CHAIN REPLACEMENT: MR. KNOW-IT-ALL

CHAINED AND GAGGED
Dear Mr. Know-It-All,

I require your wisdom. I ride a YZ250 two-smoker, primarily off-road but occasionally on an MX track. I was taught that I should only change my chain and sprockets all at the same time, and that it is not good to change one piece only. Is that true? I run the Renthal Twin-Ring sprockets, and those things seem to last forever. The front sprocket, not so much. Is it bad to change just the front sprocket if the chain and rear sprocket are in spec? I would also like to change my gearing occasionally for different terrain. Sometimes I’m in higher-speed riding, and other times riding is slow and technical. Is there a preferred method for changing gearing without changing all three items (chain and both sprockets), or should I just take the hit and buy a whole different setup when I want to change gearing?

Thanks so much for your help.
“Crash 185”
via mrkknowitall@hi-torque.com

In a perfect world, changing out all three items in the drive system is preferred. This was really set in stone in the old days when chains were the weak link in the drive line. Back in the ’70s swingarms flexed, the gap from the countershaft sprocket to the swingarm pivot was substantial, and sprocket materials were suspect. Chain wear was problematic, and it was a procedure encouraged by all top-line mechanics to change out both sprockets and the chain simultaneously.

Mud is rough on your driveline so care and feeding is important. When the sprockets are totally worn, it’s a good idea to replace the chain and when your master link looks like this it’s time for a driveline refresh.

But, it’s definitely not a rational operation if the chain/sprockets are in proper condition and you’re simply making a gearing change. Today’s high-end chains are incredibly efficient and well-built. I prefer using an O-ring or X-ring chain where the rollers are sealed. In the off-road world where the elements can infect your drive, these are almost mandatory. Also, today’s rear sprockets are stronger, lighter and you have the option of a dual material or stainless steel if you’re an off-road enthusiast.

As far as making changes, the easier option is swapping out the countershaft sprocket. Going 1 tooth lower on the front equals 2 1/2 teeth on the rear (some folks say it’s closer to 3 teeth). This way you can run the same chain and readjust it at the rear wheel. Going to a 2- or 3-tooth-larger rear sprocket would require a new chain. Not a cost-effective option for most.

What is my plan of attack here? My off-road machine is a KTM EXC dual-sporter. I have a spare wheel and run 14/52 for off-road and 14/50 for faster terrain with more road. With the KTM, you can simply turn the axle adjusters around to set the proper chain adjustment for either the 50 or 52. Now, good luck, we’re all counting on you here! 

ChainMr KIAMr know-it-allSporcket