prighello

Hello,

I have searched for answers to this but cannot find one definitively. I have a 1985 Schwinn Worldsport roadbike which has a Shimano Light Action groupset. It has stem mounted friction shifters that click but are not indexed. The freewheel is 7 cogs and the crankset has 2. My rear derailleur broke and I need to replace it. I am a little hard up for cash as I was recently laidoff due to Covid 19. I am trying to keep this beast running til I am gainfully employed again; it is my outlet for health and sanity right now!

I went to the LBS and they told me I need to replace the RD and shifters. Which means upgrading to indexing. I "think" this is not quite true. That all I need to do is replace the RD. My understanding is that friction shifters are pretty forgiving and RD's don't care how many gears you have? What I'd like to do is use a modern RD since they don't make mine any more. Can I use a something like a Shimano Claris 8 speed or Sora 9 speed RD with a 7 speed freewheel and friction shifter? Please let me know and thank you for the help.

Bill Kapaun

You DO NOT need to replace the shifters.
Anything from a low cost Shimano Tourney will work.
Do go too far up the food chain. As the number of speeds increases, the cage gets narrower.

Dwillems26

Yes, friction shifters whatever brand work with whatever brand RD. Don't go higher than a 9 speed RD or you won't be able to set the stops right and your chain might slip off the cogs.

prighello

Thank you for the swift replies Bill and Dwillems! So I should try to get a 7 speed RD for the best match? I ask because it looks like that is the Tourney one and it looks like it is made of plastic. I want to make sure I don't get something too cheap that is prone to failure in a short period of time.

HTupolev

Friction shifters on a mid-80s road bike? Basically any lower-end RD will likely work. You probably want to avoid 10/11/12-speed stuff because the cage might be too narrow for the chain. If you're unsure, the safe bet is an entry-level MTB derailleur like an Altus M310 or Acera M360; they'll work great with almost any friction drivetrain from that era.

alcjphil

A Claris rear derailleur would be ideal for this application. Designed for 8 speeds, it can easily handle the width of chain you need. Good quality, it would last for years. No need for an indexed shifter

prighello

This is what I thought. One last question, how do I know what cage length to get?

alcjphil

Don't know, did you include information about your freewheel and chainring cog counts?

HTupolev

It's a matter of chain wrap, which is the total amount of chain that the rear derailleur needs to take up between the small-small and big-big gear combos. For example, if you had a 52-36 crankset and an 11-32 cassette, the chain wrap that you need is (52-36)+(32-11) = 37 total teeth of wrap. Shimano tends to list wrap in their specs as "total capacity." You'll want to get a derailleur that has at least as much wrap as your drivetrain requires. "Too much" wrap isn't really an issue.

Longer-cage derailleurs have more wrap than shorter-cage derailleurs.

squirtdad

IIRC the light action (which was underated) was short chage...... so almost anything will work..... and if $$ are tight you might see if there is a bike coop close or a different LBS that deals with older bikes... you might be able to get a used one really cheap

dsbrantjr

IIRC my World Sport had 52/39 and 12/25 or 12/28 freewheel

prighello

Okay, so the Crankset is 52/40 and the freewheel is 28-11. So, based upon the formula above, the slack would need to be 29. So, it looks like a Shimano Claris shortcage would work since the total capacity is 37 teeth. Thank you folks for all the help. Also, will check out a coop as it would be cool to just replace it with another light action rd.

caloso

Once you get 10 posts, could you post a picture of your bike? An ice blue 85 WS was my parents' HS graduation gift to me and I rode that bike through college, law school, and commuted to my first job on it. I wish I still had it.

Miele Man

I can send you a rear derailleur. Whereabouts are you located?

Cheers

prighello

For sure, I was going to PM you to get your email and just send a pic but I guess I need 10 posts to do that as well.

prighello

Wow! Thanks Miele Man. I am in Arizona USA. It looks like you pm'd me but I need 10 posts to see it. I will get there. I suppose I'll start an introduction thread to hit the needed post count.Thank you for your kind offer!

Miele Man

What the heck. If you don't waiting for it to arrive I'll send one out to you as soon as you're able to send me your address. I'm in South Central Ontario Canada so it'd take about a week to get to you. I think you can get my email address by clicking on my user name.

Good luck and cheers

Dwillems26

Yes, shimano Claris is their entry budget grade. I have it on my bike and love it.

Length depends on your gears. The bigger the difference in your gears the bigger the cage. So if you have 3 gears up front get a long cage. 1 gear up front you might be ok with a short cage. please don't take my weird though since I'm not that experienced with this part. Please wait for someone to comment or do a search. Park tool and shimano's website has good info on it.

prighello

Thanks for the info and have a great day!

prighello

Here yeah go. Missing original bars, seat, and break levers. Wish I had them but the original owner swapped them and didn't save them. I've been riding this bike for three years now and love it.


Worldsport

Miele Man

Can you post another image but from the drive side?

Cheers

prighello

For sure, please see below.

Miele Man

Okay and thanks. I'm pretty sure I have a Light Action rear derailleur in my rear derailleurs box. I'll get it into the post for you tomorrow.

Cheers

Edit. I looked through m y spare parts and I do have a Light Action rear derailleur. I'll send it out tomorrow.

Cheers

JohnDThompson 

1) If you haven't changed the gearing, get one similar in length to the original unit.

2) When in doubt, go longer. There is no penalty besides a few grams extra weight in having a longer cage than is necessary. But too short a cage can mean either not being able to tension the chain properly over the full range of gears, or damaging the derailleur by exceeding its range.

prighello

Awesome! Thank you so much Miele Man, I owe you one