Change in 25HD chain?

Technical Technical Discussion
1

I think there has been an unannounced change to Vexpro #25 roller chain in the last year or so. Can anyone corroborate this experience?

http://i.imgur.com/0ZM6y2Ol.jpg](http://imgur.com/0ZM6y2O)
*Click to embiggen
*
The new chain is very clearly visually different (dark matte surface finish instead of glossy lighter gray).

Triple Helix also has some evidence that the new un-stretched length is different as well. The .018 adder](https://www.chiefdelphi.com/forums/showpost.php?p=1397554&postcount=26) we typically apply to c-c distances now appears to be way too big.

2

“A noble DarkSoul embiggens the smallest chain.” - Jebediah Vielkind-Neun

3

I’ll jump in and say this happened before the 2016 season. 319 used 2363’s .018" C-C add and had some serious tension issues. Serves us right for not testing it ourselves though…

4

Chain stretch debigulates drive train performance.

5

Some method of tensioning the chain is always recommended by the manufacturers
http://www.renoldjeffrey.com/nmsruntime/saveasdialog.asp?lID=1019&sID=2750

Page 229

Chain Adjustment
To obtain full chain life, some form of chain adjustment
must be provided, preferably by moving one of the shafts.
If shaft movement is not possible, an adjustable idler
sprocket engaging with the unloaded strand of the chain is
recommended. Generally the idler should have the same
number of teeth as the driver sprocket and care should be
taken to ensure the speed does not exceed the maximum
shown in the Quick Selector Chart (see page 234).
The chain should be adjusted regularly so that, with one
strand tight, the slack strand can be moved a distance
“A” at the midpoint (see diagram below). To cater for any
eccentricities of mounting, the adjustment of the chain
should be tried through a complete revolution of the large
sprocket.
A = Total movement
C = Horizontal center distance
Total movement “A” (in.) = C (in.)
K
Where K = 25 for smooth drives
50 for shock drives

6

Yeah, we have two different colors of chain as well. I didn’t know about the issue because we just had a policy of color matching to be safe because things like C-Cing involves math that confuses and scares me.

7

The issue in this case isn’t a problem with tensioning the chain, but with the fact that the chain seems to be out of spec. At short runs our normal C2C distances + 0.018" works like ti did in the past, but with long runs we run into issues. Pointing to the possibility that the chain is not actually the 0.25 length it should be.

8

I’ve been campaigning this for a while now…

I’m a firm believer that the adder only works to accelerate the ‘stretch’ of the chain anyway. By having that super sweet & tight initial assembly (because of the adder) you end up making the stretch process happen even faster because there is more tension in the chain at the starting point. Not to mention, with fairly tight chains, even the initial process of getting them on the sprocket can accelerate this (if you’re creating closed loops and trying to ‘jump’ them onto the sprocket).

I’m anti-adder and pro-tension-it-the-‘right’-way or just come up with a solid maintenance plan to replace your chains every X hours.

I’m Brandon Holley, and I endorse this message.

-Brando

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