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Old 10-10-2009, 07:19 PM   #1
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Default M-04M Gearing and diff questions please

Hi Guys,

I installed a Ezrun 60A Esc with a Ezrun 9T (3000kv) Brushless motor yesterday.



Problem i'm getting is, on the straights as soon as i apply anything over 1/4 throttle at slow speeds or 1/2 throttle at higher speeds the cars spinning out.


I fitted a 24T Pinion gear and it helped, but ideally i'd like to up the gearing a little more.
Problem is there's physically no more room for a bigger Pinion gear and after a few hours searching i've not been able to find any smaller Spur gears that fit.

Any suggestions or options with regards to gearing?

Lastly,
As the car is spinning out i figure if i tighten the diff then both wheels will spin so it'll stop the car spinning out so much under acceleration.

I have the diff in pieces on my bench, but it's looking pretty much non adjustable.
If i apply thick greaser and/or thicker shims will this make any noticeable difference and help lock up the diff more?

If not is there any diff available that is more adjustable?

Looking through the manual it list 2 diffs as hop up's
#53070
#53267

Both look to contain different parts.
Does one work better than the other?


Cheers
Mark
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Old 10-10-2009, 07:23 PM   #2
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Should also add.

Once the cars eventually going it feels a lot sharper and smoother on the new motor.

As it also spins out the same on the stock motor there's no real point going back.

I've also adjusted the Esc punch and this helps but only very slightly.




Cheers
Mark
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Old 10-10-2009, 08:54 PM   #3
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The problem is likely those tires, and the rear springs..

The diff needs to be nice and loose for turning the corners efficiently. The more free the better. What you have should be fine for now.

If you want to upgrade, I'd take the TA03 ball diff (53267) over the Manta Ray diff, the thrust bearing is in one piece. It's what I use. Nice and smooth.

Are those the stock tires? You'll need either S-Grips with soft inserts, or 6D Type-A with the firm inserts. M-Grips or stock tires are too hard to give the grip you need back there, but might be okay for the front.

You'll also want the TRF short red springs and oil shocks in the rear... I'd just get the whole set and you're good. http://www.tamiyausa.com/product/ite...oduct-id=53333
Or simply go with this nice damper set, it's all you need and it includes the springs you'll want.. http://www.tamiyausa.com/product/ite...oduct-id=54000

The M04 is a great car on carpet once set up right, unfortunately the stock stuff just isn't good enough.
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Old 10-10-2009, 09:28 PM   #4
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Hi,

Thanks for the advice much appreciated.

On the rear i have the M-Grip (50684) tyres with 53255 sponges.


On the front it's 50583 tyres with the standard sponges.


I'll order some new tyres.
Out of these 3 in what order are the the softest/the most grip?
http://www.etamiya.com/shop/tamiya-5...re-p-4505.html
http://www.etamiya.com/shop/tamiya-5...re-p-4432.html
http://www.etamiya.com/shop/tamiya-5...re-p-3795.html

I'll order that damper set as well thanks.

Is it worth ordering the 3racing 3 degree hub carriers as well?


Cheers
Mark
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Old 10-10-2009, 09:45 PM   #5
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Ah, yeah, use the M grips up front for sure..

As for the tire stickiness, from most to least, it's Type-A, Super Grip, Type-M, then kit tires..

Type-A's do wear down quickly, though.. you might be best off with the Super Grips, and you'd be fine with firm inserts (dark grey sponge strips) on those..

As for hub carriers, 2 degrees is good, I think 3 would be too much and add additional wear to the rear tires.. I have the 2 degree plastic ones from Tamiya, work like a charm.
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Old 10-11-2009, 04:31 PM   #6
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Fantastic thanks again.

I been searching around and have everything i want from 1 Ebay supplier so i'll be placing n order soon for the suspension, tyres and diff.

A friend from a car forum i'm on advised that there is a fast gearset available the M05 by 3racing (#M05-02).
Comes with:
# Spur Gear 33/21 (1pc)
# Spur Gear 35/21 (1pc)
# Counter Gear (1pc)

I figured i'd order a few pinion so i can see what fits best.
Only spanner in the works though is the fact i keep coming across these 0.4 Tamiya pinions (e.g. #53690).

Are these a different pitch?
My current pinion gear just looks like a normal 48 pitch gear.


Lastly,
What's your views on the various hop up's available by 3racing, Tamiya, yeah racing etc?

The vast majority seem to be for the M03, but the suspension should be exactly the same right?



Cheers
Mark
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Old 10-11-2009, 05:48 PM   #7
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Another quick question please.

I've just measured my current 24T pinion and 37T Spur.
With the correct gapping both together are 36mm.

Is there a chart that gives the diameter of each pinion and spur in 48 pitch?



My thinking is this is about the limit i can physically fit in the gearbox.
If i purchase the M05 fast gearset it'll give me a smaller spur so i can then fit and bigger pinion, that should be better as:
a/ It'll stop wheelspin and make the car slightly easier to get off the line.
b/ It'll give a better top speed that my new motor can now push to.

As i posted about the gearset comes with a 33T spur, so if i could find out the diameter of a typical 48p 33T spur and the diameter of pinions around 28T to 32T it'll give me some idea of what pinion to order.
It'll also be handy as the hole in the motor case the pinion has to pass through is only 15.5mm.


Cheers
Mark
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Old 10-11-2009, 09:11 PM   #8
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9t is way too much power for this car
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Old 10-12-2009, 12:33 PM   #9
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Quote:
Originally Posted by gixer View Post
Fantastic thanks again.

I been searching around and have everything i want from 1 Ebay supplier so i'll be placing n order soon for the suspension, tyres and diff.

A friend from a car forum i'm on advised that there is a fast gearset available the M05 by 3racing (#M05-02).
Comes with:
# Spur Gear 33/21 (1pc)
# Spur Gear 35/21 (1pc)
# Counter Gear (1pc)

I figured i'd order a few pinion so i can see what fits best.
Only spanner in the works though is the fact i keep coming across these 0.4 Tamiya pinions (e.g. #53690).

Are these a different pitch?
My current pinion gear just looks like a normal 48 pitch gear.
It's a "Metric" 48 pitch gear.. they're close, but there are differences. Robinson makes metric pinions, I use their steel one, much more durable than the aluminum ones Tamiya makes.

Lastly,
What's your views on the various hop up's available by 3racing, Tamiya, yeah racing etc?

The vast majority seem to be for the M03, but the suspension should be exactly the same right?
If you're doing any kind of TCS racing, you have to keep to Tamiya hop-ups.. otherwise, they're all the same, 3Racing is usually cheaper by quite a bit, and they all work well.

The M03, M04, and M05 all adopt the same suspension and drivetrain parts, the only difference is the chassis and where it puts the motor and servo. I still have the original front aluminum knuckles with my M04, still work great. They tried to get lighter weight with 5x10 bearings on the M-03M/R parts, but have since gone back to 5x11 bearings.. go figure..


I've just measured my current 24T pinion and 37T Spur.
With the correct gapping both together are 36mm.
Is there a chart that gives the diameter of each pinion and spur in 48 pitch?
Hmm.. not sure.. I'm surprised you could fit a 24T in there. I don't know of any chart, bit I guess you could calculate it based on your current pinion.. for a 25T, calculate what percentage 1 tooth is to 24 teeth, and increase the 24's circumference by that percentage. Diameter would be easy to get after that.

My thinking is this is about the limit i can physically fit in the gearbox.
If i purchase the M05 fast gearset it'll give me a smaller spur so i can then fit and bigger pinion, that should be better as:
a/ It'll stop wheelspin and make the car slightly easier to get off the line.
b/ It'll give a better top speed that my new motor can now push to.

As i posted about the gearset comes with a 33T spur, so if i could find out the diameter of a typical 48p 33T spur and the diameter of pinions around 28T to 32T it'll give me some idea of what pinion to order.
It'll also be handy as the hole in the motor case the pinion has to pass through is only 15.5mm.
Well, according to the speed gear set it would allow at most a 24T pinion, you might be able to fit a 25T.. not sure, I think it's all down to trial and error. But at that point, like that previous post said, 9T is a bit fast, might just end up melting the gears at that point. I know plenty of folks using a 13.5 BL, and the default gear ratio actually suits that motor really well. Otherwise, it's not a very large car, so it may not be suited for that kind of speed.
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Old 10-12-2009, 03:18 PM   #10
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Absolutely fantastic response thank you very much.


I had the same thing with the stock 540 motor, only rather than the car spinning out on 1/4 throttle it simply spun out on 1/2 throttle.

Only real difference is, with the 540 motor is was extremely difficult to recover once it started spinning, with the BL motor the car feels sharper but also smoother.

I've ordered:
4 x Type A slicks (53340)
4 x Super grip (53254)
1 x 3Racing Alum Ball Dif (#M03M-01/LB)
1 x 3Racing Fast Gear Set (#M05-02)
1 x Tamiya Sponge (#50686)

I've swapped the shocks around for now if that helps i'll order the shock set you recommended.

Fingers crossed a mixture of the diff, tyres, softer rear and gearing will help.
If not i'll try a slower motor.


Massive thanks for all your help and advice, especially you Jam-ehz you've been a great help.

I'll keep you posted on how i get on.



Cheers
Mark
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Old 10-12-2009, 06:15 PM   #11
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Quote:
Originally Posted by gixer View Post
Absolutely fantastic response thank you very much.
I had the same thing with the stock 540 motor, only rather than the car spinning out on 1/4 throttle it simply spun out on 1/2 throttle.

Only real difference is, with the 540 motor is was extremely difficult to recover once it started spinning, with the BL motor the car feels sharper but also smoother.

I've ordered:
4 x Type A slicks (53340)
4 x Super grip (53254)
1 x 3Racing Alum Ball Dif (#M03M-01/LB)
1 x 3Racing Fast Gear Set (#M05-02)
1 x Tamiya Sponge (#50686)

I've swapped the shocks around for now if that helps i'll order the shock set you recommended.

Fingers crossed a mixture of the diff, tyres, softer rear and gearing will help.
If not i'll try a slower motor.


Massive thanks for all your help and advice, especially you Jam-ehz you've been a great help.

I'll keep you posted on how i get on.
No problem at all.. let me know how it goes.

As long as your softest go in the back and harder ones go up front, you should be good..

I'd check on exactly what that ball diff part is.. the part number you listed is just for the gear and screw to rebuild one.. Of course, if you want a replacement TA03 diff gear, that should do the trick since Tamiya doesn't really sell those separately.

If it is the whole ball diff assembly, just watch out, because there have been some out there that require you to actually drill out the bearing holes to allow for a larger shaft, much like what the M-05 has as an option. It's often not worth it, I'd keep the TA03 one..
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Old 10-13-2009, 11:03 AM   #12
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Looking on the 3racing site, they have M03M-01/LB as the part number for this part.
http://www.3racing.hk/products.php?products_key=2584



The rebuild kit they list as M03M-01RG.
http://www.3racing.hk/products.php?products_key=2584




I'll keep my fingers crossed that i don't need to start drilling the casings.
But looking at the casings i think your correct.
I don't see how the new diff is gonna fit without some modifications.

I've just measured my casings and drive shaft.




Unless they have made the external diameter of the drive shafts smaller i can't see how they are gonna fit without some modification.

The section that holds the drive pin looks to be very thick (4mm ish) so it is possible they could take some material from there.

But as the internal section is 6mm they'd have to make the external section 6.6mm to fit through the hole.
I can't see them holding up for very long at only 0.6mm thick.

So no doubt your correct i'll need to remove some material from the drive shaft hole


Cheers
Mark
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Old 10-13-2009, 11:33 AM   #13
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Well i've been looking on the 3racing site for around 3 days now, and only NOW have i found the Technical Support Center section

Yep you were spot on Jam-ehz, you do indeed have to expand the hole.


Oh well, that'll teach me to check properly rather than rushing in to buy something.

I'll still fit it though, as i've found the stock diff is extremely notchy.
When holding 1 wheel i can feel the drive gets very tight at 1 point then very loose on the rest of the rotation.

I'm pretty sure the problem is somewhere in the diff because as i say even with the stock 540 motor the car spins out on the straights with the wheels pointing forwards.

The thing is it sins out THAT quickly there's very little i can do to catch it.




Cheers
Mark
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Old 10-17-2009, 02:51 AM   #14
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It seems like your problem is too much power and not enough traction. Changing to a ball diff or locked can actually reduce the traction in the turns. Instead of only the inside wheel spinning, with a locked diff both wheels will slip. I think you could probably do some work with springs and dampers to improve the rear traction.

Step 1) Get some silicone fuel tubing to pack the front shock shafts. You need to measure precisely the amount of shock shaft that is exposed at normal ride height. Then cut lengths of fuel tubing that can be used to fill this gap on each side of the car. This greatly increases the roll resistance of the front suspension. It will stabilise the car and allow the rear suspension to do a better job.

Step 2) Get some oil filled shocks for the rear. Use two hole pistons with light/medium damper oil and soft springs to allow the rear suspension to deliver maximum grip. I have built a modified M04 with TL-01 long suspension arms. I used standard tamiya touring car shocks, but the "super short shocks" are probably a better length for the standard M04 car.

Step 3) You can get another set of super short tamiya shocks for the front. I had these on my M04 based touring car. Get the "ultra hard" short springs and use the shock pistons with the single holes. The idea is similar to step 1, just to make the front suspension as stiff and inert as possible.
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Old 10-17-2009, 03:20 AM   #15
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Thing is though it spins even before i turn the wheels.


The problem is on the straights not on the turns.


If i give it slightly too much throttle as the cars pointing forwards on a straight bit of road then the car does a 180 turn.


As i say it also does this with the stock 540 motor as well, just with the 540 motor it does it at half throttle rather than 1/4 with the BL motor.


I've stripped the diff down and all looks ok.
But it's extremely notchy, if i hold 1 wheel and turn the drive by hand it spins freely for say 3/4 of a turn, it's then a lot tighter on the last 1/4 turn.


Fingers crossed the parts i've ordered will allow me to run the 3000kv motor and provide a little more entertainment.

If not i think i'll buy a Cup Racer and just transfer my Roadster shell over.




Cheers
Mark
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