DOES a M Chassis Car NEED Tire Foams?

[Carmine A 2046]

5 hours ago, Dakratfink said:

That is actually solid advice. 

For a carpet track I might try no foams ( for a little more grab and sidewalls flex) however, on my driveway, with bumps and cracks between the pavement blocks, the kit foams seem to help the oil shocks I have installed dampen instead of running over cracks on essentially “flat” tires 

Thanks for understanding the "spirit" of my advice! 

I'm certainly NOT against the use of Foams. They're in 90% of my Vehicles! One thing that many People don't understand... is that the Tire Foams actually simulate "air pressure" in these little Tires! 😉  Too firm or too large of Foams, and they will act like the Tires on your real Car, inflated to about 50psi!!! 😲  The center of the Tread will prematurely wear out, and you'll lose a considerable amount of Traction.

Of COURSE, too SOFT or no Foams in heavy Cars will do the exact opposite. The outside of the Tread will prematurely wear out, you risk Sidewall and Wheel damage as well. 

There are SO many variables.... It's impossible to give accurate advice without personally seeing the Car.  With just the Minis.... The RWD ones (M02, M04, M06, M08) - many of them won't steer well, with any Foams in the FRONT Tires!!  On the FWD ones, the Rear end is so light, that too firm of Foams will cause Oversteer and general lack of control. (Although I have no knowledge of the M05 Ver. II Pro and the M07)  I keep hearing that they're much better balanced, and need Soft Foams in the Rear. 

MY problem, and reason for this Thread, is that with Kits supplied with Foams... WHAT KIND, DENSITY and REBOUND are those Foams!!?? 😖😲 

With RC Crawlers and Trail Trucks, understanding that they're 3X as heavy and have Tires that are often TWICE the height of the On-Road Car Tires... 

Foam Choice is CRITICAL, especially in Competition. But the choices of Foams are expansive, with SPECIFIC information about the Foam size, density, rebound, sidewall support and a number of other things that in this end of the RC Hobby - just don't matter! 

My point is - WHY can't WE at least have some information and specs on 1.45"  1.7" and 1.9" On-Road Car Tire Foams?? 

Instead of "here's your Foams. Use them!".... 

Tire Foams COULD be a valuable Tuning Tool, IF we had any clue about them!!  WOW I wrote a lot about this. I am passionate about it though.  I mean, when we buy Motors, we usually get an informative spec sheet with them!! Same with ESCs, Servos, Dampers, and a few others. 

If I get a Tamiya B-Zed Motor... I'll know the size, amp draw, power output, number of windings (Turns), top speed in RPMs and a few other things. 

If I get a set of Foams, I get...... Foam. 😖😞

[rich_f 233]

On 8/9/2020 at 9:30 AM, Carmine A said:

Too firm or too large of Foams, and they will act like the Tires on your real Car, inflated to about 50psi!!! 😲  The center of the Tread will prematurely wear out, and you'll lose a considerable amount of Traction.

Do you think this is actually the case or are you just making an assumption based on what happens to actual pneumatic tyres?

Let's think about this for a second - in a real pneumatic car tyre, over-inflation causes the the physical size and shape of the tyre to change. It bloats out the centre, making the contact patch rounded instead of flat, meaning the centre of the tread wears more quickly. 

With a hard RC foam insert, it is the same physical size as any other firmness of foam insert. The contact patch is therefore the same as with any other insert. 

It is easy to see how the edges might wear down faster if the insert is too soft or non-existent, because there is nothing to support the centre of the tyre. But if the foam is too hard, I'm finding it hard to see how the centre would wear out more quickly. 

I've always used inserts (of varying hardness) and have raced on carpet and tarmac and I can't recall ever having the centre wear out before the edges of a tyre. The failure point is always at the edge. 

[berman 5315]

1 hour ago, rich_f said:

Do you think this is actually the case or are you just making an assumption based on what happens to actual pneumatic tyres?

Let's think about this for a second - in a real pneumatic car tyre, over-inflation causes the the physical size and shape of the tyre to change. It bloats out the centre, making the contact patch rounded instead of flat, meaning the centre of the tread wears more quickly. 

With a hard RC foam insert, it is the same physical size as any other firmness of foam insert. The contact patch is therefore the same as with any other insert. 

It is easy to see how the edges might wear down faster if the insert is too soft or non-existent, because there is nothing to support the centre of the tyre. But if the foam is too hard, I'm finding it hard to see how the centre would wear out more quickly. 

I've always used inserts (of varying hardness) and have raced on carpet and tarmac and I can't recall ever having the centre wear out before the edges of a tyre. The failure point is always at the edge. 

You're forgetting centrifugal mass. When a tyre spins, the weakest part of the tyre, the centre, expands. Pull the throttle on an rc car, and the centre will expand making the contact patch smaller, and in the case of a fwd m chassis, when it diffs out (hold one drive wheel) the tyre with no load will expand and spin the centre contact patch of the tyre until it gains traction.

Will it wear out faster than any other part of the tyre? Probably not. There is too many variables (power/camber/caster/drive/foam/tyre/weight etc etc).

You are both right though, outer front tyre wear is a FF characteristic when pushed, 1:1 or fwd m chassis.

 

[rich_f 233]

38 minutes ago, berman said:

You're forgetting centrifugal mass. When a tyre spins, the weakest part of the tyre, the centre, expands. Pull the throttle on an rc car, and the centre will expand making the contact patch smaller, and in the case of a fwd m chassis, when it diffs out (hold one drive wheel) the tyre with no load will expand and spin the centre contact patch of the tyre until it gains traction.

Spinning the wheels at full throttle while off the ground and holding one wheel still (thereby doubling the rotational speed of the other wheel) is one thing, but expecting this to happen when the car is on the ground is quite another, especially considering that m-chassis cars (at least in my racing experience) are usually powered by not the most powerful of motors. 

Racing tyres are often belted so that the centre section is even less likely to expand. 

Also, when a tyre expands like this, it tends to pull the edges of the tyre inward. With the harder foam inserts, this movement is more restricted, making centre tyre wear less likely due to this effect, not more. 

As you say, there are a lot of variables and if you start cranking up the power, for instance, you are going to start to see ballooning. By this point you have lost grip and performance in terms of lap times, so it's not really something you'd want in practice anyway. 

[DayRider 311]

I might be just repeating everyone here but I use the soft m-grip 60d tyres because I run concrete and I have found using soft foam gets me the best traction. I run m05 and m07. I'm in the middle of building the m08 and going to try the same set up. Hope this helps

[Carmine A 2046]

10 hours ago, DayRider said:

I might be just repeating everyone here but I use the soft m-grip 60d tyres because I run concrete and I have found using soft foam gets me the best traction. I run m05 and m07. I'm in the middle of building the m08 and going to try the same set up. Hope this helps

That DOES help, thank you!! Like everything, circumstances are going to dictate actions......

I'm not trying to emulate a Scientific Debate about RC Tires.... I'm just going on my experience. 

9 Years of Semi Pro Buggy Racing - both 1/10th electric and 1/8th Nitro...   Plus 30 years of general RC experience beyond that.

I could add my 30 years of 1:1 Racing experience, in IMSA, SCCA and NHRA....   But that's not entirely relevant to vehicles weighing less than 5lbs! 

Now.... Holding a Car off of the ground, holding one Wheel and goosing the Throttle - BESIDES being detrimental to your Diff Gears - WILL cause any RC Tire to "Balloon". Except for the very few (and very expensive) Belted RC Tires....... 

On the subject of RC Tire Foams, I was initially ASKING for ideas and opinions. I'm GETTING that, and I appreciate it. I have not however, claimed any conclusions or facts on the subject!!!  Just want to be clear on that.

In my case, with VERY soft, 60D, S Grip Tyres in Front... I suspect that some kind of Foams will be necessary. BUT, going TOO firm, will Negate any advantage that a soft Tire gives you in the first place. Therefore I'm trying my Homemade Soft Foams in the Front. At least I'll KNOW what sort of compound I'm dealing with!! 

In the Rear, with 60D M Grip, I was going to try it initially with no Foams. It may turn out that I'll need some type of Foams in the Rear as well.... But as mine sits on the Workbench, with Battery fitted, there's NO flattening of the Tread at all on those Rear Tires. That tells me that the VERY LEAST amount of rubber is actually meeting the Road!!  I don't believe that Foams are needed on the Rear Tires, in THIS CASE.

The Rear of a M Chassis Car with FWD, is very light indeed. One of the jobs a Tire Foam does, is SIMULATE air pressure, giving the Rubber Tires some structure. 

On M Chassis Cars that are RWD, the opposite is true - plus the decreased Traction caused by the front Tires LIFTING under acceleration! 😲  I suspect that ANY Foams in Front would hurt what little Traction is there in the first place.  ...... Then again, maybe the softest possible Foams might be necessary in this case, to keep the sidewalls from folding in on sharp turns. 

TOO Firm, or even the wrong shape (too tall), WILL force the center of the Tread into an Arc - SIMILAR to gross overinflation in a real Tire. Punctuated by the fact that there's NO Belts in the Tires, to hold the Tread firm! This WILL cause premature wear in the center of the Tread, because the center will always have the most contact, regardless of Vehicle speed.

I didn't realize the can of worms I had opened!! 😖😲  I'm not even Racing my M05, beyond an occasional weekend Club Race. I'm just trying to find information, and maybe establish some sort of standards, that this corner of the Hobby has NEVER had. M Chassis Cars need love too!! 😉

THIS is the initial plan I've come up with for Front Foams.... I KNOW them to be a 0.2psi density Foam, probably softer than Tamiya's "soft" Foams. I'll work up from there!

[DayRider 311]

When I first started with the M05 I use the foam and the slick tyres it came with. I think it was the hard foam. They seemed to last ages and when they warmed up they was quite a lot of grip. But if I over did it into sharp corners, the back end would let go and spin out.

Now I forget the name of the spray you can use to treat your tyres, but a friend of mine uses it. He would spray the hole of the back ones and rap tape around the out side of the front one and only treat the inside of them.This helped with more grip in the rear.

 

[Carmine A 2046]

@DayRider I used something similar, conveniently called "Liquid Traction". This was a long time ago, and I'm pretty sure they don't make it anymore...  It softened the rubber SO much, that chunks of rubber would FLY off of the Tires during Racing!!! 😲

[DayRider 311]

3 hours ago, Carmine A said:

@DayRider I used something similar, conveniently called "Liquid Traction". This was a long time ago, and I'm pretty sure they don't make it anymore...  It softened the rubber SO much, that chunks of rubber would FLY off of the Tires during Racing!!! 😲

Yeah that rings a bell. After using the slicks I move on to...bi think they called 49's. They were okay, again with hard foam like the slick.

[Carmine A 2046]

4 hours ago, DayRider said:

Yeah that rings a bell. After using the slicks I move on to... I think they called 49's. They were okay, again with hard foam like the slick.

Haven't heard of that one... But most of those "cheater liquids" just turned Rubber to GOO. 😲😖  There were one or two that actually worked, but I can't recall them.

[DayRider 311]

They are just a little bit small than the 60D

[Carmine A 2046]

WOW! I didn't think these Tires came even SMALLER!! 😲

[DayRider 311]

On 8/12/2020 at 10:57 PM, Carmine A said:

WOW! I didn't think these Tires came even SMALLER!! 😲

Yeah quite a few options. In UK you can pick up a full set for about 14 quid so thats I think about 20 bucks.

[Otis311 196]

Could somebody please clarify the difference between the following two common 60D foams:

- TAM53255 - Tamiya M-Chassis 60D Inner Sponge Inserts (4) (Hard)

- TAM50686 - Tamiya M-Chassis 60D Inner Sponge Inserts (4)

It seems like the 53255 are typically suggested. I bought some 60D foams a while ago and can't remember the model number. I did not like them though. They seemed to fill the S-grip tire way too much and made them have a ballooned tread. I ended up just using some 55D foams I had on hand. Is it normal for the 60D foams to stretch out tires like that? It was kind of unusable. I am going to buy some of the new "soft" 60D radial tires and would like to get the proper foams. Any help would be appreciated.

 

[Pylon80 2628]

58 minutes ago, Otis311 said:

Could somebody please clarify the difference between the following two common 60D foams:

The Hard foams are harder

Seriously, I have tried multiple time to use 'hard' foams and it was never a good result (M chassis, 26mm touring and 32mm touring wheels/tires). The tire bulges out too much and the result is a much reduced contact patch with very little grip.

I would simply recommend the regular ones which work very well.