Slot.it Nissan GT-R GT3, 2022 DiSCA GT3 Spec

Hello Gio
In addition to Gary's remarks.

As GD mentioned before Sponge tires are more commonly used in 1/24, in general the perception of using sponge tires on 1/32nd cars is that they provide too much grip.
Which was why at the time we started the DiSCA GT3 formula we went for the then hardest compound available for 1/32nd scale, the Procomp3.
But immediately I started lobbying at Scaleauto to produce the hardest compound in their range, the Procomp4, for 1/32 as well.

Scaleauto Procomp4 is a harder compound than the Procomp3 (40-45 shore vs 30-35 shore). In general the harder the compound, the less the side wall of the sponge tire will be able to deform/flex and as such the less grip it will provide.
To a certain extent a harder compound will also have a lower wear rate. And from an organisers point of view... a bit less grip and bit more durability was what we were looking for.

As Gary mentioned "...the Procomp4 is easier to drive when new as they aren’t so grabby on the surface". This is a result of the harder compound deforming less when the wheels are trued.
All sponge tires deform slightly during the trueing process. The pressure applied during trueing bends the sidewalls slightly outwards which results in a minimal "convex" profile as the sidewalls bend back "up" after the trueing is finished.
Again the harder the compound the smaller the deformation, meaning that straight out of the box the Procomp4 has a less "convex" profile than the Procomp3 and will perform better with a more neutral handling.

One would expect the lesser grip of the Procomp4 to result in a higher laptime than the softer Procomp3 and over one lap, under ideal conditions, with a fine tuned set-up... this would be correct.
But not over the full duration of a DiSCA GT3 race. In general on the Procomp3 the lap times would tend to drop during the first 20 -30 minutes of the race, after which they would tend to start rising again.
This is due to decreased ground clearance caused by the tire wear which increases the magna traction and causes the car to develop more and more grip...to the extend that the car gets bogged down on the track. Requiring you to push harder and harder to maintain the same laptimes. It also increases the motor temp which results in less power.
With the harder Procomp4 you still have the same process of decrease/increase in lap times but with a lower wear rate the handling of the car will remain stable for a longer period than with the Procomp3. As a result your average laptime over the full race duration could be lower than those achievable with the Procomp3.

Procomp4, can they last long enough to run two (60 min.) races? My answer would be yes and not only because the harder compound can provide a lower wear rate but also because you have more tyre to begin with.
On DiSCA request the Procomp4 wheels are trued to a bigger diameter than the Procomp3 wheels (20.9mmø vs 20.6mmø)
This increase in tire diameter was requested to provide a bit more wriggle room for cars with stock Sideways and Black Arrow pods that (depending on set-up) could struggle to pass the 1.8 mm ground clearance on new tires...and the bigger tires look better too 😇

A last word on the durability, as I mentioned before, a harder compound will also have a lower wear rate...to a certain extent. Tire wear is mainly caused by the amount of tire spin.
For the optimum performance of a sponge tire a minimal amount of spin is required.
But with a set up that is too loose, and/or a driving style that hangs the tail out on every corner entry and exit...you might end of with just the same wear rate as a softer compound ...or worse.

With kind regards
Tamar

Kevan said:

Before I get shot down what about silicone tyres, true out of the packet and last years.

Click to expand...

No drive-by shootings here, but here goes why...


The main issue with silicones is that they only work on a track where only silicones are used. You can't mix rubber and silicones on the same track...
Can't run DiSCA GT3's with silicones and the next (or even same day) a DiSCA WEC endurance with rubber tires on that same track as the rubber tires won't have any grip left.

Also, the wear and tear of the tires is part of the race strategy and setup of your car (certainly for endurance-type events such as DiSCA WEC, where tire changes are part of the race strategy).

Also, some DiSCA events are run on permanent tracks, which would mean that all other club races should also have to be transferred to silicones.
So you want to run Group 5 cars the week after a GT3 race with silicones? Bad news, no grip whatsoever... Unless you change to silicones...
While DiSCA events are only one weekend a year on a certain track.

Too much disadvantages related to the use of silicones.
Foam tires don't have these major issues. Yes, they do "polish" the track surface to some extent, but not as much as silicones do.

Scaleauto ProComp are mounted on the rim already. Makes them even easier for hand-out. And yes Kevan, treatments are prohibited.

The other factor which is slightly less relevant now we have a 63mm width, but when it was 62mm to allow Scalex bodies to be more competitive, the 9mm sponge tyre made it easier for the naturally wider cars (Sideways, Black Arrow) to “come down” to width than it would have been for a 10mm or wider tyre.

For example, NSR glued and trued tyres might have been a good hand out choice, but at 11.5mm, they’d have been too large to allow some cars (including NSRs own) to conform at 62mm.

Before anyone asks, we changed to 63mm for this year (ignoring covid delay) because there’s now a much wider (pun intended) variety of cars on the market now. When we launched, Scalextric had the most bodies available and they were generally narrower, being more true to scale. In combination, cars like the (amusingly under scale) Sideways 720s at 66.5mm look very silly with a 62mm axel width having wheels tucked well inside the body!

From France, I can get a pair of sponge tires for a bit more than 8€, it's not cheap but they are on a wheel:

So, overall the price tires + wheels is fair, IMO.

About the wheels ''length'', why not set a limit by car model?
Like the McLaren 720S, as you said, why not take advantage of this car design?

Because one of the things DiSCA rule sets set out to do, especially with GT3, is to facilitate as much variety as possible on the grid. Would you like to race a 62mm Porsche against a 66mm McLaren?

And the fact is that we’ve achieved that. If you look at our GT3 grids over the years the range of different cars has always been apparent. Scalextric body cars have both won races and achieved podiums and I think thats a direct result of us balancing the width around narrower cars.

Anybody that’s been racing slot cars for a long time knows that whether it’s a club race or national competition there’s always that one car that’s favourite for any given rule set. A look at the UK Analogue GT3 Nationals for example sees several years of “every car is a Corvette C7R” and has now become “every car is a Scaleauto Viper”. That sucks in my opinion. I’m not singling out this series btw, it happens everywhere.

Except DiSCA…

While it’s not quite true that every car in a twelve (plus..) car grid is unique, it’s happened on several occasions, and if there are duplicates in a field then there’s usually only two of any given car. That’s a huge win for the ruleset and one of things I’m most proud of having achieved with DiSCA as a whole.

While it’s true we could BOP every single car individually the amount of work to do that and amount of cost we would incur to test everything would be astronomical. While I wish that administering DiSCA was my full time job, it isn’t. I don’t even have regular access to a track, and Tamar, Gio and others are extremely valuable to our organisation because they do, and can test here and there.

DiSCA has a donate button on it’s website which has only been used once since 2015. And while I’m not lobbying for donations I would like to use it as an example that people don’t care what it takes to create solid rule sets and organise competitions of a high standard. They just expect it to happen. And again I’m not complaining, I’ve done this long enough to know this is just how it is. But if anyone has expectations for individual car BOP then you better get clicking that button so we can buy every car on the market, chip it, and spend 8 hours a day testing 😉