Carrera X-Bow Aftermarket Tires
The Carrera KTM X-Bow is a popular 1:32 slot car available in several liveries. Like most 1:32 slot cars, upgrading the X-Bow's stock rear tires is an easy, popular upgrade to improve the car's performance. However, there are some challenges when upgrading the X-Bow's rear tires that might not be readily apparent. Before you purchase the PGT-21126XXD tires, please take a couple of minutes to better understand some of the inherent "challenges" with the stock Carrera plastic rear wheels and how this affects tire fitment.
First, the stock rear wheels on the X-Bow, like many other Carrera wheels, are not a single piece of plastic. This means there are separate molds for the "inner" and "outer" sections of the wheel. In a perfect world, when these sections are assembled, the resulting wheel would be symmetrical (i.e. the diameter of the inner and outer sections of the wheel, to either side of the center rib, would be the same or very close). In reality, they are not as the picture below clearly shows.
In particular, please note the diameter of the outer portion of the wheel (D1) is SIGNIFICANTLY larger than the diameter of the inner portion of the wheel (D2).
But the Stock Rear Tires Seem to Fit Well...
The stock rear tire has a relatively flat contact patch; however, keep in mind the stock rear tires are as hard as a rock and as a result, don't offer much grip. This is probably why you're here in the first place - you want a tire with more grip. A closer examination of the inside portion of the tire reveals the tire does not fully seat on the wheel (see photo below).
Again, this is because the wheel is asymmetrical - the diameter of the inner portion of the wheel is smaller than the diameter of the outer portion of the wheel. Because the stock tire is so stiff, the center rib is dictating the overall profile of the contact patch.
So Why Don't Aftermarket Tires Fit Very Well?
In general, aftermarket tires such as the Paul Gage PGT-21126XXD will fit on the wheel; however, the contact patch is not very flat (see photo below).
This is NOT a tire issue but rather a symptom of the underlying problem that is a wheel issue! Because the aftermarket tires are made from a softer, more flexible compound than the stock tires, the aftermarket tires try to follow the profile of the wheel. If the wheel is not symmetrical (again, we clearly showed it was not above), there is no way for the aftermarket tire to compensate. The result is a contact patch that is not very flat. This is NOT an issue with the aftermarket tire design.
So How Can the Contact Patch Be Improved?
There are at least three (3) general approaches to improving the aftermarket tire's contact patch.
1) Replace the entire rear axle assembly with aftermarket parts including CNC-machined wheels that are symmetrical. This will typically cost somewhere around $30.00 USD. This is not a viable option for many racers due to the cost and effort involved.
2) Modify the stock rear plastic wheels by sanding the outer (larger OD) portion of the wheel until it matches the diameter of the inner portion of the wheel (i.e. try to make the wheel symmetrical). Because the difference between the diameters of the inner and outer portions of this wheel is so great, there may not be enough material available to remove. The result could be a compromised or ruined wheel.
3) Sand the aftermarket tire's contact patch until it is flat. For most racers, this will be the easiest and least costly solution. The picture below shows the material on the "high" portion of the contact patch that must be removed. Note this will be MUCH easier to sand when working with a Paul Gage Urethane tire (i.e silicone tires are very difficult to sand).
A Tire Sanding Machine is the Easiest Way to Do This!
While you could sand the tire using a piece of sandpaper taped to your track, he CG Slotcars Tire Machine will make quick work of a project like this. For more information, please click on the link below.