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Old 05-13-2014, 02:49 AM   #1
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Default In need of help. my car wont drive straight

Hello everyone, I recently got into the hobby and fell in love. I have an HPI Sprint 2. When I purchased the car everything was fine. A few months went by and the car would lean towards the left then when I pull on the throttle it takes me to the right as if I'm turning right. I messed around with the trim on the remote and the turnbuckels and couldn't get it. I took it to my local hobby shop and they said try replacing the rear differential. I replaced both front and back. Still doing the same thing. I replaced the c-hubs and servo and still can't get it to go straight. So I took it again to my local hobby shop and they tried to mess with
it and even they can't get it. So at this point I don't know what els to do. The car also has a new brushless motor and brushless esc. If anyone could help me that would be greatly appreciated. Thank u in advance
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Old 05-13-2014, 05:51 AM   #2
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Probably a bound up broke part. I just got back into this so I'm busy hitting everything in sight. Breaking steering seems to be a specialty. Disassemble the front steering looking for any sign of cracked, scuffed or misaligned parts. If not up front, check the rear hubs and make certain all rotating parts are free and smooth. Anything you can find on the bench will show up 10x at speed. Could be buried deep so don't get discouraged.
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Old 05-13-2014, 05:59 AM   #3
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Is the car badly tweaked?
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Old 05-13-2014, 06:04 AM   #4
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I would pull out the bearings and make sure they are free. Look at the out drives. I hate to say this but some hobby shops have someone in there that might not be good at fixing your particular problem. Especially big shops like Hobby Town. Look for some local racers or drifters to help you.
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Old 05-13-2014, 07:57 AM   #5
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There can be multiple issues causing the car to track/pull to one direction, but could be something simple.

These are toy cars but at the same time the amount of speed these cars do for there size, the smallest "bit" that's out of whack will cause this issue. I would do the following:

* Inspect all wheel hub bearings and all (4) drive axles. If you have only 3 wheels applying power this will cause issues.

* De-Tweak the chassis... Loosen all lower/upper bulkhead screws also top deck and give the chassis a slight twist then tighten all screws

* Make certain the rear ball diff is cleaned/lubed and working properly

* Rebuild your shocks with fresh oil (one shock could be dry of fluid)

* Up-Travel/Droop - Make sure you have some up-travel (equal at all 4) wheels. If you have none or very minimal up-travel at one wheel this will create problems. Up-Travel is vital on these cars

Below are two videos that I think you'll find very handy and may possibly assist in solving your problem.

http://www.youtube.com/watch?v=dYLvImYUBt4

http://www.youtube.com/watch?v=OQt6iv175mw

Hope this helps
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Old 05-15-2014, 11:35 PM   #6
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Hey everyone thanks for all the help. I have been trying to reply but every time it keeps telling me error. So let's hope this works now.
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Old 05-15-2014, 11:40 PM   #7
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Quote:
Originally Posted by PACaSteel View Post
Probably a bound up broke part. I just got back into this so I'm busy hitting everything in sight. Breaking steering seems to be a specialty. Disassemble the front steering looking for any sign of cracked, scuffed or misaligned parts. If not up front, check the rear hubs and make certain all rotating parts are free and smooth. Anything you can find on the bench will show up 10x at speed. Could be buried deep so don't get discouraged.
So I looked over the car just a lil bit didn't do much work yet but found that a post on the main chassis is broke. I already picked up a new one so I will be tearing the car apart maybe tomorrow. So when I break it down I think I'm ganna replace all the brearings and I'm thinking of doing the turnbuckles. I don't know if it will do anything.
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Old 05-15-2014, 11:42 PM   #8
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Is the car badly tweaked?
I wouldn't say so. I have let people look at it and they have tried to adjust the toe but that's about it. Nothing really big.
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Old 05-15-2014, 11:44 PM   #9
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Originally Posted by snoopyrc View Post
I would pull out the bearings and make sure they are free. Look at the out drives. I hate to say this but some hobby shops have someone in there that might not be good at fixing your particular problem. Especially big shops like Hobby Town. Look for some local racers or drifters to help you.
I took my car to 3 hobby shops and they can't seem to find the problem.
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Old 05-16-2014, 06:13 AM   #10
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Quote:
Originally Posted by got addicted View Post
I took my car to 3 hobby shops and they can't seem to find the problem.
Have you checked the servo? Are the gears damaged? A few missing teeth can cause some weird issues, especially if it is a cheap servo that likely doesn't center well when not damaged. Did you pull the bearings out to make sure they were spinning freely? Just turning the tires and assuming they must be fine doesn't cut it. Pull the shocks and make sure the lengths are the same L front to R front and L rear to R rear. If the shocks are oil filled make sure that all four have oil and the damping feels consistant. While the shocks and tires are off raise and lower the suspension arms. Do they fall freely under their own weight or are they bound. A little binding is not acceptable if you want the car to work correctly. If there are roll bars I'd disconnect for now unless you know how to tweak them correctly. You can do a simple test for suspension tweak by using the edge of a table as a fulcrum. Put the fulcrum point at the center of the chassis with the rear of the car off the table and slowly lift the rear watching how the front suspension settles as it compresses. If one side dumps quicker than the other either put more spring preload on that side or remove some from the other. Once the front suspension is compressing evenly do the rear of the car. Make sure all four tires are glued to the rims.

Most of all don't assume anything on your car is correct until you check it yourself. Good luck.
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Old 05-16-2014, 06:35 AM   #11
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Quote:
Originally Posted by got addicted View Post
Hello everyone, I recently got into the hobby and fell in love. I have an HPI Sprint 2. When I purchased the car everything was fine. A few months went by and the car would lean towards the left then when I pull on the throttle it takes me to the right as if I'm turning right. I messed around with the trim on the remote and the turnbuckels and couldn't get it. I took it to my local hobby shop and they said try replacing the rear differential. I replaced both front and back. Still doing the same thing. I replaced the c-hubs and servo and still can't get it to go straight. So I took it again to my local hobby shop and they tried to mess with
it and even they can't get it. So at this point I don't know what els to do. The car also has a new brushless motor and brushless esc. If anyone could help me that would be greatly appreciated. Thank u in advance
It is a sprint 2 the steering linkage is horrible. The middle link develops slop the older the model gets.
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Old 05-16-2014, 08:37 AM   #12
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Really haven't told us anything, but not steering st8. is it under power or coasting? Toe-in or out frt end? You got enough to post photo yet? Car with a light throttle start pulling to the right?
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Old 05-16-2014, 09:02 AM   #13
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M 2 pennies worth. Disassemble the entire car, clean and inspect every part. Anything cracked, broken, or stripped out gets replaced. Check the bearings to see if they are gritty. Slowly rebuild the car, ensure screws arent over-tight and everything moves freely, but doesnt have slop. Check servonlike mentioned above. If these steps are followed, and issue still persist, then you just have a ghost in the machine.
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Old 05-16-2014, 12:50 PM   #14
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If it pulls to one side under acceleration only, it has to be unequal power distribution. IE one wheel is getting more power than the other.

This might be caused by
Differential
CVD's or Dogbones
Binding of CVD or bearings
uneven tire wear
Body rubbing against a tire

Disconnect your driveshafts from the differential. Do both turns spin freely?
With driveshafts connected place a piece of tape on top of each wheel on that axle and turn over the belt/driveshaft. Do the wheels stay in sync or is one going faster than the other? IF so it might be diff.

Something as simple as putting your tire on too tight can cause this.
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Old 05-30-2014, 01:06 AM   #15
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Quote:
Originally Posted by Chaz955i View Post
Have you checked the servo? Are the gears damaged? A few missing teeth can cause some weird issues, especially if it is a cheap servo that likely doesn't center well when not damaged. Did you pull the bearings out to make sure they were spinning freely? Just turning the tires and assuming they must be fine doesn't cut it. Pull the shocks and make sure the lengths are the same L front to R front and L rear to R rear. If the shocks are oil filled make sure that all four have oil and the damping feels consistant. While the shocks and tires are off raise and lower the suspension arms. Do they fall freely under their own weight or are they bound. A little binding is not acceptable if you want the car to work correctly. If there are roll bars I'd disconnect for now unless you know how to tweak them correctly. You can do a simple test for suspension tweak by using the edge of a table as a fulcrum. Put the fulcrum point at the center of the chassis with the rear of the car off the table and slowly lift the rear watching how the front suspension settles as it compresses. If one side dumps quicker than the other either put more spring preload on that side or remove some from the other. Once the front suspension is compressing evenly do the rear of the car. Make sure all four tires are glued to the rims.

Most of all don't assume anything on your car is correct until you check it yourself. Good luck.
I have a new servo..I did take the car apart and checked part by part. What I found was a broken bulkhead so I replaced it.All the bearings are fine, I had replaced all of them a while ago. But I still went ahead and thoroughly checked every part....Im going to try all the stuff you suggested and see what I get. thanks.
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