Classic & Vintage - Freewheel Question???

I'm replacing the freewheel on one of my bikes which now has a (Suntour Perfect) 6 speed
I am thinking this will be it's replacement
http://www.niagaracycle.com/product_info.php?products_id=5151
and want to know if it's a direct swap other then a possible H/L limit adjustment of the RD? Does it make a difference that it's SIS compatable since I have friction shifting?

The only problem would be if you had one of the short cage derailleurs that can't handle up to 28T. So, if your current frewheel is at least 28T you know you're OK and will probably require only a minor travel adjustment. You'll find the shifting much improved. If you're installing a new freewheel, a new chain would also be adivisable.

Another challenge could be if your Suntour Perfect is "Ultra" spaced, i.e. a 6 speed in a 5 speed width. If this is the case, the Sunrace might be too "thick" for your hub.

H/L adjustment: Yes, without a doubt you'll need to tweak the screws.

HyperGlide: Even without indexing you'll notice a big improvement in shifting. Add a modern chain into the mix and it improves more.

Spacing: If your current bike has 126mm spaced dropouts your good to go.

What's wrong with the Suntour freewheel? Worn cogs? Other than that, I've never see one fail. And they shift fine.

But yes, if you need to replace it, getting another Suntour is expensive.

And yes, check whether you have an narrow-spaced ultra-6, or a standard-spaced 6. If it turns out to be an ultra-6, you may want to replace it with a standard 5-speed, unless you feel like fiddling with spacers and re-dishing the wheel.

Measurements can be found here:

http://sheldonbrown.com/gloss_sp-ss.html#spacingk7

Another challenge could be if your Suntour Perfect is "Ultra" spaced, i.e. a 6 speed in a 5 speed width. If this is the case, the Sunrace might be too "thick" for your hub.
IIRC, Perfects were not available in Ultra spacing; only Winner.

IIRC, Perfects were not available in Ultra spacing; only Winner.

John, I have a couple of Perfects and a New Winner which are Ultra spaced. I even have the Suntour gauge to check the spacing.

What's wrong with the Suntour freewheel? Worn cogs? Other than that, I've never see one fail. And they shift fine. ...

They outlast European freewheels, but they do eventually fail. I had to scrap a 7-speed New Winner body when the removal prongs started to crack, out of fear that if I reinstalled it I would never be able to remove it again.