The Carbon Years

August 4, 2022 § 2 Comments

When the Toblerone IBOC eventually cracked, I was not surprised. If we learned anything from the proliferation of MTB frames made by some guy who knew how to weld back in the early 1990s, it was that aluminum frames frequently developed cracks. On this frame the damage was at the rear of the seat tube if I recall. Where the rear triangle was welded on, most likely. Now, of course, the presumption was for an improved production level from Mongoose, at the time a relatively big bicycle company (they’d made BMX bikes ever since 1974) compared with the boutique upstarts like Mammoth. Frames were made in the far east somewhere, most likely Taiwan, IIRC. One assumed some degree of manufacturing consistency and quality. But still…aluminum has some generic issues as a bike frame material and who knows how much was really going into testing and quality control? Manufacturers changed things up every model year and argued back and forth about the type of aluminum being used, their heat treatment, welding approaches, etc. For a bike company working with Taiwanese (?) factories, who knows whether they used the same ones from year to year….or even within a year. At any rate it was not too big of a surprise to find a welded aluminum MTB frame had cracked.

Since I had paid for the frame, albeit under the contingency race program, I put in a warranty claim. This was in the 1994 model year by this point and Mongoose was no longer making that welded aluminum IBOC Pro SX Toblerone frame. The top level was now a beautiful carbon frame, dubbed the IBOC Team SX, which used a lugged-tube construction. Instead of the full monocoque carbon layup we see in most modern use, this strategy used straight carbon tube sections bonded onto (aluminum?) lugs at the dropouts, head tube, bottom bracket and seat tube junctions. It even came in a lovely green color!

1994 IBOC Team SX (not mine)

Mongoose also had, to my recollection, a more conventional looking aluminum frame somewhere down list. A little bit of googling suggests that the IBOC Comp SX from 1994 used the same lugged and bonded design, but the tubes were all aluminum. A hybrid design for the IBOC Pro SX used the carbon tubes in the front triangle and the aluminum rear triangle, note the rear end looks like the one on the 1993 Toblerone frame. The lugged and bonded approach gave the company a nice modular solution to making frames to fit three levels out of two.

The distributor wanted to give me one of these lesser frames, I think it was the Comp SX, arguing that aluminum equals aluminum. I argued vociferously that top level frame equals top level frame. I seem to recall the weight of the new aluminum IBOC Comp SX was much higher than my 1993 model, an argument which was also deployed. Weight weenieness was very much a thing back then and frame weight was a strong argument for (in)equality.

1994 IBOC Pro SX (note Aluminum rear triangle)

In the end, I won the argument and received the green IBOC Team SX. It was sweeeeeeeet! Perfect geometry for me, where the Toblerone had been a little bit long in the top tube. The 1994 frame was stiff where it should be, comfortably compliant where it could be and quiet! None of that loud pinging you got with an aluminum frame. Light, strong. Minimal slope to the top tube fit my style preference. The geometry seemingly designed with the assumption you’d use a Mag 21 fork on it. The perfect mountain bike.

My 1995 Mongoose IBOC Team SX during the occasional commuter days

After at least a year I managed to pull out one of the water bottle mounts, possibly due to me not prepping the screws enough and possibly due to an actual manufacturing flaw. At any rate, I complained to the distributor and got *another* IBOC Team SX frame, this time the 1995 model which came in black. It was the same as the 1994 frame as far as I could tell. Same awesomeness. This was my most comfortable ride all through the dark days when I wasn’t riding much. That started somewhere in the late 90s, not sure I ever raced the 1995 frame. For the next two decades, I’d occasionally take a MTB ride, or go through a several week phase of commuting on it with slick tires installed. It didn’t seem to matter how fat or out of shape I got, hopping on this bike always felt totally natural.

Three fantastic MTB frames for the $250 contingency racer program. Not too shabby!

Epilogue: Notice how all of these bikes have bar ends fitted? I am just saying.

Also: The bike warranty deal during the first Golden Age of mountain biking was variable and weird. Frequently they would say that racing voided the warranty. Occasionally some language that was basically “no taking this mountain bike off road or you void the warranty”. So most people who bought a bike from a shop and broke it would just lie about not racing. Given that I bought a bike frame under a racer contingency program, this must not have been a Mongoose concern.


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