W4IVR

I have a 3 X 7 / 21 speed Hybrid road bike...I'm want to change the 3 chainring to a 1 chainring...can I use a 1 x 10 MTB crankset with the 7 speed cassette already on the bike? Will the same chain I used with my 3 x 7 work with a 1X?

SkyDog75

Yes. (Assuming you get a crankset whose bottom bracket type is compatible with your frame.)

...but you don't necessarily need to change your crankset. You may be able to just put your desired chainring on your existing crankset. Heck, you could even use one of your existing chainrings and remove the other two. (A chainring designed for 1x or single-speed use would be better, though, since it won't have shift gates designed to help derail the chain to the next lower ring.)

You may want to consider a chain guide to keep your chain from derailing off your chainring. On a multi-chainring bike, the front derailleur serves this purpose.

Also, you may want to consider the gearing range you're going to lose. One of the things that makes 1x drivetrains practical is cassettes with a large number of cogs and very wide range. With only 7 cogs, if you go to a wide-range cassette, you're going to have big jumps between gears. If you don't opt for a wide-range cassette, you'll be sacrificing gearing at the top or bottom end of your gearing range.

Yes.

W4IVR

The bike is a Vilano Men's Performance Speed Shimano Hybrid Bike...I bought it new 2 yrs ago and I live in the mountains of Tennessee and have no use for the 48 chainring or the 38 either for that matter...I spend 75% of the time climbing a hill/mountain...so I was thinking either a 36 1X or a 36/24 2X...Just wasn't sure what issues I would run into...

W4IVR

The bike has a square spindle BB and I'll be changing it to a Hollowtech ll...

catgita

You are probably changing to a threaded external bearing bottom bracket.
There is no issue using an 11s 1x chainring with the wider chain for your 7s.
Don't do 1x with a chainring designed for shifting.
Using your existing parts won't control the chain as well as the full matched system, but unless you are planning serious cyclocross or mountain biking, probably a non issue.

JohnDThompson 

Specifically, chainrings designed to be used in double or triple setups with indexed shifting will have ramps and pins to facilitate shifting between the different rings. With only a single ring, this can be a problem, especially on the largest and smallest cogs in the rear, where the chain angle is at its most extreme. A ramped/pinned ring may drop the chain in that situation.

The solution is easy, though: use a ring designed for a single speed, or a vintage (pre-index shifting) ring as these will lack the modern ramps and pins.

SkyDog75

You do ride down the hill once you get to the top, don't you? (That's where the bigger rings come in handy.) ;-)

I honestly don't mean to be a smart alec by pointing it out, but if you're not planning to make a change to your cassette, you could get the exact same effect by simply not shifting out of your small chainring up front. No changes to the bike required. And you'd still have your upper gears available if you ever found a need for them.

catgita

It isn't the ramps and pins that are an issue, it is the smaller teeth. The chain never contacts the ramps and pins if you are not shifting, but the smaller teeth don't hold the chain as well.

gilpi

On my 3 by 8 Cannondale trail bike I started by just leaving the middle ring in the front but in rough trails the chain would drop. I purchased a narrow wide ring from Amazon and works great, quiet too. Another thing I had to do was to remove one link from the chain.

W4IVR

Thanks for the help!!

fietsbob

Keep the triple crank , and just replace the middle chainring.

the middle on a triple is in a good chainline, as a single..

take off the rest of the chainrings.. one source of a reasonable single ring is Surly Stainless steel.

long wearing and you can flip it over to wear twice as long.




.....

veganbikes

I would suggest not running a 1x7 even mine which has some decent vintage components is just a pain. Running an 11-32 7 speed set up just leaves me with so many gaps in my gearing and going to a smaller cassette would leave me undergeared for certain trips. For reference I am running a 38t in the front and 11-32 SRAM 7 speed cassette in the back.

Upgrade your drivetrain (which is a decent idea anyway due to the bottom end spec on Vilanos) and maybe run a 1x9 or 1x10 and have a better range and easier time find parts of some quality which will last longer and stay in tune better and shift more smoothly. Going with a Deore rear derailleur and a narrow wide chainring with a 9 or 10 speed cassette/chain would improve things quite a bit. That is what I am considering myself on my homebrew hybrid as it will solve many gearing issues.