GT12 Help..

[SlowOne]

To add some notes to a great reply...

Originally Posted by Xracer

Mmm a list to contend with there but I can try and add some light that I hope concurs with the thoughts of others.

First and probably a good starting point in Shore hardness, this is the measured hardness of the raw sheet material from which the tyre rings are cut, the lower the Shore number the softer the rubber compound. Start with around 50 front/35 rear for a GT, 50 front/35 rear for a Zen. Go down on the front for more steering, and up on the rear for more rotation.
The tyre hardness will vary from the outside to inside as the rubber is stretched onto the wheel, the bigger the starting diameter the softer the tyre will be but attempting to measure a actual tyre hardness is not a true Shore measurement but can only really indicate a difference from one tyre to another, not the actual true Shore value but an indicator only. Not strictly true. Hardness will vary depending on where the tyre is cut from the sheet. Stretching it over the rim makes little difference. As stated, there is a variation on tyres with the same hardness number on the label, but not so as you need to worry about it.
As the tyre wears or is trued down the actual hardness will increase slightly because of the pre-stretch onto the rim. More effect is seen from the fact that as the tyre gets smaller it moves round less on the track. Smaller tyres make the car more precise in handling. Anything from 46 rear/44 front downwards is OK, bigger than that will make the car feel imprecise.

I believe it is commonly considered that the smaller the tyres the better the cars handle mainly due to the lowering of the roll centre of the car, there may be more debate on the actual physics of this to follow. See note above. Tyre diameter has no impact on roll centre as the main weight of the chassis is always in the same place relative to the roll centre due to ride-height adjustment. Again, less tyre means more precise handling, but the roll centre is not the cause of that.

I am led to believe that starting at 44-45 mm for the rear and 1-1.5 mm smaller on the front will deliver a good handling car and give some degree of tyre life, assuming you don't 'chunk' them on the barriers in the meantime!
The softer tyres can chunk very easily unless some reinforcement of the tyre edge is carried out, some use superglue, some use Shoo Goo or an equivalent. GT12 tyres are pretty robust; I find Contacts the best in this respect. It pays to run a bead of superglue across the tyre/wheel joint (Zen have an excellent range - e-mail them for recommendations) on the rear. For the fronts, run superglue right up the sidewall until it meets the tread. This prevents the car rolling and makes it handle much better.

I have also found that as supplied the tyres are not always very true, I have had some up to 1 mm eccentric, so a truer is needed initially as this plays havoc with the cars handling. Too right!!

When it comes to tyre wear then this depends of a lot of factors, circuit layout i.e. sharp corners or sweeping curves, driving style, aggressive or smooth, repeated application of additive rather than changing tyres for each heat as some do.
The actual rubber compound being used will deliver differing wear rates irrespective of the original shore hardness too.

I have measured tyres to try and establish wear rates and I have seen somewhere between 0.2-0.5 mm per heat, depending on the tyre hardness being used, the carpet type, condition and grip level, surprisingly the higher rates were measure when racing without additive on 32 Shore tyres though! I get a bit less than that per race, but it really does depend on the carpet and the additive. SXT 3.0 is good just about everywhere. When the grip comes up them Spider Grip Green is better.

As for tyre truers, there are a number on the market, sometimes hard to get hold of but Hudy, 3Racing, Integy, Fastrax to name just four and of course you will need suitable mandrels depending on the wheel type you are using. If you can't run to a tyre truer, then see if someone at your club will bring theirs along or do some tyres for you. Once you have them at the starting point, there's little need for the truer until you need to restore the stagger (difference between front and rear diameters) as the rears usually wear faster than the fronts. Less stagger gives more rotation, but only up to a point. Fronts should NEVER be bigger than rears. Don't sweat on not having a truer - make a friend of someone and use theirs. Coffee and beer for your time on a truer usually smooths that path! If you are anywhere near the Shootout series at Chesterfield club, come along and someone will sort you out for free.

I hope this goes part way to answering your emerging questions.

Me too, but come back if you want more help.

[northernerbill]

Guys this has been a great help. You can usually find something on youtube etc explaining this kind of info but apart from demo's nobody had gone into how much to remove and the science etc.

Again many thanks and I've opted for the fastrax manual truer and arbour.

[SlowOne]

That'll work! Always beware of things on places like YouTube etc. Just because someone can make a video doesn't mean they know what they are talking about!

When you've trued a tyre try to smooth it out with some 80 grit abrasive paper and round off the edges a bit so it doesn't dig in when cornering - round off between the tread and the sidewall. Newly trued tyres will be a bit iffy until they smooth out, so give them time in the early part of your first race. HTH

[mark christopher]

With the low roll center kit we are all going 45 front or less, 42 or the new 40 shore.

As you tube comment above,all the Info posted is not always correct....

[northernerbill]

Yeh cheers for the further info. I'm no RC/racing newbie (or youtube experts for that matter) BUT am a total newb to GT12 and all that it brings.

The Chichester guys where really helpful and forthcoming with help when I asked but you want to crack on with stuff in between and this thread with all your advice is helping me and I Know others too. Ta

[stucartwright]

So pleased this thread is providing so much use to the GT12 newbies..
Keep it going lads! I will be back with more questions no doubt soon... (Oh joy I hear?!)

Stu

[stucartwright]

Calling any Surrey GT12/TC or Micro Racers.

Trying to start up a club in Surrey. Check this out, get in touch and let us know your interest!!

If anyone can post this as much as possible in the relevant communities, would be hugely appreciated.

facebook.com/SORCCC

Best Wishes
Stuart

[SlowOne]

Originally Posted by stucartwright

So pleased this thread is providing so much use to the GT12 newbies..
Keep it going lads! I will be back with more questions no doubt soon... (Oh joy I hear?!)

Stu

Oh joy...! (Is your driving better than your hearing yet Stu?!!!)

Only kidding. Glad this thread is proving useful to so many people.

[stucartwright]

That must be northern humour.... haha
Look forward to seeing what I've got by the time winter comes around and the nationals!! Am sure you won't be under threat.. Or might you?! haha

[SlowOne]

I would never make so bold as to predict a result with someone I only know on the 'net. Look forward to meeting you Stu, and whatever the result we will have some (GT12) fun!

[stucartwright]

Definitely!!
This GT12 lark is amazing... You've all been so helpful. Is it easy to get your name down on the GT12 nationals list? Or does booking in go seriously fast?

[northernerbill]

Just wondering, if any of you guys have bought the Lipo strap hop up, and then also bought the low pivot conversion only to find its now too tall.

So just wondering what you've done, are going to do or if a new strap is coming soon.

Pic shows height of the up stands with the strap played next to it at the height wants to be at.

[stucartwright]

What I did was pad out the strap, with a bit of foam so it reaches down to the strap. Lots of guys I've seen have machines down those posts so the strap fits flush. Too much like hard work for me. The padding works great, can send pick when I'm home tonight if nobody offers up anything better.

If you've not tried the lower rear pod yet, it's the biggest hop up ever. The handling goes from an articulated lorry to an F1 car. Bring on even more fun!

[shinytopman]

Hi Northernerbill,

What i did with mine was replace the two screws with 30mm x m3 (the long suspension spring screws).
Replaced the 6mm x 3mm plastic spacers with ally ones (got from ebay) to stop the crushing/bulging.
Ontop of the bar i fitted a 5mm x 3mm ally spacers. M3 nut ontop to hold it all down tight.
Battery strap fits perfectly the right height after that and fasterned down with an M3 thumbnuts from ebay, (HPI do nice ally ones cant remember the part number off hand).





HTH's Shiny

[northernerbill]

Great ideas.

I have swapped the rear most 3mm plastic spacers for RC4WD 3mm alloy spacers

Then swapped out the forward 6mm plastic spacers for RC4WD 5mm alloy spacers, so that boom is 1mm lower or probably 1/2mm lower due to plastic compression.

Then I have fitted thick foam to the lipo brace which is gripping the battery very well.

Whilst tinkering on this lot I noticed the two plastic ball arms that run fwd to back either side of the battery slot caused the rear axle to have play. My kit is essentially brand new having done one meeting, and balls being removed for todays work. So I opted to fit the blue O rings on all the ball joints which has removed this, knowing it affects damping I figured an axle running true is the better option.

[SlowOne]

Originally Posted by stucartwright

Definitely!!
This GT12 lark is amazing... You've all been so helpful. Is it easy to get your name down on the GT12 nationals list? Or does booking in go seriously fast?

Booking in is via the BRCA website. It does go reasonably fast, but if you get on there within a day or so you're pretty much good for a place.

We discussed this today at the EGM and I hope everyone will be pleased with the National diary and venues once the Committee has it all sorted and published.

Provisionally you can expect a drivers information pack to announce the series and give the relevant information and the target date for booking in to open on the BRCA site in plenty of time for the first event It is intended that pack will be mailed to all BRCA members so if your information is up to date on brca.org then you should get one.

My advice is to make sure your brca.org information is up to date, to try and log on and get to the event entry area to be sure you can see any current entry areas. If you have any issue with that mail the contact on the site and get it sorted. You'll be pretty p*&^d off if it doesn't work on the day!!

Someone will make sure information is posted here, but keep an eye on brca.org for the definitive information. HTH

[stucartwright]

Top info SlowOne...
Many thanks.. Only joined a few months ago, so all info is up to date.. Look forward to getting involved in the nationals...

[stucartwright]

On that same note lads.
What transponder do you recommend? Want to get my own obviously. Is MRT simply the best?

[mark christopher]

This car needs the o rings removing from the side links, when using the side dampers that are not needed, and prevent the side dampers working properly.

Originally Posted by northernerbill

Great ideas.

I have swapped the rear most 3mm plastic spacers for RC4WD 3mm alloy spacers

Then swapped out the forward 6mm plastic spacers for RC4WD 5mm alloy spacers, so that boom is 1mm lower or probably 1/2mm lower due to plastic compression.

Then I have fitted thick foam to the lipo brace which is gripping the battery very well.

Whilst tinkering on this lot I noticed the two plastic ball arms that run fwd to back either side of the battery slot caused the rear axle to have play. My kit is essentially brand new having done one meeting, and balls being removed for todays work. So I opted to fit the blue O rings on all the ball joints which has removed this, knowing it affects damping I figured an axle running true is the better option.

[shinytopman]

Hi Stu,

The responsible thing to say is get a mylaps transponder. Best is a hybrid as its backwards compatable from RC4 to the older timing system (RC2 and RC3).
The number you get if you buy new is allocated only to you but you will need to move it from car to car.

Or

You can get an MRT one they are clones and use cloned numbers from old units so 1 transponder has 11 numbers to chose from ( 1 main and ten alternatives numbers, in the VERY rare situation that you get a number conflict).

If you phone MRT they can do you 2 (or however many you need) transponders with the same main number so in affect 1 number for all your cars.
If you get MRT get the newer RC4 compatable ones that covers you for wherever you wanna race.

PS did i mention they are also cheaper and support is second to none!

So for me its a no brainer.
(All mine and Toms car are equiped with small black, gold lettered beauties. )

HTH's.
Shiny