Is this deal too good to be true? m.aliexpress.com/item/…

Seems legit...

Also will this Acera RD-M390 9-speed RD work with a Shimano 8-speed shifter and freewheel?

Seller said "not recommended for 8-speed", but I've read in many places that all that matters is the shifter matching the freewheel, at least for 6/7/8/9-speed drivetrains

I'm trying to replace what seems to be a fake Tourney TX35 that got badly bent by someone. I was able to straighten it to a usable degree, but it still skips at gear 6 and sometimes at 7, also the shifting is quite sluggish and slow. I really hate how it is connected to the hanger with a piece of steel that acts like a second hanger and could also bend slightly and ruin shifting performance, while unlike the hanger, it is really hard to straighten.

While I'm not sure, I think that the chain slips by riding on top of the sprocket teeth, and once it is disengaged from all teeth it would skip a link distance and fall back into the sprocket and engage with the teeth. It only happens when under load, so it is quite hard to diagnose. Does this mean that the derailleur is actually fine, and the problem is in the freewheel? I doubt the freewheel is worn because it is quite new.

The chain is also new. I measured it and found no stretch.

Well, the whole bike is quite new, and I've been using it for around 3 months now.

@toonie aliexpress is a gamble - I've lost money there before. It will be a knockoff.

Hmm wiggle and CRC don't have any 9 speed mechs

Wow talk about arrogant resellers

I'd suggest you rock down to your LBS and talk to them

Also look around your location for a bike cooperative.

For $14 you could try that mech, but don't have high expectations. Though being non-bent would be better than a bent one :)

Found an alivio 9 speed for $70 NZ. torpedo7.co.nz/products/SHDRRN540/title/…

I can't find an acera grade one, or a tourney grade (which is second to bottom)

A deore is $5 cheaper than an alivio for me... interesting

Ahh a TX35 is $23 NZ locally.... trademe.co.nz/1954427788

I see what you mean about the crappy hanger-hanger

@Tooniis well there's my stream of consciousness on the problem

I'm looking for 8-speed derailers not 9-speed ones. The only reason I'm asking about this one is because of that deal. Notice that I asked about whether it would work with an 8-speed shifter and freewheel or not.

Also please don't get me started on the lack of "LBS"es as you know them in this country. I like to call the bike shops here toy stores; as they sell more kids toy-grade bikes than real bikes. Also over here if anything other than an inner tube breaks in your bike, you either get a new bike and throw the old one, or accept getting an overly priced piece of crap that has poor performance and will not last 2 months. And even worse, you can usually only choose the first choice.

It's ironic how I tell you not to get me started, but I start anyway

The bike I bought had loose spokes, a bent hanger (which I straightened later myself), and the handlebar was slightly misaligned. I bought it anyway because it's impossible to find a better bike.

sorry to hear that - yeah I misunderstood the 8/9 speed point

So, 6/7/8 speed all use the same "gap" between cogs

but 8/9/10/11 do not have the same space between cogs

so a 9 speed mech will move across the same total width but the cable pull would have to be for an 8 speed (ie the shifter has to be 8 speed)

for the price its probably worth trying

You can always order stuff from Wiggle or CRC or any number of on-line shops. The cost of shipping is often waived if you buy enough.

@Tooniis How about this one ?

cycleomania.com/product/…

Right - its 0030 on Wednesday here and i have work in the morning

@Tooniis good luck with the shopping !

Alright. Tyvm for all the info.

bicyclerollingresistance.com/specials/…

Rolling resistance of GP 5000 23 to 32 mm. Good read.

Yeah - still a price premium.

I just ordered 4000 on clearance

cos they're 1/3 the price

They are steals now.

Unless one needs tubeless or three new sizes the old ones are as good as the new ones.

Shimano 140mm XTR brake rotors cost only EUR30. That's the typical price for SLX rotors.

I wonder if I ought to change to 140 mm rear. Rely on the cooling fins to compensate for less heat dissipation.

Oh dear.

The small stuff needed for the new wheel set did cost another 150 quid.

Ouch what else did you need?

rotors, cassette, skewer, valves

ohh yeah fair enough

and i always used the slightly more extravagant of the two or three options on my shortlist

may as well add new rather than reusing the old stuff.

yep - not duraace but not tourney

however, the wheel build was 40 cheaper

in the middle.

adapters for my present rotors would cost half as much as new rotors.

how worn are your old rotors ?

cassettes are tedious to swap,

and i didn't like my 11-42 all that much.

Did you go new chain at the same time ?

next to no wear whatsoever.

still got two spare chains.

I'll run down this chain with the old wheel set.

I'll keep knobby tyres on the old wheels.

but with disk brakes its no quick swap between wheelsets. requires faffing with caliper alignment.

I wonder how the pro's do it with their wheel swaps during races.

perhaps their high end stuff is to such fine tolerances it doesn't matter.

Multiples of the same identical wheel, tso minimal variation.

More likely, it isn't and the riders must not complain.

I don't buy that.

heh I'm sure the pros complain to each other.

sure, but have you noticed how they do it now?

Apparently they talk a lot in the bunch.

Nope - have I missed something ?

Pro mechanic in an interview. Disc brakes are wonderful. With our new formula one tools we brought down throug axle wheel change from 15 team cars passing down to 11. Its as good as QR/rim brake where 7 passed.

hid their criticism in an article about their super cool new battery powered drill with hex bit that holds the TA.

The stars get replacement bikes.

The domestiques probably have to live with brake drag.

I mean with IS 6 bolt rotors its sensitive to not torquing all bolts within something like 1 Nm.

Heh or manually twiddle the brakes while riding ?

worked with rim brakes.

I've seen pros fiddle the caliper rim brakes while riding

I suppose some would be up to pack out their torx driver and play around at the caliper at their drop outs.

I'm pretty negative here.

Disc brakes have their good sides.

However, they aren't that far better than rim brakes.

And there are quite a lot of drawbacks.

the balance between those gets worse the less muddy and rough the terrain is.

I neglected aero though.

A little disc rub now and then causes probably less drag than what is gained by discs aero benefits.

better rim profiles, smoother flow at for crown, rotor/caliper where air flow is already turbulent.

Fair enough - I've never owned disk brakes... beyond my budget :)