BigRock on street tires

stefangun

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Hi there,

just got my BigRock today together with some nice new tires. They are from Louise and are called "MT Rocket". They have 1/2" offset at the wheel. Gave the BigRock unbelievable grip on tarmac (car park racing today).

These wheels are about an inch wider than the stock ones. I've got the impression that the stock servo is too weak for them. Couldn't completely return to middle position in stand. Will change for an TS-910 or 900 as soon as they hit my bench next week.
I also got the offroad MT Pioneer to try out at the weekend. Will keep you updated!

Greets,
Stefan.
 

lonee

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I did not try these wheels on the Big Rock because I used them on my 1:10SC. The smaller wheels / tires are ballooning already on 1:10.
Same with Louise or Duratrax on 6S on the BR... But Proline Big Joe II are not better :(

On the other hand which stefangun had correct described.. This tires have a lot of grip on normal temperatures!
In wintertime an temperatures below 0°.... Its like drift wheels; nothing on grip.
Nearly the same like the original BR-tires!, they start working when the getting warm!
;)

Regards,
lonee
 

stefangun

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Just threw in fully charged 2x3S LiPos and let the wheels rotate freely. Well, well - this is the tire ballooning everyone talks about, then ;)

Tires expanded to ~double the size. I'll report how they behave on track as soon as I come to it. But I think I'll just tape them to stop/reduce ballooning.
 

stefangun

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OK finally got to street race track today and emptied 2 battery packs. Unfortunately, it was raining now an then and so the track was quite wet. Beforehand, I taped the MT Rockets from the inside to counter ballooning at high revs.

For this, I baked them in the oven at 160°C / 320°F for ~40min. Then I could remove the rubber from the rims very easily by hand. Apart from the hefty burned rubber stench, it worked like a charm. After that, I cleaned the rim and the rim-contacted rubber from residues of glue using a Proxxon (aka. "Dremel") with a small sandpaper tip. Then I wiped the dust off the inner rubber with some motor cleaner. Finally, I taped the tires from the inside using two layers of gaffa tape ("Gorilla Tape" or something). Re-assembled tire, foam filling and rim back together. Last step was to glue the rubber tire onto the plastic rim using super glue ("CA glue") and then let it dry for ~ 2hrs.

I kept to this videos here for the process:

Well, the ballooning is now gone completely. When running freely on the shelf, the tires still do some sort of "ballooning" at the sides. But the taped middle area keeps nicely in place. Racing on (wet) road using 3S and ~2/3 throttle didn't lead to any balloning whatsoever. So for me this problem is now solved and I will tape the next wheels which suffer from heavy ballooning, too.

Conclusion of the track day: The MT Rockets are not very good on wet tarmac. But they seem to wear pretty slow. Hopefully we got some dry weather very soon so I can test them on dry and hot tarmac. Will keep you updated!
 

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stefangun

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Just a quick update: Grip on dry tarmac is very good at ~10°C (50°F). Does backflips with 4S batteries (!) on hard acceleration (and front-flips when braked too harsh). I also had to be careful with the steering wheel as the BR tended to side-flip on sharp cornering at speed. Overall, I would recommend these tires for dry road-racing. Price was not too bad (~70EUR for full set). But they balloon as hell in stock condition. Nero BRs stock servo is way too weak for these big wheels, though.
 

lonee

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Same with Proline Big Joe II. Servo too weak and same effects like yours.
The side flip tendency you can reduce with setting the suspension a bit lower.
Negative point is that the tendency is going to support front and backflips without changing the setup of the shocks.
Harder springs, soft shocks, reducing the suspension way, sway bar (I have no idea if it possible, never thought about that), modifying wheel hubs front and rear (HR alu parts), steering upgrade... It´s a lot I think..

I am also looking for an quite stronger servo, maybe an Corally which should have 18, something Kg on 6V.
Maybe I put later in an separate BEC to get 7,2V or 8,4V to get more torque without toasting the other electronics.
 

stefangun

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I will replace the servo by a Trackstar TS-910 which is said to move 30kg/cm (168lb/inch) at 7,4V. External BEC is also on the to-do list for next week.

Regarding suspension - is the Nero BR equipped with swaybars? I've not yet completely disassembled this monster but found none so far. My "old" Sabertooth has front+rear swaybars and their effect on reducing rolling is tremendous.
I don't think I'd like to lower the BR. It is a monster truck and I rather will have to learn to drive it carefully to prevent random flips (followed by "walks of shame" to re-flip it back on its wheels) than to change the ride height. Suspension by the way is really good IMO. Smooth ride over bumpy roads and handling is well even at off-road bashing courses.
 

lonee

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It´s up to you, but to get an good control on the street, it is better to keep the center weight as low as possible.
Completely different to off road. I would like to set brake and push level separate on the ESC but the BLX200 didn't support that.
Also I could not find a way to use my cr4t, which I use for several cars, for the Nero, because of using telemetry and ABS.
The cr4t did not support the 4-position switch we need for switching the diffs.

Anyway, mainly I like my Big Rock, the small issues of trouble will be fixed on the time when they grows up! ;)

Sorry for bad grammar, english is not my main language..

Regards
lonee
Have a nice weekend!
 

stefangun

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Okay so I replaced the stock servo by the TS910 and fed it with 7,3V using 10A external BEC. Steering is MUCH better now. But although I fastened it completely, the servo saver still has too much flex. Servo arm is moving without problems but the force is compensated in the servo saver. I'll try the alloy servo arm by hot racing and give you an update.

http://www.hot-racing.com/index.cgi?partnumber=NRO4801;c=1019

https://hobbyking.com/en_us/hobbykingtm-q-bec-variable-output-10-amp-6-25v-sbec-for-lipoly.html
 
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