cooleric1234

First of all, I'm kind of new to the idea of working on my bike so I have a basic question. I have a 2003 Giant Cypress hybrid bike, and I'm looking at replacing the derailleur cables and housings. I went to buy some from an online retailer I trust (specializing in mountain bike equipment) and I noticed there were two sizes: 4mm and 5mm. I'm not sure which one to get. Does it matter? What if I only want to replace the cables, and keep the existing housing? What does the measurement refer to? Can I go measure the existing housing and get an accurate estimate of what size I need? Thanks.

capwater

4mm for shift cable, 5mm for brake cable. Never, ever use shift cable on a brake. You can slide with just the cables assuming the houosing is in good shape.

cooleric1234

Thanks for the reply. I'm still a lit bit confused though. Let me see if I can explain it more clearly. Looks like there are just two sizes of cables: 1) brakes, and 2) shifters. So that's not an issue. The problem is in the housings. There are three sizes, or types, of cable housings: 1) 4 mm derailleur, 2) 5 mm derailleur, and 3) brake cable housing. Which derailleur cable housing size should I get? Does it matter? Based on your post I imagine I'll go for the 4 mm for shifting, but I just thought I'd double check.

The web page is below. I bought from these guys a while back because I just wanted some cheap ferrules and they would ship small items cheap via USPS. Seems like they have good prices on brakes and cable cutters too (two other items I want to get).

https://www.utahmountainbiking.com/sh...nts_cable.html

capwater

4mm for shift cable, 5mm for brake cable.

Those measurements are for the OD of the cable HOUSING. Shift cables use 4mm housing, brake cables 5mm.

seely

Actually, I use 5mm cable all around, shift and brake. It seems MUCH less problematic than 4mm which I suspect can be a bit restrictive. We frequently clear up customer's persistent shifting issues by going to all 5mm.

dafydd

SIS-style housing comes in both 4- and 5-mm OD, and 4-mm coiled housing is not unheard of on older bikes. I agress with seely that 5-mm all around works best, despite of the huge weight and aerodynamic penalties.

TallRider

Brake cable housing is typically 5mm.
Shifter-specific housing, which are compressionless for the purpose of indexed shifting (so shifters stay lined up with derailer positions) come in both 4mm and 5mm varieties.

So note: 5mm compressionless shifter housing is different than 5mm brake cable housing.

I haven't found meaningful difference in the functionality of 5mm and 4mm shifter housing, but I've not compared them carefully, either.

Michel Gagnon

No difference between 4-mm and 5-mm shifter cable housing in ideal conditions. But add a bit of water, snow, ice, -20°C... and the 4-mm cable housings will need to be cleaned whereas the 5-mm cable housings will continue to be reliable.