Tire chatter?

[Bal r 14]

I'm posting this here because it isn't really about tires. Background: My track is new, about 16 hours of use at the most. It is routed MDF, 61' long, sealed and painted with 3 coats of semi-gloss latex, so it is smooth. It's also clean. It gets vacuumed, wiped down with a damp cloth and when it's dry gone over with a micro cloth. Before use I clean urethane and silicone tires with tape and run laps. I continue this process until the tires stay clean. Over the last several weeks I have been experimenting with different tires, first rubber, then urethane that has been sanded and trued, then clean, glossy urethane and finally silicone. The glossy urethane and silicone have a definite performance advantage on a clean track. However, cars with silicone tires experience various degrees of tire chatter. So do the cars with glossy urethane, but much less.

I am new to silicone, so I'm trying to figure this without a clue as to what I'm doing. Rounding the edges of silicone tires seems to help a little. Pod float doesn't seem to do much, but I may be doing it wrong. I think it's time to ask the experts.

The cars in the middle of the track are my "junkyard". They are not the cars I am referring to.

[Kevan]

Without video it's guessing time. Assuming you have tons of grip as silicones like clean tracks then don't forget these cars don't have a differential so in corners the inside tyre will be scrabbling as its spinning faster than the track surface its going over.
Are your tyres glued and trued?
How do the cars handle?
Are you mag racing?
Have you got ballast in the cars?

[Bal r 14]

It has been my limited experience that Quick Slicks don't need trueing and it would be difficult if they did. I put them on my Tire razor to round the edges. So, while I'm there check for true and any variance is extremely small. I usually insure the wheels are true, but I've only seen one NSR wheel that wasn't. My experiments with different types of tires has been mostly on NSR cars, as they seem to exhibit the most differences depending on tires used. I have glued the Quick Slicks on when they didn't fit real tight on the wheel.

If by mag racing you mean magnets, it's a routed MDF track with copper tape.

I have not used ballast to correct this chattering condition, as I didn't know how or where to use it. Hence, the creation of this thread.

[Pappy]

A lot of things can cause chatter. A loose motor, worn out bushings, not enough float in the motor pod and/or body, out of round wheel or tire, slightly crooked axle.

[RichD]

The more grip the tires have the more likely it will be that the car will have some chatter. Some reasons for chatter have already been mentioned. Another reason is chassis flex, especially in the area between the motor and the rear axle carriers. Chatter and hop are often seen with anglewinder cars like Nincos. Gluing the motor to the chassis is often helpful. Sometimes bracing needs to be added between the motor and the rear axle carriers. If the car has a motor pod experiment with loosening the pod screws and try adding tape to the bottom of the chassis.

[Bal r 14]

The chatter is definitely more pronounced with my anglewinders and I have observed the chassis of several has a great deal of flex behind the rear axle to the point where it attaches to the body. .

[Bal r 14]

I should mention that most of the cars I'm experimenting with have had very little previous use, maybe 1 - 2 hours actual use and all are sidewinders or anglewinders. I recall having a Studebaker R3 Golden Hawk many years ago that exhibited the same type of chatter when accelerating hard, to the point where I could break an axle. It was caused by poor weight distribution and weak leaf springs. I'm thinking I need to translate that into slot car terms.

[Aptosc6]

One thing I didn't see mentioned: tire rubbing on bodywork. It happens and some body styles are more prone. Look inside the wheel wells (front and rear).

[Aptosc6]

Sometimes you can reprofile the tire where it rubs.

[Fathead59]

If the tires are rubbing on the inside of the wheel wells can't you open it up the wheel well a little bit

[Bal r 14]

I had to trim the top of the rear fender opening on the Matra-Simca. I don't like to modify the bodies, but sometimes it's all you can do.

[Brumos RSR]

SirChrisGuyW addressed this a few months ago. This ma solve the majority of your chatter issues. See his rear end set up, this also works for anglewinders.

[chrisguyw]

Hello Bal r 14,.........Tire chatter can be 2 separate issues, which will require 2 different fixes...........in the case of your "Stude" exhibiting chatter, this was the result (as you indicated) of having "weak" leaf springs,......this resulted in axle "tramping" under hard acceleration, and this is also seen in a slot car with a chassis that has too much longitudinal flex. This is seen as "chatter" or "bounce" on corner exit/straight line acceleration.

Mid corner "chatter" can be attributed to many things,......out of round tires, bushings with too much slop, body/tire rub, etc. etc, but, most commonly on a "plastic" slot car chassis, it is the result of too much rear end torsional flex, and, or insufficient stiffness in the triangle formed by the pinion and the rear axle uprights............this is made more apparent with cars with stronger torque motors, or grippier tires.

In very simple terms, grippier tires or stronger motors tend to place more torsional load on the rear end of the car, and the flimsy plastic motor bulkhead and uprights flex in relationship to one another .....once it flexes to a certain point, the chassis will snap back in the opposite direction and "chatter" results.

So the first thing to identify, is whether you are seeing this under hard acceleration or mid corner......................As with most plastic chassis cars, I am confident that your issue is with a chassis that is torsionally too soft, and independent flexing of the rear axle uprights..........it is unlikely (but not impossible) that you experiencing axle "tramping"

So, the easiest remedy is to use a less powerful motor or less grippy tires, but, I imagine, that slower lap times are not what you are after 😀........so,.......try the following !!

A few simple/low cost fixes.......do all !!

1/ Glue and align your rear axle bushings......check first to see if there is any slop in the bushings.
2/ Glue/True your tires.........as most silicones are reasonably true, truing is less of an issue than with urethane/rubber tires, but gluing is highly advisable.
3/ Radius both outside, and inside edges of you tires
4/ Glue/screw your motor into place
5/ Try not running a pod with free play........you can either snug the pod a touch, or, use silicone washers or tape to control torsional pod rotation/movement.......the pod should flex, not flop around, (particularly on wood tracks).

A little more involved.........

Fabricate or buy a brace for the rear axle uprights..........this will eliminate the independent flexing of the rear axle uprights which causes.......axle binding (friction), poor/irregular gear mesh, and critically,.. "chatter".

You can make a brace out of piano wire/brass etc/ and use it to eliminate the flex in the uprights.

This is a Thunderslot chassis with a piano wire brace, glued with rubberized CA between the axle uprights.





The following brace was made from brass strip, formed into a "U" and glued along the edge of the motor bracket, with the legs running along and under the bushing cups.........a bit hard to see, as I painted the brace black.




The other option is to buy an axle tube/bushings. Sloting Plus made these over 15 years ago to alleviate the "Ninco hop" found most visibly in the Ninco anglewinder chassis. These come with quality oilites installed, and are a huge performance improvement to any plastic car chassis where they can be fitted. They do come in three lengths, so, you will need to measure from centerline to centerline of your rear uprights.
I use these in any anglewinder/sidewinder that I can. SCC carries these (Sloting Plus) axle tubes.

This is a Ninco Ferrari 360 that I built more than a dozen years ago using a Sloting Plus axle tube,




I use them in a variety of plastic car chassis...........and they are well worth the effort/expense !!
This tube has been notched for motor can clearance.



Cheers
Chris Walker

[Bal r 14]

I am following a lot of what you said and have eliminated the chatter in most cases. Tires are radiused, motors are screwed, slop removed from the pods. Only two cars still have an issue, an NSR Porsche 908 and Slot.it Matra-Simca. My fault, as both have motors that are more than the chassis was meant for. Some of your bracing tips should help.

[chrisguyw]

A couple of questions on the front end set-up of your cars..........have you trued the front tires??,........do the front tires run on the track ??......do you use set screws to position and maintain the vertical positioning of the front axle/tires ??

[Bal r 14]

Yes to all of your questions. I position the front tires so they just touch. They are painted with nail polish, too. I do not like how much the Matra-Simca tires touch and how shallow the guide sits, so I will switch it for a Slotting deep wood guide. It's thicker so it will raise the tires up a bit more.

[Bal r 14]

I had my first racing session today for a couple hours. The cars with silicone tires had a significant advantage over those with urethane. We all observed that the cars with rubber tires did far worse than they used to. The NSR Mosler sidewinder on NSR rubber was always very competitive before. Now it has no chance, it slides too much. Several of the junkyard cars behaved as though they were on ice, over the entire track; 45 second lap times ( track record is now 6.011). They have never done this before. The silicone seems to be breaking down whatever "rubbering in" had been done before.

Here's another interesting observation. ThunderSlot cars seem to unaffected by changes in track conditions, on stock tires. They are not as fast as any of the cars running silicone, but they are far easier to drive. Some of the best racing was with 3 ThunderSlot cars. My grandson won a race with a ThunderSlot car and he never wins. I'm going to have to buy more of these.


Here's an update: from all the responses I got, I decided to look at the wheels of the Slot.it Matra-Simca. Sure enough they were not true and more significantly, were not the same diameter. They were off by one unit of whatever is on that gauge (It's an old mechanical micrometer with most of the markings worn off). So I turned them both to the same size. No more chattering. I did replace the guide, too.

[Broman62]

Excellent information Chris...Thanks!!!

[Brumos RSR]

We typically stand when reading posts by SirChrisGuyW

[Kevan]

I had my first racing session today for a couple hours. The cars with silicone tires had a significant advantage over those with urethane. We all observed that the cars with rubber tires did far worse than they used to. The NSR Mosler sidewinder on NSR rubber was always very competitive before. Now it has no chance, it slides too much. Several of the junkyard cars behaved as though they were on ice, over the entire track; 45 second lap times ( track record is now 6.011). They have never done this before. The silicone seems to be breaking down whatever "rubbering in" had been done before.

This has been mentioned umpteen times over many years, silicones clean the track surface at the detriment of other tyre types being used.

[Bal r 14]

Well, make that umpteen and 1. I would not have expected such a dramatic change in so short a time. At this point, new PG urethane tires seem to do fine, as do Thunder Slot tires.

Forgive me if I post things that are obvious to many of you. But, at this point it's all pretty new to me. I have been doing this since about March and most of my time has been spent building tracks; two so far, both routed MDF, first one was 44', current one is 61'. (Shooting for 100' on next track).

[docdoom]

urethane tires tend to grain when they are run. worst on heavy cars . if you give them a wet sand before you run them they are good but will fall off as you race. but before they do there good for at least 1/2 sec

[mattb]

You have to decide on what kind of tires you want to run and then stick with that for all your cars. We run 1/24 with silicone, probably best traction there is on a clean track. if running 1/32 on a wood track, I would probably use only urethane.

[Bal r 14]

I seem to have already converted all of my NSR, Sideways and Slot.it cars to silicone. It wasn't intentional, just sort of happened. I tested my Thunder Slot cars on silicone vs stock tires actually prefer the stock tires; that may change over time. While silicone delivers the best performance, it doesn't yield the most realistic handling characteristics. So I am somewhat perplexed.

[HO RacePro]

I paint my HO scale MDF tracks with a white or a light gray gloss epoxy paint, and I only run silicones on them. You can see silicone residue on the light-colored paint. The old saw about silicones ruining traction for any other tires -- well -- there seems to be a basis for it.

Silicones have their best traction on a glossy surface. So good in fact that if you push a car with a new set of siiicones sideways on a clean, glossy surface the upstream tire will actually fold under itself rather than slide. There is your hop. Radiusing the tires will prevent that.

Fixing all the slop in a chassis is a good start, but you also need to add shock-absorbing features to your car. Traditional shock absorbers are floating bat-pans or rattle plates. Blue painters' tape between the motor pod and the chassis is a common trick in 1/32nd. I have even used foam servo-tape to hold two halves of an HO chassis together. There is always going to be shock-energy affecting a running car, and there has to be some way to get rid of it. The easiest fix is to adjust the body mounts so the body floats a little -- even the newest newbie has heard of that one.

Give it some thought. Try something. I bet it helps.

Ed Bianchi

[Bal r 14]

Foam tape sounds like a possibility. All of my bodies are adjusted to have a little float.

[Bal r 14]

After several more days of running silicone tires and testing recommendations, I have observed a few things:

1. Radiusing the tires definitely makes a difference in reducing chatter.
2. For most cars, the stiffer I make things the better. For one car, it doesn't help, while one other seems to prefer float. I have no idea why.
3. The more I run with silicone, the worse it gets for other types of tires. So I just ordered $80 worth of Quick Slicks to convert another batch of cars. Damn, just bought a bunch of PG tires, too.
4. The track was pretty smooth to start with, but seems to be getting smoother where there is a lot of use.

Here's a question: How long do silicone tires last?

[Pappy]

We ran one set for the whole 24 hours in the Michigan 24 one year. The car was getting pretty low but still had legal clearance. What amazed me was the outside corners of the tires were completely square and the car cornered a lot better at the end of the race than it did at the beginning. We were actually passing a couple of the other cars in the race.

[Mickey thumbs]

Re: #4. My mdf track painted with flat latex floor paint has also become significantly smoother over the past two years. At first PG urethanes were the best choice, but as it became worn smooth the Quick Slicks became superior. Converted all my cars and am racing happily ever after.