Losi'91 Detroit Worlds Prototype - HISTORY - by Lou Sola

The 1991 Team Losi "Pro SE / Detroit XX" Prototype

While there is now a wealth of well-known and documented information regarding the Associated "stealth" prototype 2WD cars used in the 1989 and 1991 World Championships, the same cannot be said about the cars used by AE's greatest rival, Team Losi.

I'll begin by stating that, although I am by no means the ultimate authority on Team Losi's history, I am fortunate to still have a good recollection of what transpired during that time, as I was a Team Losi driver and a huge fan back then—and remain so to this day. Lou Sola.

A Brief Losi Timeline

In 1988, Team Losi released the 2WD Jrx2, equipped with a graphite chassis, an easy-to-build and smooth LRM transmission, and the famous 5-link suspension. It pushed the boundaries of what a competitive RC racer should be and is still regarded today as one of the most innovative RC cars of all time.

The Jrx2 swept the racing scene, capturing numerous national titles and a host of other major championship wins worldwide.

Early in 1989, Losi released the JrxT, the truck version of the Jrx2. Based on the buggy, the JrxT featured extra-long front shocks and a longer chassis with a 30-degree kick-up. Most of the "team" drivers at that time had switched their buggies to the longer chassis with long front shocks, as the car with the 30-degree chassis and long front shocks was much more stable.

By September of that year, at the 1989 World Championships in Sydney , the Losi team was using this long chassis and long shock setup, along with prototype rear "H" arms, which would soon be released as a conversion to eliminate the 5-link rear end. Some of the cars were also equipped with vertical side rails that served to stiffen the chassis and hold the batteries in place.

This was the extent of the 1989 'prototype' Losi. Of course, we all know what AE and Yokomo brought to the party that year—stealth prototype cars and 2.2" diameter tyres.

Not long after the 1989 Worlds, Team Losi released the Proformance (or Proformanance! ) kit as an upgrade to the JRX-2, bringing it to the same spec as Jack Johnson's ROAR National-winning car.

This kit included a longer graphite chassis, the conversion to H-arm rear suspension, longer shocks, springs, and the mighty 17x3 "Jr's Choice" Team Losi Revolution motor.

 

By 1990, Team Losi had released a full kit version of the Jrx2 + Proformance kit combo, called the "Jrx Pro". For all intents and purposes, this was the 1989 Worlds car with some extra bits and pieces, such as a revised rear shock tower and the red dished Losi logo rims.

For the next year, the majority of the Losi team ran the Jrx Pro. It was a great car with superb rough track handling, but it had a tendency to push (understeer).

In Australia, to try and combat this understeer , some of  the team drivers used locally made swept-back front arms and experimented with MIP bell cranks, which offered different Ackermann adjustments and helped a lot.

Around this time, Team Losi also released the "Junior2" , which became another milestone in the RC industry.
A budget-friendly racing kit, the Junior 2 included bushings instead of bearings, molded plastic shock towers, and, most importantly, the first injection-molded plastic composite chassis in a modern 2WD racing buggy. This car and Losi's injection-molded composites influenced the development of 2WD buggy racing for the next 20 years. By mid-1991, some team drivers began using modified Junior2 chassis on their Jrx Pro cars, as the composite chassis was lighter and stiffer.

 

The 1991 World Champs in Detroit

The 1991 Worlds was an event where every manufacturer introduced some kind of prototype part or car. Team AE had set the bar at the previous IFMAR World Championships, and Team Losi was determined not to be shown up again. With a very peculiar track surface and the now-famous "surf's up" section, the Detroit track proved to be more than just a challenge.

Based on the research , which mainly involved scouring the internet to find every available picture and reading every available story, this is what I  have come up with.

It seems that there were at least four or five different variants of this same car, all having minor differences—whether they used a slightly different front or rear shock tower, a different front C-hub, some slight changes to the steering bell cranks, or different front arm widths. These variations likely played a part in the car's development.

Team Losi rolled out a car that could be described as a "XX-Pro SE" prototype. This car used the complete rear end assembly of the Jrx Pro but had a new type of rear shock tower. All this was mounted on a modified Jr2 composite chassis, which now featured proper Ackermann bell cranks and a narrow , hinged front bulkhead that allowed for kick-up/caster adjustment to 20, 25, or 30 degrees via different top decks. The front shock tower could accommodate both longer and shorter shocks, and the front arms were longer and swept back to place more weight forward ( maybe the Aussies were onto something ! )  This car no longer had wheel bearings in the rims but instead utilized an inboard bearing /spindle setup, which would later debut on the Losi XX.

And, of course, almost without saying the most important part of this car: Team Losi once again showed innovation by designing their viscous-filled "shock absorber" for the transmission—the mighty Hydra Drive slipper clutch system.