Single chainring conversion

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6/19/2018 6:17 AM

Hello all, I am new here but have been on Vital for a while haha. Anyways I have a SR Suntour crankset (square taper) and I was looking into ditching the 3 ring to run a 1-by setup. Upon later investigation I realized the rings were riveted on the cranks. I looked online and found that the second largest ring was a 32T, which was the size I was gonna run. My question is could I just drill out the 2 rings which I don't want and just run the middle as my single? I'm very handy and DIY, I also don't have a ton of money to drop on a new crankset.
Thanks guys, hope you can help!
-Evan

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6/19/2018 8:08 AM

That's entirely possible, and would leave you with just one ring up front. But kinda central to modern one by set ups is the use of a narrow wide chainring to aid in chain retention. So if you do it, you'd really want to add a chain guide to the system. It's a bit of extra weight, but not the end of the world. I've been one by with a chain guide since the original 48 tooth MRP came out back in the late 90's.

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6/19/2018 8:18 AM

Ok, thank you so much for helping out with my confusion. I just figured to go narow wide I would need a whole new bottom bracket and crankset which would run well over 200 including tools. I think I'll just go that route instead with a chain guide.

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6/19/2018 9:43 AM

You may find that a crank upgrade will be less than you think (a quick amazon/jenson/etc) search finds SRAM NX or GX level cranks with a 32 n/w ring for $75-$90, and a $20 bb you'll probably be happier with the results. The stiffer crank/bb and n/w retention benefits being the most noticeable. Especially since you're gonna need $30-50 for a chain guide you're half way there.

That said, if you're rear derailleur doesn't have a clutch mechanism (seems plausible if your bike came with a square taper bb and riveted chainrings) you may be better off with the chainguide.

If you can make do with this configuration for a while and save your pennies you'll find that whole drivetrain groupsets are shockingly cheap these days. A full SLX set with a crank (one listing from Fibica?!? included brakes!) can be had on ebay/chainreaction for ~$300 and the SRAM NX Eagle (just announced) will have you shifting 12 speeds for under $400. I realize you said you're trying to do this on the cheap, but if you're otherwise happy with your frame and wheels, these are worthy upgrades to a pricepoint configured bike.

I rocked an old 1x9 hardtail converted from a 3x setup for years and was super stoked on it and my daily commuter is a square taper 3x crank with only the middle ring setup as a single speed. Don't feel like you _must_ spend big $$$ to have a bike you can go out an have fun on, but if you're looking to improve a bike you already love and ride often, the quality of the "bargain" level components these days shouldn't be overlooked.



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6/19/2018 10:59 AM

I completely agree. I am going to run that middle ring until I can buy a decent crankset and swap the whole BB out. If you wouldn'tmind taking a look at smething else real quick, I have this bike: http://www.bikesdirect.com/products/gravity/fsx_2.htm and I am trying to put a DNM rear shock to replace the stock spring one. Do you think it will fit?

DNM shock: https://www.amazon.com/DNM-Mountain-Shock-Lockout-165mm/dp/B00R5OA7HA/ref=sr_1_1?ie=UTF8&qid=1529328909&sr=8-1&keywords=dnm%2Brear%2Bshock&th=1&psc=1

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6/19/2018 11:30 AM

The important measurements to determine whether it will fit or not are:

Eye-to-Eye measurement with the shock fully extended (center-to-center)
Stroke Travel (protip: take the spring off to measure) the extended=>compressed travel distance of the shock stroke
Bushing/Mounting Hardware Measurements: width (note: may be different at each eyelet), I.D. (bolt hole size), O.D. (bushing eyelet insertion size)

A useful diagram listing these measurements:



Whether or not a shock will fit your frame will depend on matching these measurements to your current shock.

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6/19/2018 11:41 AM

Here is the spring shock that is currently on it. I think it will fit but i need some clarification. What do you think?

spring shock: https://www.amazon.com/Speed-Spring-Shock-Suspension-Mountain/dp/B078T1GSG1

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6/19/2018 12:02 PM

The relevant measurement's aren't listed there, and many shocks are made in a variety of eye-to-eye and stroke configurations. Best bet is to make these measurements yourself with the shock on your bike.

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6/19/2018 6:50 PM

Thanks B0bg. I totally forgot about the clutch derailleur. Never had one myself.

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6/20/2018 1:56 PM

Re. the 1-x conversion, check this crankset out: https://www.srsuntour.com/collections/featured-items/products/zeron-1-x?variant=45338041742

I just finished a build and used these cranks and they're a pretty crazy value. Cranks, ring (albeit a 30T, not 32T), and BB included.

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6/20/2018 2:09 PM

MTBrent wrote:

Re. the 1-x conversion, check this crankset out: https://www.srsuntour.com/collections/featured-items/products/zeron-1-x?variant=45338041742

I just finished a build and used these cranks and they're a pretty crazy value. Cranks, ring (albeit a 30T, not 32T), and BB included.

Wow. That is a huge score, especially if it comes with BB and chainring. I'm not sure if the bottom bracket is the same diameter that is on my bike currently. If someone could clarify then i will definitely be purchasing this in the future. Thanks for showing me that's an awesome deal!

My bike: http://www.bikesdirect.com/products/gravity/fsx_2.htm

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6/20/2018 4:29 PM

MTBrent wrote:

Re. the 1-x conversion, check this crankset out: https://www.srsuntour.com/collections/featured-items/products/zeron-1-x?variant=45338041742

I just finished a build and used these cranks and they're a pretty crazy value. Cranks, ring (albeit a 30T, not 32T), and BB included.

TheB33st wrote:

Wow. That is a huge score, especially if it comes with BB and chainring. I'm not sure if the bottom bracket is the same diameter that is on my bike currently. If someone could clarify then i will definitely be purchasing this in the future. Thanks for showing me that's an awesome deal!

My bike: http://www.bikesdirect.com/products/gravity/fsx_2.htm

Looks like it’s a standard 68mm BSA threaded BB. The crankset I mentioned comes with a BSA BB and spacers for a 68mm BB. Looks like you’d be good to go 👍🏼

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6/20/2018 4:52 PM

Make sure you get the right crank arm length...I noticed the SRSuntour site is out of stock on the 175mm model which is probably what's on your bike (linked description doesn't specify). Measure center-to-center spindle to pedal axle.

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6/20/2018 6:32 PM

Awesome! Thank you guys for confirming that will fit. I have a 8 speed cassette, do you think 30T will be enough power for hill climbing? I still do BMX so my leg power is strong hehe.

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6/22/2018 3:57 AM
Edited Date/Time: 6/22/2018 4:07 AM

Regarding the bottom bracket, it looks like that Suntour crankset should work since it is using a threaded bottom bracket, commonly referred to as "English" or BSA. One important note is that the mountain bike standard is for the bottom bracket shell to be 73mm wide, and it is 68mm wide for road bikes. Same thread dimensions. If you have digital calipers see what the width of the bottom bracket is (frame only). Although the frame specs say 68mm, I'd expect it to be 73mm, and a crank designed for a mountain bike will have a spindle long enough for that. If the frame is actually 68mm, then there are bottom bracket spacers available to take up the extra room so the spindle isn't too long, effectively making it 73mm wide again.

Regarding the gear range, what is important is the size of your largest climbing gear, not the amount of speeds. Back in the day I rode a 32T front ring with a 34T as my easiest climbing gear. Ran without issue, but a few sections required some extra leg power. I'm guessing yours is either a 30 or 32 tooth back there, which isn't as easy but is doable depending on your area, and you have a smaller front chainring which helps. There aren't a lot of 8 speed cassette upgrade options available but if you have a 32T rear now, I know 34T 8 speed cassettes do exist which can make life a little better if 32T isn't enough. As a rule of thumb, getting a larger climbing gear in the rear makes things easier than getting a chainring the same amount of teeth different in the front.

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6/23/2018 6:36 AM

Thank you guys! All of you have been very helpful and really explained what I need to do to make sure these parts fit.
Thanks again.
-Evan

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