Which chain on Duraace 7900?

Discuss light weight issues concerning road bikes & parts.
Mr.Gib
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by Mr.Gib

tommasini wrote:
Where's Dave S when you need him to rebuff this nonsense that Campy chains "stretch" more than Shimano (poster should first get a clue that chains don't stretch........they wear due to high mileage and lack of proper lubrication by the user).


I dispute that chains don't stretch. I just pulled a worn chain off one of my bikes and instead of sizing the new chain on the bike, I figured I would just measure off the worn chain. Same number of links on the new chain was 1 cm shorter. BTW, I clean and lube chain every ride - yes every ride. (Use mostly Tri-Flow.)
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

by Weenie


mcarr810
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by mcarr810

KMC x10sl reliable and quite simply the best

subzro
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by subzro

Mr.Gib wrote:
tommasini wrote:
Where's Dave S when you need him to rebuff this nonsense that Campy chains "stretch" more than Shimano (poster should first get a clue that chains don't stretch........they wear due to high mileage and lack of proper lubrication by the user).


I dispute that chains don't stretch. I just pulled a worn chain off one of my bikes and instead of sizing the new chain on the bike, I figured I would just measure off the worn chain. Same number of links on the new chain was 1 cm shorter. BTW, I clean and lube chain every ride - yes every ride. (Use mostly Tri-Flow.)


What everyone calls stretch is actually the pins and sleeves wearing, thus creating the illusion that the chain has stretched. I don't have a problem with people calling it stretch, it's a bike industry thing.

notsoswift
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by notsoswift

mcarr810 wrote:KMC x10sl reliable and quite simply the best

Yes

But the DA7800 (well7801) is actually very good and I used them for years without issue and I feel they last a little longer than the KMC. (only just on my second KMC though)

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kavitator
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by kavitator

I have shimano quick link...will go to fixed pin

http://www.youtube.com/watch?v=qwn3QwH3mkc

Smeagol
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by Smeagol

If I'm not wrong, 7800 pins are compatible with the new 7900/6700/5700 chains as all 10 speed pins have the same length.

Only difference between the new and old pins are that the old pins have 2 rough points - 1st when you first push it into the chain and 2nd when the pin is about in the correct end position. The new pin has only 1 rough point when it is at the correct end position so as to avoid any confusion.

bikedoc
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by bikedoc

7800 pins deffinatly dont work with 7801 chains, they might hold together for a couple of rides but thats it.
Shimano didnt make it very obvious that they where different, i found out after trying to join a 7801 with 7800 pin, 3 attempts (on the workstand) later i went online and after a bit of searching found out. Thought i was going mad as normally i can join a shimano chain in seconds. This was a few years back just after 7801 came out and i was working in a shop, we had chains in boxes coming from shimano with the wrong pins.

As for quick links try this, fit one, go for a few rides then measure chain wear over a section where the quick link is and then over a section where it isnt. Bet the section where it is shows more wear.

I go back to the experiment i did a while back of joining 3 different brands of chain together to make one and running them on my MTB to see how they wore under exactly the same conditions. the shimano chain was still fine long after the other 2 had died. and where the joins where (i used sram quicklinks) they where really bad.

rgkicksbutt
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by rgkicksbutt

Thats quite interesting. How did you determine wear? Just measure centre-to-centre of the pins?

SRAM 9-speed links have been nothing for trouble for me on the MTB. Yes, the quicklink was installed properly. This was before I worked at the shop, but I installed it, my dad did, 4 different mechanics at different shops did, so I am confident it was together correctly. But, often when I would do some fast downhilling on my hardtail (still just XC trails though) the quicklink would come apart, not even pedalling, I would get to a pedalling point and have no chain. This happened about 5 or 6 times, 2 in a race. Then I picked up a KMC quicklink and I haven't had a problem with one for 4 years now (though I did explode a X9SL after about 2000 km, but the quicklink was still good!)

btw, I have ~4500 km on my current 7900 chain, using a kmc link, from the chain before, and it is shorter centre-to-centre than the rest of the D-A link according to my callipers.

Mr.Gib
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by Mr.Gib

subzro wrote:
Mr.Gib wrote:
tommasini wrote:
Where's Dave S when you need him to rebuff this nonsense that Campy chains "stretch" more than Shimano (poster should first get a clue that chains don't stretch........they wear due to high mileage and lack of proper lubrication by the user).


I dispute that chains don't stretch. I just pulled a worn chain off one of my bikes and instead of sizing the new chain on the bike, I figured I would just measure off the worn chain. Same number of links on the new chain was 1 cm shorter. BTW, I clean and lube chain every ride - yes every ride. (Use mostly Tri-Flow.)


What everyone calls stretch is actually the pins and sleeves wearing, thus creating the illusion that the chain has stretched. I don't have a problem with people calling it stretch, it's a bike industry thing.


But you haven't explained how the same number of links on a used chain can be longer than the same number of links on an unused chain without any stretching. For your position to be valid you must explain this. (Of course I agree that pins and sleeves/rollers wear - does that result in a longer chain?)
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

maquisard
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by maquisard

Yes of course it does, subzro is correct. Do you honestly believe the metal links elongate!?!? :shock:

Small amounts of wear to pins and rollers add up over a chain composed of 100+ links. This can easily make the chain increase in length but the plates themselve do not lengthen.

Mr.Gib
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by Mr.Gib

maquisard wrote:Yes of course it does, subzro is correct. Do you honestly believe the metal links elongate!?!? :shock:

Small amounts of wear to pins and rollers add up over a chain composed of 100+ links. This can easily make the chain increase in length but the plates themselve do not lengthen.


I don't really know if metal can elongate or not - never studied the subject. I do have trouble understanding how the roller wear could increase length. Pin wear makes more sense to me but if the pins are wearing so much that a chain ends up significantly longer, why don't we see more pins failing completely. This would also suggest a fair bit of play around the pins in any direction, something I haven't really noticed. I'll have to take a closer look next time I change chains.

An interesting test would be to apply force to a chain that matches that of a cyclist but the chain should be fixed so that friction is removed from the equation. Maybe hang a 200 lb weight from a chain for a couple of months and then measure.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

maquisard
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by maquisard

You are questioning fundamental mechanical engineering principles and seem in belief that your opinion is correct.

Sorry but it isn't.

In modern parlance, "Google it".

May I suggest http://en.wikipedia.org/wiki/Roller_chain#Wear as a starting point.

rgkicksbutt
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by rgkicksbutt

Don't worry Mr. Gib, chains 'stretch' by definition, it's just the picky/proud people that get all fussy about what is actually causing the lengthening.

According to oxford dictionary: stretch - be made or be capable of being made longer

Therefore, the chain as a system, stretches. It gets longer. And we measure the chain stretch.

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tommasini
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by tommasini

rgkicksbutt wrote:Don't worry Mr. Gib, chains 'stretch' by definition, it's just the picky/proud people that get all fussy about what is actually causing the lengthening.

According to oxford dictionary: stretch - be made or be capable of being made longer

Therefore, the chain as a system, stretches. It gets longer. And we measure the chain stretch.


Stretch implies that a component of the material elongated. With chain wear, something else (the pins and pin bushings) actually wore away (decreased in size). Look at it this other way. When you put mega miles on your tires they decreased in diameter. Would you suggest to your cycling buddies that they shrank due to your mega thighs? .005" of wear on a pin and bush combo (a gnats ass) over 106 links adds to about 1/2" of elongation in the chain.

If you're proud that your watts can stretch a new chain then I'll suggest instead you have terrible chain maintenance habits.

Cheers!!

rgkicksbutt
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by rgkicksbutt

tommasini wrote:1/2" of elongation in the chain.


Look up stretch in a thesauras, elongation is there, and vice versa.

I am not denying that the 'stretching' is not from lengthening of the links, I agree/know, it is from the wearing of pins and pin bushings, what I am saying is that the chain as a whole, is stretching, elongating, lengthening, drawn out, extended, made longer, what ever word you want to use

by Weenie


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