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View Full Version : Turning right twitchy but turning left smooth?


Mead
2010.09.03, 08:59 PM
My car is kinda undriveable exiting a right corner, the rear end will snap around and head for the inside wall. However, exiting a left corner - its nice and smooooth. Anyone know why the car is twitchy turning right?

Setup: 015, 90mm HM, 20d on 0N mini wheels, 6 pinion, lowered on shims, rear axle shimmed for minimal play. Stock diff and everything else. RCP track.

Car used to run good very competitive - now I cant get it back to previous handling characteristics :mad:. Stock radio settings are limited :o, I just dial back throttle trim (with fresh batts) to limit the punch. Now I drive carefully when exiting a right, very gentle on the steering.

My next adjustments is 8 pinion to limit acceleration. Any ideas?

EMU
2010.09.04, 03:24 AM
Check the t-plate for cracks, try a different one. Make sure that the motor wires are not binding the rear suspension. You may need to glue the rear tires down to the wheel, especially since you are using narrow tires. Make sure not to get any on the sidewalls.

What front tires are you using? Do you have a damper?

pfcparts
2010.09.04, 02:35 PM
Overzealously tightened lug? :)

Maybe something got inside the bearing/s on
that side? Check both front and back.

Also, I usually leave abit of play on any diff
to prevent binding.


parts

EMU
2010.09.04, 03:08 PM
Normally a stock diff that is too tight and binding on the mount will hook left hard, and push right. So Im thinking the problem is elsewhere. I do leave a little play on it as well. Just enough that you can see it move...

What body are you using? Is there enough clearance? Check that the motormount doesnt hit the side clips (havent driven an HM in while, so dont know if this is necessary).

Mead
2010.09.04, 05:30 PM
Check the t-plate for cracks, try a different one. Make sure that the motor wires are not binding the rear suspension. You may need to glue the rear tires down to the wheel, especially since you are using narrow tires. Make sure not to get any on the sidewalls.

What front tires are you using? Do you have a damper?

Hey thanks, I'm on my second stock t-plate :mad:, but plastic seems to work best, very soft. I have the '3 set carbon t-plates' ready to go but even the narrowest plate is hard compared to plastic.

Motor wires are kinda long but they don't interfer, I will double check. Tires are taped on good. Kyosho 20 degree all around.

Damper - JMHO I see no difference between the stock shock and oil filled from a stock motor performance standpoint, I tried with both. I maybe wrong but just my gut feeling, if anything oil filled is heavier, higher CG :o right now I'm on stock shock but a softer red spring.

Mead
2010.09.04, 05:39 PM
Overzealously tightened lug? :)

Maybe something got inside the bearing/s on
that side? Check both front and back.

Also, I usually leave abit of play on any diff
to prevent binding.


parts Like u I thought the right rear nut was too tight but it's not, I added a little slop between the right rear wheel and diff, but no cure. Currently there's microns of play between the right nut and wheel, between the right wheel assembly and diff, between the diff and the motor case, motor case and left wheel assembly. There's no binding of any kind, wheels spin freely either direction... hmmm

Mead
2010.09.04, 05:53 PM
Normally a stock diff that is too tight and binding on the mount will hook left hard, and push right. So Im thinking the problem is elsewhere. I do leave a little play on it as well. Just enough that you can see it move...

What body are you using? Is there enough clearance? Check that the motormount doesnt hit the side clips (havent driven an HM in while, so dont know if this is necessary).
Thanks, I'm thinking of greasing up the gear diff. But other then that my plan is limit acceleration :( with 8 pinion, and radio trim. I'm running a MINI body and wheels. I also have a Beetle and it handles slightly better, slightly less twitch, maybe the vw is heavier? I've played around with shims and such that there's no body rub at full lock, rebound or full articulation in the rear.

BTW anyone know what kinda grease is good for the diff, without going to the hobby store, anything around the garage that will work?

herman
2010.09.05, 09:24 PM
maybe time to change tires?

EMU
2010.09.05, 11:51 PM
Ive heard of people using Vasaline in their gear diffs in a pinch... Ive never tried it.

You should look into FRP or lexan t-plates if you like them soft. The plastic distorts pretty quickly, and isnt a long lasting t-plate.

Does the body or chassis bottom out if you push down on the top of the body lightly?

What direction do you run the track in?

Mead
2010.09.06, 02:28 PM
maybe time to change tires? I'm kinda gonna do that... I re-sanded them, to remove the 'glaze'. It seems the hooking is the result of too much bite? :eek: I always thought tire wear = less traction.

Mead
2010.09.06, 02:43 PM
Ive heard of people using Vasaline in their gear diffs in a pinch... Ive never tried it.

You should look into FRP or lexan t-plates if you like them soft. The plastic distorts pretty quickly, and isnt a long lasting t-plate.

Does the body or chassis bottom out if you push down on the top of the body lightly?

What direction do you run the track in?
Thanks, theres no bottoming out of any kind.

We run counter clockwise and it's sorta the cause being the track is left turn bias. I decided recently to rotate tires side to side to even out tire wear. The hooking problem became much more noticeable :mad:. (btw now that I think about it, a left turn push developed too, right hook - left push, getting close :p) So I re-rotated the tires back to previous and it helped! but I ran out of track time to fully confirm. Later this week I'll have more pratice to narrow down the fix. If tire rotation caused the hooking then the 015 HM is hella sensitive :eek:

Thanks for the vasaline idea, worthy of an experiment.

EMU
2010.09.06, 03:18 PM
The glaze on the tire could be adding to it. Since your car turns lefts more than right, the right front should be more worn, giving a smooth turn, and left less worn, giving more grip in the corner. Both rear tires should have sufficient wear to pronounce this effect. Try putting some new rear rubber on, and see if it helps. Keep the front the same...

From what I understand, you are using 4 narrow wheels. 20d tires... in general, you may want to try less front grip.

Just remember, that as tires wear, you have more contact patch, since they start round, and the patch gets flatter...

I almost exclusively used ATM 40d slicks on the front of my 015's, and they worked very well. I now use them on my narrow MR03 with equal results. You may want to give them a shot, with Kyosho 20d radials in the rear.

color01
2010.09.06, 05:14 PM
Should've caught onto this thread sooner, but let me add in two cents:

- Vaseline is not going to be strong enough to help, it seems to "give up" when you load it enough in a corner. Proper silicone diff grease is much better for this, although you will have to try several types (probably 7-15k will get you some results). If you don't want to buy any, just go ask a local racer or the track owner, most Mini-Z enthusiasts are very generous and helpful. :)
- Petroleum-based greases can work, but there have been worries about it degrading the plastic over [a long] time. Just keep that in mind when searching around the garage.
- Kyosho 20d tires all around is typically considered excessive, your front 20's must be significantly unevenly worn if you have been running a left-biased track. EMU's right, you should definitely consider harder front tires. Anything other than Kyosho 20's will wear more evenly (and slowly!) in the front, and the switch will also allow you to get off the stock T-plate for something a bit more durable and more flat (less tweak, if it's a good T-plate).
- (edit: see below post by EMU for more info)

Hopefully this was helpful -- seems I remembered wrong about the gear diff characteristics, see EMU's post below for the right stuff. :)

EMU
2010.09.06, 05:48 PM
With a gear diff car, its the other way. Left turns normally hook a bit, and right turns are smooth. One reason why most tracks circulate clockwise. This is primarily due to the additional mass (diff shaft) attached to the left wheel, in comparison to the right, as well as the additional friction that the left wheel has over the right (bearings in motormount). As you accelerate, the right rear wheel will accelerate faster, making it steer a little left, and as you let off throttle, the right wheel will slow down faster as well. This is still noticable with a ball diff, but considerably less so. I find that a lot of people run their ball diffs very loose to mask this to an effect. I typically use a tighter ball diff setting.

Scrapper
2010.09.06, 08:14 PM
i never knew that i gotta get a ball diff on my 02

color01
2010.09.07, 12:31 AM
Thanks for correcting me, Eugene. :)

Mead
2010.09.07, 10:30 PM
The glaze on the tire could be adding to it. Since your car turns lefts more than right, the right front should be more worn, giving a smooth turn, and left less worn, giving more grip in the corner. Both rear tires should have sufficient wear to pronounce this effect. Try putting some new rear rubber on, and see if it helps. Keep the front the same...

From what I understand, you are using 4 narrow wheels. 20d tires... in general, you may want to try less front grip.

Just remember, that as tires wear, you have more contact patch, since they start round, and the patch gets flatter...

I almost exclusively used ATM 40d slicks on the front of my 015's, and they worked very well. I now use them on my narrow MR03 with equal results. You may want to give them a shot, with Kyosho 20d radials in the rear.
Re: tires - I get ur drift :rolleyes:, I stick with 20d because of the amazing cornering speed, it's the only thing in my bag of tricks because the 015 has slow fets. I catch up in the corners. People are surprised I dial a 015 without traction roll. Don't get me wrong, I'm not a great driver, and will never beat a competent 03. I have fun hanging for a few laps before getting dropped :D

btw your diff post was also enlightening, good info

Mead
2010.09.07, 10:51 PM
Should've caught onto this thread sooner, but let me add in two cents:

- Vaseline is not going to be strong enough to help, it seems to "give up" when you load it enough in a corner. Proper silicone diff grease is much better for this, although you will have to try several types (probably 7-15k will get you some results). If you don't want to buy any, just go ask a local racer or the track owner, most Mini-Z enthusiasts are very generous and helpful. :)
- Petroleum-based greases can work, but there have been worries about it degrading the plastic over [a long] time. Just keep that in mind when searching around the garage.
- Kyosho 20d tires all around is typically considered excessive, your front 20's must be significantly unevenly worn if you have been running a left-biased track. EMU's right, you should definitely consider harder front tires. Anything other than Kyosho 20's will wear more evenly (and slowly!) in the front, and the switch will also allow you to get off the stock T-plate for something a bit more durable and more flat (less tweak, if it's a good T-plate).
- (edit: see below post by EMU for more info)

Hopefully this was helpful -- seems I remembered wrong about the gear diff characteristics, see EMU's post below for the right stuff. :)

Thanks, very helpful. I've been giving my tires a lot of thought. I don't have a great pit selection. I've played with sanded down 40d thanks to all my ASCs but there's too much push, undriveable. 20d matches my driving style best and I'm able to have fun out there. I'm not noticing excessive wear, or maybe I'm not racing enough :D.

Anyways through a combination of re-sanded tires, higher pinion, and backing down the throttle trim I'm able to drive the car without too much 'hooking'. It's still present so I finesse the right turns until I figure out what to do next. I was able to battle and turn in some hot laps today :cool: Thanks everyone.

herman
2010.09.08, 02:59 AM
hmm... appart from sanding them down to take the glaze out have you tried rotating the tires?
front left tire goes on the rear right;
front right tire goes on the rear left;
rear left tire goes on front left;
rear right tire goes on front right...

all the other tips given out are really really great and was a delight to read... :D

you might want to try a 30d front... but if you think that 20d is ok for you then that's whats best...

hope this helps...

Mead
2010.09.08, 10:44 AM
hmm... appart from sanding them down to take the glaze out have you tried rotating the tires?
front left tire goes on the rear right;
front right tire goes on the rear left;
rear left tire goes on front left;
rear right tire goes on front right...

all the other tips given out are really really great and was a delight to read... :D

you might want to try a 30d front... but if you think that 20d is ok for you then that's whats best...

hope this helps...Thanks, I never thought about crisscrossing tires... worth a try later.

OK a rear wheel question: I'm about to try another body that uses a rear W wheel. If I use a N wheel (w narrow tires / correct offset) for the rear, what kind of handling characteristics can I expect?

Mead
2010.09.11, 08:53 PM
Anyways through a combination of re-sanded tires, higher pinion, and backing down the throttle trim I'm able to drive the car without too much 'hooking'. It's still present so I finesse the right turns until I figure out what to do next. I was able to battle and turn in some hot laps today :cool: Thanks everyone.
I thought the hooking problem subsided but it's back :mad: I installed 40d sanded up front and to my surprise it works! (but I had limited track time, not 100% sure). During the tunning process when the car was brand new, 40d were pushing mad (and spinning out). I settled with 20d and it drove fine for months. Then this hooking problem arises and the remedy is back to 40d tires? :confused: weird.