marbles and klag and tire degradation

[tracyridge]

hello
A question to all who use aftermarket urethane tires, Or makes them. Do the tires you use degrade ? wear out? And life span? 1000 laps? give or take.
As you can see in the photo there is quite a lot of "marbles" or "klag " as the brits say, on this car . A would guess that's about 600 laps on those tires.
Now these are tires i make myself using a urethane rubber.A 2 part mix . I get it at Smooth-on. Its is available in different hardness's I use a 30 grade .
which is towards the softer end. Do you lose grip if you go with a harder compound?
We run on a digital wood track ,so magnets are not a factor here .
Any thoughts anyone?

thanks
john

[Aptosc6]

Looks like your getting your money's worth out of those tires!
All rubberish products wear (think of your real car). Most people use them until ride height suffers or grip goes away. A thousand laps may be correct for your tires, some others maybe a little less (thinking NSR).

[RexCadral]

Holy cow! I have cars with Paul Gauge "firm" urethane tires (Shore 40 I think?) and I have put over 1000 laps on my track (latex painted plastic, half-magnet) and am not seeing that kind of debris inside the cars. My track is ~63' long, and there is one stretch where you can open the car all the way up, otherwise it's "technical". I don't even get that kind of debris when I "true" the tires on track with a piece of sandpaper. I'm guessing you're using a much softer compound.

[RichD]

Urethane tires may degrade and become brittle as time goes by, but that does not seem to be a common problem. I did have some urethane tires that had been in storage for some time, they were 5-6 years old when I discovered that they had turned red and were very fragile. I just examined some urethane tires that are on a class of cars that has not been raced for years and those are OK.
Urethane tire do wear out faster than silicone tires, I would estimate that they wear out 2-3 times as fast on 1/32nd cars. I have never seen urethane tires get shredded like the ones in the picture. That might be the result of using a 30 Shore formulation. You would expect that softer tires would have more grip, but my experience with glued and trued tires is that soft tires tend to roll under in the corners, so their contact patch is less than with firm tires. A 40 Shore formulation might have more grip. When a car slides a lot the tires will wear faster. For each lap a car that slides is effectively going further. If the tires slide across braids that are flush with the track surface they may tend to get chewed up.

[Modlerbob]

My track is constructed of MDF painted with acrylic paint. I use Paul Gage pgt and xpg tires. I get quite a large number of laps out of those that don't decompose (turn orange and fall apart). The xpg's seem to go south at a higher rate than the pgt's. I live in Florida and the room where my track is located isn't climate controlled when not in use, so it suffers from a wide temperature range. An average set of tires lasts with use at least 6 months. Tires that aren't installed yet seem to have a pretty good shelf life but those that are on cars and don't get run seem to have the most problems. Silicones seem to last forever. Sponge tires on the few 1/24th scale cars I have dry out in about a month. OEM tires from Carrera seem to degrade very quickly. Most of my front tires are those that come with the cars and many after a year or so either turn to goo or start cracking and dry out. Traditionally it is more difficult to find replacement tires for the front but I have noticed lately that some vendors are selling and labelling tires that are made specifically for the front.

[MrFlippant]

Tire dust on the inside of the car body/chassis is common with any kind of tire... though maybe not silicone? Definitely happens with rubber and urethane.
It's not a bad idea to clean it out when it gets that bad, but it's only a problem for racing when it stick to the tire itself. I've not had that happen with any urethane tires I've used, but it can happen with softer rubbers, especially when various treatments are used, or if they get abused on a tire truer.

[Bal r 14]

No dust with silicone.

[Kevan]

Holy cow! I have cars with Paul Gauge "firm" urethane tires (Shore 40 I think?) and I have put over 1000 laps on my track (latex painted plastic, half-magnet) and am not seeing that kind of debris inside the cars. My track is ~63' long, and there is one stretch where you can open the car all the way up, otherwise it's "technical". I don't even get that kind of debris when I "true" the tires on track with a piece of sandpaper. I'm guessing you're using a much softer compound.

If you're truing the tyres there's always rubber dust.

[Bal r 14]

I switched to silicone to avoid all of the hassle and mess. No gluing, no truing, no dust!

[Kevan]

I would probably do the same if I wasn't a member of a club that specifically outlaws silicones

[Bal r 14]

Our group only allows silicone.

[Kevan]

Silicones are a no-brainer, almost a one-off purchase as they last YEARS!

[Mickey thumbs]

When my MDF track was new I ran Paul Gage urethane tires as they gave the best grip. They created marbles on the track that looked like an F1 track at the end of a race. Nothing as bad the dust in your pic, but a nuisance to clean up. After about a year the painted surface was worn smooth and silicones gave a better grip so I switched over. You may want to try a couple different Shore rated commercial urethane tires then match your home brew to the one that offers the best balance of grip and wear.

[73emgee]

I believe the weight of the car can contribute to excessive tire dust. On a recent build for a urethane only proxy; I noticed, once my total car weight approached 90g the XPG tires starting throwing off what I consider an excessive amount of rubber. The inside of my car looked like your photo and there were tire crumbs all over the track, I reduced the weight and switched to the harder PGT compound, which resulted in an significant improvement in the tire dust inside the body.

Bob

[Kevan]

I'd say the compound swap contributed the majority of the tyre dust reduction.