Best bike derailleurs according to redditors
We found 146 Reddit comments discussing the best bike derailleurs. We ranked the 91 resulting products by number of redditors who mentioned them. Here are the top 20.
We found 146 Reddit comments discussing the best bike derailleurs. We ranked the 91 resulting products by number of redditors who mentioned them. Here are the top 20.
You can't fix that. Send the pic to the seller and demand satisfaction. Probably the bike was not packed properly for shipping, or the shipper brutalized it.
If you can't get it replaced for free, the part is $20: https://www.amazon.com/Shimano-Tourney-Derailleur-RD-TY300-Direct/dp/B01D2WQ0TM and you can install it easily yourself.
You may or may not need to take the bike to a shop to have the derailleur hanger (silver piece) straightened. If you bought the bike mail-order, ask them to send you a new one of those too.
This is a direct replacement.
Here is how to replace it
In broad strokes there are five things you need to consider, in order of importance:
1 - How does the derailleur mount to your frame? If you have a hanger with a threaded hole below the dropout you use the "normal" modern style like so
Otherwise if your dropouts (mostly older frames) don't have a hanger you need to use one like this or get an adapter.
2 - (Again broad strokes, there are exceptions) you need to consider the brand. Don't mix Shimano with SRAM.
3 - You need a derailleur for the number of cogs in your rear cassette / freewheel. A 10-speed mountain rear derailleur won't work with 9-speed mountain shifters, for example. There are, again, exceptions but that gets very complicated very quickly.
4 - You need a rear derailleur capable of taking up all the chain slack your gears will create. The rear derailleur not only shifts the rear, it also uses that long dangling cage with two pulleys to tension the chain. The amount of chain used when in the big chainring up front is a lot more than the amount of chain used when in the small. The rear derailleur doesn't shift those front chainrings, but it does take up the slack. You need a rear derailleur which can take up all the slack your chosen drivetrain can generate. (BigChainring-SmallChainring)+(BigCog-SmallCog)=How much slack a drivetrain generates. The longer the "cage" the more chain slack a rear derailleur can tension, but the worse it shifts (in theory) and the more likely it is to get hit by trail obstacles (because it hangs lower). That's why most people run the smallest cage they can. Cages come in three general length categories: Short, medium, and long. MTB cages are almost always medium or long, and road cages are almost always short or medium.
5 - Clutch or not. Clutch derailleurs are (in theory) harder to shift but they don't bounce around as much off road, preventing the chain from bouncing as much on rough terrain, decreasing the chance of the chain popping off the front chainring.
.
As far as "what's better than what": Longish article on Shimano and SRAM's heirarchies
Get this Altus rear derailleur (assuming I correctly counted you have an 8 speed cassette). $21 shipped. Big pulley and jockey wheels are great, it’s a small upgrade from your current model.
Here’s a rear derailleur removal and install video:
https://youtu.be/IN4-jFRD8-Q
Parktool has great videos on adjusting or overhauling a rear derailleur but not one specific to removal and installation.
Is the shifting indexed (single click for each gear) or friction? If it is friction, get whichever suntour or shimano derailleur is cheapest online. It should be one without the hook also called a derailleur claw. A used one would be less than $20 online, or you could get something new like http://www.amazon.com/gp/product//B000F5EGAA/ref=twister_dp_update?ie=UTF8&psc=1
It's a great bike for the price. For what it's worth, I've done plenty of loaded touring in mountains with similar gear ratios (compact crank with 11-28t cassette). Others will say your lowest gear ratio (1.2) isn't low enough for mountainous touring. Depends on your strength and how much you're carrying.
To get it lower, you can buy an 11-34t cassette which will bring you down to a 1.0 ratio.
However, I'm not sure the derailleur it comes with will fit an 11-34t cassette. If it doesn't, you'll need a mountain bike rear derailleur like this.
In short, you're looking at $30 or $70 to upgrade to a traditional low touring gear ratio, not including labor.
my bike is a rehabbed 99 GT XCR-4000. here's a brief summary of my current configuration, with costs & reason for replacement. I should note that I wanted to buy a cheap bike to get into the sport and learn how to do maintenance so if I got a nice bike I wouldn't be actively destroying it. I've had the bike for a few years now and replaced a bunch of things. anyways, this is roughly in the order that I replaced things.
Stock: Frame (duh), seat tube, head set / stem.
new:
Shifters: Shimano Alivio 3x9. the shifters were shot when I bought the bike, had a set of microshift ones that lasted a year but sucked and broke. $65 for the pair
Drivetrain: new chainrings $10-$30 each, cassette $35, chain $22, Front Derailleur $20, rear derailleur $68. The drive train was such a mess when I got the bike, I've destroyed some good components from being a noob. all straight now though. kept the 3x9 arrangement since the sifting wasn't holding back my riding at the time.
Fork: Rockshox recon silver solo air $200 the 15 year old rockshox judy was sticky, heavy (coils) and the only damping was the stiction of the tubes. Super happy with the replacement, it's steel so not super light but the adjustable rebound damping made a huge difference. when I bought it they had rim brake mounts as an option on the amazon page, not sure if that's still available. the rim brake version that I have does have disk mounts as well.
Wheels - $100 craigslist. the stock wheels were a mess and impossible to true well - I broke a spoke on my rear wheel which then got sucked into my RD, destroying that and breaking another couple spokes in the process. decided to say screw these old things and bought a new set of wheels, this time with disk brake hubs - thankfully my frame had mounts for the rear.
Disk brakes: avid bb-7 - $60 ebay(new). purchased at the same time as the new wheels, went with mechanical because I didn't want to deal with bleeding hydraulics, though this is the one thing I would change. I would get hydraulic brakes because I feel like I'm adjusting the pads on the mechanicals every ride or two (huge pain in the butt). Also bought avid FR-5 levers $16
handlebars - Ritchey comp alloy $30. crashed and bent my bars pretty good. I didn't want to change out the stem so I bought the closest approximation to the stock bars that I could find cheaply. also decent 25.4mm mount bars are freaking impossible to find.
I should note that this is certainly not the proper way to maximize the quality of the bike for the money. The total is around $700, though I've spent more than that over the 4 years I've had the bike since I've replaced a couple things multiple times (chains, etc.).
if you want a retro bike, these are the best things that I've found to replace the components as they break. If others have found better stuff in terms of bang for your buck, let me know. The only things I've replaced to "upgrade" the bike are the fork & disk brakes, though since it was time for a new wheelset the brakes made a lot of sense to purchase at that time.
Pretty sure that's Claris running gear.
The rear derailleur looks like 2300 series.
Here's a 2300 triple crankset in silver ... use your imagination to paint it black and get rid of the granny chainring. Clearly the same family.
This would be typical for a base-level bike built anywhere from ~2010 - ~2015 or so... (leeway one year or the other based upon when the groupset was released and the bike spec'd out by the manufacturer).
Misunderstood, I thought you wanted to replace the DT shifters with brifters.
Your bike here is a 5-speed -- which refers exclusively to the number of cogs on your cassette. It doesn't matter how many chain rings you have in the front. 5x2 means you have a 10-gear range, but we still refer to these bikes as "5-speeds".
The problem is this: 5-speed bikes have a spacing for the rear wheel of 120mm -- which is very narrow compared to modern road bikes. You have two options: track down an old 5-speed rear wheel that works, or you could buy a (comparatively easy-to-find) 6-speed rear wheel and bend the frame to suit its 126mm width. While that sounds like a recipe for disaster, steel is supple and wouldn't really mind the 6mm bend. If you go down the 6-speed route, you will need to replace the shifters and rear derailleur to match a 6-speed drivetrain. Do not attempt to buy a wheel that works with 8, 9, 10, or 11-speed drivetrains, as they simply will not fit the bike.
The cassette you linked would work fine for a 5-speed setup. This is an example of a derailleur that would conceivably fit that bike.
For brakes, almost anything will work. Tektro make some very nice dual-pivot brakes that you can make work with that frame.
Bottom bracket is the set of bearings and spindle that hold the crank arms to the frame.
don't a friggin get an X9 for that bike... its like putting a corvette engine a tercel. doesn't make sense and won't even work. your bike had a tourney rear derailleur which is the most entry level shimano has. upgrade a bit to this acera for $20 and call it a day. It'll shift better than what you're used to and won't break the bank. it will work with your existing stuff as well. simple as removing the busted one and installing this. watch some videos and you can get it done easily.
I'd make this comment even longer if I could, but I'm tired. I've got a 1975 Raleigh Grand Prix and have done everything and more to it, and can answer any question you have when you start working on it. I also race a 1974 Raleigh International in collegiate races and some of the parts are from a Grand Prix. Most of your stated questions were already answered so I'll address some other things.
Check the serial number on the bottom bracket (or left rear dropout). 1974-onward models are on the bottom bracket and have a logical serial number that works as follows: My serial number was WB5... which meant W = Worksop factory, B = 2nd fornight (2-week period) of 5 = 1975. The Worksop factory was the best and the N = Nottingham factory was the worst - not because of build quality, but because they used non-standard bb and headset threading (26tpi). My Grand Prix had a 24tpi standard bb and a Raleigh 26tpi fork/headset, so I'm not sure what happened there.
The drivetrain should be just fine with a replacement chain - my recommendation for any 5-8 speed application is a SRAM PC830/580/870. Sunlite sells a very affordable but effective rear derailleur if you want to replace yours, but the existing one should work fine. The front derailleur will also work great, and I still use that same model. Those downtube shifters, IMO, are actually better than same-era Campagnolo shifters because honestly, levers are quite simple, and these are very solid and have a nice, sharp edge that makes flicking them with your fingertips very easy. I recommend removing the washers and cleaning them, or cutting new ones out of a thin sheet of copper - made mine just like new. For what it's worth, the Huret groupset was a nice step up from the Simplex groupset, and the all-metal Huret components will work just great, particularly with that new chain. Regarding the cottered crank/bottom bracket, be sure to either re-use the original hardened steel cotters or new ones from bikesmithdesign.com. Do not remove or reinsert them with any tool other than a cotter press. If you follow the right directions, servicing them is actually quite simple. Repack and set the bearings carefully, and you shouldn't have problems - Raleigh cups and spindles are legendarily hard and wear-resistant. If you need a new freewheel, be sure to get one with a 14-17-20-24-28 combo (or a 6-speed Shimano 14-28 freewheel), NOT one with a 16t 4th gear in place of the 17, because it's mathematically incorrect. That one is matched to a 52/40 crankset - if you get something with a 14-16-19-21-24-(28), technically a 52/42 is the correct matching crankset. I wouldn't do a 7-speed, spreading the frame and figuring out how to space it properly will be a headache.
Regarding the paint - you may want to keep it as-is and just sand and touch up the rusty areas. This is a high-tensile steel bike (though a nicer one), so I am almost certain not enough metal got rusted away to damage the thicker steel tubing. The paint, however, was generally very good, and is a candy-coated finish that looks very good touched-up. You won't be able to replicate it. I would keep it.
For potential improvements, your best bet is the wheels. While I wish I had kept my Maillard hubs, the steel rims are unfortunate on these frames. Alloy rims are an excellent upgrade, as are moving to 700c rims and getting some nice tires (Clement Strada LGGs are decent). It'll shave a lot of weight while leaving the bike's character intact, and gives you a lot more tire options. You may notice the front brakes are Weinmann 610s and the rears are 750s. The rears are longer-reach than the fronts (this was common practice among bike manufacturers, though I have no idea why). In my experience, putting a 750 on the front will be enough to run 700c rims front and rear.
Keep in mind this is a high-tensile frame, albeit a nice one, so don't go too crazy. I ultimately moved up from mine to an International, but the Grand Prix is still in my stable and I ride it whenever I go home (college student). It's got Nervex lugs and imo the geometry is decent. Just take good care of it and you'll have it a long time.
https://www.amazon.com/Shimano-Tourney-8-Speed-Mountain-Derailleur/dp/B00O7XMG1C
​
Like that one?
​
There are a couple of others that want me to chose between 'direct attachment' and 'with riveted adapter' like this one:
​
​
https://www.amazon.com/Shimano-RD-A070-Road-Rear-Derailleur/dp/B007Q4PBNO/ref=asc_df_B007Q4PBNO
​
Thanks.
​
Watching youtube videos about how to replace and adjust a derailleur right now...
​
(edit: also https://www.amazon.com/Shimano-RD-TY300-Derailleur-Compatible-Upgraded/dp/B01GO02W5K/ )
Yes. They come with a small plastic shim for use inside the clamp on a 28.6 tube. You can see the plastic shim In two of the pictures on this page: https://www.universalcycles.com/shopping/product_details.php?id=83997&category=71
For that matter you can see the shim on this amazon listing as well: https://www.amazon.com/SHIMANO-Dura-Ace-FD-R9150-Derailleur-Adapter/dp/B01M9AEDBG/ref=sr_1_2?dchild=1&keywords=shimano%2Bbraze%2Bon%2Badapter&qid=1572039385&sr=8-2&th=1&psc=1
Use the shim for 28.6, don't use it for your 31.8 :)
Thanks for the advice! I am indeed using friction shifters so it seems I can replace it with a regular shimano like this one? The other alternative is to buy a used
http://www.amazon.com/dp/B003ZM9REA/ref=cm_sw_r_an_am_at_ws_us?ie=UTF8
That is an 8 speed derailleur, so replacement is very easy! Any Shimano 8/9 speed derailleur will work, new or used. RD-M310, RD-M360, and RD-2400 are three inexpensive ones I found on amazon. Also, going used will often let you get a higher end model for less money. I would suggest either getting a RD from your LBS or if buying off the internet, run whatever you find by us
Ten bucks, if you've got Prime (and why wouldn't you?).
Here you go
You may also need a new 7/8 speed chain, if you're still on the bike's original 5 speed chain it won't be compatible, but your chainrings and cassette will be fine.
Make sure you get a 9 speed or lower MTB derailleur. Unlike road derailleurs, Shimano has a different pull ratio on their 10 speed MTB derailleurs. If you buy a 10 speed derailleur, it won't be compatible with your shifters.
Something like this Deore M591 should drop right on
This Alivio model should also work, and is a bit cheaper
Either one of those should allow up to a 34 tooth cassette on the small chainring. Just make sure you don't shift to it on the large chainring unless your chain is sized correctly.
I scored this Rockhopper for $50! Now I’m looking to modernize pretty much the whole thing. Please critique my build list below. Would you get anything different, or better, or maybe anything else that would be better value? Did I miss anything? Do you think all of this will work together? It will be my adventure bike for bike packing, gravel, off road touring.
FOMTOR 25.4 stem 60mm 35 Degree Bike Handlebar Stem Riserhttps://www.amazon.com/gp/product/B07G71CZG6
UPANBIKE Road Mountain Bike Bicycle Stem Riser Adapter 1 1/8" φ22.2mm https://www.amazon.com/gp/product/B071LLR8PR
Action 1-1/8" W/Adjuster Black Cable Hanger Fronthttps://www.amazon.com/gp/product/B06XCSKWCQ
KMC X9L 9 Speed Chain Gold Coatedhttps://www.amazon.com/dp/B0789HPV7M
Wheel Set 26 x 1.5, Mavic x M117, Deore M530 9Sp Hub, Blk SS Spokes, 32Hhttps://www.amazon.com/dp/B0033H53VI
Shimano Deore 9-Speed Mountain Bicycle Rear Derailleur - RD-M591https://www.amazon.com/dp/B003OWPRLI
Maxxis DTH 26 X 2.15 60A Kevlar Blackhttps://www.amazon.com/dp/B004XIT4YS
XCSOURCE MTB Mountain Bike Crankset Aluminum Bicycle Crank Sprocket and Bottom Bracket Kit 170mm CS400https://www.amazon.com/dp/B01LWXUV7I
RaceFace 104mm Single Chain Ringhttps://www.amazon.com/dp/B00D3FG6ZW
​
Edit: Adding Shifters and Cassette
SHIMANO Deore SL-M590 9-Speed Shift Lever
https://www.amazon.com/dp/B00IKVJF8Y/
JGbike Sunrace 8 9 10 Speed MTB Cassette 11-40T 1 Wide Ratio Including 22mm Extender - for SRAM Shimano-Type splined freehub Body
https://www.amazon.com/dp/B01MRLWHEO
Figured out the size! Wanted a black one would this work?
Edit: forgot link SHIMANO Dura-Ace FD-R9150 Front Derailleur Adapter Black, 31.8mm/28.6mm https://www.amazon.com/dp/B01M9AEDBG/ref=cm_sw_r_cp_api_i_OJ2SDbNCNESZ3
if you search for the product number on google you'll find http://bike.shimano.com/content/sac-bike/en/home/components11/road/sora11/rd-r3000-ss.html which says that it is only good for 32 teeth.
this one is good for 34T - see http://bike.shimano.com/content/sac-bike/en/home/components11/road/sora11/rd-r3000-gs.html
edit: do you have friction shifters? if not then you need to also check that the new derailleur is compatible - it needs to move the same amount per "click" as the old one.
no problem. Glad I could help.
here is a bit cheaper one.
The part number on the claris derailleur is FD-2400 if you want to look for it elsewhere since it doesnt seem to be on prime.
They are even cheaper on ebay if you are looking to really pinch pennies.
Gl and feel free to pm if you need help.
Will I be happier with the shimano acera?
Its made of steel like my old one and I like the idea of nice shifting on my refurbed bike. Then again I also like money and your recommendation for the matching tourney cheapo model. Let me know what you think.
LHT Frame - $520 after tax
Chukker Wheels - $85 x 2
Tires Schwalbe Marathon Plus RLX 700 x 45 C Bicycle Tire - $54 x 2
Alloy Headset Spacers - $7.89 x 2
Shift Levers - $60
Chain - $10
Brake Cables - $10
Brakes - $15 x 2
Extra Long Shift Cables - $6
Derailleur - $24
Cassette - $17
Crankset - $40
Spindle - $24
Headset - $45
Seatpost - $20
Brooks Saddle - $145
Rack - $35
Brooks Panniers - $150 x 2
Brooks Bar Tape - $65
Tools
Saw Guide - $41.36
Starnut Setter - $22
Do you really have the derailleur hanger? You should post the pic of broken one so that we can make sure.
If you do have the derailleur hanger, I think you can use something like this. Shimano Tourney.
https://www.amazon.com/Shimano-Tourney-TX55-Speed-Derailleur/dp/B003ZM9RDQ/ref=pd_sim_468_10?_encoding=UTF8&pd_rd_i=B003ZM9RDQ&pd_rd_r=X7ESM3A6V3YXM80YCV7T&pd_rd_w=k6Gma&pd_rd_wg=hsYVC&psc=1&refRID=X7ESM3A6V3YXM80YCV7T
Upgrading it will be quite expensive. However, it'll provide you with a wealth of knowledge, frustration and, at the same time, fun.
Depending on your existing hub, you may or may not need a new hub to put your new cassette on.
With a wide enough range of gears on your rear cassette you can get away with a single chainring, so there will be no need for a new crankset/front derailleur/front shift lever.
As /u/fclbr said, you can choose downtube shifters in order to keep your existing brake levers. There are also bar-end shifters, and if you go for a single chainring, it won't be that expensive.
All-in-all, consider if this bike's right for you, size and geometry-wise, as your decision may be a bit rash. If it is, then I'd say go for it.
Rear derailleur - $20
Cassette - $20 - I recommend going for the 34t max sprocket. It'll allow you to stick with a single chainring
Bar-end shifters - $55 - they are 9-sp indexed, but they also work in friction mode, which allows you to freely adjust your gear
Downtube shifters - $14
Cables/outer cables are negligible costs.
Thread rejack! I noticed that the bike in those pictures has the same style lower mounted front derailleur with a brace (not a clamp) as the one I thought was broken on my bike. Cool.
Also, in my novice opinion, that bike looks great. If it's comfortable, I wouldn't hesitate to grab it at $400. A new entry level bike like a Trek 820 will run you about $360 + tax. I think for a few bucks more, this would be a superior bike.
Take for example the rear derailleur. The 2007 comes with a Shimano Deore (confirmed in the pics). Here it is on amazon for $50. A new 2012 Trek 820 comes with a Shimano TX35. This goes for $12 on amazon.
Again, take this with a grain of salt as I just bought my first bike. This is just from some of the knowledge that I've gained in the past few days. Good luck.
*grammar edits
>None of the modern bikes I listed for comparisons’ sake had disc brakes. All had linear pull, just like the ‘00 Specialised.
The bike you link to has disc brakes
​
>well you can just cut your sentence there. It’s a steel crankset. It’s cheap, it’s shitty, and it is heavy.
How is it shitty? How much heavier are the cranks on the modern bike vs the older bike? 4lbs difference in bike could be the coil suspension fork alone. Additionally, both the OP's bike and the Pitch are "Forged Alloy". Guess what? Probably the same stuff. The components you get on a bike like the Pitch aren't as shitty as you seem to think they are.
​
>Modern Geometry
You realize that with aluminum, specifically, they have modified their manufacturing techniques in the frames to be more compliant where it matters while remaining stiff where power is transferred? I rode an aluminum road bike from 2000 for 17ish years. My butt definitely knows the difference between it and the modern CAAD bikes that Cannondale is putting out. Just because you aren't aware how the modern changes to MTBs affect construction doesn't mean they don't exist.
​
>That is a change from the past where MSRP was used as an advertising gimmick to get the rider to think they were getting a great deal- when it really never actually came off sale.
This hasn't changed. The OP bought a year old model, which can bring a bike down 30% in cost. I've only bought one bike (high quality kid's bike) at full value, and have probably bought 7/10 of the bikes new from a shot that I've purchased new in the past decade.
You are only picking out any possible negative comparisons to fit your narrative and haven't provided any actual contradictions to my points, just a lot of hate.
hey could you give info regarding what chain are you using? and regarding slx derailleur is it this one ?
That's a long cage, which you probably won't need looking at your bike.
See this link for more information on cage length.
http://www.amazon.com/dp/B007Q4PBNO/ might be better. Read the above link though and work out what cage length you need.
This is tempting then. If all I need to do is drop this in and tension it, I'm probably going to do that vs anything else. Seems like it'll be quite a worthwhile upgrade especially if I can use my existing shifter, chain and cassette !
that link also indicates this derailleur is a copy of an older version of the Shimano Tourney derailleur. the modern replacement Tourney doesn't look exactly the same but it will do the same job for cheap. make sure to match the style of derailleur hanger to the broken one, notice in the first link the topmost part of the der. has a little slot for the axle to slide into, whereas the second link has a simple bolt. this is what you are matching.
http://www.amazon.com/Shimano-Tourney-TX35-Derailleur-Speed/dp/B003ZMH69S/ref=pd_sim_sg_1
http://www.amazon.com/Shimano-Tourney-TX75-Speed-Derailleur/dp/B003ZM9REA
Sorry about the late reply, but here you go:
Shimano Acera 6/7 speed rear derailleur:
http://www.amazon.com/gp/product/B000F5EGAA
It has plastic roller gears for the chain! I have not ridden it much, but something tells me when a stick lands in, it won't shred it up like my xtr. You might want to spend more for a better one.
I'm not sure what the cage length is but if you get another, you'd probably be best off with a medium cage, but you might need a long cage. Check this for more info: http://forums.mtbr.com/showthread.php?t=205890
Here is the cassette: http://www.amazon.com/gp/product/B001BY7ZP2
I got the 13-30, but I think i'd recommend the 13-34 for the lower gearing.
Having a look myself and I found this: http://www.amazon.com/gp/product/B007Q4MDI0/ref=as_li_ss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B007Q4MDI0&linkCode=as2&tag=faqloadcom-20
What do you think? Should it work?
Thanks, WildMan. I've found the same M310 Altus you've linked to, but it has DL at the end?
https://www.amazon.co.uk/gp/product/B005CMUQU0/
Would this be my best option? I'll order those then.
ok last thing http://www.amazon.com/dp/B007Q4PBNO/ or http://www.amazon.com//dp/B007Q4PGPM/
whats the dif with Smart Direct Mount or Smart Mount with Bracket
This is the one I picked up, not sure if it has the clutch on it though. It does seem to shift better than the stock derailleur.
http://www.amazon.com/gp/product/B000YBCNAA/ref=oh_details_o09_s00_i00?ie=UTF8&psc=1
So, bit of an update, this is what I ordered earlier and wanting to make sure they're compatible/good choices:
Cassette:
SRAM PG850 8 Speed
Rear Derailleur
Shimano Alvio 8 Speed
Chain
SRAM 850
and I was unable to find any 'cheap' single bar end shifters, most were the 'extreme' kind that have bars extended out in front of the rider(unsure what that is called); however, was able to find a 'good' deal for a right Shimano Sora ST3000 8 Speed shifters.
From my understanding, I could mix/match many of the parts except the RD and the sifter should be the same brand. They all should be 8 speed?
The one part that I have reservations about is the rear deraileur as I would prefer something more 'roady' than the Alivio but unable to find any that are '8 speed'; would it be possible to get a 9 speed Shimano RD and have it still function well?
Lets see, I take it you didn't even look at the 2 bikes.
Trek 7.2 FX.
It is all of $25 on amazon. Toss in another $27 for the rear derailleur.
Compared to the 549 EUR http://www.bikemarket24.de/diamant-achat-herren-saphirschwarz-bern-silber.html
The price difference in gearing alone is where the difference is.
Also includes a bike rack. A lighting system. Seatpost suspension.
Oh, and a 3N20 Dynamo $90 on amazon.
If you bought the Trek and tried to turn the Trek into a commuter bike like the Diamond you'd end up spending more.
Compare apples to apples and then you can do a price comparison.
Here's a 399 EUR one. 7 speed, with dyno. http://www.bikemarket24.de/hercules-13-city-7-nexus-rt-14518.html
Here's another for 299. http://www.bikemarket24.de/kreidler-raise-rt-limited-spectro-7-gang-13811.html?price=3%2C100
Please link to a commuter bike in the US that even close to that feature set for $392.80 AFTER taxes.
I made a mistake and typed 8 instead of 7; Sorry about that.
I found this, but it only goes to 7 gears.
There are a few details that matter for your derailleur.
If neither of the above apply to you, then you can buy just about anything else out there.
If you don't have indexed shifting, or if you do, and you have less than 8 gears in the back, then you can get away with really cheap cables. WalMart and Amazon sell a Bell-branded kit with everything you need for $6.
Take note of the cable routing as you take the old parts off, and use the old housing sections as a guide to cut the new ones (even if you need to make some changes). Also, read this first. You don't really need special tools, but you will need to do some clean-up work on the cut housing ends with a file.
https://www.amazon.com/Top-bike-Tourney-Derailleur-RD-TY300-Direct/dp/B01D2WQ0TM/ref=mp_s_a_1_1_sspa?keywords=tourney+7+speed+derailleur&qid=1572404682&sprefix=tourney+7+speed&sr=8-1-spons&psc=1&smid=A19ZVD46PHVPF7&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExRzRJSFFYOVc2MzZDJmVuY3J5cHRlZElkPUEwNTA4NDI0Mzk3Nlk2NVZJMFRFUyZlbmNyeXB0ZWRBZElkPUEwNDkzNzAwMkYzMUtJMk5OUTVONyZ3aWRnZXROYW1lPXNwX3Bob25lX3NlYXJjaF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
Thank you for your thoughtful response.
Someone suggested this, which can take 34T cogs:
https://www.amazon.co.jp/SHIMANO-%E3%82%B7%E3%83%9E%E3%83%8E-%E3%83%AA%E3%82%A2%E3%83%87%E3%82%A3%E3%83%AC%E3%83%BC%E3%83%A9%E3%83%BC-RD-R3000-GS-ERDR3000GS/dp/B01D8CP9B6/ref=sr_1_1?s=sports&ie=UTF8&qid=1506107852&sr=1-1&keywords=RD-R3000-GS
Will the cage itself still crash, though？
Your shop doesn't ship to Japan, does it? xD
This looks like it might work
https://www.amazon.com/Sunlite-Short-Cage-7spd-Derailleur/dp/B001HD8Q4Q/ref=sr_1_6?s=outdoor-recreation&ie=UTF8&qid=1497773398&sr=1-6&keywords=bike+derailleur
I'm not sure I understand your question, but I use this derailleur with a bar end shifter on a 9 cog 11-34 cassette.
https://www.amazon.com/Shimano-Deore-RD-M592-Rear-Derailleur/dp/B00WJGWJUC
You just need a new derailleur. Basically anything will work, but you can get this guy for $20, you after you swap it over (sort of complicated, but doable with little knowledge), you'll be rolling.