PXrider

I posted this in the 41 but I would like to hear from some bike mechanic types too.

I have a carbon frame bike with SRAM Force shifters and derailleurs that I have had for about a year now. This was my first bike with brake lever shifters, so I had nothing to compare it to other that my 7 speed down tube Shimano 105 setup. Overall I have been happy with the shifting performance but one thing has always bothered me. When I'm riding with friends on similar (mainly Shimano) bikes I notice that when they shift the rear derailleur I hear a distinct "thunk" sound. When I shift on my bike I don't hear this. Is this a SRAM thing? Or do I have something setup wrong?

mconlonx

You may be hearing their shift action better because your shift action is happening behind you--I assume the sounds you're comparing it to are people riding close in front of you? SRAM generally tends to be more clicky at the shifter, more thunky at the rear derailleur/chain/cass. If you're not unhappy about your shifting, it's really a non-issue. And/or your bike may be adjusted better than theirs.

fietsbob

Index shifting is all about that ka - thunk ..

Andrew R Stewart 

I'll add an extra aspect. The worse the rider often the louder they shift. That is they don't release pressure on the pedals during the shift and the resulting chain tension make the noises louder. So maybe you're shifting with better technique then they are. Andy.

alcjphil

One thing that can affect the noise made when shifting is the actual frame design. Monocoque frames with large diameter tubes are much noisier than lugged carbon frames. What type of frame do you have? Years ago I made a switch from a titanium to a lugged carbon fiber frame using the same components. Everything ran much quieter, noises that I heard before were gone. Your frame can make a difference

PXrider

Thanks for the responses. To answer the question - I have a Planet-X Nanolight carbon frame so it is a monocoque type frame.

One observation that I had for double-tap is when the actual shift occurs.

When downshifting to a larger cog (increasing cable tension) the actual shift occurs after the first click as you continue pressure on the shift lever to the second click.

When up shifting to smaller cog (reducing cable tension) the actual shift occurs after the click as you release the shift lever.

All this to say that for up shifts, any resistance in the cable, shift lever or derailleur will slow the shift. Perhaps I have some resistance somewhere in the path that is slowing the shift a little. As I said, functionally the shifting seems OK as it doesn't skip or miss a shift. It just feels like it could be a little more crisp, especially on up shifts.

Downshifts appear to be more affected by how much pressure I put on the shift lever. Presumably, because cable tension has to be increased to actually make the shift happen.

Perhaps I'll look into replacing the cable and housing (I do have almost 3500 miles on the bike) over the winter. One other idea I have read about is to make sure that the cable loop that goes into the derailleur is long enough so that the cable can move easily. I think the video I saw said it should be 36 cm.

Camilo

Interesting. My Sram (red) shifting is quite a bit louder than my Shimano (Ultegra) or any other Shimano I'm familiar wtih. I like Sram better, but it is louder.