frogman

I am putting new derailleur cables on my touring bike. Under the bottom bracket there is the black plastic cable guide for the cables to slide in. What's
best to do, put some grease in the grooves or leave them dry. ?

Bob

Troul 

teflon grease the guide.

Crankycrank

I've always left any plastic guides dry. The plastic provides enough slip and grease just attracts dirt and gums things up.

Le Mechanic

I like to put a little slick honey on the cable. Same as on the cable before it goes into the housing. The plastic cable guide is going to get gunked up no matter what. That's the low point on the frame, so it generally ends up sticky from sports drink, sweat (trainer riding), dirt and whatever else the tires throw up at it. Windex works pretty well to keep that area clean and the cables sliding smooth.

Broctoon

Sheldon Brown recommends greasing it: https://sheldonbrown.com/autoshift.html

Andrew R Stewart 

I think the answer is somewhat dependent on your location. In Moab I'd run the cables dry. In Seattle a thin lube on SS cables. I the winter of the rust belt stainless, grease and then a lot of periodic cleaning and lubing. Andy

dsbrantjr

I use synthetic grease there and only there on my cables. I use lined housings and die-drawn stainless inners and have found that lube impairs their function and catches dirt. I find the area benefits from frequent clean/lube.

frogman

Looks like the synthetic grease is a good option. I will give that a go. Part of me says it needs lube after Sheldon's info. The other part of me says grease will attract dirt. The synthetic grease may be less prone to be a dirt magnet.

thanks guys

Self Evident

I take a short piece (~6") of deraileur cable housing and remove the inner sleave. I then slide that onto the deraileur cable and position it under the cable guide under the bottom bracket. The cable slides better in it, dry, than with any lube and without the sleave.

frogman

Great idea on the housing inner sleeve !

cyccommute 

There's nothing about synthetic grease that is less prone to trapping dirt. Any lubrication is going to trap dirt.

Sheldon Brown is just plain wrong on this one. The cable hanging up on the cable guide and causing ghost shifting defies logic. The cable guide is a plastic material... probably nylon or ABS. This makes it sort of a self lubricant because the plastic will slide along the cable rather than providing any mechanism to trap and hold the cable. The plastic has a low frictional coefficient. Adding lubrication that then traps dirt will actually increase the friction because the grit gets imbedded in the plastic and does provide a mechanism for increasing friction.

If the interface were metal on metal, then, yes, lubricant would help but metal on plastic is pretty slick and shouldn't need grease.

hairnet

Never had an issue keeping it dry. I would not want to create a spot that will collect dirt and grime.

WizardOfBoz

I put some of Shimano's super expensive SIS-SP41 Shift Cable Grease on the guide in the 1999 Lemond Zurich I'm retromodding, but now I think I'm going to clean that off the guide and the cable (to get rid of any dirt) and will put the 6 inches of inner guide on the thing, with new application of fancy grease over the part of the cable that rubs against the guide.

WizardOfBoz

I understand and agree with you, but this does beg a question. For brake cable, Shimano states (on page 13 of the Dealer Manual):
"Do not apply grease or other lubricants to the inner cable. "

However, for the derailleur cable page 5 of the Rear Derailleur Dealer's manual advises:
"Grease the inner cable and the inside of the outer casing before use to ensure that they slide properly."

This would be coated steel on plastic in both cases. One source of data for friction (here) shows that lubricated metal on plastic has about 1/3 or 1/2.5 the friction of unlubricated. So there's a reasonable difference. It would be nice to know how the coefficient of friction varies with dirt! In any case, this 1/3 factor is why I think I'll lube the cable, and the dirt is why I plan to use the cable liners.

But if you were to make the point that there's a lot of folks who've never lubed those cable guides, and who's shifting works great, I'd agree.

Jean_TX

I use heavy duty silicone spray to lube that area. The silicone doesn't seem to attract/hold dirt like oil-based products do. I also use silicone spray for the inside of the cable housings for the same reason.

frogman

Jean,

I like the silicone spray technique, and for the cable housing too, just spritz the cable with silicone spray and insert into the housing, nice ! I use silicone spray on my SpeedPlay lollipop cleats to keep them working smoothly. Works great.

Bob

Jean_TX

The silicone works great. I re-habbed my '89 Klein last year and put on new Jagwire Sport cables & housings. I flushed the housings with silicone first and sprayed silicone on the cable itself before inserting them into the housings. There is absolutely no preceivable resistance now when I activate brakes or shifters. And in my experience with silicone spray, it won't wash out with water. Yay...

frogman

I just finished installing the new shift cables and housings. Did the silicone spray as you described and also spritzed the cable guide with silicone spray. Did a test ride this afternoon and smooth as silk. I also spritzed my speedplay lolipop cleats. I believe I am eligible to be a member of the silicone spray lube club.

Kapusta

I leave the guides and the cable dry for the reasons others have mentioned. The only time I have ever had an issue was one time when I was riding below freezing temps and water getting splashed on the cable guide froze up. This was on an MTB on trails. I had been doing winter riding for a while before this ever happened, I guess that in most cases, when it is below freezing, there is not a lot of un-frozen water to splash around (unless it is salty). And on my commuter I have long fenders. So I guess that in that case, a lubed cable would have helped.

Anyway, after that I just ran full length housing for the rear shiftier on that bike because it often sees a lot of slop (it is a 1X setup).

migrantwing

I have used silicon spray for the insides of the shifters and cables/inners for a while now. Someone gave me a cheapo can of the stuff and I thought I'd try it to refresh some old cables and inners on a friends daughters bike I serviced. Works great.

GromitDog

Dry but clean, maybe some dry teflon lube if you are anal. Anything else is a dirt trap.

practical

I don't grease any cables. I was taught to do it - especially when putting on new cables and housing. Maybe I'm wrong, but not it doesn't seem to affect the performance by not greasing them. So, if it ain't broke don't fix it. Besides, I don't want to create grime.

frogman

Here's what I use.

Jean_TX

That spray sounds like it could be the ultimate "non-gunky non-dirt-attracting" lube. Where did you buy that?

Troul 

I have the same product, also have the competitor's kind. For the price to quantity from the amount of uses as well as thus far experiences, I don't see the value. Leaves a cloudy tough coating on the surfaces that it is sprayed on, which can be a pita as you want to be careful as to not wipe it away from where you intended to spray it, but then you don't want your bike to look like it has a bunch of what appears to be "white overspray paint" all over the place.