Nerobro

iTrader: (2)

TL;DR: My Mini has strange handling, and I'd like some help.

Well that was an annoying visit to the track. Diffing out madly, but at least not rolling at first. I made some changes and things got much worse.

If you want to know more about the car.... It's at the bottom of the post.

So, I brought my M05 went back to the track. It rolled over more than a happy dog looking for tummy rubs. I glued the sidewalls of the tires, ran it on pavement for a few minutes to clear the over, and my goodness did that help the rollover issue. I was.. happy. Except, I couldn't put power down until I was done wtih a corner. Adding power mid corner just brought on massive wheelspin.

I've heard that adding Tamiya AW grease to the diff is a reasonable plan. I was also told that Tamiya AW grease was "just" anti-seize. ... It's not. I discovered that putting permetex antiseize in the diff on my M05. So "a little" stiffened up the diff.. but also made it feel gritty. But we'll get back to that.

The three different methods I used for "locking" the diff lead to the same behavior. The car, that had a fairly safe push behavior, ended up being almost undrivable. Any steering input was exponential, and leads to snap oversteer. This was with the lightly gooped diff, my diff locker, or the diff packed with antiseize goop.

Adding preload to the front shocks, seemed to help. But there was still the "steering a little, always got me more steering than I wanted".

So after two batteries of beating my head on an un-drivable car, I went and cleaned out the diff, and put it back to normal tamiya grease. Which, thankfully, brought the car back to how it was to begin with. The car did start rolling though... I think either hte glue job is wearing off, or the track was picking up traction as the day went on.

After some testing on the street, I found that my toe in wasn't set the same left and right. And I was running a fair amount of rear camber. The cars current setup is with about 2deg of toe out in the front, with absolutely identical toe in links.

My ultimate goal is to have a car that's stable on corner entry, and can accept the application of throttle mid corner, leading to push, rather than diffing out.

So what do you suggest?

Full car specs:
M05, v2 chassis
Bearings
Stock arms
Stock Springs
Ultra Mini CVA shocks - 2 hole, Yellow (400) oil.
Yeah Racing metal Steering setup
Yeah Racing CVDs
Yeah Racing Metal Rear Upright
Tamiya Adjustable camber links (only in the rear)
Zippy 5000mah 2s 20c LiPo
Turnigy DFT-303 short servo
Tamiya TBLE-02 ESC
BlueMX Reciever
21.5 Sensored Brushless Motor
20 tooth pinion
Stock M05 Tires.

What I have to work with:
Tamiya AW Grease
Tamiya Shock Spacers
Various Shock Oil
500k Diff Oil
Stock rear uprights

What's in the mail:
M05 Version 2 suspension arms

Papi

I found another picture of M07

gigaplex

iTrader: (2)

First of all, kit tyres are fairly rubbish. Start by getting some appropriate tyres. I've heard that the kit tyres can work on carpet as rears, but they're rubbish for asphalt and wear out really fast. Snap oversteer is usually a lack of rear grip. And you'll get massive wheelspin if your front tyres don't have much grip. Given that you've got a bunch of non-Tamiya upgrades I'm guessing you're not following TCS rules. Are there any mini drivers at your track you can ask for advice regarding tyre choice?

Next, download the archived version of rc-mini.net at https://docs.google.com/uc?id=0ByGYc...xport=download and read through the M03 build-up and M03 race setup, followed by the M05 race setup. Most of the stuff in the M03 section still applies to the M05. That should get you to a pretty decent baseline setup.

If you're using the stock long silver springs, get some proper springs so you can get a decent ride height without preloading the springs. Do you have any spacers/orings in your shocks to reduce the droop?

How heavy is the car, and how is the weight distributed?

sosidge

You haven't told us the parts that really matter - tyres, surface and current diff settings.

Diff - Reading between the lines, you are using the kit gear diff. Unless there is a rule that means you HAVE to use it, don't use it. An oil-filled gear diff is the best solution. I use the 3Racing gear diff with a medium-weight oil (around 30k off the top of my head) and that works in most conditions for me.

A good Tamiya option is the TA03 ball diff. Final option is tweaking the gear diff with greases and shims but even if you get it working, the setting will change over time so it is a high maintenance solution.

Tyres - are critical. Let the local "fast" racers guide you because they have probably done the testing already and you can just copy what they are using. Superglue on the sidewalls is a magic solution for traction roll on carpet, without compromising traction (it seems you are on carpet).

Assuming you have built the car well, suspension settings and weight distribution are just tweaks. Most of a mini's setup is tyres and diff.

Nerobro

iTrader: (2)

First, I do appreciate your replies.

So tell me about tires. I'm asking because these tires feel like they're pretty sticky. Am I seeking harder tires? Softer tires? How about sauceing the tires I have?

This answer again? Hah. I'm going to need to do something about this. About TCS, I'd like to keep my changes ~in line~ with TCS, so I could potentially pony up the $150 and do a quick conversion to TCS legal. But, that may just be a pipe dream.

What are proper springs? With the stock springs, the car doesn't droop much, or at all, really, harder springs are just going to make that situation a little worse. I ended up preloading the front springs as that seemed to produce a little more push, and avoid the rollovers.

I'll get the thing weighed, and corner weighted tonight. I wonder what surprises we'll find.

Black CRC Carpet, it always seems really sticky to me. It's common to see VTA cars bicycling on it.

Yes, I'm using the kit gear diff. It's wide open at this point, with just a little tamiya grease in it. With the access problems in the M05, i'm not sure a ball diff is a good idea. Though, I will say, I got pretty good at getting in there over my bench sessions this weekend.

The 3Racing diff is something I could.. emulate... with the factory diff, but it would be a maintenance hog. Got it, get the sealed gear diff, or seal the diff I have. ;-) Any reason I should avoid the YeahRacing version?

So I'm feeling a bit... confused. "not enough rear traction" but "kit tires are ok in back". So.. are they sticky, or not? I feel like with the same tires front and rear, I should be able to solve this problem with springs or other suspension settings. And I'm still feeling a little weird about the differential situation. A LSD in a real car, never made the car want to snap around like that for me...

Well.. I have a 150 meg zip file to download and read.... and condense... and repost...

bertrandsv87

iTrader: (2)

Two degrees of front toe out will cause alot of sudden entry steering with a big push in the middle&exit of the corner... Your static toe out is also less than the dynamic toe out in the front wheel drive m05: so you might have over four degrees dynamic toe out if you factor in the suspension play, making the problem worse... I would reduce the front toe to one degree or a little less...
Also, I would reduce droop as much as possible, with CA glue on the front tire sidewalls+1mm ca on the threads...
For the front diffing out, you will need to put stiff springs in the rear, contrary to popular belief, and softer front springs, and drive slightly on power around the turns(do not lift off completely)....

Nerobro

iTrader: (2)

I've done a lot of work to suck out the play in the steering. I've got two tricks left in my book, and I will be doing that tonight.

As it stands, I've shimmed the bellcrank to sit against the top of the supports. Any force on it would push it to the top of it's posts and change the toe in. So.. I pushed it to where it naturally wanted to be. That took a solid half degree of play out of the steering. By shimming the knuckles, I lost another degree (the knuckle can't move up and down, and introduce steering angle now..) I should also put 2mm of spacers under the bellcrank, to reduce bump steer... At leas thats what I've seen on setup sheets.

I'll try getting rid of all the toe out.

So.. what spring set should I buy? I've got the ultra mini CVAs. The setup you're suggesting is what you do for a real FWD car.

My most consistent laps have been with driving with some power on in turns. Before I glued the sidewalls, it was diffing out that maintained corner speed without tipping over.

bertrandsv87

iTrader: (2)

Good work ! I would put the blue or white springs in the rear, and yellow springs in the front to start... If yellow fronts get to be too soft, then try blue, but ca on the threads is very important with a low profile tamiya body slammed down all the way....

gigaplex

iTrader: (2)

I've never raced on carpet before so I'm not the right person to answer that question, however I've heard that M grip rears S grip fronts work well on carpet. Not sure if that still applies to the newer black carpet. Apparently the kit tyres can work on carpet if you prep them correctly, but when I tried them on asphalt they had little grip and wore out really fast. It would have been a waste of time and money trying to stick with them and tuning around them.

Heh. It's only 3 pages this time and shouldn't take long to skim through. The key parts to pay attention to are the diff, shocks, tyre, and suggested upgrade sections. One thing I'd add is that adding one or two extra spacers in the stock gear diff does work well, contrary to what the article suggests. But definitely get the proper AW grease.

Shorter springs, such as the Tamiya 53333 set. Your ride height is almost certainly too high if you're using 60 diameter tyres, no droop limiting spacers, and are preloading the long springs to remove the remaining droop. Preload is usually a bad idea as the springs lose their initial linearity, and ability to soak up small bumps. Aim to get your shocks to a ballpark 56mm length end to end, and only use preload adjustment to set ride height with the shorter springs.

The Yeah Racing version has the wrong number of teeth. It'll change the gear ratio and I wouldn't trust the mesh. Don't try to pack and seal the stock diff, others have tried and failed.

monkeyracing

iTrader: (10)

We switched to the new carpet for the second half of our race season. I fought with my car, as did everyone else, but solutions were found. Here it is (my setup) in a nutshell.

- Yellow springs all around. I ran the black ones, but the whites are about the same. 40wt oil. Ride height as low as possible and level. Shocks, end to end, are about 55mm.

- Rear toe in is a bit vague, are there's so much slop, but I've got the parts on for 2.5°. Front is a few degrees out. Camber is about stock out of the box.

- Diff - 3Racing with 1 million or heavier is our local go to. I've had good success with the stock diff, with 2 extra shims PER SIDE and a LITTLE antiwear grease. You can use the case screws to adjust tension. A very small hole drilled into the chassis will allow access for adjustment.

- I had good luck with M Grips on the front, with glued sidewalls and first trad block. Rears are some 3 year old S Grips, or kit tires. I like the S Grips as you can make hem more or less grippy as needed.

I've got one of the Yeah Racing diffs on the way to mess with and compare to my 3Racing diffs. This is just great timing, of course, since the next car has been announced and it uses a totally different unit and everyone knows I can't resist a new mini. Tamiya, you ruthless, brilliant bastards!

gigaplex

iTrader: (2)

For a total of 6 washers? That's a lot.

Nerobro

iTrader: (2)

Well, the spring set has been ordered. As have some proper shims for the steering rack. And it just struck me I should have ordered two sets of springs. YEY!

Getting slop out of the rear end, is possible. Most of my efforts haven't been that effective. I still have a few degrees of "vague" back there. Solving it would be a matter of using the setscrews in the aluminum uprights, taking the contact points from the sides of the upright, to the ends of the lower pivot pin... (that's what they do on touring cars) Is it worth the effort? Is it TCS legal? :-)

monkeyracing

iTrader: (10)

They fit in no problem and even cranked down, the diff will still turn. It takes a Few minutes of breaking in, but it works. I just chuck it up into my cordless drill and spin it a little. The problem with running only one extra shim per side is the diff gets notchy. For some reason the extra shim I use smoothes it out quite a bit.

OSherman

iTrader: (3)

Nerobro

iTrader: (2)

I went to the track tonight, with "just" the M05 to run on the roadcourse.

I'm down to half a degree of camber in the rear wheels. I am down to a degree of toe on the front. And.. . I can drive it. it still diffs out, and as traction comes up during a run, it starts to get tippy again. I think I need to re-glue the tires.

For tire glue maintenance, do you strip the existing glue? or do you just glue overtop?

Springs and sealed diff are in the mail.

On the ride height question, the ultra mini shocks have the ride height very, very low as it stands. somewhere in the ballpark of legality. When the carbon arms come in, I'll get the droop setscrews in them, and see how much further I can go.