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Old 02-01-2015, 04:45 PM
  #13411  
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What is the proper way to tighten the factory servo saver that is in the middle of the steering rack? I had the nut for it come loose during a race. I tightened it up snug and in one race it was loose again, so I tightened it a bit further and on my first crash in the next race the steering rack busted in half.
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Old 02-01-2015, 07:13 PM
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Originally Posted by killeraxemannic View Post
What is the proper way to tighten the factory servo saver that is in the middle of the steering rack? I had the nut for it come loose during a race. I tightened it up snug and in one race it was loose again, so I tightened it a bit further and on my first crash in the next race the steering rack busted in half.
Flush to top of lock nut and red Loctite.
Best solution is to glue (JB Weld) the stock rack and use a servo mount servo saver. I went this route and haven't broke a rake in at least 100 runs.
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Old 02-01-2015, 07:31 PM
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I have no real proof on this, but I think the one of the reasons the steering rack breaks on the TC4 is that the servo saver spring digs into the plastic and weakens the component. Eventually everyone will break a steering rack on a TC4. When you buy your replacement rack, just use the shim/washer from the original rack on 1 side of the spring and the shim/washer from the new rack on the other side of the spring before you install it. Once I started doing this, I have had less issues with breakage.

Another thing that will always help is a wider front bumper. The stock bumper that comes with the car could be a bit wider. Parma used to sell a wider/harder bumper for the TC4, but it doesn't seem to be readily available. Parma still makes a generic bumper that can be cut to fit any car. Here is a link (http://www3.towerhobbies.com/cgi-bin...?&I=LXPUR6&P=7).

Finally, if anyone is having issues with the screw coming loose on their servo saver, it is time to replace the locking nut (because the nylon in the nut has worn out). You could use Locktite (or similar) to secure the screw. But since it can be a pain to work on the rack, you might as well replace the nut while you are working on the steering rack.

I have found the easiest way to gain access to the steering racks on both the TC3 & TC4 is to remove the entire front diff case with the chassis braces still attached. Remove the 4 screws holding the diff case to the chassis, the 2 screws holding the front chassis braces to the chassis, the 1 screw holding the diff case to the upper bumper mount, pop off the ball cups holding the shocks on the a-arm, and finally pop off the inner ball cups from the front camber links. While this seems like a lot of effort, it really only takes a few minutes and you can remove this whole assembly and will have easy access to the steering and a-arms

Hope this info helps.
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Old 02-02-2015, 02:20 AM
  #13414  
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Thanks for the help. My front diff is really tight. I'll loosen it and when my steering rack and kimbrough servo saver comes I'll reset my steering endpoints. I'll pick up a larger foam bumper to better support the body and protect the car
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Old 02-02-2015, 03:28 PM
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Front diff to tight will cause "chatter".

Running a solid axle and I don't have chatter.

Is it a ball diff problem then?
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Old 02-02-2015, 03:40 PM
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The problem is that the universal drives used on the TC4 or any other car that doesn't use a double-jointed Cardon Joint is not actually a constant velocity drive. The issue is that when you crank your steering over to the lock, the internal carrier and pin need to rotate a long way in the axle and driveshaft, overcoming friction the whole way, over and over again. This problem does NOT go away with running a differential on the front, you just don't hear it because when the inside wheel is chattering and binding (it has a lot more angle in the turns than the outside) the diff makes up for it and the action appears smoother. Want to run standard axles without binding? You need to run much, much less steering throw.
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Old 02-02-2015, 06:36 PM
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Originally Posted by DesertRat View Post
The problem is that the universal drives used on the TC4 or any other car that doesn't use a double-jointed Cardon Joint is not actually a constant velocity drive. The issue is that when you crank your steering over to the lock, the internal carrier and pin need to rotate a long way in the axle and driveshaft, overcoming friction the whole way, over and over again. This problem does NOT go away with running a differential on the front, you just don't hear it because when the inside wheel is chattering and binding (it has a lot more angle in the turns than the outside) the diff makes up for it and the action appears smoother. Want to run standard axles without binding? You need to run much, much less steering throw.
I'm not getting the "chatter" (that I can tell), is this because I'm racing on asphalt not carpet?
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Old 02-03-2015, 09:36 AM
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Chances are that if you are getting chatter on the track, it's due to binding. If you are binding, you likely have too much throw in the steering. If you have too much throw, you likely have a pushing problem and need to work on the setup to get more steering response. My TC4 prototype has tons of steering and I actually have the DR turned way down which introduces far less front end scrubbing.
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Old 02-03-2015, 03:48 PM
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Originally Posted by DesertRat View Post
. Want to run standard axles without binding? You need to run much, much less steering throw.
Ballpark how much steering I should run? I have the original plastic dog bones front and rear. Ran a spool for about say 14 battery packs, then switched to a lightweight front ball diff. All at 100% steering dual rate and the 'more ackerman' setting on the front bearing carriers.
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Old 02-03-2015, 04:29 PM
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For a long time I have glued a small spacer to the c-hubs on my TC4 to physically limit the steering angle and it reduces the chatter to virtually nothing.
When you look at the steering at full lock on the inside wheel the way the steering arm works once you get past a certain steering angle the steering arm has almost no control over the hub and it allows the chatter, I will put up a pic tonight of the spacers on my car.
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Old 02-03-2015, 04:33 PM
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Originally Posted by RotorTruck View Post
Ballpark how much steering I should run? I have the original plastic dog bones front and rear. Ran a spool for about say 14 battery packs, then switched to a lightweight front ball diff. All at 100% steering dual rate and the 'more ackerman' setting on the front bearing carriers.
I typically run between 10-12 degrees of steering on my TC4 (20-24 total from lock to lock).

No chattering noticed, using a ball diff on the front.

Mark
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Old 02-08-2015, 08:26 PM
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Last edited by Racer X79; 02-09-2015 at 10:36 AM.
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Old 02-08-2015, 09:16 PM
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So I need taller front body posts for my new TC4. Looks like the HPI 6507 universal arms are discontinued. Is there a new part number?
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Old 02-10-2015, 10:09 AM
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Originally Posted by djmoose View Post
So I need taller front body posts for my new TC4. Looks like the HPI 6507 universal arms are discontinued. Is there a new part number?
I used these from a TC3. They are taller.

https://www.google.com/shopping/prod...ed=0CFQQpiswAA
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Old 02-10-2015, 04:18 PM
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Hopefully it's ok to post this here but I have a TC4 club racer in good shape I am looking to sell. What do they normally go for?
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