Madeupname

Hello!!
I hope someone can help!!

How long is a seven speed bike chain?

Do I fix the derailleur cable first, or put the chain on first??

thank you!!

Madeupname

Hello!!
I hope someone can help!!

How long is a seven speed bike chain?

Do I fix the derailleur cable first, or put the chain on first??

thank you!!

cb400bill

Merged duplicate posts

bboy314

Length depends on the bike it’s going on and its drivetrain parts. Generally install chain before shift cable, but before doing any of that you should educate yourself a little. Start with www.sheldonbrown.com

Iride01 

Chains you buy are typically longer than what you'll need for your bike. If you have a tandem or a recumbent, then standard chains might not be long enough. So just count the number of links on yours and you'll know that you have to get a chain with at least that many.

You'll have to size the chain though. So if you don't have the tools and knowledge, you'd be better off just letting a bike shop put one on for you. Same for your derailleur cable. Not knowing what's wrong with it, it's impossible to recommend what you do for it other than a bike shop will be your best bet for the current information you have given us.

Bike shops in my area aren't very expensive for such work.

sweeks

If you're replacing the chain, just lay the old and new chains side-by-side, then cut the new one to the same length (allowing for the joining link). You'll need a "chain tool" to remove the extra chain.
The recommended Sheldon Brown site is a good place for information. Another good source is Park Tools.

veganbikes

About this long. I would get your derailleur set up first and then measure the chain for the length you need and properly take it apart and put it together. Keep in mind the 7 speed era started in the mid 80s we are now in the 12 speed era so if it is modern 7 speed the quality is not going to be great so you may need to adjust more often and replace parts more often.

70sSanO

Most mfg’s, SRAM, Shimano, KMC sell 8 speed chains for 7 and 8 speed drivetrains since the cog spacing is very close.

John

JohnDThompson 

Chain length depends on your specific gear range and chainstay length. If you have the old chain, trim the new chain to match. Otherwise, this may help:
https://www.parktool.com/en-us/blog/...-length-sizing

It doesn't really matter, but you'll need the chain installed in order to adjust the derailleur or check its adjustment.

mpetry912 

Madeupname There are a couple of ways to set the proper chain length. Some people run the chain around the largest rear cog and the big chainring (not going thru the derailleur) and then add 2 links.

I personally set the chain length so that when it's on the smallest cog and smallest chainring (both shift levers relaxed) the derailleur cage is just barely off the limit stop - at full chain wrap up.

On a classic campy derailleur it will look like the below. If you have a wide range triple, there may be some extremes of chain tension and slack that you will not be able to use.

pics always help

/markp

kcjc

^ this. Here's another post with a video from Art's Cyclery on how to do it, https://www.bikeforums.net/20781951-post1.html

Yan 

That would work fine on an officially compatible groupset, but if you accidentally followed this procedure on a mismatched drivetrain, you could end up with a too-short chain which would cause your drivetrain to explode the first time you ride the bike.

Sizing big-big and ending up with your derailleur unable to take up all the slack is no big deal. Sizing small-small and ending up with a too short chain will snap your derailleur off, probably damaging the frame in the process.

kcjc

Uhm? That's BS. At worst, you would end up with a chain that might be too long. It's based on the chain ring and rear derailleur; branding plays no role except for the length of the derailleur cage (and pulley for those that buy into that crap) and the number of teeth on the front chain ring. My bike on the trainer is a mix of drivetrain, and it works fine if you follow directions.

Yan 

You could certainly end up with a chain that's too short if you sized the chain based on only the small chainring and the small cog. The small chainring and cog have no idea how big the large chainring and cog are.

Accidentally follow the procedure in that video with a short cage derailleur and an incompatible wide range cassette and crankset. Your drive train will be damaged the first time you shift into big-big.

Try it.

Pratt

For my bike, I lay the new chain out on a board and put the old one next to it as a guide. As pointed out above, different bikes will require different lengths. My bike is a Bruce Gordon, Rock and Road, with a 7 cog rear. It is designed for loaded touring and, accordingly, has longish chain stays, however, I usually remove about 8 links from the new chain to fit the bike.

kcjc

Please stop with the misinformation.
It doesn't matter if you stay within the manufacturer's limits on derailleur capacity. Going outside of it can lead to damage, and it's called user error, whether by choice or ignorance.
Many, many times, and still doing it with no ill effects. I run it with my MTB, road, and cyclocross bikes. Single, double, and triple cranks.

• MTB: 7s 42/32/22 with 11-28 cassette & '94 Shimano Deroe LX & Shimano Deroe XT derailleurs
• Road: 7s & 11s using 53/39, 52/42, & 40/34 chainring with 12-24 (7s), 12-27 (7s), 11-25, 11-28, 11-30, & 11-34 cassettes and short cage (Shimano DA 7400 & 90s Campagnolo C-Record), medium cage (Shimano Ultegra 600, Ultegra 6800, Shinamo DA 9100, & SRAM Red eTap), and long cage (Sensah Empire Pro & Shimano Ultegra R800). My bike on the trainer was using a Shimano Ultegra 600 with an 11-25 & 11-28 11-speed cassette.
• Cyclocross: Sensah SRX Pro 1x with 36 & 40 front and 11-40 & 11-50 cassettes

bboy314

I would consider telling someone to size a chain based on the small ring/small cog combo, without knowing anything else about their setup, misinformation or at least bad advice.

RCMoeur 

For 40+ years, I've always set the chain length based on the largest front chainring / largest rear cog, with the rear derailleur set up appropriately and the tension (lower) pulley about a 135 degree angle to the rear axle (where up is 0 degrees). Although using the large/large combo is considered "cross-chaining" and not entirely optimal, the chain should be long enough to enter this combination.

As others have stated, setting up the chain length based on minimal sag in the small / small combination can result in a chain too short to shift onto the large/large (or even several large rear cogs when on the large chainring). In the least-worst case, the chain simply refuses to shift, whereas other scenarios involve potential damage to the chainring or derailleurs.

Another thing I've learned through experience is to never presume the components on a bicycle are the ones it was sold or speced with.

I also don't always trust the "lay out the old chain and compare" method, as the previous chain may have been too installed short or too long by some other owner or mechanic. In addition, excess wear can make a worn chain measure out to 3 links longer than optimal/original. Using the large/large method avoids this.

biker128pedal

Like others have said you will need a chain tool. If you have the original chain count the links. The length depends on the length of the chain stays, cassette cog range, chain rings and derailleur. If the have not changed why reinvented length. Knowing the number of links will ensure you buy enough chain. Realistically any off the shelf 7 to 8 speed chain will work. A quick link should come with the chain to join the ends on the bike.

KMC makes good chains and come with a quick link. Here is one on Amazon.

https://a.co/d/3bNdGQr

kcjc

And you would be very misinformed

kcjc

And you could be wrong if that was used with a rear-suspension bike or 1x. If compression is not accounted for, both would be in the wrong. You should be able to figure out the 1x for yourself. Small-small basically comes up with the same chain length as long as your rear derailleur b-screw is adjusted correctly and within the manufacturer's limits on derailleur capacity.

It wouldn't make a difference. The controlling parameters are the front rings, cogs, and derailleur. Either method applies

Agreed

bboy314

In the real world it’s actually quite common for people to change cassettes and/or chainrings for lower gearing, going outside of the rear derailleur’s spec’d limit but adjusting the b screw to make it work. Sometimes a bike in this situation will need a new chain installed. What do you suppose happens if the new chain is sized using the small/small combo as the only guide?

Yan 

Yeah, it does matter.

That's the whole point I and multiple others have been making this entire time. Never assume when an unknown bike arrives in your hands that the owner has installed compatible parts. The guy could have no idea what he's doing.

You ever been involved in a community bicycle recycle workshop? People just go to the parts bin and slap whatever parts they find on the bike. Then they come to you for help installing the chain. If a bicycle has wrongly selected components and you blindly follow the small-small procedure like a doofus, the drivetrain will be damaged the first time the bike is ridden.

The video, that's in a pro mechanic workshop context. Presumably a pro mechanic is checking components for compatibility first. You can't transpose that to a general population context. The OP of this thread being a prime example. He knows nothing about bike drivetrains and he's here asking for help. Nobody knows what parts are on his bike. Perhaps he doesn't even know himself.

You have no idea what you're doing and the terrible advice you're giving could cause damage.

Stop.

kcjc

Yes, I worked for 3+ years at the University of California at Davis' Bike Barn and two other shops during summer breaks while completing my civil engineering degree. There was no parts bin, but plenty of doofus working on their bikes and asking for help. I helped them to get everything in working order or let them know how much it would be (and did some of the work) if they didn't want to do it themselves. I'm guessing you don't go out of your way to help much.

So stop spreading misinformation and the fear-mongering. It's just a different way of sizing the chain and doesn't guarantee damage to the bike.

kcjc

When did I say it's the only way? We each have a preference, but you are attacking mine with misinformation.