Color0's Micro RC Blog -- A technical brain dump from the mind of yours truly...
Anatomy of a Mini-Class Racer
It definitely has been a while since I last wrote an article for this site. So to kick off the continuation of this blog, let's take a look at the short-wheelbase "fun" racing class known as the Mini, or 90mm, or SWB class.
Rules for this class vary from track to track, but the general idea behind it is to make some use of cars and bodies that normally would not be competitive. That means that the 86 and 90mm wheelbase cars come out to play, as well as the tall wagons and minivans that normally see shelf time more than anything else.
Depending on the track, the rules can be more specific, for example: narrow bodies only, no MR02 chassis, no dish wheels, PN Stock 70t motor only, etc. As it is intended to be a non-competitive, "fun" class, this means that you might as well bring out bodies that look nice rather than perform well, use realistic-looking rims rather than those silly dishes, and bring your used racing batteries out of retirement for another shot at victory.
And keeping that in mind, let's dissect this particular specimen that I put together for 90mm class racing.
The first thing to note is that Kyosho's FC3S RX-7 is one of the narrowest bodies made, originally listed with wheel offsets spec'd at 0N in front and 0N in the rear -- on an MR01. That doesn't mean we have to listen to Kyosho though, as the car here manages to fit 1.5N in the front and a full 0W in the back, courtesy of some rear axle bearings stolen from an MA010 (they're thinner). The wheels I chose are a set of Volk Racing RE30's; you can also steal wheels from your Autoscale bodies or ask a fellow racer for some, anything will work for this class as long as they're not broken.
Underneath the FC3S is an MR015 chassis, in keeping with the non-competitive theme. The front end need not be a pricey expenditure at all, just some stainless steel kingpins and a set of springs will be enough (there's some gratuitous alloy on this car as I purchased it second-hand). A couple shims underneath the knuckles to lower the ride height will do wonders for countering traction roll -- I bought mine in bulk from McMaster-Carr.
The rear end features PN Racing's latest 90mm MM motor mount, as well as a ceramic ball diff. You don't really need either of these things for this class of racing, but I do like PN's motor mounts because they're almost guaranteed tweak-free, and ball diff was left over from a previous car.
Said 90mm motor mount actually comes with the disk damper carbon plates; I completed the assembly with some leftover Atomic parts, and voila, we have rear damping. A disk damper or side damper is definitely recommended for any RWD car; without it, the car will chatter, and can potentially traction roll, during high speed cornering.
Having the fastest batteries is not the point of 90mm-class racing; I'd rather save my wallet and get the cheapest ones. A Main Hobbies carries Protek R/C AAA batteries, and they pack a decent punch and runtime at a ridiculous $2/pack (at the time of this writing, at least).
Although I mention this last, tires are (as always) the most important part of car setup, and this particular car wears PN 20 slicks up front and Kyosho 20 slicks in the rear. This seems to be a pretty potent combination as long as you don't YANK the steering, an important consideration of driving any high-CG Mini-Z.
And that's about it -- remember, the whole point of Mini/90mm/SWB class racing is to not have to stress over setup, motors, batteries, or even winning. Just go out there and have fun, your hatchbacks and minivans will thank you for it.
Rules for this class vary from track to track, but the general idea behind it is to make some use of cars and bodies that normally would not be competitive. That means that the 86 and 90mm wheelbase cars come out to play, as well as the tall wagons and minivans that normally see shelf time more than anything else.
Depending on the track, the rules can be more specific, for example: narrow bodies only, no MR02 chassis, no dish wheels, PN Stock 70t motor only, etc. As it is intended to be a non-competitive, "fun" class, this means that you might as well bring out bodies that look nice rather than perform well, use realistic-looking rims rather than those silly dishes, and bring your used racing batteries out of retirement for another shot at victory.
And keeping that in mind, let's dissect this particular specimen that I put together for 90mm class racing.
The first thing to note is that Kyosho's FC3S RX-7 is one of the narrowest bodies made, originally listed with wheel offsets spec'd at 0N in front and 0N in the rear -- on an MR01. That doesn't mean we have to listen to Kyosho though, as the car here manages to fit 1.5N in the front and a full 0W in the back, courtesy of some rear axle bearings stolen from an MA010 (they're thinner). The wheels I chose are a set of Volk Racing RE30's; you can also steal wheels from your Autoscale bodies or ask a fellow racer for some, anything will work for this class as long as they're not broken.
Underneath the FC3S is an MR015 chassis, in keeping with the non-competitive theme. The front end need not be a pricey expenditure at all, just some stainless steel kingpins and a set of springs will be enough (there's some gratuitous alloy on this car as I purchased it second-hand). A couple shims underneath the knuckles to lower the ride height will do wonders for countering traction roll -- I bought mine in bulk from McMaster-Carr.
The rear end features PN Racing's latest 90mm MM motor mount, as well as a ceramic ball diff. You don't really need either of these things for this class of racing, but I do like PN's motor mounts because they're almost guaranteed tweak-free, and ball diff was left over from a previous car.
Said 90mm motor mount actually comes with the disk damper carbon plates; I completed the assembly with some leftover Atomic parts, and voila, we have rear damping. A disk damper or side damper is definitely recommended for any RWD car; without it, the car will chatter, and can potentially traction roll, during high speed cornering.
Having the fastest batteries is not the point of 90mm-class racing; I'd rather save my wallet and get the cheapest ones. A Main Hobbies carries Protek R/C AAA batteries, and they pack a decent punch and runtime at a ridiculous $2/pack (at the time of this writing, at least).
Although I mention this last, tires are (as always) the most important part of car setup, and this particular car wears PN 20 slicks up front and Kyosho 20 slicks in the rear. This seems to be a pretty potent combination as long as you don't YANK the steering, an important consideration of driving any high-CG Mini-Z.
And that's about it -- remember, the whole point of Mini/90mm/SWB class racing is to not have to stress over setup, motors, batteries, or even winning. Just go out there and have fun, your hatchbacks and minivans will thank you for it.
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