my right shimano 105 5800 shifter was having trouble engaging the 11 cog in the back. I diagnosed it today, and found the cable frayed inside, but not until after i drenched the internals with wd40 to clear the gunk out. now that the frayed cable is out and the new cable is in, I'm noticing that there's more drag in the shifter. Is this because I washed away the factory grease that was in there, or maybe the cable i'm using now isn't as smooth as the old one that was in there? there does not seem to be any extra resistance going into the cable housings, so I think it's coming from the shifter.

what do you think?

I think there is still a piece of that frayed cable inside the shifter.

Did you inspect the housing end in the shifter? I've seen the strands of the housing push through the ferrule and interfere with the shifter function.

Did you use the same shimano PTFE coated cables?

The routing for 105 and really all the under-the-tape shifters, is very dependent on low friction cables. If you used non-PTFE cable there could definitely be additional drag in down shifting.

like i mentioned, the cable housing doesn't seem to produce any extra resistance.

i don't think the cable in there right now is ptfe coated. i heard that stuff can flake off and gunk up your derailleur.

but i think you're right in that's the cause. i fished out the old cable, and it is much smoother than what i have on there now. the extra force doesn't bother me. so long as my shifting is still precise, and no extra wear is being done to the shifter, I'm fine with it.

WD40 is NOT a lubricant. It's great for getting water out of cracks and crevices (the WD stands for Water Displacer), but it doesn't have very good lubricity and if left in place gums up. (As an aside, if you are cutting aluminum stock with a circular saw with carbide blade, WD40 works great as a cutting lubricant. If you are into that sort of thing.) It really should not be left in any mechanism you don't want to gum up. I recently saw a video (Art's cyclery? GCN?) that recommended Boeshield T-9 Bicycle lubricant for brifter mechanism.

I just went through the frayed STI cable experience myself. The RD cable frayed and snapped. I was able to get the cable end out of the brifter, and I think I got all the frayed cable strands out. My steps were to pull up/peel back the rubber brifter cover, find a few threads of cable end sticking out the outboard side if the brifter, grab these gently with a needle nose plier, and (while gently pulling), actuate the small derailleur lever (the one that lets the chain go to a smaller cog) repeatedly. This allowed the little barrel to rotate, and this exposed the lead cylinder that is the end of the Bowden cable. Once exposed, it was easy to pull out the main carcass of the cable end out, and I did not see any additional cable strands. I may just have been lucky.

I just spoke to Shimano Customer Service about lubricating cables. Most folks on the web say don't add lubricant, but the Shimano customer service guy said that Shimano Special Grease (which I take to mean special grease for cables, SP41) may be used. The Dealer Manual also recommends this grease.

I'm going to get the grease. (Sigh. I've really bought into the Dura Ace mystique, no?) I think I'm going to put some in the little guide that the cable runs through on the inboard side of the brifter. One other thing: folks have made the case that making sure you use a cable end with a ferrule is key to not fraying cable ends. The Shimano cable comes with such a cable end, and it has a key on the outside diameter to ensure that it doesn't rotate. I suspect that this is important.

Definitely should not be using WD40 on a bike ever.

While there is SP41 from Shimano which is "recommended" my shop uses a variety of different lubricants. My personal preference is a drip bottle of Tri Flow. Really and lubricant that your local shop sells will be perfect. Just lube the cables up their entire length and move the housing over it. Make sure to especially get the ends of the housing, because that is where the most rust builds up.

Also, when replacing a frayed cable, it is always best to replace the housing with it. The frayed cable can damage the inside of the housing and cause extra drag on the new cable, causing the shifter to not function properly.

My brifter lube of choice is CRC PowerLube with PTFE (Teflon). About three bucks a can at many auto parts and home improvement stores.

just sprayed some white lithium in there. much better.

LOL.

It has about a dozen or more totally valid applications. I use it almost every day in the shop.

AAnd now WD 40 company, has more products than the stuff they hose down jet engines on planes ending up in Jamaica Bay,
or the Hudson river..

It is much better to use a degreaser and a lubricant. WD40 can cause issues with the bearings if you get it in the wrong spot.

As a professional bike mechanic, I'm perfectly aware of where WD40 doesn't belong, and I most often don't have time to be anal-retentive when it comes to silencing squeaks from brake calipers or levers, or de-gumming shifters, or what have you. And there are some applications where anything else just wouldn't make sense, since it's just about the best thing for the job sometimes.