suncruiser

All right, so my neighbor wants to upgrade the running gear on his Wal-Mart Hyper dual suspension mountain bike. Standard 21spd 3/7 split. I'm pretty sure the bike has a direct mount RD, which is going to be likely the first point of upgrade-itis. It's got a Crap shimano unmodel derailleur on it now, I think a TX50 or something like that. What I'm wondering is what better derailleurs may for this in the 7spd range with a direct mount? I already told him he'll need to recable and switch to a rapid fire shifter to do this, along with a new chain.

Before you start on the "get a better bike" line of thought, I've gone over this with him. He wants to stick to his hyper, so that's what we're doing. I think sharpening up his shifting, swapping to good tires and tuning it up will make a world of difference.

Bill Kapaun

TX 50 should be adequate for 7 speed. TX 50 what? You need shifters & DER to match. Sometimes one component is no brand junk.
I'd probably look at the cables & then shifters. It may also have some crap freewheel without the shift "enhancements" that a name brand will.

Bonzo Banana

I'm all for upgrading cheap big box bikes but as soon as you add dual suspension into the mix I just feel it's wasted time and money because the suspension is next to useless, has no benefit to riding, wastes a huge amount of rider power and throws up problems and can end up with the bike being scrapped fairly quickly.

Many such bikes have terrible freewheel wobble because the threads on the rear hub and possible even inside the freewheel aren't quite parallel so there is wobble and it doesn't matter if you put a Deore rear derailleur on there it cannot compensate for the freewheel moving in and out and this can make adjusting difficult and mean the tolerances of adjustment have to be so perfect to get good shifting.

If I had that bike and had to use it I would spend serious time adjusting everything to the best possible state and look for a cheap freehub based rear wheel that I could put a 7 speed cassette on. I might also look out for a cheap ok front suspension forks like Suntour XCT or even go rigid for the front forks and end up with a weird soft-tail bike. While I don't like these cheap dual suspension bikes I often find the rear suspension is better than the front which is often too weak to be safe and bottoms out far too easily. I remember adjusting the rear suspension on such a bike to the highest tension level and it could be adjusted to provide a fairly ok ride only really moving with an impact to the rear, it was a heavy bike but did work as intended and seemed strong. Of course there is massive variation in such bikes I'm sure just my experience.

The cheap rigid framed bikes from walmart or other sources can be upgraded to nice bikes with the right parts and ride very well. They might be a little heavy because of their un-butted simple frames but still make very nice bikes in my opinion. Good workhorse bikes especially with their abusable steel frames.

HillRider

Any pre-10-speed Shimano MTB rear derailleur should work with Shimano or Shimano compatible 7-speed shifters. However, as Bonzo noted, if the freewheel or hub doesn't run true, no upgraded derailleur or shifter is going to help.

daoswald

There is also

rosefarts

Set the stops right, make sure the cable and housing move freely, and make sure the rear loop of housing isn’t too short and causing friction.

Its $15 worth of housing and cable plus your time.

Also check the chain to make sure there aren’t stiff links. Make sure the crank and rear wheel are not wobbly.

And that is all you can do really.

Don’t get nice tires, just replace worn out with similar cheap ones.

Aubergine 

I have improved those BSOs by replacing the knobbies with lighter, non-knobbed tires. They don’t need to be fabulous tires, just better for the usual street riding.

AnkleWork

What exactly is wrong with the derailleur? Any Shimano would likely be the best part of that bike.

What aspect of riding do you think will improve by swapping a single part? How much do you think it will improve? Will anyone be able to perceive such an improvement?

HerrKaLeun

Shifting quality on the rear depends more on the shifter than the RD. But there aren't really good 7-speed shifters if you look for crisp precision a la SLX and above.

I'd just maintain or replace the shift cables and properly adjust. That may make things better.

maybe get a used wheel with freehub and make it 1x10 or 1x11. That way you also can ignore the FD, which likely is equally horrible. Note that FD shifting quality depends more on the FD than the shifter (opposite to rear shifting).

Did your neighbor give you a budget at all? All those people saying they don't want a new bike for some reason think because the bike cost new $100, any $25 should give them a super excellent bike.

Darth Lefty 

I mean, what’s the budget? You could just go buy him a Trek 900 series

Retro Grouch 

What, exactly, are you trying to accomplish?

suncruiser

Sorry if I miss anyone in here. The bike is his only mode of transportation, and he seems rather in love with the bike, he's not interested in buying another machine (no matter how I try and shift his focus to a better bike. I've tried guys. But to no avail)

Not entirely sure what is wrong with the rear end, he's had it tuned up several times and can't get it to shift reliably for more than a week, something seems to walk out of adjustment. The RD has some interesting play in it, kinda shakes side to side in places it shouldn't. (None of mine do this, seems odd to me)

The chain is part of his chain jump problems, it's stretched out enough to come a little over 1/2" off the big ring at the front. That needs replaced. I know that. He's complaining about it chunking (jumping) while he's riding it.

I'm hoping a new derailleur(altus has made my list), chain and shift mechanism will sharpen up his shifting, make it more reliable.

As for the tires, I think he's wanting the flat protection from a higher grade set up. Goat heads suck out here. I think there's another phoenix rider here in the forums, he can probably confirm that.

Oddly enough, his FD shifts rather well, at least seems so to me, goes into the commanded gear with no complaints. I'm currently working on adjusting the brakes on the bike, i think he needs a new barrel adjuster at the lever. Cable Keeps popping out.

Budget, he's trying to stay in the cheap and get things repair by repair while upgrading the running gear in the process.

3alarmer 

...sorry, but I, too, am of the opinion that you would do your friend a better service by patiently explaining why the dual suspension BSO will soon die and all those upgrades you added for him will be wasted. The suspensions on these are notorious for failure in various creative ways, and repairing them is virtually impossible.

You can probably upgrade the BB without spending too much money, and that's usually one of the first things that goes out.

I dealt with a lot of this level bike repair at the bike co-op here, because in general, that's what the homeless guys here end up on. You quickly reach the point where it's cheaper (and easier and more reliable as transportation) to trade up to something that has fewer moving parts, like a low end steel or aluminum cruiser, or a used but still solid non suspension mountain bike.

There are so many of those around now at cheap to giveaway prices that they're your best option.

HerrKaLeun

That is not how you measure chain elongation. Take a steel machinist ruler and measure 12 links. If it is 12-1/8" or longer, replace. Or measure 10 links and if they are beyond 25.5 cm, replace. If the chain is longer, it is safe to assume it ruined the cogs and possibly chainrings.

I think your neighbor needs a reality check. A good bike will cost at least $300 assuming he gets a good used ones that requires only minor repairs.

Should you buy any new parts, make sure to buy parts you may be able to re-use on a better bike. Keep the old ****ty parts to put back on when he finally sells or donates the bike.

88Tempo

For a $100 you could upgrade the bike with new stuff. Although I'd be looking for a donor bikes for parts or if you have a coop you can go to.

7 speed shifter/brake lever combo Shimano SLM 310 left and right side or the EF51

Shimano RD-M310

Shimano FD-M313

a Shimano compatible derailleur hanger.

HillRider

Another voice that says you are throwing good money after bad. Your well intended attempt to improve his bike is going to fail sooner or later and more likely sooner.

You (and your neighbor) can save money and have a better outcome by getting a better quality used bike from Craigslist or similar source. Do you have a bike co-op or "bike kitchen" in your area that rehabs used bikes at low cost like 3alarmer mentioned? Take your neighbor there to shop.

Retro Grouch 

1. Check all of the shift cable housing ends. When I have encountered a derailleur that would drift out of adjustment that quickly, what I eventually found was a bad cable housing end that was gradually shortening itself through use and screwing up the indexing. You could adjust it, but the cable housing would just shorten itself a little more and drift out of adjustment again.

2. In order to index properly, the derailleur has to move in the same plane as the cassette cogs. It's common for a bike that's used daily to bend the derailleur or hanger out of alignment. Assuming this is a claw mount derailleur, shift into a gear that makes the derailleur arm point straight down. Then look it from the back to see if the derailleur arm seems to be pointing toward the tire. If it is, just bend it back with your hands. It's pretty easy to get a 7-speed in alignment well enough to function. 9-speed and up I prefer to use an alignment tool.

3. Regardless of how you measure it, I'm betting that chain is worn out. If that's the case, I'd give it a test ride with a new chain but my bet is you are going to need a new freewheel too.

4. If you can feel slop in the derailleur pivots that's probably worn out too. If I were doing it, I'd probably just replace it with what was there previously.

That's quite a few parts and we haven't even talked about brakes yet. Department store bikes are so cheap to buy that the economics of tuning one for constant reliable use tend not to pan out very well. The parts bill for the stuff indicated above will come pretty close to the original cost new. What you'll end up with, however, is a crummy old bike that has a few new replacement parts. A new bike will have every single part brand new, every part designed to work with every other part, and come with a new bike warranty.

Kapusta

First, I will pile on to the “throwing good money after bad” train.

That said, if you want to improve the shifting, there are probably more important things to do before buying new components (this is assuming you have already tuned it as well as possible with the cable tension and limit screws):

1- Set up the cables and housing correctly. These bikes usually have The cables and housing cut WAAAAAY too long, which degrades performance (especially with cheap cables/housing)

2- check the hangar alignment. Preferably with a tool. If you don’t have one, consider buying one. It will do a lot more good than whatever money gets wasted on trying to upgrade this bike.

Otherwise, if he wants to spend money on this, do so with things he can use after he wisens up and gets a new bike, such as pedals and shoes. Or (and I know this sounds absurd on a BSO) a dropper post.

dedhed

Having been in the same, "fix my bike that's not worth fixing" conundrum here's what I usually do.

Go to the coop and buy decent used stuff. Altus, Deore stuff is usually around cheap. eyeball hanger for straightness, 7 speed eyeball is usually "good enough"
new cables, housing, ends.
Lube everything well including brake pivots.
Tighten up & true wheels as best you can, don't worry about even spoke tension - it won't happen.
Make sure the headset is adjusted as well as the quality allows.
Unless they're really bad just shove some grease in the hubs and adjust. BB same thing.
adjust derailleurs as well as you can for the gears they typically run in if you can't make it happen through the whole range.

Make sure they understand you're putting lipstick on a pig and you're giving them the best you can with what you have to work with.

Loose Chain

A neighbor child had one of these. It would not shift correctly because it was not designed to. The rear end wobbled about so that the chain line would change and cause phantom shifts. These are perhaps, singularly, the worst BSO in existence. And mind you, I said the worse BSO and mind you that "it" in no way qualifies as a bicycle. This is a waste of time. There are much better options for far less money. Some people will go to any expense to save a dollar. Your friend is not serious about a bicycle for transport or sport, whatever the case may be, and you are wasting your cycling mechanic-ing time on him. If he/she were serious, they would invest in a bicycle that would not waste your efforts and good intentions upon.

HerrKaLeun

Best advice for any shifting issue. Get a $50 tool off amazon and you will be impressed by how much hangers are out of alignment, even new ones. there actually should be sticky or forum rule to not even post a shifting question before hanger is verified.

There is no eyeballing to verify. trust me, i tried and ended up buying the tool just to see my hanger was quite out and straightening resolved all my issues and made adjustment a breeze. That and check cables. BSO use horrible cables and housing and after some use they suck even more.

bakerjw

I used to be in the camp of "cheap frames can make good bikes." I am now in the camp of "cheap frames make barely decent bikes." There are many videos on Youtube of people on box store bikes breaking frames due to bad welds. When I see the "Full Suspension" frames in WalMart they make me cringe.
All that said. I have a Giordanno tandem that has been upgraded. It is a POS cheap Chinese tandem with horrible everything.
Because they were all junk, I initially swapped out...

• Wheelset (bad bearings even when cleaned and greased)
• The BBs (bad bearings even when cleaned and greased)
• Crankset
• Brake calipers.

I have since upgraded the derailleurs and went to 105 shifters. I now have a tandem that shifts great. Rolls great and stops well. But... It is a damned heavy overbuilt aluminum frame. Being a tandem, it was worth it to get us into a tandem inexpensively. But what I spent on the initial component replacement would have bought me a good used road or mountain bike. We are getting a new tandem frame built and almost all of the components will come across to it when I complete that build so keep in mind that components can be brought forward.

I know what you are dealing with though. Some people get it stuck in their head and will not listen to reason. The first step IMHO would be to get a good wheelset on the bike so that you know that the hubs are good. Wheelsets can always be moved along when upgrading other bikes. It is one thing that we are doing with our new tandem.
The second step would be to take him to bike demo days or similar. Our local mountain bike club does that and local shops bring demo bikes. Put him on a real full suspension bike and let him see the difference.

fietsbob

with low cost BSO , simpler the better .. the 1 speed ridgid , on one side,

A "Wal-Mart Hyper dual suspension mountain bike). that's quite the opposite .

So, just do repairs, getting it to work at all is an upgrade , yes?







....

HillRider

A couple of observations:
1. The bike is question is a 7-speed so the precise alignment needed for 8+ speeds, particularly 10-speed isn't as critical and eyeballing should be enough.
2. The tool you bought to align your rd hander was undoubtedly used on a good quality frame. The bike the OP is working on isn't and never will be. Don't waste the money.


I agree completely. If he really were truly serious about wanting reliable transportation, he wouldn't be so insistent on your making this thing work and would agree to get something that can be made to work. Apparently he doesn't value your experience or time.

Ironfish653

@retro-Grouch and @dedhed have a pretty good lists. It's about what i've done on BSO tune-ups.

I would try to replace as few parts as necessary. Minimize the cash outlay. Get a take-off RD (A-series or Tourney) don't spend more than $5-10 for it. New brake pads can be had super-cheap as well, and help if you're trying to reset a badly-adjusted set of brakes.
Probably a new chain, as well, again don't spend more than $10. I have been able to get KMC Z-51s for $8 from the co-op, but the $10 BELL-branded chain from WM will do in a pinch.

If you have the time, you could probably find some nice thick 'cruiser' tires for cheap, other wise figure $40-50 for new rubber ($20/each) and more like $75 for flat-resistant.

All the tuning in the world also won't get over that really crap FS frame. Some of those are so badly designed that the only way to make the rear suspension not mess up the driveline is to bolt it all down so it doesn't move.

A quick look through my local CL turned up a decent selection of bikes for less than $100, some old GT and Raleigh MTBs, and some 7-speed cruisers and 'comfort' bikes that might hold up better.