gio_se

Hi everyone!


The derailleur on my bike unfortunately took a bump and got a bit damaged.


I currently have a Tourney TY300 (the damaged one), a Shimano MF-TZ500 7-speed 14-28 freewheel, a Shimano Altus M315-7R shifter and a SINGLE SPEED 52T Crank.


Now, I know that all Shimano derailleurs for MTB up to 9 gears are also compatible with 7 speeds because of the same pull factor.


My doubt is about compatibility with the smaller/larger sprockets on my freewheel.


For example: I would like to mount a more modern rear derailleur, for example the Deore M592.


From Shimano specifications, The M592 has:


Low sprocket Max: 36T

Low sprocket Min: 32T (mine is 28)

Top sprocket Max: 12T (mine is 14)

Top sprocket Min: 11T


The same for most of Shimano's newer 9-speed derailleurs.


But, is this REALLY a problem? Would I have problems with the pulleys touching the freewheel?


(yes, I know I could mount a compatible derailleur like another tourney or acera, but I would prefer the deore)


Thanks!

hokiefyd 

You wouldn't have a problem with the derailer pulleys touching the freewheel sprockets. In fact, with an RD-M592, I think you'll have the opposite problem -- the gap will be pretty large and you won't be able to get it close enough. I don't think you'll have a problem on the small end, despite your top sprocket being a 14T vs. a 12T. I do think your problem will be on the large end, and I don't think shift performance will be as you hope.

Also -- if you have a 52T crank, this may be a folding bike or a recumbent with a small drive wheel (20" for example). You may run into ground clearance concerns with a long cage derailer like an M592.

I'd recommend an RD-M315 or RD-M360 for your application...the M315 has a pretty short cage and will fully support your current freewheel. It would also easily support a 14-34 freewheel if you eventually changed to a Megarange type.

Andrew R Stewart 

The 14-28 cog range is well within the 592's capacity. One usually balances the B screw against the chain length to "adjust" the gap between the underside of the cogs and the guide pulley (and if they do touch it's called "pulley knock"). IIRC the TY300 is/was available in a medium cage and a long cage length. If yours is the long cage version (often uses a "GS" sub designation) than I suspect the chain length won't need changing. But any time one installs a different der some adjustments are likely needed.

Not mentioned yet is whether the der attachment hanger has also been bent (a common result of a crash, a fall over or entanglement in the wheel's spokes). This should be checked and corrected before any replacement der is installed. Another aspect is the cable. The last loop of housing going from the frame to the der might need lengthening, some of the Tourneys had a shorter housing loop then the 592 will want. So a replacement cable and that last loop of housing might be needed. If so take the opportunity to place a drop or two of lube on the shifter pivots and ratchet pawls. Next is the chain. Depending on how the der got messed up the chain can sometimes end up with a twisted link or two. Again this needs checking for and correcting before a replacement der will work nicely. If the chain is already well worn and is replaced, a replacement cog set might be in order too. The last bit is the frame's drop out slot. Although less common than bent der hangers some incidents can pry open the axle slot.

If all is handled well the 592 der should work well. If some aspect is overlooked that der could end up like the TY300. Andy

gio_se

Thanks to both: the current derailleur is the RD-TY300-SGS, long-cage, the bike is a 20-inch folding and the hanger is undamaged.

--Premise: I already have an Acera M360 on the way to at least temporarily resolve this issue, but I wanted to install something more modern and efficient, which is why I would like the deore--

But, after both of your answers now I am even more confused :-D

Hokiefyd: from what you say I might have a gap problem especially on the larger sprocket, so in theory better to stay on definitely compatible solutions like m310 or m360.

BUT

Andrew: from what you say since the bike already mounts a long cage derailleur (and enough cable/housing), I should be able to mount it with no problem (but I don't get the point about the capacity of the 592)

your two versions collide (hence my confusion :-)

I apologize for the doubts, but this is my first time dealing with this bike/transmission.

hokiefyd 

I agree with Andrew R Stewart that the M592 will physically work. What I'm saying, though, is I don't think it's going to work as well as you hope. It's designed for larger cassettes than what you have...and I don't think you'll be able to adjust it so that it'll work optimally with your freewheel. I think you're going to have a sizeable gap between the upper jockey wheel of the derailer and your freewheel -- and the larger that gap is, the less precise the shifting will be. I think the RD-M360 you already have coming will be a better fit for this application.

Oh -- and you're right about the RD-M310 model number (I typed M315). RD-M310 is the derailer to which I was refering.

gio_se

Okay, thank you!

So let's rule out the deore.

Let's consider the Sora RD-R3000-SS (edit: or also the Shimano 105 RD-5701-SS)

If I understand correctly, it could be compatible and at the same time also a good choice as:

1- it has a top sprocket max 14
2- it has a low sprocket min 25
3- it is a short cage so I would have a better ground clearance and a snappier shifting
4- it has a compatible pull factor

All correct?

hokiefyd 

I'm pretty sure you're squared away on all of that above, yes. I think Sora 9-speed (road) is compatible with mountain 9-speed, which means it should work well when paired with the right other parts (like a 7-speed shifter and 7-speed cassette or freewheel). I think some have stated that mixing 7/8/9-speed stuff sometimes doesn't work out perfectly, but I've had pretty good success with it.