Taking off the third chainring.
 

Over the past month or so, I have realized that I no longer use the third chainring on my 3x8 drivetrain. There are 4 screws located around the chain ring that appear to hold the third chain ring to the second chain ring. I tried to unscrew these but they have a very shallow hole and are very hard to unscrew. I'd like to convert my drivetrain from 3x8 to 2x8 but these screws are the only thing screwing it up. (pun intended). I assume that this, like many bike parts, need special tools to take apart. Is it possible to take off the third chainring on this drivetrain? Will I need a special tool? Or should I just replace the 3 chainring drivetrain with a 2 chainring one?

Josh

What brand/model crankset do you have? if its Shimano, there'd be a FC-xxxx part number stamped on the inside of the drive side arm, along with a length like 170mm and probably Shimanos VIA stamp they put on /everything/.

Depending on what model crank you have it's possible that the chainrings are riveted together and can't be separated. Otherwise, chainrings that are bolted in place usually require a 5 mm Allen key on the bolt side and, sometimes, a spanner to keep the nut from turning. If you can remove the chainring or substitute a double crank, you will have to reset the front derailleur's low limit screw to keep the fd from shifting to a nonexistent ring.

Josh- The answer depends on what spec crank you have. Are the rings held together by rivets that are made to look like screws (chainring bolts)? Or actual bolts? Some of the bolts use 5mm some use 6mm and some use a Torx fitting. Almost all the time you'll have to remove the crank arm from the BB axle to get the freed up granny ring off. This removing the arm makes getting at the bolts much easier. The removing of the arm usually does need a specific tool (a crank arm extractor and a retaining bolt wrench for the common tapered square designs). So the answers to both ring removing, tools needed and whether replacement arm is needed depends on what you really have. For some reason my X-Ray and telescopic vision is down tonight, or I'd have just looked at your crank and given you the short answer... Andy.

I believe that it is a Promax crank. I can't confirm until next week, sorry. I found the size of the allen key, which is 4.5mm, but as stated in the first post, the hole is very shallow and I can't get any leverage to take it off. I haven't checked the other side to see if it's riveted but again, I can't confirm until next week.

Josh

A proper double is inboard more than a triple, and to remove the 3rd chainring ,
1st you have to remove the Crankset, then as I say, its better to get a shorter BB .

Ignoring the 3rd chainring is Free.. just adjust the stroke limit screw in some more.

yep, rivets

I agree with Fietsbob, why not simply ignore the third chainring and only use the other two? A double chainset isn't just a triple one minus the inner ring.

Anyway, leaving it on is the only easy option, seeing as it's riveted. I suppose you could drill out the rivets, but why bother? It's not like you'll notice the reduction in weight.

Manufacturers of low-end cranksets sometimes make theirs look like the better ones by installing rivets that look at first glance like chainwheel bolts from one side. You are the recipient of that piece of creative marketing.

I have already adjusted the FD to not go past the 3rd chainring so the 3rd chainring is now just a nuisance.

Simply locking out the third chainring on a triple isn't the same as a having double crankset - doubles are generally further inboard than triples, allowing you to use more of the sprockets on the rear with the large chainring.

When I use the third chainring (rarely) with the highest gear on the rear, the chain clinks up against the derailleur and with the 2nd and 1st chainring, this rarely happens. Annoyance is another reason I don't use the third chainring.

Josh

So when you use it and cross chain, it acts like a typical small ring when cross chained?
Don't cross chain and it won't be a problem!

It's much more annoying to need it and not have it.

"When I use the third chainring (rarely) with the highest gear on the rear..." So don't do it; the same ratios are available with other gear combinations which are more efficient and less wearing on your chain and chainrings. When you get out of the largest few cogs on the back shift out of the small chainring.

you can always use a dremel or cutoff wheel. and then clean it up with a file. even a hacksaw, it you have the time.

it will be a hack (he he he) job, and eventually you may want to replace it with a double...

Other than eliminating whatever weight your granny chainring weighs, what do you think you will have accomplished?

That's because you aren't meant to do that, it runs the chain at an angle which causes faster wear and, as you've seen, can cause it to rub on the front derailleur cage. I don't usually use my small chainring with anything other than my lowest 3-4 sprockets (on a 7 or 8-speed).

you shouldn't ever use that gear anyways. thats both hard on the chain and small rear sprocket. the small front chain ring should really only be used with the larger(lower) half of the rear gears, for extreme hill climbing gears.

rodney dangerfield:

"a friend goes to the doc and tells him as he lifts his arm up, ""it hurts when i do this."" doc says, ""don't do that""." :)

OP: Get a chainring fastener bolt tool; "Park Tool CNW-2, Chainring Nut Wrench" or other brand as desired.

Easy to find on amazon or ebay for a few bucks. All the ones I have seen look the same, but be sure to eyeball you bolts and compare to what you find before spending. Note that the tool is normally used to keep the bolt half on the backside from spinning while you tighten the front side with a hex key. Without it the bolt will spin and you will not be able to fully tighten it to specs.

/K

It appears the OP's crankset is riveted, but he can't confirm til next week.

Try a 13-21 or 12-19 cassette in back before you scrap the third ring.

30x21 provides a low gear like 39x27 and 30x19 is like 39x25 although you won't have big gaps in your gearing.

indeed, my hybrid, with a 48-38-28 front, I'm using a 13-26 8-speed rear, and its perfect for me. I can climb a mile or so of 8% grade, which is about the steepest thing I have to get up, and thats out of shape and overweight. I only use that small 28 ring on big hills, rest of the time, I'm on the other rings (big one on the flats, middle one on moderate/short grades).

I have an 11-32 cassette on the back but I'm not sure what the numbers are on the front though. But here's my plan for the summer (or when I have money):

I want to put disc brakes on the front and rear on my bike but my hubs aren't compatible with 6-bolt disc brakes. That means I have to get new rims. New wheels mean I need to move the cassette over to the rear wheel. I think I might as well replace the cassette along with the chain. You with me? 6 items. My current cables and housings are too short for use with disc brake calipers. 8 items now. Also some rim tape, lube for the housings, a chain whip and lock nut, a torque wrench for the cassette. Uugughhghgggasgsndlgsijng. IS THERE A MULTI-TOOL FOR THIS STUFF!!??

:bang: <--- Moi

You haven't told us what bike you have, but if it has riveted chain rings, it'll probably be like trying to upgrade a YUGO.
You may be better off looking for a bike that has those items already.