XRAY - Model racing cars

Hello,

Lets say I have a very soft tire (e.g. Sorex 20) that I want to use on a relatively high grip carpet track. What kind of insert should I use to prevent overheating as much as possible but at the same time make it driveable?
I.e. what should I look for: Foam insert, moulded insert, much airgap, little airgap, hard insert, soft insert etc.?

Also, would anti roll bars (or a high roll centre) help prevent overheating with less amount of weight being transferred causing less friction?

Regards

I run pit D20 slicks and run JB yellow (2 piece) inserts and they seem to work from start to finish. If the grip is really good though I would say JB blues would be better.

just my 2 pence woth

I have tried the Sorex 20s on a large high grip track. I used the 26mm Yok038M inserts but on a 24mm rim. This really filled the tire out with absolutely no air gap, and if it was an open, sweepy layout then they worked well.

A mate uses the B-Type mediun Sorex inserts (medium air gap) for tighter more technical tracks and goes really well. In fact, no one can catch him!

So, fast tracks - fill the tire, slow tracks - have some airgap.

James

I agree with Hagberg and Big Jimmy G.

Primarily tires overheat because of friction forces inside the rubber itself. To prevent overheating two things need to be addressed: (1) dissipate excess heat, (2) prevent too much internal friction in the rubber from occuring.

The first point is relatively easy to address. If allowed enlargen the air holes in the wheel rim to let more air in and out of the tire. The airflow through the tyre will dissipate the heat. Moreover running a larger air gap will allow more air to directly flow past the tire dissipating heat even faster.

The second point takes a bit more work. The key here is to "dampen" the internal forces that build up in the rubber and also try to reduce the maximum force applied. The latter is something you achieve if you allow more chassis roll. If combine more chassis roll with more damping (slowing the chassis roll) you also reduce the maximum force applied. The extra airgap will help too as it allows the rubber to move a little before taking up the full force applied during cornering.

The last piece of the puzzle should now be obvious, softer inserts will also help to keep the tire temperature down.

All this does have negative effects too though. Harder inserts (and less air gap) will allow faster cornering assuming the car keeps traction that way and the tires don't overheat. The same is true for running less chassis roll. Thicker damping slows the transition which on tighter tracks is usually not something that would improve laptimes.

So the trick is to find the right balance. This depends on your driving style, the tires, the track surface, the track layout and the track temperature.

Did I scare you guys yet?

They are not necessarily overheating yet although you are getting close. It sounds from your write-up that you are just about on the ideal temperature but can probably get away with a little bit more heat in the tires before they will loose traction.

The squeeling is caused by exactly what I wrote about before, friction inside the rubber itself. Since you were running softer rims, inserts and a big airgap the tires can move around a lot before friction builds up inside the tires. That's why it took so long before the tires started squeeling.

If you want to experiment I would suggest running with larger air holes (say 2.5mm). Driving more smoothly is allways a good idea off course, but the key is to find the best setup for your driving style, not the other way around . As discussed before harder inserts will make the tires heat up faster and more, but you may want to try that anyway to reduce roll resistance. A larger airgap is something I wouldn't try as it sounds like you have a pretty large airgap already.