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Tamiya mini cooper

Old 07-01-2015, 12:53 PM
  #24226  
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Hey Eric. ..my car doesn't corner well under acceleration and my diff isn't locked. Can I glue the diff together to lock it up or is that a bad idea. I've heard a few guys have done it but it's kind of a big job to get it out in the m05. Is it worth it to try or is there a locking diff I should by and replace instead.
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Old 07-01-2015, 01:00 PM
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Locking your diff will make the car push (plow/understeer) more. Have you tried softer front springs, but or raising rear ride height a little? Either will help turn in. Beyond that, stiffening the rear, or a less toe out on the front can also help.
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Old 07-01-2015, 02:01 PM
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Originally Posted by monkeyracing
Locking your diff will make the car push (plow/understeer) more. Have you tried softer front springs, but or raising rear ride height a little? Either will help turn in. Beyond that, stiffening the rear, or a less toe out on the front can also help.
I have stiff shocks on the rear and soft in the front. Now the diff and tranny have been used pretty good. I have no where to race but I do drive the hell out of this thing. It's an m05 stock internals and I usually only have pavement/road to drive on. Now what is the difference between a ball diff and the one that's stock??? And what are some other upgrades I can do to the gears inside to help with drive train parasitic loss other than ball bearings which I still have to put in.
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Old 07-01-2015, 02:08 PM
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Yellow springs on rear white on front. Pic won't upload lol from phone
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Old 07-01-2015, 02:38 PM
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Definitely get ball bearings for the internal gearing, in fact anywhere those white plastic shim things are present!

When you say your car doesn't corner well under acceleration, what exactly is it doing?

The ball diff helps (pretty dramatically actually), but letting the car keep power through a turn. W/ the stock gear diff' if I remember correctly my cars gears would just spin through a corner and i'd lose quite a bit of speed. W/ the ball diff that mostly went away. You have to tighten the heck out of the ball diff'.
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Old 07-01-2015, 02:54 PM
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"When you say your car doesn't corner well under acceleration, what exactly is it doing?"

"The ball diff helps (pretty dramatically actually), but letting the car keep power through a turn. W/ the stock gear diff' if I remember correctly my cars gears would just spin through a corner and i'd lose quite a bit of speed. W/ the ball diff that mostly went away. You have to tighten the heck out of the ball diff'."


Exactly what you described is what happens. It just doesn't go in the corners as good as it could...and it just sounds horrible. What ball diff do u recommend and what do u mean tighten the hell out of it.

Also what are a better tire for pavement and which foam inserts are the best.....or are tamiya tires good but I just have to deal with them wearing pretty fast lol?

Last edited by M05 newbie; 07-01-2015 at 03:17 PM.
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Old 07-01-2015, 03:20 PM
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the TA03 ball diff',
53267 - TA03 Ball Differential Set

http://www.tqrcracing.com/shop/produ....asp?p_id=2172


You just want to make sure you really tighten it, ...you don't want to tighten to the point of breaking it, but you do want to tighten it quite a bit. Most Tamiya parts you tighten to the point of resistance ...tighten a screw until you feel a bit of resistance then stop. W/ the ball diff' it's a bit different, you want to tighten then give a 1/2turn extra for good measure. Just make it tight is the point!

With the stock diff' you probably notice that around corners if you give it throttle the motor continues to spin but the wheels dont, or not at the same rate that it should. With the ball diff in place this is reduced quite a bit. You can go through a corner still giving it throttle and the tires will roll at a speed closer to what the motor is doing.

BUT, my driving style and I believe the desired driving style of most is to let off on throttle around corners and let the car kind of roll through, then get on the throttle on turn exit. ...roll in, throttle out. The ball diff' helps carry a lot of this speed/momentum through the turn, better than the stock diff.
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Old 07-01-2015, 03:23 PM
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- i used to be able to hear the gears moving and the motor revving around corners but the car wasn't going at the same speed. ...with the ball diff' this effect is reduced. Hope that helps.
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Old 07-01-2015, 03:43 PM
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You just want to make sure you really tighten it, ...you don't want to tighten to the point of breaking it, but you do want to tighten it quite a bit. Most Tamiya parts you tighten to the point of resistance ...tighten a screw until you feel a bit of resistance then stop. W/ the ball diff' it's a bit different, you want to tighten then give a 1/2turn extra for good measure. Just make it tight is the point!

With the stock diff' you probably notice that around corners if you give it throttle the motor continues to spin but the wheels dont, or not at the same rate that it should. With the ball diff in place this is reduced quite a bit. You can go through a corner still giving it throttle and the tires will roll at a speed closer to what the motor is doing.

BUT, my driving style and I believe the desired driving style of most is to let off on throttle around corners and let the car kind of roll through, then get on the throttle on turn exit. ...roll in, throttle out. The ball diff' helps carry a lot of this speed/momentum through the turn, better than the stock diff.[/QUOTE]

Awesome. And ya that's what it does. Now when I turn left and keep the car in a circle all the way to one direction and then go full throttle it makes a bigger circle than when I go right at full throttle. Is this a mashed diff?? Or is that normal lol
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Old 07-01-2015, 04:02 PM
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Awesome. And ya that's what it does. Now when I turn left and keep the car in a circle all the way to one direction and then go full throttle it makes a bigger circle than when I go right at full throttle. Is this a mashed diff?? Or is that normal lol
Two things,
1) going full throttle in turn (or circle) will spin the ball diff' but not as much as w/ the stock "gear" diff. Hence why I was suggesting that it is preferred to roll through a corner and throttle out.

2) yes, having speed in a circle or corner will make the turning radius a bit larger. The car wants to push outward w/ speed. You do get a tighter turn radius when going slow. This is pronounced w/ F1 cars.

The ball diff is a must (in my opinion) for racing. For parking driving and donuts it will help, sure, but jamming on the throttle will make the ball diff' spin. When racing the Mini, you really want to feather or touch the controls lightly. I feather the throttle around long corners and let off on tight ones, ...full throttle only on the straights, but I try to not be overly aggressive w/ my driving. It's really a balance of gentle controlling and feathering. ..that's how I describe the best way to finesse the mini.
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Old 07-01-2015, 04:07 PM
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Originally Posted by eR1c
Two things,
1) going full throttle in turn (or circle) will spin the ball diff' but not as much as w/ the stock "gear" diff. Hence why I was suggesting that it is preferred to roll through a corner and throttle out.

2) yes, having speed in a circle or corner will make the turning radius a bit larger. The car wants to push outward w/ speed. You do get a tighter turn radius when going slow. This is pronounced w/ F1 cars.

The ball diff is a must (in my opinion) for racing. For parking driving and donuts it will help, sure, but jamming on the throttle will make the ball diff' spin. When racing the Mini, you really want to feather or touch the controls lightly. I feather the throttle around long corners and let off on tight ones, ...full throttle only on the straights, but I try to not be overly aggressive w/ my driving. It's really a balance of gentle controlling and feathering. ..that's how I describe the best way to finesse the mini.
For 2.....what I meant was that left and right are significantly different on radius size when I do the same thing. Is that normal?? I.e left is a big circle and right is a little circle....normal?


And is there a tougher/better tire for pavement that will fit the mini
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Old 07-01-2015, 05:19 PM
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Originally Posted by Redko
Hi Granpa,

would like to ask for some advice.
running on mid to high traction carpet, M-Grip tires with all round hard insert, Medium wheel base.

What will you suggest for shock rebound?
build it to zero rebound or full rebound ?

Thank you in advance !
First, let me tell you that I race primarily on outdoor, low to med grip asphalt. I've only done 20-30 races on carpet.

With that being said, I almost always use zero rebound for a number of reasons. The first being they are the easiest to build. The second is trying to build, say four 2mm rebound shocks, is very difficult. Third, once you build them, they don't stay that way.

Full rebound is never a good idea cause a lot of the shock action depends on being able to compress that little air bubble between the bladder and the cap. The shock will really stiffen up as it compresses and will affect the handling in an adverse way. There are other reasons, but a long winded dissertation was not part of what you were requesting.
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Old 07-01-2015, 05:54 PM
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I've been following the discussion on diffs with some interest. I hope you guys don't mind if I insert my input. You can ignore if it's not welcome.

What a differential does is to keep drive to the outside wheel even if the inside wheel has lost traction. The term "diffing out" refers the inside wheel lifting or losing traction and spinning while the outside wheel does not have any forward drive. This is the problem with the stock gear diff. What's required is to maintain drive to the outside wheel even tho the inside wheel has lost grip. Consequently, guys will shim the stock gear diff, which, if done properly is very effective, or go to a ball diff or after market oil filled gear diff.

For most situations, the "looser" you can run the diff, the better. The reason for this is that the tighter the diff is, the more resistant it is to turning. This is why what Monkeyracing said about a locked diff is true. The advantage of the ball diffs is that you can adjust this fairly easily. the after market gear diffs require you to change the oil, which is a messy and tedious operation.

Also, though I didn't quite understand why you would want to really "tighten the screw" on a M05 ball diff. That diff is designed to be run fairly loose. Trying to stiffen it's action by cranking down on the screw will only cause the diff screw to break in time. If you want a Stiff or tight diff, it's better to go to a TA03 ball diff or an oil filled gear diff. There is plenty of information on how to make those diffs work.
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Old 07-01-2015, 05:59 PM
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Originally Posted by Granpa
I've been following the discussion on diffs with some interest. I hope you guys don't mind if I insert my input. You can ignore if it's not welcome.

What a differential does is to keep drive to the outside wheel even if the inside wheel has lost traction. The term "diffing out" refers the inside wheel lifting or losing traction and spinning while the outside wheel does not have any forward drive. This is the problem with the stock gear diff. What's required is to maintain drive to the outside wheel even tho the inside wheel has lost grip. Consequently, guys will shim the stock gear diff, which, if done properly is very effective, or go to a ball diff or after market oil filled gear diff.

For most situations, the "looser" you can run the diff, the better. The reason for this is that the tighter the diff is, the more resistant it is to turning. This is why what Monkeyracing said about a locked diff is true. The advantage of the ball diffs is that you can adjust this fairly easily. the after market gear diffs require you to change the oil, which is a messy and tedious operation.

Also, though I didn't quite understand why you would want to really "tighten the screw" on a M05 ball diff. That diff is designed to be run fairly loose. Trying to stiffen it's action by cranking down on the screw will only cause the diff screw to break in time. If you want a Stiff or tight diff, it's better to go to a TA03 ball diff or an oil filled gear diff. There is plenty of information on how to make those diffs work.

All info welcome...now it's s bitch to get that diff out pardon my language but how do I adjust it so that it's good. Looking into a ball diff most likley. Best bang for the buck. What's your suggestions to this aswell? Not to undermine Eric at all...he has been very helpful..like red green said....we're all in this together!! Lol
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Old 07-01-2015, 06:01 PM
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Originally Posted by M05 newbie
For 2.....what I meant was that left and right are significantly different on radius size when I do the same thing. Is that normal?? I.e left is a big circle and right is a little circle....normal?


And is there a tougher/better tire for pavement that will fit the mini
Try this. At slow speed see if the turn radius is different going left or right. Sounds like you have your steering set up wrong. I'd explain, but it's in the manual.
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