mountain bike shifter replacement
 

I would like to replace the shifter and derailer on my Scott mountain bike. The bicycle is about 7 years old and the shifter has been a constant source of frustration. The entry level bicycle has Shimano Acera parts on it. I am hoping to do this job myself. The shifter appears to be sticking, so what happens is that when I hit the trigger to downshift it doesn't do anything, its almost like the trigger isn't attached to the mechanism. It stays in the gear "4" that it is currently in and if I flex the trigger up or down I can usually get it to catch.

The bicycle has an integrated shifter and brake lever. I can take photos and post if that would help.

I would also like to replace the derailer, a few years ago I crashed and broke the rear derailer cable tension adjustment. The mechnaic didn't have a replacement derailer handy so instead he just put it back in so that I could get back to riding.

What tools will I need (chain breaker) and additional parts / pieces to do this job?

If somebody could post links for the recommended parts. I am a recreational rider who maybe rides 400-500 miles a year but my spouse has recently found a renewed interest in riding so I would like to have a properly functioning bicycle.

There are a few options. If you want to try it, the sticking problem could be the cable gummed up in the housing or even the trigger gummed up. I have loosened the cables, pulled them out and shot WD-40 though the housings and that sometimes helps. I have also taken the dust cover off the shifters and used WD-40 and then Tri-flow after things have dried out and had good success. But if the shifter is worn out, you need to replace it.

Is it 8 speed?

John

Here's a list of things you may need:

• Metric hex (Allen) wrenches.
• Chain breaker if your chain doesn't have a quick link.
• If you break the chain with a chain tool, you'll want a quick link (or special connecting pin for Shimano chains) to rejoin the chain. You shouldn't reuse pins that were driven out from a modern chain. Pushing the pin out removes a peened lip from the pin, making that pin more likely to slip and fail in the future.
• New grips might be necessary if you can't remove your existing levers without damaging the current ones.
• Cables and housings for your new shifters. Possibly for brakes, too. Some new levers come with.
• Cable/housing cutter. (A Dremel with cutting wheel works as well.) You don't want to use diagonal pliers or other cutting tools that can crush/deform the cable housing, or don't give a square cut.

How many "speeds" is your current drivetrain? Asked another way, how many cogs are in the gear cluster at the rear wheel? Shifters need to match the cassette (gear cluster) for number of speeds.

yes it is an 8 speed.

My concern with taking the cables out is that the group doesn't have a cable tension adjustment on the shifter; it is just on the derailer but that one is broken. Hence the goal of replacing the derailer and shifter at the same time.

I will however take the dust cover off and try the WD-40. I don't have tri-lock, will any fine spray lubricant work? I have a graphite lubricant that I have used for motorcycle cables in the past.

My budget is as little as makes sense (IE, If the cost to do it right is $200 so be it, but I don't want to spend $200 if I can do the job just as well for $100) That being said, could you post links to a recommended place or a forum sponsor that would have all of the parts that I need in stock? Also, what is a fair budget for each of the parts that I would need? Can I do just the right side of the bar without doing the left?

I would think any fine spray lubricant would work. I've never used any graphite lube on cables. The first thing to do is figure out if things are gummed up.

The problem you have with integrated brake/shifters is that you have to replace the entire unit, not just the shifters. For what you do, I would probably replace with an 8 speed Alivio/Acera brake/shifter, an M410 looks decent. An M410 for the rear derailleur. I usually buy off ebay and the cost isn't too bad.

As already mentioned, you may want to replace cables and housings and a chain, KMC is cheap, but that is up to you.

John

If possible, I'd check out your local bike shops that have spare parts bins. You could walk out with all of the parts you need for $25.

Those shifters that are connected to the brakes are pretty much terrible. They constantly break. Replacing them isn't that hard. You could even replace them with a friction shifter if you wanted to. Those will almost always work.

so i am thinking I have 2 options.

This looks very similar to what I currently have. It looks like I can "buy it now" for around $25 shipped. along with the matching derailer.
Shimano St EF50 8R Bike Brake Shifter Lever Right Silver V Brake 8 Speed New | eBay
Shimano Alivio M410 SGS 8 Speed Long Cage Rear Derailleur Black | eBay

However, if I wanted to upgrade. I could pick up a set of Sram x4 shifters and an x5 derailer. The total cost would be around $60 after shipping and a brake lever.
2012 SRAM x5 Rear Bike Derailleur 9 8 Speed Long Cage MTB Alloy Black New | eBay
SRAM x4 Bicycle Trigger Shifter Set 3 x 8 Speed x 4LEFT and Right New with Wire | eBay

Is the SRAM stuff worth the extra $20? If I have to replace the grips at $15, I am thinking it makes sense to spend the money if its money well spent.

Not that familiar with SRAM stuff, but I would think it would be comparable. probably better than theEF50. The only issue has to do with the integrated brake/shifter. Technically you have to replace the entire unit and the SRAM are just the shifters without the brake levers. You might be able to cut the shifters off the old integrate brake/shifter unit, but I have no clue if the SRAM will fit with your cut levers without moving the shifters off to one side.

If you are only going with the right shifter, this one looks to be a better bet, and they end pretty low also.
Shimano Alivio St M410 Right Brake Shifter 8 Speed 22 2 MTB Cross Bike New | eBay

And you can always see if there's anything local as suggested above.

John

Thank you to everybody who offered advice and suggestions. I took the advice of others, took the dust cover off, sprayed wd40 liberally into the mechanism while working it up and down the gears, this seems to have helped, I still need to spray some lubricant into it but it is functioning perfect now and I was able to save $100 on new parts.

If you haven't done it recently or ever, I myself would replace the shift cables and housing and add a barrel adjuster while you do it.

Amazon.com: barrel adjusters: Sports & Outdoors

The cable was replaced a few years back; where does that adjuster go? the barrel adjuster on the derailer is broken from a crash. The bike shifts like it used to, sometimes on an up or down shift I have to press the trigger a little past until it snaps into gear but it works.

Where does that barrel adjuster go, does it go up by the shifter or down by the derailleur?

There are inline adjusters etc., but considering paying about $10 for an adjuster, I'd just spring for a new RDER and avoid the hassle of inserting it inline.
Depending how the cable is seated in the broken adjuster, that may be a constant source of poor shifts, if the housing end is moving around.
Fix it right for around $30-35.
BTW, Acera is plenty good enough for 8 speed.
I have an Acera & Altus RDER's on my bikes that shift 9 speed fine.

Would it be possible to replace just the broken barrel adjuster? You could probably salvage one from a junk bin at a co-op or an LBS.

potentially; I wouldn't be opposed to putting a higher quality rear derailleur in, but until I have a problem of something not working, I am not going to mess with it.