UKC

I have an old (more than 10 years) Decathlon mountain bike that I use for commuting, and it needs a fair bit of work.

I need to replace the whole drivetrain so for simplicity I'm thinking about converting to a 1x setup, but is this a good idea?

I'm looking at a 32T chainring with a 10-speed 11x36 cassette (all Shimano), obviously replacing chain, cable and shifter too.

My commute is all on road with a few hills, but in a big city so it's very stop-start, and I'm rarely above 30km/h.

A 34 chainring might be better if I can find one. Any thoughts?

In reply to James FR:

If your chainrings are bolted on it might just be a case of removing the chain rings you don't need and replacing the middle one with a compatible 36t chainring. You could then fit a bash guard where the big chainring was. If it's riveted together you might need to change the whole crankset, you will need to know what kind of bottom bracket you have.

In reply to James FR:

How many cogs on the cassette at the rear currently?  And what is the rear axle type/spacing?  This will determine what is possible.  You'll also need to see if a 1x front chainring is available for your crank spider type.  1x without a proper narrow-wide chainring to retain the chain would be tedious I think.

Chainring size will depend on what wheelsize you have and tyre type (road/gravel vs slow nobbly).

In reply to James FR:

10 speed might fit the old freehub if it is Shimano HG or compatible.

https://off.road.cc/content/feature/which-freehub-body-do-i-need-sram-shima...

In reply to James FR:

I ride a 32 chainring with an 11-40 cassette. I love the one chainring setup with a wide range rear cassette. Other people prefer the smaller jumps between gears a closer cassette provides. My system would work much better with a 10-50 cassette but they're not commonplace yet, Sram do them but they are very expensive.

In reply to jiminy483:

If you have an 11-40 cassette you could consider a 11-46 or even an 11-50/51 to get a wider range however you would possibly need a longer cage mech or goatlink to allow this with the 50 tooth option. Lots of cassettes widely available in this range. 

In reply to sxrxg:

It's more the 10 part than the 50 part, 40 is nice 50 would be nicer but I can manage. 10 on the bottom however, that one tooth makes quite a big difference to the bottom end, with a 10-50 I'd swap the 32 for a 36 up front and still have higher and much lower gears. 

In reply to sxrxg:

Also I'm running 9 speed so would need new shifter, chain, mech and the cassette!

In reply to jiminy483:

Highly possible you might need a new back wheel too, depending on the hub. Honestly at this point it's probably cheaper/easier to just get a new bike, set up 1x already. Assuming you don't need a wheel: for hilly commuting on a road/light gravel the absolute dinner plates being suggested here are totally unnecessary. You'll want AT MOST and 11-40 on the back, maybe even an 11-34, and a 40T chain ring. 

In reply to James FR:

Just take the front derailer off. 9 speed is overkill for a city commute.

In reply to jiminy483:

You could look at a 11-46 9 speed cassette, should work with current hub (and possibly mech but this might depend upon cage length). Then put a 36 upfront. Would give a slightly harder ratio than 10-32 for speed and then be slightly easier at the other end of the range. Only compromise would be the larger jumps in ratio between gears. 

In reply to James FR:

Some notes:

- 1x without a proper narrow-wide chainring is a ball-ache, the chain will fall off at the slightest bump unless you have a front derailleur or chain-guide. Narrow-wide chainrings are unfortunately not that cheap.

- When you get a new chainring make sure of the number and diameter of the bolts on crank before buying. Also, as another poster said, make sure you can actually take the chainrings off, some cheaper cranksets have the rings riveted on and are not replaceable.

- Installing one chainring on a 3x crankset requires shorter bolts and/or spacers. You can buy nice spacers that make it look neat, or just bodge it with some suitable washers. A pin tool helps to remove and install the bolts, but you can usually make do with a screwdriver and allen key. Make sure to install the single chainring in the 'middle' position.

- 32T x 11x36 sounds about right given your route. 34T would also be fine but is harder to find. 36 on the back is absolutely fine as long as there are no proper hills.

- The freehub width for shimano 8, 9 and 10 speeds is the same. So if you already have a shimano setup then you can just replace the drivetrain and not worry about the wheel or freehub.

- Good for you for keeping your old bike going. I dislike posts that say "you might as well just buy a new bike". If the rest of your bike is perfectly fine, then it's great to keep it running!

In reply to James FR: I converted an old road bike triple to a single. I just removed the derailer and outer ring. I kept the inner ring in case I need it for large hills so I can kick the chain down and then manually put it back on. 

I have had the chain slip off a few times but only if I am changing a lot of gears quickly, so I have gotten used to this.

Hope this helps. 

Euge

In reply to James FR:

1x has the following advantages

• on a FS bike as it simplifies the design of the suspension around pedalling loads from different sized chain rings.
• Improves tyre/mud clearance 
• reduced maintenance, only 1 gear cable, shifter
• Front derailleurs are prone to clogging with mud and sticks when bikes are ridden offroad.

1x has disadvantages

• requires enormous cassette sprockets to give the same kind of low gear as you get with the granny ring on a triple, which are more expensive than traditional sized ones.
• large steps between gears, this has sort of been mitigated by the moved to 12speed

What drivetrain does the bike currently have?

What BCD is the crankset, does it even have removable chainrings?

Is the existing drivetrain actually worn out, have you used a chain checker to see how worn it is?

I fitted a 30T front ring and ran that with an 11-36 cassette, this was more than adequate for 30km/h as long as your learn to spin the pedals rather than grind away. And the gears were low enough that I could still spin up 10% gradients

Shimano is the way to go on a budget, SRAM's low end stuff is plasticky and wears out very fast in my experience.

In reply to ianstevens:

It's a mountain bike.

In reply to sxrxg:

It's not worth the cost atm, I don't even ride it as getting anywhere good involves long stretches of country roads and I'm terrified of riding on roads having been smashed by cars on a couple of occasions.

Might upgrade the lot if I can get a house near the hills. Or I might just get an electric mountain bike because I'm lazy and old and they're more fun for me.

In reply to Alun:

I agree but this is also a bike industry problem in that new bikes can be bought for a lot less than the price of the components, even without factoring in the labour time.

And yes, I am justifying my own recent purchase of a new bike! (although I'm going to do up the old one and pass it on anyway)

In reply to James FR:

How about going the other way...? Fitting 3-ring front to a modern bike...?

In reply to jiminy483:

Used for commuting. In the city.

In reply to James FR:

To be honest, unless you've got most of the bits lying around already and it's all compatible you'd probably be better to just buy a new bike. Basic functional commenter bikes are pretty cheap these days. 

In reply to all:

Thanks for all the replies and input. I know it would probably be more sensible just to get a "new" secondhand bike but I'm trying to see if I can get everything working again for not too much money, and educating myself at the same time.

To answer some of the questions:

The current crankset is also going to be replaced, the chainrings are very worn and are indeed riveted on. The bottom bracket (square taper) _seems_ okay and I don't think I could remove it anyway.

The rear dropout spacing is 135mm with an 8 gear cassette so it's hopefully okay to take 10 gears.

Wheels are 26" (yes, it's an old bike) with 26 x 1.5 Marathon tyres.

At the moment the cost is roughly 150 euros (crankset + rear derailleur + cassette + lever + chain) which for me is close to the budget limit. If I go for it I'll report back here.

In reply to James FR:

If you search eBay for "SHIMANO Deore M4100 1x10 Speed MTB Groupset" you'll find some groupset options within your budget.

Not sure about the quality of the non-Shimano stuff mind you. As Gary Fisher said: "Strong, light, cheap. Choose two"!

In reply to ianstevens:

I was talking about my bike.

In reply to James FR:

One of my bikes is a Shimano Sora 1x9 with 42t NW chainring in the front and a 40-11 cassette in the back. Works like a charm, the only annoying thing is the big jumps between gears. I'd say this is somewhat mitigated by going to a 10 speed of course. 

Does that 150 euro budget estimation include a narrow-wide chainring? You're going to have a bad time without one. 

In reply to NorthernGrit:

Perhaps the solution is a cottage industry buying new bikes and breaking them for parts?

In reply to James FR:

Sounds like a good plan. I converted my 3x9 MTB to 1x9 a few years ago, it was very straightforward to do and works like a dream.

I changed to a narrow-wide 32 tooth chainring, mounted in the middle position on the triple chain set, and bought a 9 speed 11x40 cassette.  At the low end of the gears it is fine, you're going so slow that you may as well walk at that point.  At the top end you'll find that 32x11 is a bit low and you'll spin out on the road especially with 26" wheels and slick tyres so see if you can get a 34 or 26.

10 speed setups have clutch rear mechs which I don't have on my 9 speed setup, I was worried that this might be a problem but in practice I've never lost the chain, the nw chainrings work really well.  I have 1x11 on my other bike and just leave the clutch turned off as it is less noisy and no problems there either!