ilcaccillo

Hello, everyone

I'm new to the forum, thanks in advance for your help.



I have my beloved bike that was from father. This bike was restored some years ago and new parts were fitted by a mechanic that is far from my hometown nowadays.







It rides very nice, but as there's no front derailleur, the chain is constantly jumping off from the front chainring.

Normally with a bump, or sidewalk, the chain jumps of.



I was thinking in installing a "Narrow wide chainring" as it's recommended by a lot of people in bikes with no front derailleur, but the system that I have installed is completely different than the chainrings I see for sale and also in the youtube videos installation.
I know there's Chain Guides pieces, but I prefer the change for a Narrow wide chainring and I don't mind the extra expense



I don't have this 4 holes for screws in my crankset









And I dont know if this type will work with my crankset setup and crank Arms:







Here is the Cransket system, bolts and crack arm I have at the moment and maybe it's something that is limited to this type of bike, and it's old, I dont know,

But could you please advice my on what Narrow wide chainring could I use with my system? or if I need to buy a new system as if it's possible to install a new system in this bike?

















Thank you so much for your kind help

Best regards



iL

trailflow1

The narrow wide chainrings you listed will not work as they are for mtb cranks.

Looking on google. Your crank is a 'Miranda Single Speed Alloy Track Fixie 1/8" 46T Chainset' with a square taper bb. The chainring isn't removable. It is fixed onto the right arm permanently. So you will need a new crankset to move to NW.

You could buy another track crank with a 5 arm spider. Keep the current BB (if compatible). Then buy a 5 hole Narrow Wide chainring. You'll want to choose a track crank with a common BCD (like 130bcd). Otherwise you may not be able to find a NW chainring.

or you could buy and convert an old triple or double road crank to 1x NW. For a double it might be 110BCD, for triple it might be 130BCD.

or you could convert a old mtb crankset, but those will have a smaller BCD (like 104bcd) compared to road cranks. If you can find a larger tooth like 46t chainring for those BCD's then that's another option.

or you could buy a new generation 1x road crank. Like a Sram Apex 1 GXP, or Rival 1 GXP.

Because your frame is a threaded bb. The options of cranksets are limited to Hollowtech, GXP, square taper JIS/ISO, Octolink, Powerspline. And the BB needs to match whichever crank type you buy.

Iride01 

Sort of looks like you might not have enough chain tension available when in the smaller cogs. Is the chain usually coming off when in them? Might be fixed by removing a couple links.

Kovkov

Get a clamp on front deraileur lock it in place with the limit screws and use it as a chain guide/„jump off preventer“.

blamester

It looks like you have a single speed chainring on there at the moment.
So it should work fine.
It maybe the chainline is off or the chain is very worn.
It should not come off when you hit a bump.
But the simplest thing as was mentioned is a chain guide or front derailleur

dsbrantjr

A chain guide is simple, inexpensive and straightforward. What's not to like?

ilcaccillo

Thank you so much.,
My system is a Miranda Alfat 1 , the chainring is 38T (not 46T)

Yes the BB is square tapper,
and yes the chainring seems to not be removable.

I will buy a new square tapper crank with spider.
Some people recommended me 104BCD, you recommended 130BCD.

I will buy a Race Face NW 38T chainring, they have both the 104 and 130 standard, as a lot of other standards.
Any reason to prefer one the 130BCD over 104BCD or any other standard?

Thank you so much

ilcaccillo

Mostly on smaller cogs (because it's what I use the most), but it also comes off in the bigger cogs.

The Chain is New, as is any component in the bike besides the Frame

trailflow1

It looked like the Track / Fixie version crankset. The design is nearly the same as Alfa 1.

I meant if buying a Track crank then choose one with 130bcd. Because some Track cranks can have weird BCD's like 135bcd, 144bcd. So it would of made it harder to find a narrow wide chainring. There are less options i meant.

It doesn't matter between 104bcd or 130bcd, whichever suites your budget. If you choose a crank with a 130 BCD. Then the smallest chainring teeth size that will fit the spider is 38t. You can only fit bigger rings if you ever want to change the gear ratio's. Something to be aware of.

104bcd chainrings can be as small as 30t and as big as 52t on a 104bcd spider. So any 104bcd crank will give you more versatility. Should you ever want to experiment with the gearing.

Iride01 

New might be the problem then if the chain wasn't properly sized? It's quite normal to take several links out of a new chain to get it to the correct size.

What doe the rear DR cage look like when in the lowest gear (the big one)? If it looks like the picture in step two of this link..... https://www.parktool.com/blog/repair...-length-sizing
then you are probably okay.


If not, go to step four to see the common method for most 2x cranksets which I think is also correct for 1x cranks.


Since you said it has occasionally happened in the bigger cogs, then does it seem like it happens immediately when you resume pedaling after coasting? And maybe tried to shift at the same time?

ilcaccillo

Thank you so much for being so helpfull Trailflow

I think I will change from 38T to 40T now, because I feel that in the small cogs it could be a bit harder seems lighter than what it could be, and it's too light in the bigger cogs.
That's my feeling at the moment for my type of usage.
So going a bit bigger on the front chainring will also help the gearing for my ridding taste.

I will look for some products and show you guys to you can tell me what you think
Thanks

ilcaccillo

Hi Iride, thank for your post.

Here are the DR cage photos in the lowest gear and higher gear






The chain doesn't seem longer, specially on the smaller cog.
But if it's a bit longer that what it should, I might go with a 40T chainring instead of the present 38T, so just that might size it properly.
I will take the bike to the local shop for chain size checkup after I install the new crack and the NW chainring.

Iride01 

Based on your pic with the chain in the bigger back sprocket, I think you need to take a link or two out of it. But without seeing it in the big big without being run through the DR I can't say for sure.

But when you have it in the small rear, grab the chain and see if it has as much tension on it as when it's in the big rear cog.

Yes getting a bigger front will solve that chain length issue. But if your gearing is currently what you want, why change rings to fix this issue without simply removing a few links in the chain which is the proper thing to do. New chains are always longer than needed. They have to be sized for the particular bike they are put on.

ilcaccillo

Sorry Iride, maybe you missed my previous post, the gearing is ok, but it's not currently what I want, I think it could be a bit better, this is what I feel at the moment:

"I think I will change from 38T to 40T now, because I feel that in the small cogs it could be a bit harder seems lighter than what it could be, and it's too light in the bigger cogs.
That's my feeling at the moment for my type of usage.
So going a bit bigger on the front chainring will also help the gearing for my ridding taste."

I pretend to take to a mechanic to check the chain length, and properly size it if needed after I change the parts (changing the chank and chainring I can do it myself)

Thanks

ilcaccillo

After checking all the options on the market, and also the shipping and duty costs and Covid time Constraints (I live in Portugal) I ordered these components:

JIS/Square taper, BCD 110
FSA Vero spider crankset 170mm arm and Rafe Face 40T Narrow wide chainring

Iride01 

I'd put a RaceFace Cadence 2x crankset on my '78 Raleigh Competition. I was very pleased with it. Never had FSA but for cranks I'm sure they'll be more than adequate.

If you still have issues with the chain coming off, you might also sight down the side of the chain ring toward the rear cassette. If it doesn't look like it's hitting about the center of the cassette stack, then maybe your chain line is off too much. Possibly might have to look at the bb spindle length and get another spindle that is shorter or longer on the drive side to get the chain wheel lined up with the cassette properly.

Those old bike frames with thin tubes sure look good.

trailflow1

Looks good. You also need to buy 5 x single ring chainring bolts.

ilcaccillo

I checked that before and it's hitting the middle of the cassette but the angles between rear cassette and front chainring are a bit off.

well I will try it with the NW it might be enough to solve the chain dropping,
I will let you guys know then

Thank you

ilcaccillo

I ordered a race face 5 bolt set also

thanks

ilcaccillo

Installed the crankset and the NW chainring,
the bolts I bought were a bit longer, I should have bought Short bolts but I didnt know.
I'm using some washers for now.

I went for a 3 hours ride yesterday and the bike runs really smooth it's great. The Chain didnt jump at all, it's really stable.
Normally in a ride like this the chain would jump from the front chainring 20 times.

I was also impressed by how smooth and noiseless the Race Face NW chainring is. It's a delight to ride the bike now.

fietsbob

FWIW , I Mix short nuts and longer chainring bolts when needed ...

a bash guard can keep your pants cuff out of the grasp of the chain..