XRAY - Model racing cars

Good call.

I'm still a nitro noob and have yet to run in a main longer than 20 minutes (and never finished even that ). However, I have calculated the following tire wear that seems to be consistent for the runs that I have completed. Keep in mind that this is tire wear while running the car hard for 5 minutes without any regard to tire wear. Also the following wear rates came after I (allowed the tire wear to be evenly distributed across both rear tires, instead of mainly on the left rear).

Start tires at:

Front - 60.5mm (left) and 59.5mm (right)
Rear - 62.5mm (left) and 61.5mm (right)

Wear rate (5 minutes):

Front - 0.8mm (left) and 0.6mm (right)
Rear - 1.0mm (left) and 0.9mm (right)

Calculated size at end of 45 minutes:

Front - 53.3mm (left) and 53.4 (right)
Rear - 53.5mm (left) and 53.4 (right)

Again, this is taking into account that I don't try to conserve tire wear the entire 45 minutes. Stiffening up the rear even more actually balanced out the tire wear a great deal as it keeps more weight over the front tires. I noticed the left front seems to take most of the abuse now (instead of the left rear), but handles it pretty good.

The good news is that I've practiced with the tires at 53-54mm and the car still handles very good. The NT1 really is a dream to drive no matter what kind of condition its in.

I'll reserve judgement until I actually get to race in an A main though.

Well...practice was interesting today. The new Max SL3 broke in really well and was by far the fastest .12 motor of the day. I ended up using the 2630 pipe (with longest 7 fin header) instead of the 2602 and the low/mid power really came to life. I then geared up 2nd gear and had massive top end that carried through the long sweeper at the end of the straight.

On the setup note, here are the changes and their respective effects that I found to work much better by the end of the day:

Increased on-power steering
* 25t side pulley (previously 26t)
* Increased ackerman by taking off steering block extension plates

Increased off-power steering and kept the rear end stabilized on-power
* 30k rear diff oil (previously 80k)

Increased entry to mid corner steering
* 22.5lb front springs (were 28lb)

Increased all around steering
* 1.0d rear toe-in (previously 2.5d)
* 1.0d front toe-out (previously 0d)
* Transmitter EPA/dual rate set to 18.5d(outer)28.5d(inner) (previously 16.5d/21.5d)

Kept the rear end stabilized on-power
* 198mm front track width (previously 197mm)

All of these changes increased the steering all around without making the car twitchy or the rear end edgy. I'm simply amazed that the rear end is so stable with this crazy setup. Probably comes from the low roll center rear upper camber link position (not sure, but I'll play with this setting again during practice on this upcoming race weekend ).

I kept swithing from the Stratus 3.1 to the Parma M throughout the day. The M ended up being the body of choice for me in the end as it simply provided more steering without being twitchy.

The track was sprayed in the morning and grip was pretty high throughout the day with enough 1/10 and 1/8 cars on track practicing. The new setup kept tire wear evenly distributed front to rear throughout three full tanks with only one left to right tire rotation after the 2nd run. With 45 shore tires front and rear the car handled really well with a very slight drift. However, the wear remained even and the rate was reduced considerably. This might be a valid option for the last qualifier of the day and/or the main as grip will be higher then.

Here's an update from this past race weekend.

Starting with the bad news...I blew up the just broken in Max Power SL3 early last week while practicing for this past weekends ROAR regional race.

The good news is that I found the problem that has blown up two motors and caused erratic behaviour in two others in the last month for me. Replacing the fuel tank solved my hot motor issues.

Now the great news!

I made the following changes to the setup and the car was easier to drive, cornered even better, and tire wear was amazing (given that I wasn't running 45 shore rears):

* Used the - Added more overall steering and the lower CG attained was noticeable to me with an increase in mid corner speed
* Switched from 42s to 40s front tires - Added more steering and evened out front/rear tire wear perfectly
* Softened front dampening by changing front shock oil from XRAY 35wt (similar to 600cst) to , with three holes open in the pistons - Gained back the mid corner traction lost from the stiffer chassis. The car also tracked over surface bumps/berms much much better and I was able to cut corners tighter riding two wheels over the berms.
* Softened rear dampening by opening all holes in rear shocks (using XRAY 35wt oil) - Same effect as above
* Raised rear roll center by changing rear inner camber link position from #3 to #1 - Increased steering response and eliminated traction rolling
* Reduced rear toe-in from 1.0d to 0.25d - It was amazing how much rear end rotation the NT1 gained, without any abrupt oversteer

Although the motor ran well enough in the early two qualifying rounds (cooler temps), I never had power more than slightly above average. However, the car was handling well enough that I could make up a lot of time in the in-field. After the first round, I was in third place about 8 seconds down on the TQ pace. But as the temps rose, so did my motor issues and over the next 3 qualifiers, my Q time was relegated to 6th. Finally, I had to retire in 9th place after 35 laps in the main running the motor around 310F. Approximately 12 laps were completed with LOW power and/or no shifting into 2nd gear.

Here is the tire wear info I gained:

Started tires (40f/42r) at:

...Front - 61.5mm (left) and 61.0mm (right)
...Rear - 63.5mm (left) and 63.0mm (right)

Wear rate (after 15 minutes):

...Front - 1.6mm (left) and 1.0mm (right)
...Rear - 1.5mm (left) and 1.0mm (right)

Calculated size at end of 45 minutes (estimating 10 minutes for the above wear rates, given the low power of the motor for 12 laps):

...Front - 54.3mm (left) and 56.5 (right)
...Rear - 56.7mm (left) and 58.5 (right)

Given the wear rate above, next time I plan on starting with a 1.3mm split between left and right tires with the following sizes:

...Front - 61.0mm (left) and 59.7mm (right)
...Rear - 63.0mm (left) and 61.7mm (right)

All four tires wore almost flat with a very slight coning to the inside and zero chunks.



IMO, for high traction tracks the 4mm chassis is definitely faster.

Nice to see, that you are working so much with the car. As you said, 4mm chassis only when you have high grip.

I hope at the weekend the weather here will be better. Since now, I haven´t had time to make some test rounds with the car. Only 2 races without training

Hi Guys,

does any one drive the car with 2,5 mm split. Is there any understeer or oversteer issues with 2,5 mm split(by using 25 side p.)

After a very nice warm weekend, I have made some test rounds with my NT1 and this time I tryed the solid axle and it was amazing how much steering I have had. The car was very stable and fast to drive.

I have used a 60k Rear diff, of course I will try a harder one.

Here's an update...

I made the following changes during this past weekends race which improved the car as the traction was higher than I've ever seen it at 301 Raceway, with constant traction rolling:

* Closed one more hole on the front shock pistons
* Increased the front anti-roll bar angle to 90d

With these changes, I didn't have to worry about traction rolling at all and the car was even more consistent. However, I had a slight mid corner push that kept me offline about 18 inches per corner unless I entered them a little slower.

Yesterday I had the opportunity to practice while the grip was still pretty high on the track from the past weekends race (no rain and some overcast clouds helped). I kept the front piston change above, decreased the front anti-roll bar angle to 60d, replaced my rear springs (2 years old) with some new ones and also put on the rear adjustable anti-roll bar at a 90d angle. With 40f/42r tires the car felt the best it ever has been being tight on the corners without any push whatsoever.

I then switched to 42f/45r tires and as predicted the car felt the same, but drifted off the apexes about 2 feet if I didn't let off the gas earlier. A quick change of the anti-roll bars to 0d front and 30d rear cured the push until I chunked the right rear tire. Then I had to deal with oversteer when turning left.

Amazingly enough, I left the chunked tire on and barely layed the rear bar down more closer to 20d and the car was perfect again when turning left.

I plan on trying a 40f/45r combination this weekend with the the anti-roll bars set at 60d front and 20d (slightly lower than 30d for insurance against chunked tires ) rear to see if it works just as well.

.

I just changed the rollcenter at the front. I took the highest hole. Now I have enough and the car still not oversteer. Of course tomorrow I will try diffrent rollcenter settings at the back.

I also use now the pink springs, with 500 Oil and 2/3 holes.

Rear antirollbar is the 2.4