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Strosfan5 12-27-19 10:11 PM

Cable tension question
 
Hi all - question regarding cable tension.

I noticed the tension on the FD when it is on the largest sprocket seems pretty stout. Really tight with respect to the tension on the RD when it is on the smallest sprocket.

The main reason I ask is that I wonder if this normal. Itís a 3x7 Shimano set up with EF41 shifters.

My assumption is that it most likely has to do with having 3 on the front (vs 2). Iíve tried to adjust barrel to release some tension but this takes away from its ability to make it onto the outside sprocket.

Rambling on here but more curious about differences in tension on FD and RD at its most tense point.

MarcusT 12-28-19 12:19 AM

If you take a look at the cable at the FD, you'll see that when you are on the outside (larger chain ring), the shifter has pulled the cable to full tension to reach it. The inside chain ring (smallest) is at the no tension position.
RD is the same thing, size wise. Smallest cog no tension, largest cog- full tension

brianmcg123 12-28-19 05:35 AM

Yes, thatís how derailers work.

Strosfan5 12-28-19 06:24 AM

I understand how the FD and RD work
but just questioning how tight the tension is on FD when it is on largest sprocket. I have checked to make sure there is no artificial resistance within the spring and the cable
path.

More than anything, I donít want it to affect the longevity of the shifter internally and how it works, etc.

But it is what it is if the tension is normally pretty tight.

dedhed 12-28-19 06:45 AM


Originally Posted by Strosfan5 (Post 21260563)
Hi all - question regarding cable tension.
My assumption is that it most likely has to do with having 3 on the front (vs 2). Iíve tried to adjust barrel to release some tension but this takes away from its ability to make it onto the outside sprocket..

Barrel adjusters technically are "cable effective length" adjusters. Moving an adjuster doesn't create more or less tension,it makes the cable housing longer or shorter, thereby moving the derailleur in or out.

Retro Grouch 12-28-19 07:02 AM

Try this: Look at where your shift cable attaches to your front derailleur. Do you see a little finger that looks like it might be a cable guide? It's not a cable guide. In fact, the cable is designed to go OVER that little finger. That little bit of difference changes the leverage angle of the cable and greatly decreases the amount of cable tension that's necessary.

shelbyfv 12-28-19 08:45 AM

Yes, IME the front derailleur operates at relatively higher tension than the rear. However, if the high limit is set too tight it can be harder to force the change to large ring.

Litespud 12-28-19 01:38 PM


Originally Posted by Strosfan5 (Post 21260563)
Hi all - question regarding cable tension.

I noticed the tension on the FD when it is on the largest sprocket seems pretty stout. Really tight with respect to the tension on the RD when it is on the smallest sprocket.

The main reason I ask is that I wonder if this normal. Itís a 3x7 Shimano set up with EF41 shifters.

My assumption is that it most likely has to do with having 3 on the front (vs 2). Iíve tried to adjust barrel to release some tension but this takes away from its ability to make it onto the outside sprocket.

Rambling on here but more curious about differences in tension on FD and RD at its most tense point.

cable tension is a function of the derailleur spring - stiffer the spring, the tauter the cable. As with any spring, it gets ďstifferĒ the more itís extended/compressed, so the derailleur cables will be tauter the further the derailleur moves from rest (toward large ring on the front, toward the large sprocket on the rear).
i usually adjust my cables so theyíre pretty taut all the time - even at rest - so the first click or two isnít spent picking up cable slack. I think of them as ďguitar string tightĒ, although I know theyíre not actually as taut as guitar strings. My derailleurs and shifters (Chorus 10) are ~ 16 years old and still fine, so in my experience, running cables as tight as possible isnít harmful


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