Leisesturm

The above post does not give me confidence that you understand enough about what you plan to do to actually do it easily and well. You also clearly don't understand just how much $$$ you are in for. Seriously, you just might be better off buying a 2x 10/11sp BIKE (used) than trying to 'upgrade' your 3x 8sp. Why not give us the make/model of the bike you want to upgrade. You also should consider getting the upgrade parts from a co-op. Putting brand new drivetrain components on a ?? year old bike makes as much financial sense as putting a brand new transmission in a ? year old car. No one does that. FWIW.

Germany_chris

This seems like an awful lot of work to not visit a web store that sell TA chainrings..$60-$80 for some chainrings or $700 (if you can find it) group set.

dedhed

https://reno.craigslist.org/bop/d/sp...396789718.html

jfouellette

Happy Holidays. Long winters… create the need for projects. Ithink It’s not just about what is the least expensive. It can be about tinkering and learning how all these bike parts work together. I probably spent the original price of the bike on upgrades. Money wise does it make sense? No but it keeps me busy. I can now have a better discussion with my LBS. PS: my bike is a minivelo so buying a new one is not much of an option in Nortn America unless I import it from Europe or Asia.

spelger

Wow, thanks. it was posted 2 months ago with is generally much farther than i look. These are the parts i had been looking for from some online sources. hopefully he will still have them available.

thanks again!

spelger

Well I completed my upgrade. After additional research I found that going 11 speed was not going to happen and so sadly was not able to grab those parts found by dedhed. I decided to go down the path of older generation 10 speed 105. Had all the parts selected and then thought about newer Tiagra 10 speed instead. Based on what I read this was the better buy both in newness and in equal performance (at least that was the claim by some).

I spent yesterday and today tearing off old parts, cleaning hard to reach areas, and getting the new bits on. I know, pretty slow, but i took my time while doing it listening to Art Bell and enjoyed the trip. I had never done this extensive change before and a lot did I learn. Funny, the Park Tools site seemed to be down yesterday. My torque wench is 3/8" drive and the tool for the BB was 1/2". Had to use a bucket with 30lbs loaded in with a breaker bar instead.

Finally finished up with derailleur adjustment this afternoon and wow! It is such a night and day difference. So quiet and really smooth shifting. Weather is crappy so still stuck on a trainer but really can't wait for the weather/daylight to change.