GT12 Help..
 

Hi Chaps
A couple of questions about GT12 if I may

I ran for the first time last night at a meeting; my overriding issues were as follows, if anybody can shade any light.

Steering was extremely sensitive, front end digging in and making it a touch lively with the back end; Is this toning down the sensitivity of my steering dual rates? What do people have theirs set at generally? I also went harder with my suspension on the rear, mistake, softer was better!

Secondly, my diff/pinion mesh seems to make a slight grinding noise, but can't seem to figure out what it couple be? Could this be a bent drive shaft possibly? It seems to grab/grind at a certain point if I push along un-powered.

Any help or advice is greatly appreciated in advance.

Best Wishes
Stuart

Stuart, can you tell us what the car is and what the current basic setup is you have on it?

There may be many things so knowing what you have started with will narrow it down... a lot!

GT12 cars all handle well and are great to drive once you have the setup sorted. Give us a bit more info and we'll have you going in no time. :thumbsup:

Sounds like an SSGT.

Go to 50 front tyres and yellow rear springs. And reduce droop to 1mm all round.

The kit spurs aren't very true. Set your mesh at the tightest point on the spur so there's just the smallest amount of play. Or replace with one of the machined spurs.

Join the gt12 circuit UK Facebook page loads of info and help on there too 1500 + members

First up, I'm not on Facebook. Maybe one of only a handful who are not!! :cry:

Thank you guys for your replies...
I have ordered 50's for the front, and i will definitely apply the suspension change.

Regards to the setup I have;
I have hopped up the side damper conversion kit, but that's about it.
I had stuck with the standard setting that was applied when I built the car. When softening the suspension before the car definitely handled better, stupidly I went harder on the back during the meet and it definitely got worse. Stupid boy!

What I noticed with other cars was, a distinct lack of body roll which inspired me to harden my suspension at the time and other cars seems to have an element of drift of all for wheels during cornering.

The other question would be the amount of break people apply to their ESC, I have relatively little set (Toro 1s ESc) and I barely used as I suspected it would make it even more tail happy!

Look forward to your thoughts chaps.

Best Wishes
Stuart

The harder tyres will reduce your body roll (as the car will slide rather than roll).

Other major factors are ride-height (3.5 to 4.0mm depending on how bumpy the track is) and body height (see if you can trim the shell at the bottom and lower it on the posts).

Thats a great tip dale.. Trimming the shell...
Never thought of that, but I have to say, mine did look a little like a bus compared to a few others!! Will give that a go!!

Thanks...

Just check EVERYTHING on the car. Things like droop/tweak can be very sensitive on these cars, even a slight change on toe-out or ride height can make it handle completely different. If you're saying it's turning in hard then a slight amount of toe-out can do that.

You just need to look over it with a thorough eye.... and then get some of the quick boys at your local club to have a look too. There's not much people can suggest in less you post a full set-up sheet and then it would still be tough without seeing the car!

Thanks Dan....
Being new to the GT12, the more you read the more I get to see what people are talking about and how they set their cars...
It appears that the suspension springs is pretty constant throughout, green front, yellow/blue back.
Tyres give or take...
Droop seems different, i hear many say 1mm, some appear to have 2mm.. Where exactly do you measure the droop angle from?

Gosh, so much to learn... When I get back tonight, I will get the setup and post.. See what you all think..

From my untrained eye, my car looked - soft (body roll) too much grip front end... Very twitchy, turned on a sixpence and felt i could barely touch the steering down the straight as it would unsettle the car and make it roll... (Not that this happened, but that what it felt like)

Hope that makes some kind of sense... As i say, will post setup tonight..

Stuart

If you mean 'drag' brake, then Non.

With today's rotors it's not needed. If you still have to much just reduce your end point from 100% to 95% and so on until you find how much you like for a given track.

Another thing I found was to move the rear spring's out rather than the kit inner holes

Foam Tyres & Additive
---------------------------



Fronts
from the inside edge apply for 1/4 width and go from there. More width gives more steering. Apply lightly, they don't need to be ringing wet

Rears
full width all the time and wet but not dripping

Try to apply rears addy at 20 minutes before applying front

Foam
Make sure you have a radius on the inner and outer edges.


Some good info in here
http://www.brca.org/sections/subsect...-articles/1144

BRCA rules are that you don't trim the shell and lower it. Trim to the lines on the shell is all that is allowed. If you are never going to race a BRCA Regional or National then fine. Having tried this the biggest impact you can make is a lightweight shell - lowering the shell isn't that effective.

The lower-grip set-up in the instructions works for everyone everywhere. Changing tyre hardness is the best change to suit the conditions. If you are really stuck, then front springs are the next change.

It sounds as though there is problem with the build that is giving you issues, but let's see when your set-up comes on to the thread.

So... My setup...
Motor Gearing - As standard
Front Ride Height - 4mm
Front Toe In - 0 (Straight)
Ackerman Washers - 1mm
Camber Plate - If I am honest, I don't know how to measure this?? Looking on Chris Ashtons set-up, he says 2º - Is this altered by the little grub screw next to the spring pushing on the chassis?
Front Spring - Green
Centre
Roll Dampers - Oil as standard
O'Rings - Blue
Motor Spacer - 2
Rear Springs - Yellow (Were Blue)
Ride Height Adjuster - Was 4 Dots, just changed to 1 Dot
Diff - Yes
Rear Ride Height - 4mm
30g Weight - Yes
Rear Droop - No idea how to measure?
Rear Droop Screws - No Idea?
Rear Suspension Position - Just changed to outside holes

Ok Chaps... Over to you!!

Best Wishes

Stuart

Rear Droop was/is 2mm.... Just measured...

Camber is via the pips on the top beam, 1.5 is kit you change the beam for1 or 2 to alter camber

If you have the damper tubes and the blue Orings in the side links your way too stiff, use the tubes and no orings

Transmitter

Do you have any negative expo dialed in? If not try -15 to -20

If your using a Spektrum tranny you have to use positive expo though.

Negative expo calms the servo's initial responce around it's neutral point.

I had initially done nothing with my tranny.
It's a core RC; I had a chap mess around with it, reduced my dual rate and I think messed with my expo.

Any info on Tranny settings and their applications would be a great help if anyone wants to fill me in?

Restore steering defaults then do the following as written by Andy Griffiths in link. Refers to KO but same principle for all steering
http://www.carsrcracing.co.uk/?p=180

Brilliant, will apply!!!

Just read the article..
Explains a huge amount, especially the volatility of my car at high speed... Thats been a great help.

I also found out last night I have a slight bend in my rear axle, so I have a new diff setup coming today from MB Models.. I didn't want to far around rebuilding, so i went for a new one. If in doubt, throw some money at it I say!!

Thanks for all the help so far chaps and I can't wait to get home and do some fettling tonight, ready for my trip to West Kent on Sunday...

Look forward to hearing any more pearls of wisdom you all have for me!!

Best Wishes

Check your droop too.

At high speed, when letting off or braking you can get a lot of weight transfer to the front if you have too much rear droop which means tonnes of steering.

You check your droop like this -

First check ride height - Lets say 4mm. Then you lift the car from the front or rear bodyposts and it's the gap from the chassis to the floor WITHOUT the wheels lifting - Let's say 6mm. You then just minus the ride height from this reading which means you have 2mm of droop. I'd say 1mm of droop all round is a good starting point so you don't get too much weight transfer!

If you just changed your ride height from 4 dot to 1 dot that could of been your original problem too.

Just keep on top of the basics and your car will handle great.

Thanks Dan, great tip about the basics...

Well, I just fitted my new diff; all the adjustments you have all recommend and it certainly seems a much tamer beast.. I think the droop has played a huge part in all of this, and secondly, the steering set up.. Negative expo and reduced travel has been a great addition.. A lot less volatile at flat out...

I think what also has helped is knowing what affects what in the cars handling.. Then I will have option when I race, rather than shooting darts in the dark!!

I am certinaly excited to get to racing Sunday; and I will be sure to post how I do...

I just got some JFT wheels and tyres, what did I fail to order?? They don't fit?? Silly me...

Stuart

The guys have summed it all up for you - get rid of the O rings in the links (all of them) and use the side dampers only. Rear droop is a tuning aid to get the car to turn in, but at West Kent with their grip you should be at 1mm or less.

Rear droop is a compromise between having the car able to cope with the bumps and getting the right weight transfer onto the front axle as you turn in. On bumpy track go to 1.5mm at both ends, but for flat tracks you should be at 1mm or less at both ends.

Remember to set rear droop with the body on. GT12 shells, even the lightweights, are quite heavy. You could set the droop on the bench and it then increases (and reduces ride height) when the body goes on. If you have a lightweight shell it's less of a problem. With a heavyweight shell set the rear at 4.5mm ride height with 0.5mm droop. With the heavy body on it will go to 4mm/1mm.

With the kit tyres no more than half the front tyres should have additive - the inside half. If you are using SXT then put plenty on as it evaporates quickly. When using Spider Grip then don't overdo it that is just a waste of additive. If you find the car is a bit grabby in the first few laps with Spider Blue switch back to SXT. When the grip is up go to Spider Green.

Get someone at West Kent to show you how to set the tweak with the coin drop method. If Luke Burley is there he'll clue you in. Without that test make sure that the rear springs are equally compressed - when the car is off the ground both springs are equally compressed on both sides.

You didn't say what grade tyres you are using. The kit tyres should work everywhere. When the grip comes up and the car seems to understeer a bit, move to 40 rears. To make the car a bit safer, switch to 50 fronts at the same time.

I don't know which class you drove before, so give these cars a bit of time to do their stuff. Don't pile into corners too fast as you will lose control of the front tyres and the car will not straighten up properly out of the corner. Slow in, fast out and hitting your apexes is the way to get the most from what is a heavy car on relatively skinny tyres.

Good luck, and I hope you get a good run at the weekend. :thumbsup:

Hi Chaps

Well, I have to say, all your help and advice was not in vein. Much better runs and I really enjoyed my time with the GT12 car a lot more.

So, I have more questions.
I really noticed how much out of balance the car was going around left hand corners. Sadly, this only dawned on me on my last run and it really was so night and day.

I looked at the balance of the car, with regards to weight... It was very right side heavy (looking from the nose to tail of the car) would this have been my problem? I have since put all my radio gear, receiver and Esc a lot more central.

Secondly, my car with body's hell is over 1kg, is this took heavy??? Why on earth is it so heavy?

This has been a really positive journey this week, I'm heading to Maritime on Thursday to get some practice in and some more racing.

Thanks in advance and Happy Easter.

Stuart

Happy Easter Stu - hope the egg fairy has been!

Not sure how you've managed to get a GT over 1000g. Can you post a photo?

Mine has the 30g weight on the back, Reedy Mach II motor, Vapex cell, Core RC servo, LRP SXX v2 speedo and an FRSky receiver. I've had to add 40g of weight to get it to 950g weight limit.

What wires are you using? 16g is all that's needed for GT12. 12g/14g will be too heavy and may interfere with the proper movement of the pod - see your note about the handling above.

Which body are you using? A lightweight shell will not only drop the weight, it will improve the handling.

The side-to-side balance of the main chassis is a key point to getting a good handling car. Also, you need to balance the rear springs to give equal weight on each on front wheel. The combined weight of the rear pod goes through the chassis at the single central pivot, so forget that.

Take all the rear pod off the car. Set out the electrics on the chassis and see if you can get it to balance from side to side. Get as close as you can.

When that's all done, put the whole car back together, ready to race, and then raise the front of the car with a screwdriver in the middle of the chassis. Spin both front wheels and gently lower the car to the ground. Both wheels should touch at the same time.

If they don't adjust the rear springs (screw one up and one down by about 1/4 turn at a time) until they do. That sets the weight of the car evenly on each front wheel.

A photo would help us give you more tips. Enjoy your race at West Kent - great club! :)

Photo on the way!!

Hi Chaps...

This is a clip of my car, one more to follow...

So SlowOne, does this shed any light why I am driving around a super tanker in the GT12 class??

Thanks for all this help, so useful and brings me up to speed with many hidden gems of information!!


Could the wires be the reason for the weight...??

Best Wishes
Stuart

Slowone..

I did exactly that with the layout of the electrics and balanced the front of my car. deviously, if I lifted the front of the car up, in the centre, there was a massive left wheel lift before the right wheel lifted, I guessed this wasn't a good balance.. its now perfect...

I am a little worried about the weight tho, the only thing it can be is the wires on the Esc... Its a toro 1s and I simply used the wires it came with. I guessed these were good enough? Silly me... once again!

I will await your thoughts on the wire, failing that, all the equipment is as you see it in the photo and I have fitted the 30g weight on the side too for balance. No other reason why my car should be so heavy..
Incidentally, the weight of the car without the body shell is 930grams, with the body shell, (75grams) 1005grams total..

Best Wishes

Stuart

Are the wires the reason for the weight? Do bees buzz, do flies fly, do bears defecate in the woods? Er... GET RID OF THOSE WIRES!!! :D :D

Take it all off, and the brass terminals on the speedo if they'll come off, and replace it all with 16g wire in just the length needed to reach from speedo to motor and battery. This stuff is the dogs...

http://www.zen-racing.co.uk/catalog/...6g-wire-p-1188

...and comes in blue, red, orange and black so you can keep the colours if you want to. Leave a little slack on the motor wires so they don't interfere with free movement of the pod, and make the battery wires such that the negative won't reach the positive terminal - stops the release of the smoke capsules in the speedo when connecting in a hurry!

Body weight suggests you have a lightweight shell so that's good.

Did you balance the chassis to get rid of the one-sided wheel lift, or did you adjust the rear springs? If you did it all on the chassis balance that might still leave a tweak in the car. As a double-check, look at the rear spring nuts.

They should have about an equal amount of the bolt showing above them. When you lift the car by the chassis, the rear springs should have an almost equal amount of slack on each side. If these aren't even close then you have balanced the chassis, but not the spring pre-load and you will still get odd handling.

Here's a pic of my GT showing both the above. HTH :)

SlowOne...
You are a superstar!!
So I ordered the wires last night... The front end is really well balanced, did it with some jewelry scales (please don't ask why I have these :-) ) and its balanced like a dream. The funny thing was, when the wires were on one side or other of the chassis it through out the balance... Doh! Can't believe how heavy they clearly are!!

Can't wait to get the new wires and see how she runs now after extra additions.

Now... Talk to me about the front end suspension conversion, is it worth getting (I've ordered anyway) but worth fitting?

I'm off to Maritime on Thuraday evening, bring it on!!

Thanks so much SlowOne for all your time. Super appreciated!

I was thinking of adding the independent front suspension to my supastox GT too... i'd be interested to hear thoughts on the value (or not) of changing to this set up... as a 'newby' to GT12 myself I've been following this thread with interest! Keep the posting going... super helpful stuff so far! :thumbsup:

None of the Schumacher team drivers use the independent front end - that's all we need to know!

I have seen one used with a carbon strap connecting the two sides. Vary the thickness of the carbon strap and it's like varying the anti-roll bar to give more or less front end bite.

Give it a go by all means, but having seen no one else using it I decided that the likes of Gale, Murray and Price - driving Gods - knew better than me splashing out on one to try it. MBA - Maybe Best Avoided!! :)

actually they do!
Marcus askel does as do others (two you list above), with the kit top beam or a brace across the bottom arms, id get the new low roll centre kit 1st though

Hi There...
I've ordered the front suspension upgrade, and will give it a try, can't hurt to see what it does..

The rear upgrade, is that the one that have a lower pivot point? Could you give me the link for that; seen it somewhere and not sure its on the Schumacher website, or have I missed it?

What i did spot on SlowOnes car, the black thin wires from your motor, what is this?

What was very interesting on Sunday at West Kent, all but one car in the A final was a Zen car, and then I noticed Zen have released a new car, or so it says on the website, April 1st.. How do these compare to the Schumacher? Not that I am going to rush out and buy one (although very tempted as I like shopping and building things....) would be hear peoples views on this too...

Mr Newbie... I am overwhelmed how friendly everyone is and I think this GT12 class offers so much competitive racing, tinkering and good clean fun rather than outdoors, mess and muck that would drive me mad.. OK when you're a youngster and have more time. I have little time and this class offers heaps of fun....

New low roll kit ordered..
:thumbsup:

black wires are his sensor cable without the sheathing.
zen has been out a while, but you may be disappointed, it comes pre built ;)

Pre built!!!!
Thats rubbish.....
Struck off the list immediately..... :cry: