Suntour ARX Capacity
 

I have done a lot of research, but keep finding conflicting info. Sheldon Brown says that nearly all RDs can handle a 14-28 6 speed freewheel. I have also seen that the max cog capacity for an ARX is 26, with a total capacity of 28. What is difference between max and total? I want to verify that a Suntour ARX can handle this range. I have got a 52/42 double up front. Any info would be appreciated.

The max is the largest cog compatibility. This has to do with the "geometry" of the derailleur's body. The idea is that you don't want the upper pulley bumping into the largest cog. It's impossible to say exactly what will work with a certain derailleur because there are other variables involved such as the derailleur hanger's exact position relative to the rear axle. I would expect your ARX to be able to handle a 28t cog.

The total capacity is the chain wrap capacity, which is how much chain the derailleur can "wrap" without the chain going slack. The formula for figuring chain wrap requirement for a given drivetrain is largest chainring minus smallest chainring plus largest cog minus smallest cog equals the total chainwrap requirement. I would expect your ARX derailleur to work with your proposed drivetrain in this regard as well.

Good advice. Thanks for the info.

An ARX GT will handle more wrap as the GT models are long cage.

The ARX is a good, midgrade model from Suntour. I have ARX on my Lotus.

A GT would be better, but I have a minty standard ARX that I am anxious to try. Sounds like it should work.

My '85 Bridgestone 400 came OEM with the ARX-GT rear deraileur, a 14x32 6-speed freewheel and an SR crank with 52/42 chainrings and tapped for a granny ring which I added. It worked fine so I expect a 28T cog will be no problem at all.

Generally, the long cage versions of a rear derailleur will clear the same maximum rear cog but just won't "wrap" as much chain. So the ARX-GT handled the wide range freewheel and the triple crank but the non-GT would have problems with that many "total teeth"even if it cleared the same large cog.

I always like to try what I have in hand first.

I've got a Suntour aRX (short cage) on my '81 Fuji Team with a 14-28 six speed freewheel and a 53/42 chainrings. Works great.

Thanks for the reply. Good to hear that you are running that setup without any issues.