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Chainring flex = chainsuck ?(4 posts)

Chainring flex = chainsuck ?niteschaos
Jul 3, 2002 4:38 AM
I found out what caused my first crash cause the same thing almost happened again. The chain got sucked down inbetween two of my chainrings and locked up my crank, almost causing a crash for a second time during a large group ride. I was wondering if this sudden jump off the chain was caused by chainring flex. I was about to stand all the way up, but instead just raised up a little to power over this next hill. When I got up the cranks locked up and almost threw me off! I'm glad I didn't stand up all the way, that would have been bad. I am riding with this crank made by Felt that goes on their entry level racer.

Do you think chainring flex could lead to chainsuck?
Jul 3, 2002 7:54 AM
the chain got between your 2 chainrings? thats not chain suck. chain suck is when u drop your chain and it gets between the frame and lil CR. that is caused by poor derailler alignment. You'd have to be a horse to flex a CR!!

if the chain is going between the 2 CR's, u prolly need to tighten your CR bolts or take it to a LBS b/c that is defiantely a problem
Jul 3, 2002 8:17 AM
actually I am. I am 215 and 6'2" and just got done with 2 years of college rowing.
Couple Thingsgrzy
Jul 3, 2002 10:12 AM
Chain suck is when the chain remains on the chain ring and gets pulled up (from below) into the lower right chainstay and jams. This can be caused by a couple factors - bad chain (twisted, worn out, no lube, dirty), bad chainrings (bent teeth, worn out, burrs, dirty), rider (waiting to shift under heavy load). Chain suck is typically seen on MTBs due to the harsh environment. If everything had been working fine then usually it's a sign that the chain needs to be replaced. However if the bike has gone without much maintenance the steel chain starts to do a number on the alloy chain rings and cogs. Lots of times you can pull the chainrings and clean them up and carefully file the burrs off the teeth. It's sort of like sharpening a chainsaw - a bit tedious, but satisfying when you're done. If the tooth profile of the CR's are "hooked" then you need new CR's.

What you're describing sounds more like one of two things. When the chain "traps" between the two chainrings either your front der. isn't quite dialed in OR you're using a 9 speed chain on and 8 speed crank. The 9 speed chain is a little more narrow than an 8 speed and as a result 9 speed chainrings are closer together. Typical advice is to stick with and 8 speed chain if your drive train is all 8 speed. If you're running a 9 speed cog set then you will need a 9 speed chain and there is an easy modification for the 8 speed crank. You need to get a 9 speed inner chainring - it has less off set and will close up the space between the tw CR's. Of course the front der. will have to be adjusted.

If memory serves me right the pin width on an 8 speed chain is something like 7.1 mm and a 9 speed is 6.8 mm - not a lot, but enough to make a significant difference in shifting performance.

Frankly I do not think much of the "after market" cranksets and their chainrings. They tend to be under engineered and cheap CNC knock offs. They look cool, but do not tend to last. There are some exceptions like TA specialties. Shimano, for example, has spent a lot of time and money developing shifting ramps and patented teeth profiles on metal that tends to have fairly high hardness (hihger end stuff) and impregnated with a lubricant. If you need new chainrings I'd advise you pay the extra $$$ for a Shimano product as long as it fits. Often times you can buy a whole new crank for less than the cost of two CR's.