Wheel rattling or grinding noise. Help!

[David]

the wheels on my pinewood derby car make these bad rattling or grinding sounds. Not really sure how to describe it other than this way. Other cars I have made this sound when I manually spin the wheels, but not nearly as frequently. I know what a good spin should sound like so it is not a natural sound. I happens like 75% of the time I spin rather than 5-10% with other cars. I am using aftermarket axles and wheels. Might I have polished the wheels too much and made the bore wider than it should be? Is this a problem? Will it affect performance? Thanks for any help. It is a Boy Scouts pinewood derby.
D

 

[Mojo Racing]

more than likely, yes... you opened up the bore, and it is sloppy on the axle.

 

[Thinkin'Bout Racin]

the wheels on my pinewood derby car make these bad rattling or grinding sounds. Not really sure how to describe it other than this way. Other cars I have made this sound when I manually spin the wheels, but not nearly as frequently.
D

I am new at this and we have only polished a couple sets of wheel bores. Your question made me think about something that happened to a couple of our wheels. We also had a couple that would vibrate/shake badly when being spun fast. It is almost like they set up a harmonic and shook/vibrated badly. If they are spun slightly slower they seem good and are quiet. Based on Mo Jo reply I am wondering if I did the same thing. I did notice that the tamyia swabs seemed a little loose in some of the bores, but I did not track which wheels they were? I'm glad you asked the question as it may have taught me something.

BTW ours also is a Scout car ...good luck in your races!

 

[HurriCrane Racing]

Are you using graphite or oil for lube. If you are using oil, you surely have a problem.
Either way, I would add a little more lube and see if the rattling subsides.

Are you using the wheels and axles straight out of the kit? They are notoriously bad. If you can use aftermarket wheels and axles, you should do so. The Rage wheels are a good option.

Depending on the level of competition in your pack, you may need to replace the wheels and axles.

 

[Thinkin'Bout Racin]

Are you using graphite or oil for lube. If you are using oil, you surely have a problem.
Either way, I would add a little more lube and see if the rattling subsides.

Are you using the wheels and axles straight out of the kit? They are notoriously bad. If you can use aftermarket wheels and axles, you should do so. The Rage wheels are a good option.

Depending on the level of competition in your pack, you may need to replace the wheels and axles.

We are required to use graphite as rules state "no oil". By adding more graphite the problems is less, but is still there. Car was scalding for the first 6-8 runs ( He had the best times of the day on this track on several different lanes) and then slowed about 0.02 to 0.03 for that last 6 runs. I am wondering if a loose bore and loss of graphite caused this change. My son won his den and then just lost to the person he beat from the den in the finals because the car slowed down. We checked on the tuning board when we got home and the steer was the same???

Edit: The other cars did not have anywhere near the same amount of slow down as us (I tracked this and confirmed it after the race) Also while the wheels showed a little dirt, They definitely did not look bad?

Thanks for the help and insight!

 

[DerbyDad4Hire]

How much gap do you have between wheel and body?

 

[Thinkin'Bout Racin]

How much gap do you have between wheel and body?

We have 0.030" on this car. The next one will be tighter ...probably 0.015" to start based on your previous recommendation.

 

[Rocket car]

I believe graphite will molybdenum does make a grinding, rattling sound.

 

[Thinkin'Bout Racin]

I believe graphite will molybdenum does make a grinding, rattling sound.

Thanks, I don't know about David's car, but ours is not a grinding noise. Ours is more like you added 5-10 ounces of wheel weight to your vehicle on one side of one wheel and then took it out on the freeway. More of a violent shake that even "buzzes " when spinning the wheel. It seems to change frequency with the wheel speed. However, maybe the next time you spin the wheel it spins freely and has minimal noise?

 

[Rocket car]

Do all the wheels do this? If it's just one there has to be something in the wheel bore. If you are using aftermarket axles with a groove in them that would explain that sometimes it makes a noise and sometimes it doesn't, depending on where the molybdenum is.

 

[Crash Enburn]

Are you using graphite or oil for lube. If you are using oil, you surely have a problem.
Either way, I would add a little more lube and see if the rattling subsides.

This would be my first thought. I've helped boys with cars that did this in the past. A liberal application of graphite cured those ills.

 

[Thinkin'Bout Racin]

This would be my first thought. I've helped boys with cars that did this in the past. A liberal application of graphite cured those ills.

It does seem like an extra dose of graphite does help the issue, but I am trying to figure out/learn what the cause is, so I can avoid/prevent it in the future. Thanks for all of the ideas so far!

 

[TRE]

the wheels arent polished good enough or the bores are bad

 

[David]

the wheels arent polished good enough or the bores are bad

Ok thanks. Driving me crazy

 

[David]

Graphite doesn't seem to help much