Kre8iv

I have recently purchased a second hand tandem bike, a Kent Intl. 22678 21-speed Dual Drive.

It is equipped with a Shimano RD TX-70 Derailleur and SL-RS41 Revoshift twist shifters.

The TX-70 does not want to index correctly. I believe it might be due to the 'slop' in the Revo shifter in combination with a slightly gummed up TX-70.

I've done my best to lubricate all the joints on the TX-70, and it did get a little better...

I have the bike on a repair stand. Let's say that I establish 5th gear. If I move the Revo shifter to 4th, I can see the TX-70 barely move, and it does not shift. If I go back to the TX-70, extend it, and physically push it to 1st gear and release, and then pedal again, it will shift to 4th. Quite cleanly. If I go back to 5th and adjust the barrel a little tighter, then it will shift to 4th, but I get cassette chatter, and it has difficulty shifting back up from 4th to 5th. This issue translates throughout most gears and neighboring shifts. As a workaround, I have to over-shift slightly, and it gets ugly fast.

The rear Revoshift on the right side seems to have a lot of play/slop in it, and I don't know how much that contributes - but I am going around in circles and am satisfied that it's too old a system to ever index smoothly and correctly.

I have a found a few rare places I can replace the SL-RS41 shifters, but cannot locate a TX-70 (and I would want it new.. which makes that search a needle/haystack)

I have a firm grasp on my bicycle and its hardware, and my bicycle knowledge ends right there. Can anyone recommend a new derailleur/shifter setup that will be 100% compatible with my 7 speed cassette?

I tried to attach pictures showing how the derailleur is mounted, but Forum restrictions prevented it.

Thanks for reading, and any comments/ideas are welcome

- Keith

base2 

So, first off Dual Drive was a 3 speed epicyclic hub with a cassette body on it that was an invention of Sachs that was later swallowed up by SRAM & then scuttled. Secondhand Dual Drive hubs are available on the used market for ~$400+tax, shipping, etc...The Achilles heel is the plastic click box & the head of the shifting pin being broken off during an impact. For which the dwindling supply on the market commands a premium price.

Your $250 Kent tandem is probably dis-ingenuously calling a two person input to the drivetrain a "dual drive" in order to co-opt a well known term for their own use.

In looking at pictures of your bike on the internet, there does not appear to be a SRAM/Sach's dual drive hub installed on the bike. Rather, a standard 3x7 drive train in conventional Captain/Stoker configuration.

The confusion caused by appropriating another companies branding is a topic for copyright lawyers.

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Having gotten that out of the way, it reads to me like there is undue friction in the cable system that the derailleur is not able to overcome. You can lube all the points of the derailleur, & while that may help, the problem is likely the zinc coating of the cables has swollen up as it oxidizes protecting the steel core within. Combine that with rust from the likely unlined shift housing being left outside or exposed to the elements & you have a recipe for a froze up system.

You may have temporary success injecting a light machine oil into the cable housing. But the real fix is new stainless steel cables & housing replacement.

Fortunately, both are relatively inexpensive to do yourself & falls under the basic maintenance category of bike ownership. If the whole project cost more than $40, I'd be surprised.

There is no reason your current system could not be restored to better than new operation as-is.

dedhed

Pretty much ANY shimano derailleur is going to work better than a Tourney (TX 70) Which is Shimano's lowest level named group.
Deore/ Alivio/Acera will all be better choices. Shifters same thing. Many replace the grip shifters with trigger. Any 7 speed Shimano rear shifter will be compatible.
You can also look at Microshift shimano compatible components.
Replacing the cables with good quality stainless inners and index compatible (compressionless) housing should also be done
Any 6-9 speed Shimano mountain (6-10 road) rear derailleur will index on your 7 speed rear cogs.

alcjphil

Agree with the above. It is far more likely that you problem lies within the shift cables, not the shifter or derailleur

cxwrench

Almost certainly it's the housing, replace both the cables and the housing. Or have someone that knows how to do it take care of it.

Kre8iv

Thanks so much for all the responses!

Due to the twist shifters being old, the plastic lenses are yellowing and the right one has some broken pieces (that don't affect operation). I have decided to start there and replace the shifters along with new cables.

I am looking at Tourney Shimano Shift Lever SL-RS45 with SIS indexing - sold by Bicycle Addiction on Amazon

The package comes with both shifters, new cables and housing.

Someone in this thread mentioned special cables and/or housings?

Question 1 : Will these shifters work ok with my setup?

Question 2 : Should I ditch the supplied cables/housing and buy some sort of upgraded product there?

Also, any specific shifter recommendation contrary to the RS45 is welcomed and I'll look at it.

Thanks again folks...

- Keith

bboy314

You will need tandem length cable and possibly extra housing for the rear shifter. Make sure you’re using lined “shift” housing (not spiral-wound brake housing). The cable can be a pain to replace in a grip shifter but it’s doable.

I think it’d also be worthwhile to replace your Tourney rear derailleur with something like an Acera or Altus, not too expensive but a huge step up in quality. A Shimano derailleur made for 9 or fewer speeds will work.

dedhed

You really don't know until you find out what they are. They likely aren't going to be long enough anyway due to it being a tandem. Indexing works best with die drawn SS inners and compressionless housing. That's not to say on lower speed (6-7) you can't get away with lesser cables. But it's a lower end derailleur with sloppier tolerances and good cables are reasonably cheap. Compressionless lined index housing is pretty much a must and readily available.
Other considerations are good quality cable cutters and housing ferrule ends.
That bike is a low end bike with little market value so I wouldn't drop a ton into it unless you plan to ride it regularly.

​​​​​​https://www.parktool.com/en-us/blog/...-cable-housing

Kre8iv

Ok... slowly but surely researching everything.. cuz I only wanna do this once

Updated shopping list:

1 set (3 x 7) Shimano Tourney RS-45 shifters
1 set Jagwire 2x Pro universal shift cable kit

The Jagwire set comes with 2800mm RD and 2300mm FD cable lengths - which is comfortably within what I need.

Now, for the derailleur, I am stuck on options...
It appears the Shimano Tourney TX-800 would be the cheap option - but would work
The Shimano Altus RD-M2000 SGS looks interesting for only about $5 more
There is also the Shimano Acera M360.

Derailleur thoughts, folks? Getting down to the nitty gritty here.

Also, do I need a separate hanger? My current TX-80 seems to be attached to a 'claw'? (looks more like a a talon!) But it appears to be built into the derailleur and not detachable/reusable.

That issue also has me kind of hung up atm...

Thanks for your patience and invaluable advice !

- Keith

Bill Kapaun

The ALTUS will work fine with your 7 speed,
I have one shifting a 9 speed which is a tad more finicky then 7.

Kre8iv

Hi Bill. Thanks so much for sharing your positive experience with the Altus derailleur.

Looks like maybe my welcome has run short here. Was it due to the revelation of the value of my bicycle - and it simply doesn't meet the standards of this community? I have always used online Forums for advice. I always try to learn from that advice and be available to help with advice to the next newbie who wanders by. Pay it forward. I don't think I was rude ever? I give up.

Anyways Bill, can you help me with the last piece of information - how to attach the Altus? If a direct answer is difficult, can you point me to a YouTube video or online resource that can help me solve that last piece of the puzzle? If any ideas come to you that you can share, I would greatly appreciate it, and definitely promise to not burden this community further. Thanks sir.

- Keith

Hondo6

First: welcome to Bike Forums.

Probably not so much "welcome run short" as your original questions having been answered. You're now asking follow-up questions - logical ones. However, many of those here offering advice are pros with the proverbial "day job" that keeps them somewhat busy. Answers to those follow-up questions could take a bit of time.

The comment about sinking a ton of money into an inexpensive bike was simply a warning that bike repair parts and the tools necessary to do the job right are more expensive than most realize when new to the sport/hobby. It's very easy to spend far more replacing a few items than you want or expect. If the bike is one you'll ride and enjoy, it may be worth it. If not, it's sometimes worth asking if the bike should be replaced instead of upgraded or repaired. Sometimes the latter may make sense.

If claw mount, Shimano RDs typically come with one built in - and not many (if any) above the Tourney level do these days. If your bike doesn't have a derailleur hanger built into or attached to the frame, you'll need a derailleur claw mount. I believe they're available on Amazon in the $10-12 range. I also seem to remember that Sunrace makes one (they make reasonably good components) at a competitive price.

Disclaimer: I've never used one, so I don't know how well they'll play with Shimano's newer "Shadow" RDs (the Acera you're looking at is such) and indexed shifting. But if you're using it for 7 speed, as Bill Kapaun says above that's more forgiving than 9+ speeds.

base2 

Kre8iv
Sorry, I've been out of town & really only been on the board the times I've been adjusting to jet lag. To cope, I have been marshaling my mental powers.

Yes, the Altus should work fine. So should the Tourney. But the Altus is way better.

The Shadow derailleurs are Dynasys. Dynasys & Megarange don't really cross-pollinate that well. In your situation NOT Dynasys is the way to go.

There really isn't anything "wrong" with a sloppy derailleur in 7 speed. They'll work fine. They'll just be a bit finicky to dial-in and tend to be vague & inconsistent in their operation unless every other part of the system is in tip-top shape. The higher the cog count the more that matters.

The Altus is probably the best choice. Like mentioned above a SunRace claw adaptor if needed is no big deal. IIRC I may have seen Altus in claw variety...But I see so many things it's hard to keep track. Again, Microshift is a good option, too. Go with whatever your LBS has in stock.

What is not a good deal is cables & housing "kits." Kits can be the more expensive way to go if you are only doing a single cable. Their market is people who are intimated by bike shop mechanics or don't have a bike shop near by so prefer mail-order. In a kit, often you are also buying a bunch of stuff you simply don't need. Conversely buying exactly what a random bean counter figured you need leaving zero room for error or custom fit based on your particular bike.

A single cable at a bike shop usually runs about $5-15 depending. Tandem length adds a slight premium as the hook on the wall with slow sales costs the shop dollars too. As mentioned, die-drawn, slick coated cables are the best. But the coating doesn't last that long, some coating fray like hair & sometimes gets stuck in the housing causing problems of it's own. Plain stainless cables are really the sweet spot, IMO.

Housing is usually $1-2/foot for the 2-3 feet you need. The LBS should have cable tips & housing ends for a nominal fee in the $0.10-$0.25 each range.

The catch to to doing this yourself whichever way you go (kit or ala carte from LBS) is you still need the cable/housing cutter pliers. Which would be a one-time cost but we'll worth it if you ever replace a cable ever again in your lifetime.

cyccommute 

You should start with the rear derailer and the cabling. Revo shifters are fairly robust while the Tourney rear derailer really isn’t. The Tourney is too flexible due to the stamped steel used in the hanger. An Altus is stiffer and will shift better.

If you feel like replacing the shifters, a paddle style like the microSHIFT Mezzo or Shimano Altus (you have to buy the left and right separately) might be a better choice.

Be aware that tandems can be a bit finicky when shifting anyway. The long cable has a bunch of stretch in it compared to single bikes even after the construction stretch is gone so the shifting isn’t as crisp as a single.

Kre8iv

Thank you. I thanked for the original answers, and incorporated the suggestion to replace the cables. The cost to go ahead and replace the aging shifters and the derailleur were not exorbitant, so it's, IMHO, perfectly logical to do it all at once.

Kind of unnecessary. And if it is necessary, then it makes it necessary for me to waste reader's time to assure them that I do enjoy the bike, and any upgrade I wish to pursue is actually desired. That's because I'm just doing research. I cannot understand how much any particular upgrade will cost until I have a list of the necessary components.

So here we go. This is a beautiful tandem. To me. To us. A husband/wife bought it, didn't use/enjoy it as much as they thought they would, and so it sat stored and covered in their garage until I bought it from them. We are 3 adults and 3 children in our family, and we put some serious time and miles on it already. It's built well. We feel extremely safe on it. While terms like 'beautiful' and 'well built' are subjective and opinion, that we feel safe while riding it isn't. To us, it's a keeper. We put it through the test - it passed. It's a family member now, no matter what the original purchase price was. Now I feel comfortable addressing any issues it actually does have. While shifting may never be perfect, it has to be able to be better than how it performs currently, and that's that. Frankly, there are times where the shifting glitches or skips so profoundly, that one might consider it 'dangerous' - as both pilots immediately lose sync. I need to make that better. I am convinced I can achieve that for a very reasonable cost.

I titled my post 'upgrade'. I didn't mean that I was going to consider slapping on a $1,200 derailleur. I meant that my original equipment was no longer in production, and so I am forced to buy something available in the current market. That's when I turned to these forums for the knowledge of compatibility. I took very seriously the idea that the cable system itself could have multiple issues. I believe that. I completely understand that as a potential weak link, whereas I did not understand that before. Terms like 'compression-less' were new to me. Using that advice, I found that Jagwire seems to have a quality product that should meet my needs and be within my budget.

Yes, that's the last question I posed, along with the information that my current RD has a claw built-in - and it doesn't seem to be removable/reusable. In researching RD 'hangers' - I guess they are called? There seems to be many different shapes and styles, and that's where my confusion comes in. If one is actually built into my current Shimano RD, then my logic assumes that I have a 'standard' (or at least was standard back then?) frame configuration for it to attach to? I'm sure the eventual answer/solution will be simple and laughable, but for now, it's brought everything to a halt and is incredibly annoying to not know what I need. Thank you for your response Hondo.

Say no more, and thank you so much for the further knowledge you contributed below. More to blame than anything else is my impatience at what I perceived as a very simple question - "how do I mount the new derailleur?"

I feel most comfortable and confident with tht as the RD solution.

The 'kit' I found will literally end up with no cable waste. I need 2670mm for the RD and 2185mm for the FD. The kit has 2800 and 2300 respectively. This kit is ~$30 or so. I would never replace just the RD cable and not the FD at that price. We're talking literally about an extra $10-15 to upgrade the entire shifting system versus just the RD portion. That's a meal at McDonald's. I'm good with that. The product is expressed as stainless steel and compression-less housing. The feedback for the product quality is overwhelmingly positive.

I need 5' 2" of housing. The kit apparently comes with 10.5 feet. Included is a variety of tips, ends, donuts, etc. All of this for $30.19 and free shipping. Unless quality of this particular company or product is in question, is this not a pretty fair deal? Let me know please!

I watched a video of a guy who used a Dremel tool, with a cutoff wheel, do perfect and precise cuts on his new housing. It's does the job with practically zero crush on the inner sheath. I have a Dremel. I assumed I was good there. Would you have any issue with that solution?

Thank you, sir. I appreciate your well thought out responses!

Sold on the Altus. That will be going on - as soon as I... figure out how it will be attached properly

Wow. Awesome. I really like that idea... again, really not that much more expensive... more research is now necessary. Thank you so much for that idea !!

Yeah, I get it. I have no expectations of perfection. It just needs to be better. Due to the age of all the components, this upgrade is completely necessary for it to run as good as it can - which will understandably run short of perfect. I'm good with that.

Cheers to you all - I am indebted

- Keith

bboy314

https://www.thebikesmiths.com/produc...BoCEwUQAvD_BwE

This is what you need in order to mount an Altus derailleur to your tandem.

JohnDThompson 

Between long cables and frame flex, there's plenty of opportunity shifting issues, particularly with indexed shifting. Friction shifting is less of a problem, IME.

I suppose electronic shifting might work well, but that doesn't come cheap.

Kre8iv

bboy314 Thank you.

Edit: I had posed an additional question, but have withdrawn it. Thank you again for your time and referral.

Leisesturm

Shift cable is always compressionless by design. Brake cable is compressionless only when so specified. I haven't found that tandem rear derailleurs need anymore (or less) work than singles. Tandem rear brakes! A different story. The rear brakes on our Kents (yes, plural) spent as much time disconnected as fully wired up. O.p. take note. Cutting a shift cable with a Dremel may be a bridge too far. Cut it with any old cable cutter that will cut cable housing and ream out the hole in the housing liner with a 1mm or 1.5mm Allen wrench. Bob's your Uncle. Late to this thread, but my takeaway after 5 (full) minutes of skim is that the o.p. needs to take the rig to the nearest bike co-op (not bike shop) and let their tech have a go.

Seriously. They work on bikes like that day in and out and they will let you watch. They are all set up as 501C3's so the cost will be nominal, if any cost at all. Maybe not even for parts. It's the best call. O.p. just does not have the background experience to be mucking around legacy indexing drivetrains. They are frustrating even when everything is new. I haven't seen anyone go through the setup for the indexing, once all the parts are in place. Or were we going to wait until the "WTF its going from 10th gear right to 8th!" posts?

Kre8iv

Good sir. By your own admission, you spent 5 mins doing what you yourself have termed a 'skim' of the thread.

You know absolutely nothing of my background, because you know absolutely nothing about me.

Yet you claim knowledge that I can't possibly possess the background necessary to replace an entry level derailleur and cable system. I will, according to you, just end up mucking it up.

I challenge you to put some money where your opinions are. Name the amount you wish to wager that I cannot complete this task, and successfully make the shifting smoother and more reliable than current. I'm confident we can find a 3rd party here to hold our individual funds until a winner is declared, and then that person can distribute the funds to the prevailing party. I am happy to video tape my entire procedure - as I did intend, if I find the time to edit it, to upload it to YouTube to benefit any others facing this rocket science project. You know, to make them understand how right you are that an individual coming to these Forums just seeking advice on replacement parts and compatibility issues will surely fall to his knees in failure. If you spent the time to come to this thread and laugh, dismiss, and roll your eyes at another gentlemen, you might as well be willing to take his money, too. It would be too easy. Please name your price sir.

And I withdraw the question regarding the hanger. I will source that elsewhere until I am satisfied I have a compatible part.

Good day.

- Keith

Hondo6

FWIW: While often used together, Shadow and Dynasys are two different Shimano designs.

Shadow refers to a redesigned RD that places the body of the derailleur closer to the centerline of the bike and under the cassette to provide more horizontal clearance and reduce chain slap. (I think the "Shadow" name derives from the fact that the body of the derailleur is often literally in the cassette's shadow when the sun is high.) It's described here. They're generally identifiable by the "b-link" required when attaching one to a frame with a conventional derailleur hanger.

Dyna-Sys (apparently Shimano's preferred spelling) was Shimano's 10-speed redesign for mountain biking, which also included Shimano's new, lower 10-speed mountain RD pull ratio. It was revised somewhat for 11-speed mountain.

While I do believe the first Shadow derailleurs were 10-speed mountain, the design has since been adopted for use in Shimano road RDs. Many recent Shimano road RDs - e.g., Dura Ace 11- & 12-speed, Ultegra 11- & 12-speed, and 105 11- & 12-speed - use a Shadow design; ditto for some Shimano 11-speed GRX. Dyna-Sys appears to be unique to Shimano mountain RDs.

Hondo6

Actually, the comment was quite necessary. Your other comments on this thread indicate you are not particularly knowledgeable concerning bike repair and upgrade activities. (Someone who had more experience would have recognized immediately that they needed a claw-style derailleur hanger to replace a claw-mount derailleur with a direct mount derailleur on a bike frame with no existing derailleur hanger.) As noted previously: those without some experience often grossly underestimate the cost and difficulty involved.

Here, you took offense when someone offered you advice you didn't want to hear. You've done the same a second time regarding a different bit of advice you apparently didn't want to hear.

"Watching a few YouTube videos" often gives one just enough knowledge to get started - and then get in trouble. It's not a particularly good substitute for experience, or for good advice. And it's also rather petty to complain about advice that you asked for and received at zero cost to you because it wasn't what you wanted to hear.

But hey: if you want to be "that guy", be my guest.

Done here; nothing further.

grumpus

Slop in a shifter can be helpful - when you shift to a larger sprocket/chainring it over-shifts slightly, which helps the chain to climb on to the next sprocket, then you release the shifter and the derailleur settles back a bit so it doesn't rub. This makes it important to have the stop screws properly adjusted so the chain doesn't throw off but does manage to climb. Slop in a derailleur is bad except where it's designed in - some jockey wheels were (still are? IDK) designed to slide sideways so they self-align a little.

base2 

I thumbs-up your post. You're right. Shadow & Dynasys tend to overlap but aren't the same. I didn't mean to imply as much. But in rereading, I guess that's the way it came out. Oops.

Hondo6

De nada, amigo. There are so many different manufacturer's designs and technologies with so many different names that I believe it virtually impossible to keep them all straight, even when you know the differences. And it's often even harder to write something so that others can read and understand what you mean without misunderstandings.

I just wanted to clarify that point to prevent misunderstanding - particularly since Shimano's current non-Dyna-sys Altus derailleur that was discussed above is a Shadow design.