New tires for the Martini Porsche 936 Turbo
This section is shared with another article to be soon published.
However, everything described here does apply to the Martini Porsche 936 Turbo rims and tires.
With decades-old models, tires generally become a serious issue. Specifically, rubber tires generally dried way beyond what the material can stand: so they crack. This not even mentioning wear if they were used or the "flat" spots due to the model weight. Examples of rubber tires after a few decades:
Many cracks can be seen on these photos, but even more are revealed just manipulating the tires. Moreover, the rubber is totally dry: any attempt to drive with tires in such a sorry state will result in their complete destruction before the end of the first lap.
There is a technique to "restore" rubber tires: glycerin. This product will restore the original black color and part of the tire flexibility by re-moisturing the rubber. However, the glycerin does not repair the tire (cracks) and does not make it suitable for driving again. The glycerin treatment should be considered as a good solution for display models.
The only one solution is to replace the tires with brand new ones: unfortunately, that is the problem since the tires of the first Tamiya models are now very rare and expensive. Even supposing you find them and you are rich enough to pay for them, these tires would have been manufactured decades ago: of course, they will be suitable for driving, but they will probably wear very fast because the rubber aging was only slowed down in the box.
So we do need new modern tires to replace them, and here comes the second problem: their size is different from any currently available. This very problem applies to kits 58001, 58002, 58005, 58006 and 58017 (front only) since they all use the same rubber tires (for foam tires, the problem is quite different). I spent several months searching and testing among Tamiya lineups (QD, M-Chassis, TamTech...) before I got a very useful advice from alain térieur on the Vintage-RC forum: Nikko Ne14.
These Nikko tires have the same size as the front tires we are looking for: nice addition, slick and radial structures are available. One more detail: they can be adapted to our models original rims after some modification. I forgot to mention that our goal is to keep using the original rims of our models and to leave them intact: the Fushs from the Porsche 934 RSR and 936 Turbo, the 935 Turbo's, the Countach's "dial phone" and the specific B2B Racing Sidecar front wheel.
First, here are the new Nikko tires (not glued on rims, piece of cake!):
The two inner grooves on these tires are a problem since they precisely go onto the rims inner edges. OK, so we are going to cut the tires (our original rims must remain intact):
First: flip the tire. Next, cut each outer groove beginning from the inner side of the tire. The result to get is shown on the second and third photos.
Before fitting the tire onto the rim, we need to place a foam insert in the tire (a hard foam, as much as possible)): the inner grooves being removed, the tire no longer holds well on the rim. The foam insert will partially remedy the problem, and gluing the tire onto the rim will definitely make a perfect fit.
Here's the final result on a B2B Racing Sidecar front wheel:
And now on the Lamborghini Countach "dial phone" front rims:
As you may notice on the last series of photos, the tire inner diameter is slightly bigger than the outer rim diameter. The foam insert in the tire and gluing the tire on the rim will definitely solve the problem.
So we now have an alternative solution to fit new tires on the original front wheels of the Porsche 934 RSR, 935 and 936 Turbo, Lamborghini Countach and B2B Racing Sidecar. The pros of this solution are the low cost of the Nikko tires and the preserved integrity of the original rims. The con is the loss of the Dunlop or Good Year marking on the tire walls.
Now let's go for a rear tire alternative, still preserving the original rims. This time, the solution came thanks to my friend Steve Warson from the Vintage-RC forum: F103.
This is close to perfection:
What we have here is a Tamiya F103 front tire fitted without any modification onto a Lamborghini Countach rear rim (the Countach's original tire is shown side to side). You can notice the tire wall is thicker than the original's and that the outer diameter is slightly bigger. However, the difference is minimal: we've got a solution!/p>
Even though Tamiya F103 rubber tires are not very available (most of the models come with foam tires), you can still find them at reasonable prices (references 53138 or 53349 or 53374).
As a conclusion, there are alternatives to replace the original front and rear tires for the Porsche 934 RSR, 935 and 936 Turbo and the Lamborghini Countach. The solution also applies the B2B Racing Sidecar front wheel (rear tires are foams).
Unfortunately, the precise dimensions can't be fully respected and the tire wall markings are lost unless you redraw it. However, these alternatives allow models to quit their shelves and to be safely driven again. I want to thank alain térieur and Steve Warson from the Vintage-RC forum for their remarkable help.