Caught from behind at Districts 2 years in a row

[cosmo9370]

My son made it to Districts and his car seemed to come out with the lead through the majority of the race pretty often but was always caught from behind by a few cars in the last 1/4 to 1/8 of the race. This has happened two years in a row, he would take the lead and lose it at the end of the race.

What would most likely cause his car to lost speed and get caught from behind by the same few cars on a pretty regular basis?

Did those cars have a better center of gravity and more weight towards the back? Better axles and/or graphite to reduce friction?

He uses a wedge rail-rider with 4th wheel raised. Rear wheels canted at 2.5 degrees. Polished axles and wheels. Car weighed 4.9x ounces, just under 5.0.

Any thoughts would be greatly appreciated. Thank you

 

[T-Bone Racing]

I think slowing down at the end of the track could be one of two things.

it could be that your weight isn’t far back enough and maybe you have way too much weight on your front wheel (basically the weight is just too far up).

It could also be friction as well but you said you polish your wheels and axles. I’ve only really used oil, so it could be that you’re using too much graphite maybe? Also, does the car wiggle down the track? If so you can add steer, and if it’s straight as could be, then maybe you have way too much steer.

Hope that helps

 

[DerbyDad4Hire]

Lots of causes! T-Bone is right. Most likely wheel bore and axle prep and lubrication along with a little alignment. I am guessing you bent rear axles. You have to use good graphite, they aren't all the same. Bump your weight up to the max and make an easy way to remove a slight bit if needed. I can help you keep them in the rear view!

 

[Jupiter 2.9]

Wheel & Axle prep.
If you have ever viewed the league races you can see the last 10 or 12 feet something happens, the quality of prep takes over. Everything looks pretty close then you see the separation happening. Better prepped cars take off & the others kind of die. Friction is our #1 culprit, that’s wheel bore, axles & hub to body contact. Everything needs to work together.
Pretty sure there’s a video on this site somewhere & D.D. lays it out step by step.

 

[cosmo9370]

Thanks for the replies everyone. I had the weight mostly in the back, COG was about 3/4 inch in front of rear axle. Actually sprung for the professionally prepped wheels and axles for him last year since I don’t have all the necessary equipment.

I did notice some wobble after the first few races. Which I thought might have been the lane of the track since it was a rail rider with correct drift in testing and didn’t happen the first few races.

One more question for canting the rear axles, do you think it matters if it is done via a bent axle or drilling an angled axle hole?

okay, two more questions. Is there anything wrong with going past 2.5 degrees? I already drilled the angled holes with the axle pro tool but we do also have 2.5 degree bent axles.

 

[DerbyDad4Hire]

Wobble would explain it also. if a rear wheel hits the rail you are done. Do not bend your rear axles. Drill them with the proper tool at 3 degrees. Bend the front dominant 5 to 6 degrees.

 

[Loud2ns]

One more question for canting the rear axles, do you think it matters if it is done via a bent axle or drilling an angled axle hole?

Been there, done that........don't do that. I spent sooooo much time trying to tune 3 cars with bent rears and without a track you still never know what's really going to happen. John's advice is solid. Drill the rears with a good jig, bend the front axle. It's way easier and you'll get better results.

 

[T-Bone Racing]

Been there, done that........don't do that. I spent sooooo much time trying to tune 3 cars with bent rears and without a track you still never know what's really going to happen. John's advice is solid. Drill the rears with a good jig, bend the front axle. It's way easier and you'll get better results.

Agreed, the more your axles are bent, the more variability there is. Scout axles are slightly bent as it is, bending them again or more will only make your times more sporadic and worse.

 

[flockshot]

After reading all this, I would say that your most likely issue (in my just slightly better than complete novice opinion) is your bent axles, and here is why. The toe in, and toe out of your rear axles are absolutely critical to performance. With bent axles you cannot accurately determine if you have toe in, because when you install the axle in 'racing' position, there is just a short axle sticking out, with a head on it, and it is covered with a wheel so, you cannot check it for toe in/out. As you roll the car on your tuning table, the rear wheels may migrate out, just as they should, but they can still be out of alignment enough to get caught from behind by a better aligned car.
If you drill your holes at 3 degrees you can put either pins, or even drill bits, into those holes and check the toe in condition of your axle holes. Then, if your holes have no toe in or out, you can use straight axles and have good alignment. Now, having said that, Scout axles are never straight, but you have eliminated the biggest issue with alignment and can work out the axle issues. Just my 2c. P.S. You will want a drill jig to do this.