chiyama

I've recently learned that you can upgrade a 6 to a 7 speed freewheel, and I need some advice on how to do it, and what parts I can buy. I want to make it a little bit easier for the really steep grades when climbing hills.

My Comp TA has the Shimano 600 SIS groupset with friction shifters. According to Sheldon Brown's article (Freewheels (Thread on Type) for Bicycles from Harris Cyclery, I shouldn't have to change my shifters. I also think my current derailleur will work as well. It will just need to be adjusted.

Here are my questions

• Will it work for my bike?
• What 7 speed freewheels will work?
  https://www.amazon.com/Shimano-MF-TZ...peed+freewheel
  https://www.amazon.com/Shimano-MF-HG...peed+freewheel
• Will I need a different chain? If so, will any 7 speed chain work?

I'm not very experienced in modifying old bikes, so any info is helpful. Thanks!

ThermionicScott 

Should be a pretty easy swap. Although 6- and 7-speed share the same nominal spacing of ~126mm, you may need an extra 1mm spacer on the drive side to give clearance between the dropout and small cog. If this is your rear derailleur, it may not like a 14-34 freewheel as much as a 13-28.

Let's see... and I *always* use a new chain when I install a new freewheel/cassette. A worn chain will quickly subtract life from new cogs.

chiyama

Thanks for the advice. I'll make sure to remember the 1mm spacer. I don't need any kind of special spacer, right? A spacer from a hardware store should be good enough?

My derailleur looks exactly like the one you linked. Why would it like the 13-28 more? How do I know what cog sizes will work well with my derailleur?

I'll also make sure to get a new chain when I switch it. Should I get a 7 speed chain just to be safe?

If I wanted to go to 8 speed, would that involve much more work?

ThermionicScott 

You bet. The spacer might not be absolutely necessary, but is good to have on hand -- the ID just needs to be big enough to fit over the axle (10mm), and the OD not so big that it gets in the way of the freewheel.

Rear derailleurs have a max cog size rating. Too big, and the jockey pulley will jam against it. Yours is rated for 26T or 28T, and while you can usually fudge things a little, I wouldn't get my hopes up that a 34T would work.

I use inexpensive but good 8-speed chains (SRAM PC-850) for my 5/6/7-speed bikes. Keeps my inventory simple, and works really well.

mountaindave 

Great advice there, Scott. Keep the 7-speeds alive!

Saint Sheldon discovered, as many of us have, that you can safely go beyond the published "max sprocket" limit, but usually only ~2 teeth beyond. In some cases, you can get a derailleur like yours to go to a 34t sprocket on the freewheel, but probably not in your situation. I have a half-step setup with a tri-color 600 RD pushing an 11-34 7-speed cassette (go spend some time googling half-step gearing ) and it's spec'ed for a 28t max, but that is more the exception rather than the rule.

Not to make you spend more money, but pick something in the range of a 30t max in the back, then figure out what you want up front to make it pleasant (e.g., smaller chainrings). I did that for a friend and she is very happy.

denny1969

I think the first two questions were answered already.

The answer is yes because the rear hub spacing is going to be wider. Six and seven speed rear hub spacing is 126 mm. Eight through ten is 130 mm. That means your rear triangle drop outs would have to be widened to 130 mm and aligned. On a steel frame, it is a straight forward procedure. Don't try it on aluminum. You also would need to get a rear wheel spaced out to 130 mm. The good thing, there are a lot of wheels available since 130 mm hubbed wheels are available for eight to ten speed spacing.

Good luck on the upgrade. Don't forget to post pictures of the finished product.

Dennis

Miele Man

Like others have said it will probably work going from 6 cogs to 7 cogs. I'd go with the 13 - 28 freewheel because the 14 - 34 one has a really big jump from the second largest cog to the 43 cog and that might make for poor or slow shifting.

A new chain and a new feeewheel at the same time will avoid chain/freewheel problems such as new teeth but worn chain = skipping under load. Also if you get a Hyperglide type chain your shifting will be better than with a chain with straight side plates. The bulges on the Hyperglide chains help shifting a lot.

As far as that 34 teeth freewheel goes, do you know anyone who has a 7 speed wheel with 32 or 34 teeth you could put on your bike and see if the derailler will wrap enough chain? Is your inner front ring a 42? You can lower the gearing a bit more if you use the 13 - 28 and a 39 chainring to replace the 42 teeth one.

Cheers

The Golden Boy 

Because all my bikes are 5 and 6 speed (and
One 10 speed), can you fudge an indexed 6 speed shifter onto a 7 speed freewheel? Let the limit screw out and just keep turning the shifter. I've used 6 speed shifters with 5 speed cogs by just adjusting the limit screw... I don't know if most shifters will have that room at the end of their traverse- or if there's a spring that pulls the shifter back...

chiyama

I'll be sure to get a hyperglide chain IF I switch the freewheel to a 7 speed. I'm going back home soon to pick up my dad's old 1992 Bianchi Virata. That may replace this bike if I like it.

Unfortunately, I don't know anyone that has a 7 speed wheel, so I won't be able to test it out. I'll also need to count the teeth on my rings currently.

Edit: My inner front chain ring is a 42