Help needed with bike chain please
 

My daughter claimed she needed a new chain so I purchased the chain and fitted it but there seems to be a big problem. It seems too short. The largest front chain set has 48 teeth and the largest rear set has 28 teeth. The chain stay is 44 cm so by my calculations the chain should be 139cm or 110 links. Am I correct in this

Typically, one uses the old chain to get the length of the new chain.

The old chain is also 139cm I wanted to check that it was correct

I use the “big cog, big ring” sizing method.

Good instructions at Park Tool

If it's the same as the previous one, and if that one fit, then you should be good.

It is the same length as the old one but that kept slipping so I was checking that the length was correct first. She thought it seemed loose

I was going to post a pic but I have to have 10 posts to do that hehe

What do you mean by "slipping"? Is this a bike with multiple external gears and derailleurs? Or is it a single speed or internal gear hub? Number of gears on the rear can make a difference on what chain you get too. If you got a 8 speed chain for a 11 speed rear, then that is going to be issues. Maybe the slipping.

You can just write the URL of you pics or vids in the plain text of your next message and remove the https:// and put a space before and after any . (dot) that is in the URL.

There are also posting limits on noobs too. Usually at five per day. Don't know how long that lasts. Maybe till you aren't so noobish, or it might be a one time thing.

Let's first get the Chain length correct first, which the video below will help with.

Park Tool Chain Length

Barry

BTW: one more post and you'll be able to post a picture of the setup.
Time to go say hello in the Introductions Forum.

what type of bike is this?

Don't bother w/ 'chain length calculators' or using the old chain unless you know for sure that it's the correct length. Use the specific instructions for the drivetrain you have on the bike. If it's a 'normal' double or triple and everything (cass, c-rings, rear derailleur) is within spec use the small/small method, it gives you the longest/safest chain.
And of course this thread should be in 'bicycle mechanics' not GD.

Hi it is an 18 speed MTB

This was the issue I had in it’s the derailleur so far forward with the chain on both the largest cogs.

https://cimg4.ibsrv.net/gimg/bikefor...129fa1afd.jpeg

I have had another go today as I realised I forgot to take into account she has rear suspension. Couple of links added (4) and it all seems good again

Great example of a calculator not working and using the old chain not working either. It's just so damn easy to put the chain on the bike and figure it out the right way.

Sorry cxwrench I didn’t mean to post in wrong discussion,

Understood... On some of the older bicycles the frame is just longer. For example I have an old Ted WIlliams Step Through. Sold by Sears long ago the frame was actually made my Austro-Daimler in Hungary. It is a long frame with plenty of room for fitting a bicycle rack and fenders. There is allot of room between the rear tire and the seat tube. I saved the frame and added parts box components to it for a nice ride. It takes a 62 inch chain to fit the 34T freewheel cog to 51T large crank ring. Its a very fast sleeper bike, and when my boys come over its one of thier favourite rides.

Buy an extra master link and add back enough links to bring the rear derailleur back underneath the cassette if you kept the rest of the chain. A normal chain is 116 links with the master link. If you don't have any more chain left it is time to just buy a new one. Remember the chain has to match the number of gears in the back. Six, seven, and eight speed are all one chain but 9 speed and above use different chains and different master links. Here in the US an 8 speed KMC chain costs about $14 on eBay but since you are using metric measurements you are probably not in the US. Then follow the directions on Park Tool to adjust it properly.

Hard for me to decide from that picture, but the cog the chain is on currently look like they might be worn. Even with the correct chain length it might still skip. If skipping is the OP's slipping.

If the bike was purchased as a used bike, then perhaps the previous owner made the chain a little shorter in a desperate attempt to solve the skipping.

Now would be a good time to replace the Shimano 14-28T 7-speed freewheel.

Amazon.com : MEGHNA Shimano Tourney/TY MF-TZ500 7-Speed Multiple Freewheel, 14-28 Tooth : Sports & Outdoors

Hi and thanks for your replies I will look at replacing the 6 speed freewheel anyway but after adjusting the chain length the gears now shift correctly and no slipping as yet.

If it's a mountain bike-shaped comfort hybrid it probably has a longer than usual wheelbase and it may be necessary to splice two new chains together. My early 2000s Globe Carmel looks sorta-mountain-bike-ish (compact frame, sloping top tube, suspension fork, etc.), but it's really a long wheelbase comfort hybrid/city bike, almost as long as a Yuba cargo bike. I spliced a pair of inexpensive KMC Z50 or comparable chains together. IIRC, I needed six links from the second chain to make one proper length chain. It's worked fine for a few years that way.

Ditto, replacing the freewheel, although I prefer SunRace over Shimano's cheaper freewheels. Both are good for the money but the SunRace are a bit better at that price level.