I recently picked up a 1986(?) Centurion Ironman Master all original in what appears to be in excellent condition for $140. After numerous injures from long distance running i felt it was time to seriously explore road biking. I live in a hilly region and the bike has the original shimano 600 SIS. It appears to be a 6 speed 24T cassette/freewheel. (ouch) . I was told that i could easily replace the cassette/freewheel with a new 6 speed 28T and that it would make a huge difference in the gearing (allowing me to better handle the hills) like this one:
https://www.ebay.com/itm/Shimano-HG22...item3cbc01394c

I have three questions:
1. Is this possible considering the design of the original hub design?
2. Will it really make a noticeable difference?
3. Any other ideas, without making major adjustments or replacements?

thank you so much...i am new to this world but consider myself very handy

jgb333

First, welcome to the (Ironman) club! You've found a real gem, and at a good price, too.

You should be able to use a 14-28 freewheel, but you may need a new (longer) chain, and possibly a longer "B" screw on your rear derailleur to ensure the upper jockey pulley does not grind into the big cog. Do a forum search for "B" screw adjustment and you'll get some good info.

I say it's possible because I have a 1988 Nishiki that came with a 14-28 freewheel, and stock BioPace chainrings (53-42). The rear derailleur is an Exage Light Action (lower quality than your 600) and it handles the 28-tooth cog with ease.

If your area is really hilly, you might be better off getting a triple crankset.

horatio,
Thanks for replying so promptly...i thought it was a good price too!
I live in southern new england (ct) so not too hilly...no long sustained climbs, but rather short and steep...
I have two problems...1. i am still learning about bike mechanics (bought the zinn guide to repair) so i want to stay away from anything overly complicated right away...2. i am super cheap

Glad to help. These older bikes are great to learn wrenching on.

If you don't want the hassle of buying tools right away, take the rear wheel to a bike shop and have them swap the freewheel for you. Otherwise you'll need a Shimano-splined freewheel tool and a chain whip. A decent chain tool is a good investment regardless (I use a Park model). Nashbar has some general purpose tool kits for reasonable cost, especially on sale. I bought most of my tools the expensive way - one at a time!

Welcome to the forums!!! what hliiy region do you live in?

Nice looking bike, are we sure about wether you have a cassette or freewheel in the back? there is a difference and the simpliest way for a novice to tell is if the center of the hub between the flanges (where the spokes thread through) is fatter on one side than the other. this may help https://sheldonbrown.com/free-k7.html

Bianchigirll,
great link...100% sure its a freewheel...close inspection shows me there is no "bulge" on one side of the hub.
btw, i live in the hartford ct area.

I got one of those new Shimano freewheels, they're great! Especially with a new (reissue?) Hyperglide chain. Let me offer different advice though. That Ironman could end up around 22lbs, which is pretty damn light. And you seem fit. I'm thinking when you get it back to spec (or better), you should be able to take it anywhere without the 28. Just using toe clips or cleats could make up for those extra teeth on a real light bike.

Mine's the 7 speed. Made in Singapore apparently.

i just automatically assumed that i would be getting clipless pedals...are you (Kanegon) recommending that i stay with the original pedals even on long aggressive rides?

The expert designation didn't start until 1987, so I would assume your bike is an 87. Going to a 28t will give you a 17% advantage. I say go for it. Don't let the macho men talk you out of it. Girls don't care what gear you use as long as you get it up the hill.

of course not. just saying hills seem to melt when you've got a light bike with clips/cleats, and that you may not need the larger sprocket. see how it goes.

CardiacKid,
WOW-WEE 17%...never would of guessed it was that much....not an "expert", but a "master"...from my research i gathered that the "master" came stock with Shimano 600, which this bike has

Sorry, I meant to say the Expert and Master designation. Prior to 1987 there was just a a Dave Scott Ironman.
There is a great website for figuring this stuff out. If I had used it, I would have told you it is exactly 16.666666%.
www.sheldonbrown.com/Harris/gears/

Nice, bike, and welcome to the forum.

1986 was the stand-alone "Ironman" designation, but we're all masters and experts here!
The red/white was also offered in 1987 on the Ironman Expert model, but with those coppery Araya rims and 600 group, you've got an '86.
It should have Nitto bars/stem, fluted seatpost with a Turbo saddle. Group is 2x6 Shimano 600 SiS indexed, with great wheels.
The Tange 1 frame is a beauty, and the paint job cleans up very well. The red can be matched pretty close with Testor's red paint pens.
The white often fades a bit to more of a cream, mainly due to the clear coat over time. Whitewall cleaner scrubbing (and quick rinsing) brings it out some.

The others here are right, you can easily add a wider range freewheel, Kanegon has a couple of Centurions, knows his stuff, as do the others here. The suggestion for a 39t small front ring is very good. If you do both, at very reasonable expense, you've got a better climber, and it will be noticeable. There is an ISO/Trade thread here on the C&V forum, and you could offer to trade your freewheel and 42t ring for a larger freewheel and a 39t. You may have to put in a little cash, but it's cheaper than buying both.

I have three questions:
1. Is this possible considering the design of the original hub design?
Yes. Eventually, you could even go to 7-sp with a freewheel and shifter change.
2. Will it really make a noticeable difference?
Yes. As an ex-runner, you're inclined to "mash" at low rpm's. Almost any change, for climbing, is good.
3. Any other ideas, without making major adjustments or replacements?
White saddle, white wrap, white housings? Purely for appearance. Clipless pedals.

thank you so much...i am new to this world but consider myself very handy
You're welcome here.

But you better not beat her up that hill LOL

I changed my '87 Ironman to a cassette with 7 speeds by putting a spacer on the inside. Then changed out the D/t shifters to Light Action barends. No problem with spacing between dropouts.
I also put triple chainrings on with 46-36-28 gearing, the rear is 12-28. I can climb anything and still decent on the flats.

RobbieTunes...Thank you for the thourough response...enamel paint pen is a must have...in regards to the 39t small ring...can i simply switch out my existing small inside ring with say this https://www.ebay.com/itm/Shimano-Ulte...item27c3523db3 ? if i go from a 24t to a 28t freewheel and a 42t to a 39t front small inner ring will i also have to get a new chain?

Bianchigirll, my sister is going to be my riding buddy...she just finished her first tri...she is older than me (40's), cancer survivor, and a triathlete...i am in big, big trouble

Beware old people.

Thanks for that info. That's EXACTLY what I need to convince a guy with an RSX 3x7 STI setup, 48/36/26 and 13-26, that he will be fine at Bike Virginia with that setup. I may swap in a bigger cassette on the rear, just to make him feel better.

Always good for him to hear it from someone who's actually done it, and used it.