4. How to Calculate Chain Length

Measure the correct length of a new bike chain.

IMPORTANT: Nuts and bolts on your bike should always be tightened to the manufacturer's specifications.

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When you purchase a new chain, it usually comes with extra length so that it is compatible with most drivetrains. How do you know how much length your bike will need? Well, it’s really quite simple…

The first step is to wrap the chain around the largest sprockets on the front and rear, so that the ends meet on the largest front chainring. For this step, it really important to not run the chain through the rear derailleur.

Next, position the chain on the chainring’s teeth at the tightest spot you could connect the chain. Now add one whole inner and outer link, so that you have approximately one extra inch of slack in the chain. That will be the optimal length for most systems.

In future tutorials I plan to discuss the different types of chain connectors and how to use a chain tool to break the chain. The following links provide some more helpful information.

Discuss this topic in the Chain Forums

01/30 Chain scenario

I recently had a chain snap and had a new one fitted. The cassette is a 9 speed, and the grip shift is a 7 speed. A mechanic used to be able to throw on decent parts for cheap; however the mechanic at the time put on new gear cables then went to tune in the gears and said that he couldn't do it because the shifter is different to the cassette. Basically leaving the bike semi ridable. Any solutions?... Read more >>

01/12 Sprockets insufficiently spaced?

Hey there, just got my bike back from the shop after a broken spoke, went for a quick ride and the 5th and 6th sprocket in the rear cassette were jumping and the chain never gripped. Then noticed that there is no space whatsoever between them. I take it that's not supposed to be the case, as the chain has no space to wrap around the tooth? Any advice on repairing this? I've included a few pics, excuse the oily filth!... Read more >>

01/10 New Chain + Cassette, Slippage when in small front and mid-to-small rear

I have an ultegra 10-speed setup, dual-front. I just replaced the chain and cassette(11-25), and it appears that my chain is too long to achieve suitable chain tension when on the small front ring, and on any ring below about the middle of the cassette, yet when on both large rings, I can't see that there is enough capacity in the chain to be able to remove an extra link without problems (derailleur is already being pulled fairly far forward). This problem manifests itself with my chain slipping around the cassette whenever I am on the small front ring and on the smaller half of the cassette. ... Read more >>

12/27 New chain AND cassette, now skipping (a lot)

I just had the bike shop install a new cassette and chain. (I've been looking around online all evening and similar threads are all about only one or the other part getting replaced and problems resulting.) I've had this Giant mountain bike 12+ years, street use only, supposedly originally made for a bike messenger company so it had 9 gears in back, no parts replacements to speak of this whole time. Partly the reason for the new parts now was how old everything was, and mostly because I was starting to experience more and more skipping in the past month or so. The new pieces should match eac... Read more >>

12/19 Chainring question

Hi I have a Shimano FC-650 crankset and am having a hard time finding a 44 or43 tooth outer ring......is this what they call a 130mm? and if so will all 5 arm (hole) 130mm rings fit? type A This is a trek bike that I am building up for expedition touring and I have all ready gotten all new rings for the inside as well as a new BB the 46 ring on it now is to tall for a heavily loaded bike to be of much use. One more thing... will all Hyper glides cassettes fit all HG hubs I mean other then a 7 speed is for a 7 speed... are the numbers after HG- referring to the gearing of the casse... Read more >>

12/17 Bike Chain Tangled

Hi all, new to the site and to bike maintenance in general, so forgive me if this is a novice question. I was riding my bike around town earlier today when the chain slipped off of the back gear. Now it has two "knots" in it where it curves back in on itself, and I have no idea how to get it back to normal. Any advice or techniques you guys can offer me will be much appreciated. [broken_image] [broken_image] [broken_image] [broken_image]... Read more >>

12/02 Chain ring is touching my frame

Hi yall. I just replaced my chain ring and crank set on my converted single speed bike, but the new ring (which is the same size as the old one -44 tooth) just starts to scrape the frame bars, when it is installed. Is the something i can do, like some kind of a washer that i can insert onto the under bracket so it gives the chain ring some clearance? I am totally puzzled as to why the new one wont fit. Thanks for looking. Peace.... Read more >>

11/23 Looking for some general advice on replacing chain, rear cassette

Hello Everyone! New to the forum, and wasn't sure where to post this. I've got a Trek 7.2 urban type bike. It's about 3 years old, and apparently wear on the chain, derail, rear tire has kinda crept up on me. My other Trek is similar, but a slightly better model. I got that one with the red badge warranty so I'm trying to get the trek shop to fix it. However, as USUAL I'm finding out the warranty is a gimmick and they are quoting me nearly $200 just to tune and fix up my 7.2 I can't afford that now. I'm pretty mechanical and fix cycles and cars, but never messed with bikes. I guess the... Read more >>

11/19 Strange Chainring Bolt

It's my first time posting on this forum - hi! I was wondering if anyone could help me out in looking for a pretty odd type of chainring bolt, please? I've searched the net rather a lot, and I can't find anything that looks up to the job. I've attached a photo of the bolt (sorry it's not that clear, but at least it gives you an idea of what I'm talking about). The unthreaded section is 10mm long, and the bolt shaft is 9mm in diameter along that section. The threaded section is 6 or 6.5mm long, depending on where I measure it. The shaft in this section is 7mm in dia. The bolt goes throug... Read more >>

10/26 Bent chain link and bike slips in and out of gear

Hey guys, I was googling around for on this matter, but it seems there could be a variety of reasons for this. I bought a second hand bike (2009 Scott Contessa 30) and after a few weeks of riding it realised that sometimes as I was cycling the bike would go quickly out of gear and then back into it. There is also a bent link in the chain. What's your opinion guys? I think the chain isn't tight enough. If you want pictures I can get some of the bike for you. Cheers!... Read more >>

10/18 Gearing Suggestions

Hi there, Right, so I'm looking to gain some lower gears on my bike. I'm stuck between getting a new chainset, or new cassette (or both?), but as always looking to keep costs down! So I have a 2009 Claude Butler Roubaix, 53/39 up front, and an 11-26 SRAM cassette behind. Sora 2300 Derailleurs (short arm on the rear one) I was hoping to just get a 11-32 cassette and do a quick swap, however I fear my rear derailleur won't be able to stretch to the 32 (lots of rear derailleurs only seem to be capable of a max 26/27T ??) - However from doing some searching online there seems to be a few peopl... Read more >>

10/17 How to remove rear wheel and replace freewheel cassette?

OK, so something recently happened with my sisters bicycle during a ride. I don't know what she was doing, but now the freewheel/cassette just spins independently from the wheel; you can also jiggle the cassette around just using your hand. I suspect a broken freewheel/tooth. I just have a few simple questions. 1. How should I go about removing the rear wheel? It doesn't have a quick-release. Every single tutorial I've found online only shows bikes that have a quick-release. 2. Is this something I can replace myself without a bunch of specialized tools? I'm pretty mechanically i... Read more >>

10/14 Broken spokes

I have (2) spokes that need to be replaced and they are on the drive side of the rim,..I attached some pics to ask you what tool do I need to remove the drive cogs (free wheel). I saw a tool,...a FR-1, 12 splines, 23mm,...But I don't know what 23mm size pertains to. Unless there is a different way to remove,..thanks in advance.... Read more >>

10/14 Chain Tension, old peugeot

hey, i picked up an old peugeot racer the other day second hand, looks to be very old, not sure what type. Iv started updating parts, and i bought new 700 wheels to fit it, they were very tight and i had to force them in, but they fit. iv also removed the gears and put in a single speed cog, but i cant get the chain to tense. the wheel when put back completely in the horizontal brackets, leaves the wheel completely crooked, aligning right, so i have to put it half way up one bracket and fully back on the other bracket, but this leaves the chain untensed, what can i do to fix this? the wheel i... Read more >>

10/14 Speed

I need speed. I have a 13-30 in back and a 24-45-50 in front. Can I replace the 50 with a 52? (Trek 1420)... Read more >>

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4. How to Calculate Chain Length

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