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Old 10-28-2014, 01:13 PM   #1
Antti OP
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Good chain length and teeth combinations

Its been here many times but once avain, wich were the best combinations?
I have now (at 690) 15/48 sprockets and I think chain has 120 links.

And at rear it looks like this, if i just get one link off it would cure this?

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Old 10-28-2014, 01:52 PM   #2
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2 links at a time, no way to add/subtract just one. As far as the 'best' gearing ratio, that's for you to decide.
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Old 10-28-2014, 02:01 PM   #3
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Originally Posted by wsmc831 View Post
2 links at a time, no way to add/subtract just one. As far as the 'best' gearing ratio, that's for you to decide.
That's not what he is asking.
He has a bad combination and the chain is landing in the same position on the rear sprocket. See the wear marks in the photo.

At the bottom of this page http://www.gearingcommander.com/ is a table (once you key in the data) to let you know how many times the chain lands in the same position.
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Old 10-28-2014, 02:04 PM   #4
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Yes, I saw that the same links are landing on the same teeth, don't see the problem. Obviously changing one tooth front or rear will change this.
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Old 10-28-2014, 04:43 PM   #5
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Yes, you need to take out two links in the chain. It looks like there is plenty of room on the adjuster.

With a 45 tooth rear and a 120 link chain I think that works out to chain hitting the same tooth every third time. That is bad.

For the rear sprocket:
With 45 tooth rear and a 118 link chain the same tooth will hit the same chain every 45th revolution. The is good, as a matter of fact, that the BEST ratio available.

For the front:
You front sprocket is probably very worn too with that combination. Switching to a 118 link should solve that too.
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Old 10-28-2014, 06:59 PM   #6
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Originally Posted by wsmc831 View Post
Yes, I saw that the same links are landing on the same teeth, don't see the problem. Obviously changing one tooth front or rear will change this.
The problem is excessive wear when it lands on the same location.

In his case 15 / 48 & 120 links it's the worst combination.
1x every rev. for the front & 2x for the rear.


But yes if he switches to a 45 rear with a 118 chain it's ideal.
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Old 10-28-2014, 08:55 PM   #7
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Originally Posted by NJjeff View Post
That's not what he is asking.
He has a bad combination and the chain is landing in the same position on the rear sprocket. See the wear marks in the photo.

At the bottom of this page http://www.gearingcommander.com/ is a table (once you key in the data) to let you know how many times the chain lands in the same position.
+1, I learned the hard way when I ran a 14/42/102 combination on a Ducati, got vibration, noise, and very rapid wear....varying either sprocket size and/or the chain length can make a BIG difference in repeat contact.
Here are the numbers from the GC site for 15/42/102, 14/42/102, and what I finally used, 15/44/104


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Old 10-28-2014, 10:48 PM   #8
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Thanks dudes!

I've red about this problem and understand its mechanics but haven't faced it my self.
Or at least haven't realized it :)

Chain and sprockets are relatively new, droven under 1500kms with them. I use Pro-oiler and usually bike gets a good wash right after drive, so I haven't noticed this before.

Gearing is just good and I wouldn't like to dump that Supersprox so I'll try to stick with it.
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Old 10-28-2014, 11:41 PM   #9
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Geez. I didn't even know this was a "thing".

My XR400's chain is at the end of its adjustment range and just starting to get a bit slack, but the gear teeth look nice & straight ( no "shark finning"). My thought was just to remove a couple of links (since apparently removing only one does no good) and running the cam adjustments inward.

Should I really remove the chain and spec it out for acceptable stretch before doing so, or can I just give it a go? Certainly don't want the chain stretched to the point it doesn't mesh accurately with the teeth, and I assume rounded teeth would be an indicator for that condition, no?

Apologies if this is too far off-topic, but didn't think my rookie question was new thread-worthy.
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Old 10-29-2014, 06:14 AM   #10
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Guano11
Oh yea it's a "thing", as mentioned earlier it can also cause vibration.
For your bike use the link (no affiliation, I just Googled it) above and input different combinations. Cutting out a few links may make matters worse. Best to know before chop.
If the chain is stretched (yes test and measure it) it will damage the sprockets.

The OP.
Without buying anything, if you just go to a 118 chain length things improve a bit. Since it's early in the chains life it's worth the effort.
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Old 10-29-2014, 06:59 AM   #11
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Originally Posted by wsmc831 View Post
2 links at a time, no way to add/subtract just one. As far as the 'best' gearing ratio, that's for you to decide.
There is such an animal known as an "offset" master link, AKA repair link.

I've never used one, though.
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Old 10-29-2014, 01:18 PM   #12
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Quote:
Originally Posted by Guano11 View Post
Geez. I didn't even know this was a "thing".

My XR400's chain is at the end of its adjustment range and just starting to get a bit slack, but the gear teeth look nice & straight ( no "shark finning"). My thought was just to remove a couple of links (since apparently removing only one does no good) and running the cam adjustments inward.

Should I really remove the chain and spec it out for acceptable stretch before doing so, or can I just give it a go? Certainly don't want the chain stretched to the point it doesn't mesh accurately with the teeth, and I assume rounded teeth would be an indicator for that condition, no?

Apologies if this is too far off-topic, but didn't think my rookie question was new thread-worthy.

If the chain has elongated that much it is almost certainly shot, but as was said you should measure it to check and you can probably do it without removing the chain. 24 links on a new chain will measure 15" exactly pin center to pin center, 15 1/8" will indicate about 0.8 % elongation, 15 1/4" is about 1.5%, etc. A lot of old MC manuals spec 2% for maximum elongation but FWIW I sometimes use the common bicycle spec of 1% max....15 1/4"/1.5% splits the difference and works OK for me.
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Old 10-29-2014, 11:57 PM   #13
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Originally Posted by NJjeff View Post
Guano11
Oh yea it's a "thing", as mentioned earlier it can also cause vibration.
For your bike use the link (no affiliation, I just Googled it) above and input different combinations. Cutting out a few links may make matters worse. Best to know before chop.
If the chain is stretched (yes test and measure it) it will damage the sprockets.
Thanks.... and done. See below.
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If the chain has elongated that much it is almost certainly shot, but as was said you should measure it to check and you can probably do it without removing the chain. 24 links on a new chain will measure 15" exactly pin center to pin center, 15 1/8" will indicate about 0.8 % elongation, 15 1/4" is about 1.5%, etc. A lot of old MC manuals spec 2% for maximum elongation but FWIW I sometimes use the common bicycle spec of 1% max....15 1/4"/1.5% splits the difference and works OK for me.
NOW you tell me I don't have to actually pull the chain (ok, I read your post too late....).
So I pulled the chain; it measures juuust beyond the "67.2 inches" spec for an elongated chain (108th pin); I'll get a new one.




The sprockets, however, look good to me. I won't be replacing them, but am not sure what the numbers stamped on the rear means? Doesn't look like it's stock, though.
EDIT: Rear is a 43-tooth as indicated by this stamp & verified by actually counting the teeth.



This stamp indicates High Carbon Steel, NOT tooth count (Thanks StainlessCycle!)




Front is a 13-toother, 2 fewer than stock.



GearingCommander site says stock is 15/45 -- That ratio is an even 1/3 or .333
Looks like I've got 13/43 -- that's .3023, slightly lower (about a 5mph difference in 5th gear, 5000rpm)

Finally, manual says "108 pins, center-to-center" to measure stretch, but that's for stock 15/45 gearing. The 108-pin chain pictured above had too much play, even with the axle cam adjusters maxed out.

GearingCommander indicates 13/43 gearing is a great combo for minimizing repeated "same link - same tooth" contacts.
It also indicates that 108 pins increases sprocket distance by about 1/2" from stock. I initially assumed sprocket distance was what I ought to base chain length on? If so, 106 pins (2 less than stock) nails the stock length, but "same link -- same tooth" suffers quite a bit.
I suspect the previous owner did all this homework (that I'm now learning) and used the 108-pin chain to minimize the link - tooth interaction. Probably a good call?

So any recommendations on what brand/type/size chain I ought to get with my 13/43 gears? 108 pins sound reasonable, or is there something else I should consider regarding length?
I don't mind springing extra $$ for the good stuff, but I'm not a racer and ride the bike pretty moderately. However, it is plated so it does a little pavement duty once in a while which I assume is harder on the drive train -- and as mentioned, I'm keeping the sprockets as-is.

Appreciate the advice so far.....
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Old 10-30-2014, 02:11 AM   #14
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Originally Posted by Guano11 View Post
Looks like I've got 13/49(?) -- that's .265 or nearly 1/4

Finally, manual says "108 pins, center-to-center" to measure
c49 means c49 high carbon steel, not the teeth count. the last number of the part # is how many teeth. jtr210-48 is 48 tooth. can't tell from your pic if that's a 48 or a 43. fwiw jt also has an aluminum variation of that sprocket if you want to go that route. jta210-xx is the part #
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Old 10-30-2014, 07:19 AM   #15
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c49 means c49 high carbon steel, not the teeth count. the last number of the part # is how many teeth. jtr210-48 is 48 tooth. can't tell from your pic if that's a 48 or a 43. fwiw jt also has an aluminum variation of that sprocket if you want to go that route. jta210-xx is the part #
Excellent. I knew someone here would know!

I took a shot at decoding and assumed "49 teeth" since I was lazy and it was easier to read than the other number (as you've noticed). It was late and I didn't feel like counting teeth.....

But now I've counted. Verdict: 43 tooth rear.
(Previous post edited to reflect that)

Thanks for the decoder ring!
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