Drivetrain Advice - Upgrade options?- Mtbr.com
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  1. #1
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    Drivetrain Advice - Upgrade options?

    Just picked up a new GT Aggressor Pro. I've done a lot of reading so I've learned a lot about real MTB so far. First time buying a decent bike, not the walmart crap.

    Granted this isn't a 2,000 bike. However it does have great reviews and overall I am pleased - except for the problem with chain drops.

    Presently I'm not doing much trail riding as I get back in shape, mainly greenways for now. Later I will do some trail riding. I'm riding every morning for now to get in good cardiovascular shape, and to work on my climbing muscles, and to work on stretching, so that I build a good foundation to prevent injury on the trails.

    The problem I noticed on my third ride when I attempted to jump a curb for the first time - chain drop on the front. Then it happened again later - except on a flat.

    Apparently the front derailleur is the lowest quality primary component on this bike. It's such crap quality, even most of the time it won't go from the front gear 1 to gear 2 without holding that thing in and messing with it while riding.

    I saw that I can get a decent XT front derailleur for under $50 new and rear derailleur for under $70. Or I could get a Deore rear derailleur for under $30. Problem is, I don't know compatibility.

    It also comes with a generic crankset - no markings at all anywhere on the crank, and it says ALL TERRA on the crank arm. Looks like I can get a Tourney crankset for $25 but I'm not sure if that's even an upgrade, or I could get an older version Deore XT for about $45 or a new XT for around $70. But I'm not sure if it's compatible because I don't know what the other numbers mean like 44/32/22.

    Also cheap plastic pedals but that's not important since my shoes which are nike running shoes have what is effectively cleats on the bottom that works fine with these pedals. They grip quite nicely in the grooves of the pedals.

    I weighed, and this bike weighs about 33 pounds. Not bad for a $350 bike.

    As far as components, it looks like this has:
    • Acera Rear Derailleur
    • Tourney Front Derailleur**
    • Unknown Shimano shifter (just says Shimano)
    • All Terra crankset
    • All Terra Cypher 27.5 tires


    ** the FD looks like this, and the cable runs down and underneath the bottom. It's a lower clamp mount.

    So, what are my options for upgrades, and what is recommended to actually upgrade? Obviously don't want to spend too much because for hundreds more you just buy a better bike since this was about $340 after tax and coupons from Dicks. It seems like a good beginner bike especially since I'm not planning on hard trail riding for awhile, but yet, way better than walmart garbage.

    Thanks!

  2. #2
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    Take it to a bike shop (not Dicks-some have decent tech guys other don't) and make sure they do an adjustment and tune on it. Dicks does "adjustments" before you walk out of the store but some of the guys/gals really don't know much about bikes. You can also check out some youtube videos on front adjustments however on the cheaper ones I've found adjustments are pretty limited. I trashed my FD altogether a few years back and just went with a 1x11 set up, less stuff on the bike and less stuff to get messed up. If you're just getting started out I personally think it's best to ride it til you break it then look in to upgrades as you go.

    Once you get on the trails and start figuring out what you want your bike to do/feel like you can start making a list for upgrades as you go.
    '14 SC Tallboy
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  3. #3
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    Quote Originally Posted by mark! View Post
    Take it to a bike shop (not Dicks-some have decent tech guys other don't) and make sure they do an adjustment and tune on it. Dicks does "adjustments" before you walk out of the store but some of the guys/gals really don't know much about bikes. You can also check out some youtube videos on front adjustments however on the cheaper ones I've found adjustments are pretty limited. I trashed my FD altogether a few years back and just went with a 1x11 set up, less stuff on the bike and less stuff to get messed up. If you're just getting started out I personally think it's best to ride it til you break it then look in to upgrades as you go.

    Once you get on the trails and start figuring out what you want your bike to do/feel like you can start making a list for upgrades as you go.
    The guy working at dicks knew his stuff and was a mountain biker for 30 years and looked the part too. Happened to get lucky, but yes, it's possible he still isn't as good as the bike shop guys.

  4. #4
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    Hey bikerider01. Derailleurs are 'dumb' devices. It is the handlebar shifters that control everything. Watch a Youtube on setting derailleurs and you'll understand. Basically derailleurs have two screws that set the limit of movement to each side, and another adjustment that aligns the derailleur with the gears.

    If you are dropping the chain, the limit is probably not set properly on that side. Either that or something is bent/broken out of alignment (unlikely the case on a new bike).

    Get a proper shop to do a tune up for you. At the same time, you can most likely use a better derailleur (XT could be overkill but they are very good). Go with the bike shop tune first.

  5. #5
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    If you are interested in upgrading for certain, I'd say look into a rear derailleur with a clutch. Chain drops while riding are typically caused due to chain slack. As the chain bounces it pulls the rear derailleur cage with it allowing the chain to become slack. Then the chain is more susceptible to jumping off.

    IF you mean you are experiencing chain drops from the front during shifting, that could be a front derailleur shifting issue remedied by some adjustments.

    IF the chain is going into the spokes or is shifting off the cassette into the frame, then the rear derailleur limit screws are adjusted incorrectly.

    Should you search out a rear derailler you need one of the same brand. SRAM shifter/derailler now you'll need a SRAM derailleur (and of the same gear range). Likewise if it's a Shimano system.

    I'm not sure why you are investigating a crank set. Just because you want to or if you think it is related. I don't think there is anything to fix with a crankset to prevent chain dropping.

    Please clarify what you mean by chain drop, if it's like I said where the chain goes slack or if it only seems to occur when you are shifting.
    If the chain is dropping from slack, it could be that the front derailleur could use some fiddling with as the cage may be gapped too far from the chain...but that's a mess and you'll affect shifting performance on the front rings the more you adjust.

  6. #6
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    The GT Aggressor was my first bike years ago and I too got upgrade-it is. I did end up changing out a bunch of parts but got very little improvements from the money I spent. It's a very outdated bike and is not compatible with most aftermarket components. I had a blast on that bike but it's still just a beginner no matter what you do to it. If you stick with the sport just ride that thing into the ground and put the money aside for a bike worthy of upgrading.

  7. #7
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    If you haven't properly cleaned the chain and lubed it, comes greased, that could be the problem. The grease is for long term storage not riding. Many good lubes, I use Purple Extreme as it lasts me months. I live in dry Arizona so eastern wetter area riders may disagree.
    agmtb

  8. #8
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    I have a similar bike, a $517 Shimano Acera 3x8 drivetrain, that's now 2x 8/9 'somewhat' upgraded without the front derailleur. There are a few options, but at your bike's level I would try keeping the triple crankset and do something unique with it below.

    Losing your chain off a curb with a triple chainring up front is not good at all, unless you were going fast. I've rode off curbs hundreds of times with triple chainring bikes and I don't think I ever dropped the chain. I assume you have the chainrings riveted instead of bolted to the crank arm spiders (the usually at this level four-armed extensions that hold each chainring to the bike). The Shimano Acera replacement 3x crankset is $50, I just put it on my pavement/fire road backup bike and was surprised how nice it is, relatively speaking. If your chain still drops, you can have the bike shop take off the largest chainring and install a (probably 34t or 36t) NARROW-WIDE chainring. You can't shift into or out of this chainring, so you would just use the small and medium chainrings to shift, and then when you are going faster over rough stuff you manually put the chain on the outside ring, and it will not drop again, or at least should not. I have this now on a 2x drivetrain, 22t for climbing, 34t narrow wide for everything else, and just manually change the chain when I'm at the bottom or top of a hill, takes all of 8 seconds to do.

    I don't think it's worth going 1x in your situation but maybe it is if you are not climbing steep stuff. If your chainrings are riveted, the cheapest complete drivetrain upgrade to 9-speed is $210, 10-speed is $310, and 11-speed is $340. But you are going to lose a lot of range and personally that is unacceptable to me, don't know your terrain situation. The other upgrade is going from the Suntour XCT fork to the Suntour Raidon (air) fork that's $250 with the upgrade discount, it is TOTALLY worth the money to do this. You will go from thunking through the rocks to skipping over them, a lot faster and smoother.
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  9. #9
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    I would focus on basics and make sure what you have is set up properly.
    -Verify chain is correct length
    -Check all settings of front and rear derailleurs...H/L stops, b-gap, etc.
    -Verify cables are run properly with no kinks
    -Maybe check dropout to ensure it's properly aligned

    Go to Park Tool website and check out some of the 'how to' videos.

    You're only into a handful of rides, give it some time and learn how to tweak things before giving up and just replacing things. With any new bike, there is some stretching of cables which requires adjustment after awhile.

    It also takes some time to get used to smooth shifting, especially with a front derailleur...when properly set up they work fine. The 22/32/42 relates to number of teeth on each gear of crankset. You can buy separate gears and dial in best ratio for your situation without replacing entire crankset if desired.
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