woodbine

My 25 year old mountain bike has a 6 speed Deore Uniglide freewheel cassette/hub and Deore 3 gear crank (18 speed total). It has Shimano SIS thumb controls for gears.

What size will my gear cables be? I think 4 or 5mm are available - does it matter which ones I fit? Are new outer cables available with different internal bore measurements? Can you mix and match sizes?

Apologies for all the questions, but I'm imagining that it's not easy to tell the difference between 4 and 5mm cables - even by trying to measure. Thanks for any advice.

Bezalel

Frame stops are sized for 5mm ferrules. If your ferrules look the same as those on your brake cable, you have 5mm housing, if the ferrules build up the end it is 4mm housing. Replacement housing does not need to have the same outer diameter.

woodbine

Thanks for your reply. By ferrules, do you mean the metal pieces at each end of the outer cables where they go into frame stops? If you do, my bike doesn't have any - the cable ends are bare.

Also, I had to edit my post - it should have read "25 year old mountain bike".

cny-bikeman

You are talking about HOUSING diameter, not cable diameter. They should take the same inner gear cable. Current gear cables require ferrules due to different construction (compressionless) than the old style (spiral wound) housing, although ferrules were quite common with the old style housing. I would recommend you read Sheldon's page on cable and housing: Cables. I'm not clear on what you mean by "What diameter will my gear cable (housing) be?" Are you installing cables/housing where there is none now or replacing it. It's always helpful to state your goal or problem before asking a question.

woodbine

Thanks and apologies if some of my questions are vague. Basically I wanted to know what cable diameters are likely to be on my 25 yesr old MTB with SIS thumb shifters and Deore Derallier shifting a Uniglide 6 speed.

Other questions -

(1) Do gear outer cable covers come in different internal bores/diameters to suit 4 or 5mm cables, or are all outer covers the same bore?

(2) I don't have a way of accurately measuring the gear cables, does it matter if you change 5mm cables to 4mm. or vice-versa?

(3) Is there any difference in operation between 4 and 5mm cables? For eg. will both sizes fit in the cable guides at the bottom of the frame under the crank?

(4) Are my brake cables likely to be 5mm? If yes, I can compare these to the gear cables to see if they are the same size or not.

The problem I have is that the bike has been laid up for almost 20 years and I am re-commissioning it. The derallier is free to move, and so are the SIS thumb levers. The levers move OK when you move them in the direction that relieves cable tension, but when you move them the other way which pulls on the cables the levers become very stiff and gear changes are difficult. So, by a process of elimination, if the derallier and levers are moving freely with cable disconnected, then become stiff when connected and pulling the cable - the cables/outer covers must be at fault.

Sorry for the confusion and I will read the article that you suggest.

JonathanGennick 

It won't matter at all if you run 4mm housing. I would just do that, tbh, or maybe 4.5mm if you buy a kit and that's what's in the kit. Pretty sure some of the Jagwire kits are 4.5mm.

woodbine

OK, Thanks. I have had a look at the gear and brake cables. The brake cable is definitely slightly thicker in dia. than the gear cables, so I'm presuming that the cables are 4mm gear, 5mm brake.

ramzilla

You can run any old cheap cable & housing for the brakes. I like the Bell cable kits at Wal Mart for about $6 or so.

ramzilla

The derailleur cables are a different matter. Indexed gearing has precise settings. If you put cheap spiral wound housing on the gears it tends to compress & go out of tolerance. Then, you start having clickitey-clack gear & chain issues. It's prudent to get the better quality cable housing for indexed systems. But, if you don't mind making regular adjustments - then the cheapo stuff will work for gears too.

scott967

There is 1.1 and 1.2 mm shift cable. Not sure when you should use what. I had 1.1 and replaced with 1.2 on SRAM and it was a ***** getting it threaded in the shifter, also making the internal bend around the BB for the front.

scott s.
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