3x to 1x conversion
 

Hi All,

I have an older Scott Metrix 40 that I'd like to do a conversion, 3x8 speed to a 1x10 speed. I'm using the bike on roads and paved trails 95% of the time, and the reason I want to do a conversion is I'm unhappy with the stock components as the shifting is pretty crummy/unstable. I thought I'd simplify by going to a 1x, and I'm looking to upgrade to better components for improved shifting and stability. I realize this means new cranks,derailures, levers etc.

Can anyone point me in the direction of compatible components/groupsets for doing this? I'm happy with my rear wheels (Shimano FH-RM 30 hub) and the bottom bracket is Shimano BB-UN 26.

I don't care about weight, I care mostly about solid dependable shifting. If anyone has done a similar conversion or can make a suggestion it would be greatly appreciated. Additional bike specs at bikeroar metrix-40-solution-2014/specs

Thanks in advance for any help or suggestions!

If you are going to ride both paved roads and unpaved trails with it then you will really be limited in range of gearing. You'll either not have a low enough gear for off road. Or you'll not have a high enough gear for paved roads.

Shimano has a bunch of 1x mtb cranks with varying sizes of chain rings if you look on their website. You'll have to match up one that will fit your BB shell. I wouldn't necessarily try to stick to your current BB. You'll limit your choices in cranks too much for what is only a 18 dollar part. Assuming of course your BB shell can handle other bb types like ISIS, Octalink v2, or even 2 piece cranks. SRAM has some too as well as many other crankset mfrs.

So what's been the problem. If your shifting problem isn't on the front, then you'll still have a shifting problem whether 1x or 2x, 3x or no x.

Thanks Iride01 for such a quick response and the info. To answer your questions-

The riding I'm doing is mostly urban roads/paved trails and I'm not using this bike for any mountain biking. I'm not too concerned of limited gearing. As a test I've been riding on the middle front sprocket (32T I think) of my 3x and the 8 in the rear can cover most of my needs. This is why I'm thinking a 1x10 can work for me. I'm also trying to limit variables that can malfunction and simplify the bike as much as possible.

I hear what you say about shifting. For me the problem has been gears that slip and shifting that is clunky. I've had the bike serviced and everything works fine for a few months and then the problem is back. The groupset is Shimano Acera and techs are telling me you get what you pay for. Or maybe gear adjustment is a constant battle no matter what you use? I've had bikes in the past but none that have functioned so poorly.

I really just want a bike that is stable and works properly.

I recently completed a 1X conversion, from 3x8 to 1x8, detailed here:

Converting Trek FX2 to 1x - Bike Forums

Most relevant portion starting at post #17. Four suggestions:

(1) You can break this project down into two steps: (a) Going to 1x8; (b) Going to 1x10. That way, if step (a) fails, at least you should be able to revert without having already bought everything you need for step (b).
(2) A new crankset is only necessary for your 1X conversion if the chain rings are riveted onto (and thus not removable from) the right crank arm, which seems to be the case (Scott Metrix 40 Bike - 2014 | REI Co-op). I used the Dimension Cyclocross crank arm set linked in my post. You can use the same (but with a 10 speed chain ring).
(3) Not strictly necessary to change the bottom bracket if you don't mind using the middle ring position of the Dimension Cyclocross crank arms, which is not as clean looking as using the outer large ring position. (But, if it were up to me, I would take the opportunity to upgrade from a Shimano BB-UN26.)
(4) For step (b), you will need a new cassette, chain, rear derailleur, and shifter (all 10 speed). Shimano 10 speed components are cross compatible, so these four components do not even need to be from the same groupset. Just make sure the rear derailleur can handle the max rear cog. Other than that, it largely depends on how much you are willing to spend on this bike.

I realize you probably won't believe this, but there is no reason your 3x8 shouldn't shift perfectly, if all the parameters are good, cables, housings, shifters, derailleurs , rd hanger not bent.

acera, alivio, it all works perfectly well if everything is good. We have a number of similar bikes in our household like this that just plain work perfectly.

Thanks so much for the detailed info SoSmellAir! The 1x8 might work and is something I should consider. Cranks are riveted so will need a change, and I'm with you on the opportunity to upgrade the BB. Much appreciated!

I totally believe djb , but I am one of the few impractical people who have spent actual money to reduce the gear range of my hybrid bike for the sake of simplicity and a clean look, and I would even admit it was more for the latter (because Shimano Tourney 3X crankset is just ugly), so please just let me lead pumpkinhed down the wrong path too.

The un26 is a good quality bb, do you own the tool to install it? Is the present bb a ball bearing one?
are you interested in doing this yourself?
re using the present crank, I've seen photos of people who have used a grinder to grind away the big ring teeth, and presto, built in chain guard.

get the rd hanger checked in case it's bent.
have you ever changed housings and cables?

I am not discouraging a 1x10 setup at all; I am merely pointing out it would be slightly less imprudent to first succeed at 1x8 before buying all the remaining components needed to further go to a 1x10 setup.

Smelly, I think this project will come down to whether the person is willing and able to do it on their own.
will require buying tools and some mechanical talent

also, it's very possible the rear hub can't take 10 speed
I have a cheapo schmeapo commuter bike, 7 speed, wanted to go to 9 , but the free hub is too short, I'd have to change it. Not worth it for what I use bike for, it has a riveted triple too. But i just it as is.

Hi djb and thanks for the reply. I agree with you, as my former bike was acera and I didn't have any problems with it for many years. It was an old bike (klein mtb from the 90's) but the shifting was solid. With this new (to me, I got it used) bike I feel the parts build quality is cheaper and I'm not getting any feedback from mechanics who have looked at it in regards to shifting issues that some parameter is out of spec. All I can chalk it up to is cheap parts.

I'm open to any ideas on what might cause a bike to need monthly gear adjustments. My expectation is that I should be able to run through all gears without issue. When I got it back from the shop (I've taken it in twice) after adjustment, everything shifts great. A month or so later gears are jumping. Maybe I need to find a new shop. My former bike was not like this, and I'm looking at it as 'they don't make them like they used to', or maybe I got a lemon.

Maybe the question I'd ask back to everyone is, if you're bike is behaving like mine, what should I be looking at?

My other question would also be if the lower quality components work fine, why does anyone upgrade? Is it weight?

I'm not a racer but I ride hard/fast on bumpy urban streets and my bike gets rattled a bit. My reasoning for an upgrade is function/durability. I don't race so weight doesn't matter.

I cannot speak to pumpkinhed 's talent (or lack thereof), but assuming that he has a basic wrench and socket set (for more than decorative purposes), the Park Tool crank puller tool is $15, and the Park Tool bottom bracket socket is $19 (both at REI). So not an exorbitant sum.

According to REI (see link above), the Scott Metrix 40 which pumpkinhed has comes with a Shimano Altus 8 speed 11-32 cassette, i.e., Shimano CS-HG31, which is the same width as a Shimano 10 speed cassette, which thus should fit the existing freehub.

Agreed. A 7 speed bike usually has a freewheel instead of a freehub, which makes most drivetrain upgrades not worthwhile.

The money you spend on tuneups could buy you a housing and cable cutter, change all the housings etc abd and that might be the issue, could be all kinds of stuff, could be a battered old bike with a beat up rd , rusty shifters, you name it.

We can't tell from the interwebs, so it's on you if you want to learn bike mechanics, a local bike coop would be the perfect place to look up, tools to use and knowledgeable folks to help you.

What shifting issues are you experiencing? Front or back or both? Hard to diagnose without lots more details. The "cheapest" (perception, not actual cost) component in the drive train is the Shimano FC-M171 48/38/28 crankset, which has riveted chain rings which flex under load. This is the prime mechanical reason for an upgrade or 1X conversion.

When my hybrid was 3x8, each chain ring can really only "use" 6 rear cogs, as follows:
when chain is on small chain ring, the 6 physically largest cogs, i.e., 1st through 6th gears;
when chain is on middle chain ring, the middle 6 largest cogs, i.e., 2nd through 7th gears;
when chain is on large chain ring, the 6 physically smallest cogs, i.e., 3rd through 8th gears,
which I understand is to be expected due to the limits of cross-chaining. Deviating from the above use led to noisy chain, regardless of adjustment of front and/or rear derailleurs.

After going to 1x8, no more FD to rub against, so 2nd to 8th gears are smooth, but 1st gear is still a little noisy due to cross-chaining. Again, this is to be expected.

curiously my commuter isn't a freewheel, but while it's a 135 hub, the free hub is short and can't take 9 speed, I'd have to change the free hub, which I just never did,

What shifting issues are you experiencing? Front or back or both? Hard to diagnose without lots more details.
The shifting issues I have specifically as possible is I shift, the gears shift, and all seems ok for a second and then a clunk. After the clunk its staying in gear but feels like it skipped teeth at the clunk. Or sometimes when I shift it's a clunk and teeth skipping right on the shift. before settling in the gear. It's such a big clunk I run through the gears to see if there's been a skip, but no skip so far. All rear gear changes. I'm trying to reduce variables by not even switching the front. The clunk happens under heavy load and on flats under minimal load, and also with different gears. Seems to happen unpredictably. This would make me think bad derailleur or teeth on rear, possibly chain. Whatever it is the chain isn't being placed properly and making such a hard shift I'm concerned about breaking the teeth. Teeth look fine (so far), cassette is clean.

1st gear is still a little noisy due to cross-chaining. Again, this is to be expected.
This is interesting, I might have unreal expectations. Maybe I'm expecting seamless gear changes, or wondering if this is possible with an upgrade.

Thanks for all the replies!

Some specific product recommendations are that I've been pretty impressed with the Microshift Advent 1x9 drivetrain I recently bought for next to nothing off a customer and threw on my hardtail that previously had 2x10 shimano gearing. In my case, I mostly appreciate that I now have a clutch, but it honestly just works fine. For 10 speed they make AdventX.

I recommend against spending money on a new drivetrain that wasn't really designed for 1x. This rules out basically any Sram 1x10 setup and most Shimano (except some of the most recent, like RD-M6000-GS, which is rated officially for up to a 42t large cog).

Generally the price of 11 and 12 speed 1x drivetrains has dropped a lot, making a lot of 1x10 setups not really that attractive by price (except the aforementioned Microshift options), but availability is weird. In particular, I'd avoid any 1x12 Sram setups in particular right now because parts availability is projected to be bad for quite some time yet.

If you want to get your existing drivetrain to work rather significantly better, you can probably get an inexpensive Shimano Acera or better derailleur or most any 8 speed Microshift derailleur and set it up and resolve your shifting issues. Shimano Tourney level derailleurs really are pretty garbage and shift unimpressively under the best of circumstances. Most front derailleurs are fine, but again, not that expensive if there's genuinely something wrong with it. If you want to try an intermediate step to see how you like 1x, get a new crankset with a narrow wide 1x chainring, and a slightly better rear derailleur set up correctly. Since you have a riveted crank, don't worry too much about getting a crank that will work with your existing bottom bracket length, although if you do, yahtzee. You can still stick with a relatively inexpensive square taper crankset. You can keep your FD in place as a chain guide to make up for the lack of a clutch, adjusted in place using the limit screws.

Four things to check based on my fairly limited experience:
(1) Does the shifting issues happen both on the work stand and when actually riding? If only the latter but not the former, maybe the cable tension is just slightly off, so you can experiment with that setting.
(2) Did someone install the wrong speed chain (too narrow) during a prior maintenance visit?
(3) Are the rear derailleur pulleys lubricated, mixed up, or installed in the wrong direction (in the case of the tension pulley, i.e., lower pulley at distal end of rear derailleur cage)?
(4) Chain and/or cassette are worn out?

When I said "noisy" in first gear above, I meant noisier due to slightly increased friction, not random clunks, which should not happen. What you call an unreal expectation, it is actually somewhat expected during the pandemic, as people cycle more and get more in tuned with their bikes' behaviors, so one would more likely notice things that are off compared to the past when riding less frequently. Assuming drivetrain in good condition and properly adjusted, Shimano hyperglide gear changes should be pretty seamless.

If you want seamless gear changes, then maybe you should consider an IGH hub.

Some of the shifting issues you describe are partly that maybe you are shifting when at a very very low cadence and putting a bit of muscle into the cranks. The slower you are going with cadence the easier you need to be on the pedals when shifting. If you are up around 85 rpm or better, then you should be able to get smooth shifts at most any power output. At least that's been my experience, though I can't say I've had issue at low cadence, though I don't try to muscle through a pedal rotation at 30 rpm while trying to shift.

And if you want to know if a 1x crank will solve your problems, then don't shift the front.

If this is a 3x bike, then leave it in the middle ring of the front as that is about the tooth count that many 1x are.

spot on with what SoSMellyAir said. I did the same with my 2014 Trek X Caliber 8. I bought a Shimano Deore 11 Speed Cassette, derailleur and shifter and an Oval chain ring for the front. Works like a charm and has plenty of range for mountain biking as well as most road rides.

By the way, according to this (Scott Metrix 40 Bike - 2014 | REI Co-op) the stock middle chain ring is actually a 38T.

Thanks cpach!

I recommend against spending money on a new drivetrain that wasn't really designed for 1x.
Good point, something I had not thought of.

I also hadn't considered Microshift so thanks for that too. On the rear hub I can only fit 8-9-10 cassette, even though it limits me to the 10 option. I'd certainly have more choices if 11 or 12 were possible.

The current derailleur is Acera, so if it is the culprit, I'd be looking for a different one. I appreciate all the ideas and scenarios you're running through, options I didn't think of.

Thanks Iride01. I definitely am not familiar with IGH, and not sure there's enough range in the gears for what I'd like. The streets I ride on can be steep in both directions and change from flat to climb pretty quickly. You might be on to something regarding technique. I'm pretty sure my shifts are happening below 85rpm, although I don't keep track of my rpms to be sure. Technique could be part of the problem. But as I've mentioned earlier, I had an older bike that shifted without the clunks I'm hearing now, and my riding hasn't changed enough to account for shift issues. This is why I thought a mechanical change is needed.

You can definitely use an 11 or 12 speed cassette on your freehub. While originally labeled 8/9/10, 11 speed hyperglide freehub bodies are pretty much a road thing. MTB 11/12 speed hyperglide compatible cassettes get away with this by dishing the large cog somewhat inbound of the spokes, which works because they're friggin' huge compared to cassettes traditionally intended for 2x/3x use and the spokes angle in towards the rim, creating more clearance with big cogs. So your options are pretty much any Shimano 11 speed MTB cassette, any HG compatible Sram cassettes (usually NX level or lower, GX 11/12 speed requires a XD driver), and any Microshift cassettes. Shimano 12 speed cassettes need a microspline driver, although the cog spacing is the same so technically you can run a Shimano 12sp shifter and derailleur with a Sram/Microshift 12 speed cassette, chain, and chainring if you really need to.

Why not? I am just curious, not trying to be argumentative. The two 1X specific features which I have read the most about: (1) a chain ring with alternating narrow and wide teeth; and (b) a rear derailleur with a clutch and/or damper, are designed to reduce the possibility of dropping the chain on bumpy cyclocross / gravel rides. If the OP does not ride on very bumpy surfaces, then a chain guide (e.g., as shown in my 1X conversion thread) may be sufficient, right?