Redbullet

Hello,

After a few hours of trial and error, I managed to fine tune a cheap new transmission on a road bike (the front derailleur was the most complicated, by far): Prowheel Ounce (triple) 50/39/30 crankset, Sunrace 8x, 12-25 cassette, Microshift shifters and derailleurs. Now it can be used with almost all combination. The chain barely rubs the front derailleur in 30/12 and 39/12 ratios, but even those are almost usable. With 50 chainring, it covers (at the limit) the whole 12-25 range, without rubbing.

However, the transmission exhibits a high noise (similar with rubbing noise, although the chain does not rub), in the range 50 x 19, 21, 23 and 25. Bigger the sprocket, higher the noise. With 50x25 (although rarely used because this is cross chain) it is quite annoying.

What can be the reason? Is there a secret to make it quieter? Could the chain be too short and stretched (although it looks that the rear derailleur still have a little spare room, maybe up to 26 or 28)?
Or… cheap price – high noise and that’s nothing to do about it?

Thanks

Slash5

Measure your chainline from the middle ring and let us know what it is. As the parts wear in it should get better.

Andrew R Stewart 

I wonder if the pulley wheels and chain are the cause of the noise. Is the rear der hanging vertically? Is the cage and it's pivot square to the der (or is the cage parallel to the rear wheel plane as the cage rotates around it's pivot)? Does the freewheel have a lot of "float" as it revolves? Noise being greater in some combos is normal and some noise will "wear in" over time. Andy.

Redbullet

Thanks for the answers. The chainline is around 44-45mm to the mid chairing and about 50mm to the large one.
Visually, the cage of the rear derailleur looks to move ok (although visual observation is not quite accurate).

I could not translate the word "der" . What is that?

During free wheeling, the cassette wobbles a little - probably less than 1 mm.

I noticed that only with the large chainring, as the rear derailleur streches for bigger sprockets, the chain starts to touch the first pulley wheel a little de-centered, before it lays on the pulley wheel's teeth. It happens gradually, only on the noisy sprockets: 19, 21, 23, 25, with 50 chainring. I thought it might be normal, as the chain starts to be "crossed" once it heads toward the biggest sprocket.

mconlonx

The Microshift shifters have a trim function. Which is a half-click which occurs without shifting, but which positions the front derailleur cage either a bit further out from small chainring, or a bit further in from the large chainring, to minimize chain rub when cross-chain ratios are chosen.

With the noise you describe in the 50 x [larger cassette cogs], try this: at the front shifter while on the 50 ring, depress the gear release lever lightly so that it clicks without shifting. If there is not appreciable movement at the front derailleur or if you can't do that intermediate click without it shifting down to the middle ring, loosen the cable tension adjustment until you start to see that movement without a complete shift. That should help with some of the middle gears.

But if you can tune chain rub out on the low end, chances are that the chain is very cross-chain in the biggest ring and you may not ever be able to completely tune out chain rub in the lowest gears while on the 50t ring. Note that there are many duplicate gear ratios with a 3-chainring setup, and consider chain rub notice to switch to the middle ring while riding.

Redbullet

Thanks for the answer. I did not know about that trim function - I thought it was some shifting failure....

However: I can do that small move without shifting only by the big lever when the chain is on the 30t chaimring. It moves the front derailleur toward 39t, but without shifting. That helps to use the smallest chainring with the smallest sprocket (30x12 ratio).

I can't obtain a similar trim with the small lever (with the chain on 50t there is no fine trim available with the small lever, to move the deraileur towart 39t without shofting). And that - regardless of cable tension adjustment.

Is that a malfunction?

Andrew R Stewart 

"der" is short for derailleur. Chainline is the relative center of the front rings and that of the rear cogs. Ideally in a perfect world both front and rear centers would be the same distance from the frame's centerline, or be in line WRT each other. In real life some small amount of offset (miss matched chainline) can exist with little to no issues. But this is not a straight forward thing. Andy.

mconlonx

It may be. I set up a friend's bike with 2 x 8 microshift system and it had a trim function as I described. I don't know for sure if the 3-speed front shifter has the same trim function. But I assume it does. Next issue I would look at is the outboard/High limit screw. If it is too tight, it might also interfere with the trim function, but if it is working with your current setup, I would think that is adjusted just fine.

Maybe someone else can chime in on whether or not the Microshift 3x shifter should have a high-trim function?

Redbullet

Thanks for the answers.

I asked Microshift about trimming. Their answer is that 3x8 shifter has only one trim position, and that is for the small chainring.

It finally looks that the noise is somehow normal and it probably will decrease a little once the transmission wear.

In fact, I probably had wrong expectations, comparing the noise of this transmission with a double SRAM Force 11, which is much quieter. But since this is a triple Microshift / Sunrace combination abd costs a fraction of that SRAM, I should probably accept that it delivers a good performance for the money.

Slash5

You mention the new parts but not a chain. Is the chain new? Also, could your chain be too tight - when you are on the large large, do you have chain slack? Can you lift the rear derailleur bottom cage and get chain slack?

pressed001

I agree with this. If the chain is new, how did you size it? What works best for me is smallest gear to smallest gear. Just long enough so to avoid rubbing between chain and RD cage (pully).
Is a 50mm chain line OK? I don't know. But it sounds like you have a pretty skewed line from what you say about the chain and pully. I don't know if there is a way to fix this. I assume your BB is octalink or square tapered and in that, it is not spaced.

Redbullet

The chain is new and it was sized by the bike producer (I only fine tuned shifting, which was not carefully done by the producer).
In 50x25 (maximum) position the chain is tensed because the rear derailleur spring is quite strong in that position. However, I think that it could further accept a 50x28 ratio.

On the other hand, the chain is skewed in 50x25 position and this ca be seen especially at the pulley wheel level (at the maximum streched position, the distance between pulley wheel and chainring becomes much smaller and this makes the chain to be quite skewed). I think the system could syill work with a longer chain (one further link). In such case, the distance would be a little longer and the chain a little less tensed. Maybe also less noisy?

Andrew R Stewart 

It's possible that an extra link of chain (actually tow 1/2" links) will help quiet down the system but not by much. What also might happen is to change the cog/upper pulley gap which is a vital aspect of shifting and noise. If the pulley contacts the cog's underside grinding/"pulley knock" happens. better ders have a screw which adjusts this gap to a degree. So chain length is a balance between a few situations.

But to your above post "the chain is skewed in 50x25 position". It is a good idea to avoid the cross over combos. The chain angles and the der cage's being fully played out or trying to take in all the chain will make these combos work less then ideal. If you were to do the math of figuring out the actual gear ratios in each cog/ring combo you'd likely find that the cross over combos are near duplicates of other cog/ring combos which will have far straighter a chain line. Andy.

Redbullet

Fully agree.
In fact, even if It has 22 usable speeds out of the 24, this is also far less comfortable than 20 usable speeds on a 2x11, because you have to navigate over 3 chainrings. I’ll search to add one more link to the chain, if I find one at a bike repairs shop - and that's all. Overall, I think the bike will meet the objective: a cheap and resistant bike for very light off road routes and for indoor trainer. And I have a feeling that those components might last for many thousands km, even if they are cheap and noisy.

pressed001

Make sure you don't make the chain too long. Put it in smallest cog front and rear and you will see if this is possible. I also agree that staying out of the cross chained gears is the best idea. Stay middle up front and smaller (higher) gear in back to avoid this high angle.