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Vintage bonded aluminum and steel

Hardy Menagh   7/14/11

In the past few years a truth has revealed itself: Unless you absolutely can't wait, there's really no point in buying a bicycle. If you can be patient (and your standards aren't too high), a suitable one will be along presently.

BeforeNear the end of June, I started out on a quick 17 mile ride. I planned it to be my last one prior to a scheduled century ride with friends, two days away.

A few miles from home, I spotted a drop-bar road bike leaning against some junk by the road. As I got closer I saw an instantly recognizable Raleigh headbadge. I stopped and examined the bike, a 1988 12-speed Technium Pro.

I had heard of Technium bikes and had cringed when I did. They were made in Seattle, Washington, USA after the Huffy buy-out of the Raleigh brand.

The Frame is Made How?

The disturbing thing for anyone who has had experience working with a variety of different materials is that these frames were made from thermal bonded steel and aluminum. The top tube, down tube and seat tube were 6061-T8 aluminum tubing epoxied to the lugged cro-moly head tube, bottom bracket and stays.

Thermal bonded, likely refers to the fact that some varieties of industrial epoxies must be heated to set properly. The type of adhesive used in this application is called "toughened" epoxy which remains somewhat resilient when fully cured. Even so, steel and aluminum have different expansion/contraction characteristics with temperature change and I had never encountered an adhesive of any kind that could successfully bond even similar metals together with any dependability whatsoever.

On hearing of a bike frame being assembled this way, I believe my initial reaction was, "Well, that's a liability suit waiting to happen".

LugIn reality, this kind of bonding technology had already been used successfully in the aerospace industry. In addition to technically advanced glue, a specially designed joint with a zero clearance, flush fitting section as well as a section to hold the adhesive and form the bond, was used. I'll also make an experienced guess that the aluminum tube was heated or the steel lug was cooled or both, before assembly. This would make the parts go together easily, then the joint would tighten and uniformly spread the adhesive as the temperatures equalized. At least, that's how I'd do it if I absolutely had to.

JointThere have been a few reports of these frames failing at the joints, especially the mountain bike frames. These failures can often be traced to bikes that were exposed to repeated temperature extremes or extraordinary stresses. These would be the kind of stresses that would likely cause welded and brazed joints to fail as well.

Compared to the thick, welded all-aluminum-tubed bike frames of the time, like Cannondale, the consumer-level Technium frames are not quite as stiff. If you lean against a wall and stand by one foot on a pedal, you can feel the frame sway slightly beneath you. This frame compares in flexibility to good quality, steel-framed bikes, but results in a bike that weighs a few pounds less than a comparable steel-framed bike.

Honey, It's not my Fault. They Keep Following me Home

Head LugsThis Technium appeared to have seen little use but the chain and cables were quite rusty. The barely-used tires were flat and badly cracked and the paint was scraped off in a few places. The bike looked like it had been knocked around a bit. However, the wheels were close to true and turned easily and smoothly. The frame joints looked and felt solid even after almost 25 years. The bike was also my size.

After verifying with the property owner, that the bike was up for grabs, I picked it up and moved it back and away from the road. I finished my ride, then returned with a car and brought it home.

Seat LugsRepair & Refit Considerations

The Technium was going to need a complete teardown, cleaning relubrication and rebuild, including spot-sanding and touching up the several small areas that had rust or missing paint. I picked a couple of days I could mostly devote to it and started in.

The bearings were in good condition although the grease was old and getting dried out. The only caged bearings were in the headset which had upper and lower roller bearings in plastic cages. I was thankful they were in good condition as suitable replacement bearings might be difficult to find.

The Technium's rear brake cable is routed internally through the top tube. I had no idea if there was anything inside the tube to help guide a new cable through, so to play it safe, I attached the new cable housing to the old one with the straw from a can of spray lubricant. I carefully pushed and pulled this assembly through the frame tube until the new cable housing emerged from the hole at the other end of the tube.

The brake pads had seen very little use, so I filed off the surface glaze and reinstalled them.

The original handlebars didn't have enough of a curve for my liking. The drops had too much of a downward angle to suit me so I exchanged them for another constant curve set with a more complete curve.

An Experiment

Drive TrainOne of the suppliers I buy parts from, was closing out a Shimano Megadrive 8-speed freewheel which went from a 13-tooth sprocket to a 34-tooth one, in a logical progression, not like the Megarange versions that skip several gears that you'd like to have between a 24 and a 34. I had no idea what I'd do with it when I bought it but now I had the opportunity to experiment on this bike. This is hill country and a 42-tooth chainring driving a 23-tooth sprocket wasn't going to get me very far. Since the Technium had steel stays, cold-setting them the minor amount needed, wasn't a problem. The indexing downtube shifter had a friction mode, so compatibility wasn't an issue. I had a spare long-cage derailer, so the change was a done deal.

The Test Ride

I'm lucky enough to live on the crest of a small but steep hill of a few hundred yards. The evening I finished the repairs, my first ride was down this hill, then back up again in the lowest, 34-tooth gear. This fully seated the freewheel and proved that the bike could do hills with much more ease than a usual-sized freewheel would have allowed. A compact double, in combination with this freewheel, could improve the climbing ability even more. Of course, a triple crankset with a granny gear would be an even better, albeit more expensive solution.

The next morning, I met my friend Don and yielded to his lifelong knowledge of the local roads, to plot a good shakedown ride for the Technium. Don chose a route that included a good uphill climb (his specialty) and a patchy potholed downhill slalom run for roughly 20 miles total. Although Don made use of his granny gear and got well ahead of me, the Technium handled the hill nicely. The frame also held together just fine through the sometimes unavoidable rough sections of missing pavement as we rapidly descended.

On the road, the Technium felt remarkably like an all-steel bike. It was an "alive" feeling, not like the anesthesia I usually associate with aluminum. I also wasn't ready for how responsive the bike is. It was important not to let my concentration wander when quickly maneuvering around imperfections in the road. The bike tended to oversteer until I became accustomed to it.

On finishing the shakedown ride, I concluded that the bike was certainly a keeper and a welcome addition to my stable.


Tubing Label

Original Specifications
(as far as I know)

Frame:   Bonded aluminum top, down and seat tubes to lugged Cro-Moly steel. Cro-Moly steel fork.
Crankset:   Shimano 105 double, 52-42 with alloy Biopace chainrings. Square-taper loose ball bearing bottom bracket.
Pedals:   Sakae SX alloy and steel with Christophe toe clips and straps.
Hubs & Wheels:   Front wheel: Quick-release Maillard loose ball bearing alloy hub, 700c Rigida Score rim made in France, 32 SS spoke, Presta valve. Rear wheel: Quick-release Maillard loose ball bearing alloy hub, 700c Matrix Titan-Tech rim made in the USA, 32 SS spoke, Presta valve (rear rim may not be original).
Freewheel:   Shimano MF-Z012 6-speed 13-23.
Derailers:   Shimano 105. Front: brazeon type with clamp adapter.
Shifters:   Shimano 105, down tube, right is indexed for a 6-speed freewheel.
Brakes:   Shimano 105 with QR.
Brake Levers:   Shimano 105.
Headset:    (paint worn off and illegible) roller bearings.
Stem:   Sakae.
Handlebars:    Italmanubri Mod Europa, Super Racing made in Italy, drop.
Tape:   Padded perforated white vinyl.
Seat Post:   Unbranded 28.8 (unusually long. May be a replacement for a taller rider).
Saddle:   Selle San Marco.
Weight:   23 lbs.

Right Side



Update 9/29/11: On September 24th 2011, I had started out on what I had planned to be a pleasant 20 mile morning ride on the Technium. I was only two miles from home when I was hit by a motorist who ran a stop sign. The view was unobstructed and I was wearing a bright red jersey but he said he just didn't see me. I sustained road rash in several places, cuts, bruises and a sore upper body and neck.

Unfortunately, the bike came through it worse, sustaining damage to everything important except the brake calipers, shift levers, front derailer, chain and cables.

The interesting thing to note and the reason I'm adding this is that, although the fork was bent sideways and the rear triangle was bent out of alignment, the rest of the frame stayed straight and none of the thermal bonded joints failed.

Crash Damage

Picassoesque picture, isn't it? Only 640 miles since the refit. Breaks my heart. Be careful out there!



Lug drawings are from a Raleigh promotional brochure.

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Copyright © 2011 Hardy Menagh