Monday, June 25, 2018

1989 Mongoose Titanium John Tomac signature by Merlin

I never really heard of John Tomac until he shocked the world by racing a carbon Yeti prototype with drop bars at the 1990 UCI World Championships. I suspect that was the case for many others. However, before JT donned the neon yellow jersey and the turquoise frame he had a successful career racing for Mongoose. First it was BMX, but by the late 80s he was racing their mountain bikes and carrying his own line of signature models. The top of the line IBOC John Tomac Signature Titanium/Steel composite frame was introduced in 1989 and featured a Titanium front triangle made by Merlin bonded to a steel rear end. At a glance this appears to be the same bike that Tomac was using to tear around on the race course... but in reality Tomes was slinging an all Ti version of the bike made entirely by the good folks at Merlin. The main difference between this bike and a regular Merlin is obviously the monostay rear triangle. The tubeset is pretty much the same as the Merlin Titanium of that time (1 1/4" TT, 1 3/8" DT, 1 1/8" ST) and the bikes actually carry Merlin serial numbers. The geometry is really the main difference with steeper 72 degree head tube as compared to 70-71 on the standard Merlin and a flat top tube (Merlin had slightly sloping top tubes).  Because these differences are subtle to the lay person and your average Merlin fan will relate the monostay design to the later Taiga model which was poised as an entry level Merlin, the Merlgoose as some of us have come to affectionately call it has for the most part been overlooked by collectors. The relative scarcity of these frames with only a handful produced means that it has largely remained hidden in obscurity. So, having this bike here in my shop is really a treat and I can't wait to throw a leg over it and see how it rides...

The build on this particular bike was not meant to be an exact replica of JT's Mongoose, but rather reflect some of the main design elements and component selections with a couple choice substitutions. I would have like a Tioga Tension Disk on this bike but wasn't able to source a nice enough one to complement the rest of the build. There is always room for improvement I guess.

I have to admit that seeing all these flashy decals on a Merlin is sort of strange. I've become accustomed to the traditional monochrome look of the majority of Merlins and this bike still throws me. That along with the more polished finish set the bike off in a way I'm not yet fully convinced I like.

But then there is that monostay, it's such a unique feature and I think it was among the first in Titanium.

A subtle sign of who's really responsible for this creation.

Even before JT officially joined Yeti's mountain bike team he was sporting their iconic straight blade fork painted in a classic red/white/blue livery.

Classic Shimano XT drivetrain never gets old on these late 80s bike. No matter how many I build I just don't get tired of it.

One of the main areas of departure from an outright Tomac replica is in the cockpit. JT was sponsored by Tioga throughout his career and rode the T-Bone stem and prestige bars. Even thought I had those options available for this build I never liked the Tioga stems and this Titanium Litespeed stem coupled with a Cook Bros Titanium bar works really well with the frame and in my humble opinion a nice alternative to a spec build. I suppose a Helfrich Titanium stem would be one even nicer option.

The symmetry of the monostay and seat tube are quite attractive from this angle. This is a really good looking bike. 

Pressed in bottom bracket was typical on the early Merlins. While it offered an sealed cartridge bearing it was a rather small unit which wore out faster than the 6003 series used in Kleins and since the BB shell was small there was a fair amount of flex under load.

That's quite a densely packed seat cluster, lots of welds in tight area.

I really like that shape of the monostay, it's ovalized in two dimensions and clearly that section of the bike took some time to design and fabricate.  The brake stop and Titanium cable guide integrate very nicely and the overall design really stands apart from other early Titanium MTBs. Litespeed and Fat Chance would build their own monostay Titanium hardtails but not for another 3-4 years.

I must say that the geometry of this bike makes the proportions look a bit squashed. I imagine it will be an active bike with a busy or twitchy front end. I'm not sure what the monostay will do for rear wheel track and overall stiffness but I would be surprised if it's a dramatic improvement over my regular 89 Merlin. 


  1. great bike. I disagree on the tioga t bone stem: it´s stiff, giving precise handling while fitting better inside the fork steerer of my fat chance than other 1in stems.

  2. I have one. It will always be treasured and always be ridden