Going to a 7-Speed Cassette from a 6-Speed Freewheel
 

I am trying to resolve a tire issue that I have with my Puch Mistral road bike. I have tubular tires now, and I am trying to go over to clinchers.

Strangely, I found that they put a 126mm hubbed wheel on at the factory even though it measures 130mm between the rear dropouts.

I sourced a set of used wheels (rear 130mm hub) that look like they will fit. The rear hub has a seven speed cassette. My old hub had a six speed freewheel.

I had assumed that it would be plug and play with maybe slight adjustment with the rear derailleur, but I thought I'd ask. Am I okay here?

If it has friction shifting and your new low cog isn't much larger.

Yes, friction shifting.

I've noticed over the decades that some big box store bikes with frames intended for wider 7/8-speed axles were being mashed with 6-speed freewheels.

I see this when I remove the rear wheel nuts and watch the drops widen up.

For bolt on hubs on a crummy frame, why not make the dropouts wide? Makes it easier to assemble.

personally, i always find a correct fit to be easier to assemble.

and most rear axles on 7 sp. Box Store Bikes have axles that are of a minimal length to prevent injury to the inexperienced riders those bikes are meant for...

Puch Mistrals are typically midrange vintage bikes....unless someone revived the name.... ;)

You're probably not tightening the axle nuts with an impact wrench.

you are correct, sir!

the only place i ever use an air impact gun on a bike is on the freewheels that i remove from bikes before i either rebuild the axle bearings,,,,, or before i scrap the wheel...but only if the freewheel is rust free and as smooth as it can ever have been... i have many in stock.... too many..

brrrrip! off they spin.... only the shimano-splined ones get the gun... all others get wrestled loose with the trusty bench vise technique.

You'll need to adjust the high and low limit screws on the rear der, but you can even use the same chain if it isn't too stretched. Not certain why your frame would already measure 130mm, probably someone screwing with it in the past, but the der should handle the 7 speed cassette, barring, as someone else mentioned, the low cog being too large for the der to wrap the chain around.

I'm the original owner--bought the bike in Vienna around '86. I don't think the bike has been altered. It also had mismatched hubs (Miche, front; Normandy, rear) from the beginning, so I assume the rear wheel was a mistake in the factory or store where I bought it.

Dedicated vintage 6 speed chains are wider and not compatible with 7 speed.

Actually, the overall width of a 6 speed freewheel and a 7 speed cassette is about the same. Regular cog spacing for 6 speed is 5.5 mm and for 7 speed it is 5.0. Both require at least 126 mm dropout spacing. Ultra 6 freewheels use narrower spacing so as to be able to be used on bikes with 120 mm dropout spacing

Not true. Chains are the same with 6/7/8 speed drivetrains. I use Shimano HG71 chains on every one of my bikes and it's even labeled that way, as are most other "8 speed" chains. All of my bikes are either 6, 7, or 8 speed and I like that I can use the same chain on all of them.

As long as you have friction shifting, you should be good to go. Naturally you'll need to adjust the limit screws. If the largest and/or smallest cog is much different, you may need to resize your chain.

You may need to check your dropout and hanger alignment. You have had some issue your bike should have been at 126. Your chain may or may not be fine with the change.

You are going to a 130 hub, have thought of updating to a 8, 9, 10 hub?

That was not the case when the OPs bike was made, and he said it hasn't had any real service.

Again, original 6 speed chains don't work on 7.

He's presumably changing out the chain along with the freewheel. Any modern 6/7/8 speed chain from Shimano, KMC, or SRAM will work just fine. The so-called 6/7/8 speed chains (7.1mm) even work on 5-speed bikes. KMC labels the X8.93 as a 5-8 speed chain, for example.

But if you actually read the thread you'll see the suggestion to put the new wheel in without changing the original chain. To which I replied.

I can't imagine changing wheels, along with the freewheel, without changing the chain at the same time. There's a good chance he needs to size the new one differently also.

It won't matter with friction shifting. The difference ctc from one cog to another on a 6sp vs a 7sp is .5mm or less, the chain won't be so wide that with friction it will make any difference. The OP can just install, adjust the limit screws and cable tension, and go ride.

Probably damaged in shipping, before the advent of prebuilt wheels on every bike if a lower to midrange bike was too poorly treated by the post office elephants we would just make sure the rim was the same and not worry much about the hubs as long as they weren't a different color. People might notice rim shape and color but not hub branding and rear wheels were easily damaged.

So what if its not? Don't be afraid...

Sounds like it's going ta be a very nice bike once ya get it set.

7 speeds on a cassette with clinchers... Yep!

I started working in bike shops when 6 speed was very common. You don't know what you're talking about - the wide chain will chatter and try to shift up the next cog. It has nothing to do with index vs friction shifting.

Yes, no one but you knows what they're talking about, tell it to someone who cares. Considering one of the easiest repairs for crusty freewheels that just wouldn't freewheel anymore was tossing a 7sp freewheel on a 6sp bike and moving on I'm sure I'm wrong and could care less what you have to say. OP, it costs you nothing to try it, have fun.

Why are your tender feelings more important on this forum than providing the facts of bicycle repair?