WT160

I want to change out a worn 42t Suntour Superbe Pro chainring on a Panasonic Team Japan bike. Looking around, I see some other sized chainrings with 43 and 45 teeth that are available. Is there anything to keep in mind if I opt for a non-standard size?

bikemig 

The thing you need to pay attention to is the crank BCD A Superbe Pro is likely 130 BCD but you want to be sure of that before buying anything. Once you know the BCD, you just need to figure out the gearing you want.

WT160

Yes, 130 BCD. So the rest is just preference? All in all, I think I might benefit from a larger ring (45t), but I do have a fairly tight ratio on the freewheel.

trainman999

Superb pro come in 130 bcd and 144 bcd you need to check what you have. What year is the bike?

WT160

Yes, 130 BCD. It's from 1986.

maddog34

another thing to look at is possible interference with the frame.. larger chainrings can sometimes become too close to the chainstay..... and your frame flexes around much more than you realize... especially older Cro-mo frames.

worth a look, IMO.

WT160

I'll take a closer look. Thanks.

WT160

Another question as I revisit this....

I know the chain is stretched, and I will replace that. The smaller chainring is also worn, hence the reason for my post. But I was wondering, how bad does it look to you all?

A picture is attached below.

maddog34

just measured a handy 48 tooth ring... it's about 7 7/8" across... i'd figure about 7 3/4" for a 45-46....

WT160

A 45t might get too close to the frame. I don't image a 43t is much larger than a 42t.

maddog34

it's not real bad... i see a bit of valley floor lengthening... can't see much "shark tooth" (loaded tooth wall gets steeper, valley floor gets deeper on that side too) yet... all that black crap is ground up pavement and rock hard lube mixed into a very abrasive cement... start cleaning... PB Blaster and a good shop rag will soften it up.

WT160

This is better than what I've got, no?

https://www.ebay.com/itm/12559645026...Bk9SR8rK8YP9YQ

Iride01 

Your other concern is whether or not the rear DR can handle the difference between the largest and smallest ring. Essentially when going from the big/big combo, it has to be able to take up the slack that will be created when you are in the small/small combo. At some point, as you increase the size difference from a smaller ring going to the larger will get to the point where shifting might suffer.

Also the BCD limits you to how small a ring can be. But some cranks get around this by mounting the smaller ring or rings on the large ring.

I don't know if ring choice and selection is what it once was a couple dozen years ago. Lately I just change the entire crank to what I want.

If your new chain isn't skipping on the rings when you pedal hard, I wouldn't worry about changing them, unless you are just wanting to change up the gearing. Visually it can be hard to tell whether a ring is worn unless you can compare it to the exact ring in new condition. Particularly the newer 10 speed groups and above.

WT160

Thanks for all the advice. I'll change the chain and see how things go.

JohnDThompson 

Going from a 42T to a 43 or 45T inner ring shouldn't require any changes in derailleur or chain length. Be aware that if you do install a new chain, you will likely need a new rear cluster as well.

oldbobcat

In the days before ramping and pinning, riders (mechanics) used to swap chain rings according to the event. Just be sure to use the alignment peg if there is one.