Replacing a quill-style fork on an old mountain bike

[Number_35]

I'm trying to bring an ancient mountain bike back to life. The bike is a c. 1986 Bianchi Grizzly, and was a really good bike in its day. A coworker's brother bought it from the bike store he worked at, allegedly for $900 new. I bought it from him for $200 in late '91, for my wife. She used it for quite a few years, but it's been hanging in the garage for about eight years.

I'm thinking of replacing the fork with its quill stem with a modern fork. The O.D. of the fork stem is 25.2 mm (just under 1"), so I'm guessing the I.D. of the headset tube (pardon my terminology) is nominally 1". So far so good.

I browsed the 'net for options, and everything appears to be 1-1/8". Besides that, I need the fork to accommodate 26" wheels and have mounts for the brakes.

This might be a bridge too far. Am I better off just using the old-style fork and stem?

Thanks all!

 

[MRC01]

I'm trying to bring an ancient mountain bike back to life. ... I'm thinking of replacing the fork with its quill stem with a modern fork. The O.D. of the fork stem is 25.2 mm (just under 1") ... I browsed the 'net for options, and everything appears to be 1-1/8". Besides that, I need the fork to accommodate 26" wheels and have mounts for the brakes. ...
Am I better off just using the old-style fork and stem?

It's going to be hard (impossible?) to find a modern MTB fork that will fit in a 1" head tube. Your best bet is most likely to keep the original.

 

[E365]

Don’t bother. Just keep it running with replacement parts if you really want to use it.

You’ll never be able to “upgrade” a bike that old into something even a fraction as good as a modern mountain bike. I’ve done this a few times in the past and have regretted it every time.

 

[y_p_w]

It's going to be hard (impossible?) to find a modern MTB fork that will fit in a 1" head tube. Your best bet is most likely to keep the original.

There are some mods made to do that, like this one being sold on eBay. Looks like a new steerer tube was welded in. Not sure if it's such a good idea though.

ZOOM FRONT SUSPENSION FORKS 1" THREADLESS STEERER COLUMN RP £89.95 RARE 1" MOD | eBay

Find many great new & used options and get the best deals for ZOOM FRONT SUSPENSION FORKS 1" THREADLESS STEERER COLUMN RP £89.95 RARE 1" MOD at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[Number_35]

There are some mods made to do that, like this one being sold on eBay. Looks like a new steerer tube was welded in. Not sure if it's such a good idea though.

ZOOM FRONT SUSPENSION FORKS 1" THREADLESS STEERER COLUMN RP £89.95 RARE 1" MOD | eBay

Find many great new & used options and get the best deals for ZOOM FRONT SUSPENSION FORKS 1" THREADLESS STEERER COLUMN RP £89.95 RARE 1" MOD at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Agreed, it looks homemade - and it's a suspension fork, which I don't need. And the conversion from UK Pounds to C$ would be a hit.

It's going to be hard (impossible?) to find a modern MTB fork that will fit in a 1" head tube. Your best bet is most likely to keep the original.

Don’t bother. Just keep it running with replacement parts if you really want to use it.

You’ll never be able to “upgrade” a bike that old into something even a fraction as good as a modern mountain bike. I’ve done this a few times in the past and have regretted it every time.

Good advice - that's just what I did. Here it is, back on the road after almost 8 years in exile (i.e. hanging up in the garage). I took it for a short ride, and it feels good. My wife took it for a spin, and was very happy with it too. Gotta love that retro Biopace drivetrain!

 

[MRC01]

Biopace! When that came out in the 80s, I was working in a bike shop. What a blast from the past.
If you ride it enough to wear out the chainrings, you can always replace them with standard circular ones. And move the front derailleur a bit closer down on the tube since you won't need the extra clearance anymore and it will shift better.

 

[Number_35]

Biopace! When that came out in the 80s, I was working in a bike shop. What a blast from the past.
If you ride it enough to wear out the chainrings, you can always replace them with standard circular ones. And move the front derailleur a bit closer down on the tube since you won't need the extra clearance anymore and it will shift better.

I couldn't get the front derailleur shifting well enough to be happy with it, and so replaced it with a new one.

The new one didn't play well with the Biopace chainrings - the radius of curvature was too small for the 48-T large chainring, not to mention the weird elliptical shape of the chainrings.

So then I removed the Biopace chainrings and installed an old more conventional 42-32-22 set I had kept from another bike. But the new derailleur didn't work well with the new derailleur either - I didn't have enough range to hit the big chainring.

Finally figured out that the original bottom bracket was extra wide, and that the conventional chainring set was standing off way too far. The Biopace compensates for this with spacers.

So I checked my supply of old bottom ends, and replaced the original (121.5 mm) with the shortest one I had - c. 110 mm.

That small difference was enough to pull the chainrings in enough that the 42-32-22 chainrings work well with the new derailleur.

Phew! Bike works well now, and I learned a lot.

Anyone want an ancient set of 48-38-24 Biopace chainrings?

 

[MRC01]

Chain alignment is important and can be tricky as it involves several variables. The BB itself has an offset, then the crank spindles have different lengths on each side, then the crank's offset, and the chainring positioning. You can also remove the rear cog and use thin shims/spacers to adjust the chainline.

The front derailleur shifts best when it's as low / close to the big chainring as possible. Mininum clearance necesssary. Biopace makes the front derailleur a bit tricky cuz it has to ride a bit higher / further away to clear the biggest radius of the non-circular chainring, which can make shifting less crisp.

A "normal" setup with a triple front: on the middle chainring all the rear cogs should be usable. On the small front, the smallest 1-2 rear cogs might not be usable. On the large front, the largest 1-2 rear cogs might not be usable. Due to gearing overlap, you don't need those extreme cross gears. Tandems can be similarly tricky to get shifting right, as the rear chainstays are typically shorter than a road bike, making steeper chain angles.

 

[Number_35]

Chain alignment is important and can be tricky as it involves several variables. The BB itself has an offset, then the crank spindles have different lengths on each side, then the crank's offset, and the chainring positioning. You can also remove the rear cog and use thin shims/spacers to adjust the chainline.

The front derailleur shifts best when it's as low / close to the big chainring as possible. Mininum clearance necesssary. Biopace makes the front derailleur a bit tricky cuz it has to ride a bit higher / further away to clear the biggest radius of the non-circular chainring, which can make shifting less crisp.

A "normal" setup with a triple front: on the middle chainring all the rear cogs should be usable. On the small front, the smallest 1-2 rear cogs might not be usable. On the large front, the largest 1-2 rear cogs might not be usable. Due to gearing overlap, you don't need those extreme cross gears. Tandems can be similarly tricky to get shifting right, as the rear chainstays are typically shorter than a road bike, making steeper chain angles.

It's pretty much set up as you described - and being me, I calculated all 24 or 27 gear ratios on one of my bikes a few years ago, and confirmed that there is a lot of duplication. And to access those extreme combinations, there's too much cross-chaining for my liking anyway.

 

[y_p_w]

Anyone want an ancient set of 48-38-24 Biopace chainrings?

I still have my late 80s Schwinn Sierra mountain bike with Biopace chainrings - I think mostly Mountain LX components. That bike saw me through college. I've replaced stuff over the years including the old school thumb shifters (with Deore XT) after I trashed mine.

SR had the OvalTech chainrings. But after a while they discontinued them but brought in the special RoundTech chainrings. They were, as they sound, round.

 

[Number_35]

I still have my late 80s Schwinn Sierra mountain bike with Biopace chainrings - I think mostly Mountain LX components. That bike saw me through college. I've replaced stuff over the years including the old school thumb shifters (with Deore XT) after I trashed mine.

SR had the OvalTech chainrings. But after a while they discontinued them but brought in the special RoundTech chainrings. They were, as they sound, round.

It's hard to get rid of old bikes, isn't it?

We have way too many in the garage at this point, and I'd have trouble letting any of them go.

And yes, for whatever reason, I'll hang onto those Biopace parts.

 

[NYEngineer]

Is that frame steel? You COULD have an 1 1/8 head tube welded in. You’d really have to like that bike.
Surly and Soma make 26” wheel forks.
Paragon Machine Works makes head tubes.

It is a sharp lookin’ bike.

 

[IndyIan]

SR Suntour XCE suspension fork 80mm V-brake 26' black 1

www.starbike.com

I can't vouch for the website but it seems forks still exist for that setup. I was actually considering converting my late 90's xc bike to a rigid fork and a 2.5"(biggest that fits with my V-brakes) front tire for extra squish and grip. It got a 80mm marz z4 air M arch which has some flex and allows the wheel to slap the rim brakes too much for my liking, and deflects off of stuff. After riding my rigid fat bike I kind of like the "direct feel" again and total steering precision.

 

[Number_35]

My wife wanted the handlebars a bit higher. I investigated a variety of solutions, and finally went simple - bought a longer (taller) quill stem. The original one had a little pulley in a cage for the brake cable to run through. The new one didn't have this, so I changed out the front brakes as well, swapping the cantilever brake for a V-brake.

She finds the bike "perfect" now.

Funny thing - it turns out that the LBS where I bought the V-brake was the same one that had sold the bike new c. 1987. Sure enough, the brother of the coworker I had bought it from in '91 had worked at the stop and had bought the bike new.

 

[MRC01]

Wow - small world!

 

[Number_35]

Wow - small world!

I know, right? Funny thing - 30 years ago, the fellow selling me the bike was adamant that it had listed for $900 new. I told the shop owner this, and he said "Nah ... maybe $675, no way $900". But regardless, it was a fine bike back in the day, and my wife likes it a lot even now.

 

[vavavroom]

There are a few YouTube videos on how to convert from quill stem to threadless. If you love the bike it may be worth the effort. However, I am not sure threadless is all that superior on non-performance bikes, mostly just more rigid and more maintenance friendly. You lose the serviceable and adjustable bearings with threadless.