Hi guys,

I have a BTWIN Rockrider 540 that I am converting to singlespeed. So far, I have the sprocket and spacers ordered and the chain from Amazon. I have two main questions that I hope can be answered. I am a complete beginner at bike engineering so forgive any ignorance that may come across.

Q1. I am aware that because my bike has vertical dropouts, that I'll need a chain tensioner. How can I go about figuring out if this will attach to my bike or not? I took the rear derailleur off and it appears I may need a derailleur hanger to attach a tensioner to, or am I overthinking things?

Q2. Currently, I have the standard 3 piece crank set that came with the bike still attached. I noticed that on the middle cog, there are 32 teeth. Would it be possible to get away with just wrapping the chain around this, instead of having to order a single speed chain ring?

Thanks in advance.

1- a chain tensioner typically mounts to the same hole that a rear derailleur threads into. Just put your hanger back on the bike.
2- If you use the middle ring of your current crankset, you need to make sure the chain is shortened to accommodate for the smaller ring. Also, that middle ring is usually ramped to aid in easy shifting. This means it is not designed to hold onto the chain, and with single speed you want to hold onto the chain.


Personally? I would question if single speed with a chain tensioner is worth the time and result. You lose out on the direct feel of single speed when you have a chain tensioner. And I would buy a narrow-wide chainring to hold the chain better then remove the other rings up front.



If you are going to just have a tensioner and keep your current triple crankset, why do the conversion at all? Just ride the bike as is in whatever single gear you want and call it good. Just dont shift and you will have the same setup you are spending time and money on achieving.

This is obviously a mechanical thread and should be posted in 'bicycle mechanics' not GD.

Attach the tensioner where the derailleur used to be. I like the Surly Singulator.

Yes, but as mentioned, a narrow-wide chainring will better keep the chain from coming off. Alternately, you can keep the front derailleur on as a chain keeper, or buy a chain retainer:

leave this board scammer

Thanks for the info. I think moving forward I actually will just buy a narrow wide chainring and attach it to my current crank. I've been doing some more digging I think I may actually be able to use my current rear derailuer to act as my tensioner. I definitely want to go with the single speed because it means I can remove some excess weight from the bike. My cassette, front derailuer and gear shifters. I also think it looks a lot "cleaner" having the single speed setup as opposed to just hard using the same gear as it currently is

Anything about gravel bikes should be in the gravel cx forum, anything about bikes from 30+ years ago should be in the involved forum, anything about road bikes should be in the road forum, anything about hybrids should be in the hybrid forum, etc etc etc.
Its easier to not swim upstream.

Alright man my bad I'm new to the forum and thought it fit to post in general. Thanks for all the info guys I'm going with a 48T chainring and 18T cog.

Is that supposed to be a bad thing? Or is that sarcasm

48/18 is more typical for single speed on a 700C road bike. About 72 gear inches. It’s at the upper end of what I would use in our moderately hilly terrain.

Something more like a 2:1 ratio or less and about 50 gear inches or so would be more typical for a SS MTB, assuming it’s to be ridden on single track. The recommendation for 34/18 on 27.5 wheels is right about there at just over 50 gear inches.

Otto

Hey many thanks for this. I'm definitely going to buy a dedicated tensioner and downsize on my chainring to a 34T.

Updating this thread incase anyone stumbles accros it from Google. A 34 tooth chainring with an 18 tooth rear cog is WAY too easy to pedal. I'm not sure why people are recommending this ratio, maybe I just ride differently? The terrain where I live is flat and then some uphill but there's barely any resistance whilst pedaling. If you're like me and like to really work yourself with not sitting down and constantly powering through uphil gradients, then definitely go for a higher toothed chainring. I'm ordering a 40 tooth and will update further with the results.

I would recommend starting out with a gear ratio of around 63 - 65 gear inches...To achieve this ratio you will need a 42 or 44 chainring up front and a 18 tooth rear cog....34 x18 ratio which you have right now is good for singletrack and off road use and is way too low for pavement use.

Thanks, the problem is my chainring is very close to hitting my frame, so I'm afraid if I go any bigger than the 40T, then my chainring will start griding against my frame!

Update: I am now using a 42T chainring and 18T rear cog and the pedalling is much better. It's actually still a little bit too easy, so I'm downsizing the rear cog to 14T.

So in the end, I went with 14 teeth on the rear cog and 42 teeth on the front chainring.

Thanks all for the guidance.

The time to determine the gears you wanted should have been before you removed the multi-gear system.