XRAY - Model racing cars

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 Post subject: Non-Official M18 & M18T(MT) FAQ
PostPosted: Thu Nov 03, 2005 06:25:50 
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Joined: Tue Oct 04, 2005 01:02:57
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Location: Washington (State), United States
Unofficial Xray M18 and M18T(MT) FAQ

This FAQ (Frequently Asked Questions) are broken down into following sections:

Purchasing: Questions that may arise before your kit purchase.
Building: Questions you may have while assembling the kits
Running: Questions that arise when running the vehicles

Under these sections will be first listed questions that effect both kits. Then it will be split into areas particular for each kit. If you would like to make a correction or add something, please PM me to have it addressed.


Both Kits
  • Q: Where can I purchase it online?

    A: Always support your local hobby shop when you can, but if they cannot or will not get Xray equipment. You can also order directly through Xray via RC America (Only for US Residents). Otherwise, check Xray's Worldwide Distributor and Dealer site too see what is available in your country/area.
    Q: Can I convert my M18 into a M18T or vice versa?

    A: No. You could in theory, but the amount of parts you would need to replace would end up costing more than the kits themselves!
    Q: What servo should I use?

    Stock (fits mount)
    • Xray XMS01MG
    • Hitec 81MG/S
    • Hitec 82MG/K
    • Hitec 85MG (requires spacers)
    • Hitec 5082MG
    • Futaba s3101
    • Futaba s3102
    • Hobbico CS-12MG
    • Muliplex Polo Digi 4
    • Multiplex Tiny S

    Non Stock- not recommended (does not fit mount. Have to shoe-goo/servo tape in)
    • Hitec HS-5X series (Smaller-non stock mount, need to find another or adapt servo saver)
    • AE/Airtronics series (Smaller-non stock mount, need to find another or adapt servo saver)
    • KO 947 (larger, may or may not fit stock servo saver)
M18 Purchasing
  • Q: Is there a Ready to Run version?

    A: Yes, Xray offers both higher quality kits and a Ready to Run version. The the Ready to Run version that comes with everything you need to get started except a charger.

    You also have the option of building a kit and getting an additional Xray "Power Package*" setup that contains all needed electronics in car. For stock use, the Xray M18 Power Pack #389100, that comes with a 180 size stock motor, and a 5 cell battery pack with a reversing esc and servo. For Mod or Outlaw racing, you can purchase M18 Power Pack Pro #389101, with a larger motor and with a Forward/Braking only ESC, servo, and 6 cell pack for racing to allow you to get up and running.

    You will need to purchase the optional aluminum motor mount the M18 Motor Holder Universal #382021, for the M18 to fit the larger motor. It is also recommended to install the optional 42tooth spur gear #385742, as this 370 engine needs a higher gear ratio than with a stock 180 size motor.

    *Power Packages do not contain a peak charger nor radio system. You will still need to confer with your hobby shop for those.
    Q: Any upgrades I should get right away?

    A: If you plan on running super hot or brush-less systems, 3 cell Lithium Polymers, or anything beyond the sedans standard specifications, you might want to invest in the optional ball differentials Aluminum Adjustable Ball Differential Hard Coated #385001, and 42tooth spur gear #385742, and possibly the aluminum optional Aluminum drive shafts #385201 at your time of purchase. Other than this, no.

    It should be noted the M18 Pro has many of these upgrades already on it.
    Q: Can it fit 6 cells 2/3A?

    A: Yes. Out of the box it can fit a shotgun 6 cell pack with its stock hold down flipped over. Some of the slightly longer 2/3A cell packs may require some material trimming on the mounts to allow a good fit.

    To fit 6 cell side by side, you will need the M18 Pro Chassis conversion # 381152.
    Q: Can it fit Lithium Polymer Cells?

    A: The M18 was not designed specifically for Lithium Polymers layouts. However, you can use them. Your main concern in finding a battery that fits is it can neither be too long nor too wide. 34mm width and under 100mm length is a good rule of thumb. A good example tested is the Thunder Power 1320 mah packs. Of course you have to make your own hold down mechanism.
    Q: What is the M18s wheelbase for bodies?

    A: 150mm
    Q: Can I fit other or aftermarket micro sedan tires and rims on my m18?

    A: Yes the m18 it uses the same hub system. The M18 Pro however uses Xrays race spec hex axle system, and will require Xrays rims to work with other brands of rubber tires. The M18 Pro axle system can be converted to use the inner hub system if a person so chooses.
M18T(MT) Purchasing


Both Kits
  • Q: What supplies do I need to build the kit?

    • Exacto or Hobby Knife.
    • Side Cutters or Snips.
    • Needle nose Pliers
    • Scissors (Curved best)
    • Body Reamer or drill bit.
    • Patience
    Q: How do I set my gear mesh correctly?

    You neither want a gear too far from the spur which will cause it to skip and wear the spur quicker, not against it which will cause binding and significantly heat up your motor and slow down the car. All you need is a slight amount of play in the spur when against the pinion. If you feel still unsafe, try cutting a small strip of paper, folding it in half and jamming it between the two gears as you tighten the mounts screws. This should leave enough room.
M18 Building
  • Q: I can't seem to fit the bearings over the gearbox pinion shaft.

    A: A batch of these gears suffered from some water swelling. Use some 500 grit sandpaper to slightly reduce the diameter of the shaft. See this official notice.
M18T Building
  • Q: My Rear end looks awkward after assembly.

    A: The Rear bulkheads need to be assembled in a specific sequence so they line up. Please see this official notice.
    Q: Can I use my super duper center shaft from a M18 in the M18T?

    A: No, the center shaft is about 5mm or so longer.
    Q: I can't get the axle bearings on.

    A: Try cutting the excess material from the axle, then use some 500 grit sandpaper and slightly reduce the radius of the axle shaft Please see this notice (unrelated, but same idea).

    After this, then use your included axle wrench on the side you used to screw the long screw through to help press the bearings into place. After you get them enough that you can see the screws thread with a rim attached, then slowly screw the nut down to finish fitting the bearings in place.

    The most effective way is;
    ChrisP wrote:
    The best solution I've found for the bearings is to use an M3 tap first to pretap 75% of the hole...this prevents the set screw from displacing material out in the middle of the plastic axle piece...only pre-tapping part of the way through still allows for enough friction fit that your set-screws won't back out.

    Q: What size Balls does the Ball Differential take?

    (10) 2.4mm
    (8) 1.58mm (1/16th"; balls work fine)
    Q: Whats that bottom extension on page 22 of the manual do on the knuckle?

    It hits the A-arm when turning at extreme angles. It keep the steering knuckles from going past the designed maximum angle, and locking up or popping the universal apart. Even if you have a computerized radio, you should keep these on in case of a crash to keep the knuckles from going beyond this point.
    Q: I cant tell how the upper arms are placed from page 17?

    A: The "FL" and "FR" markings face upwards; the arms, "swoop back" when looking straight down.


Both Kits
  • Q:Spur Gear "D" ring is warping?

    A: The easiest method is to wrap the shaft on the D area with 1 layer of Teflon tape. Then slowly push the Spur on. Newer releases of the gears are made from a harder material, and should not have this issue.
    Q: My Motor is overheating?

    A: Try gearing higher (meaning use a smaller pinion). If possible, use a larger spur also in conjunction to reach higher gear ranges. You may also invest in a Xray Aluminum Heatsink Micro Stock Motor #382040, for stock M18 size, and Xray Aluminum Heatsink for Super Size Motors #382041, for larger 370 size motors or M18T size.
    Q: What pitch is the M18 series?

    A: 48 pitch Standard/Imperial. This is not to be confused with .5 module (Metric) or .6 module (Metric 48 pitch). Though it is possible to use .5 metric pinions, be aware these are a slightly finer pitch and will cause more drag which will cause both spur and pinion wear than normal, increase motor heat, and make gear noise more pronounced).

M18 Running
  • Q: I hear clicking from my differential?

    A: The metal rod that holds the differential together may have shifted. Take the differential out to make sure it's in place. To eliminate this, you may consider upgrading to the optional Aluminum Adjustable Ball Differential Hard Coated #385001.
    Q: The m18 one way is breaking my stock universals?

    A: A one way puts a greater amount of strain on universals, use the optional Aluminum drive shafts #385201.
    Q: The car is veering one direction or another, and cant keep in a straight line?

    A: This can be caused be a variety of things. Anything from your electronics, to your car set-up. If you believe it is something with your vehicle.
    • Try lifting the car and throttling forward. See if the front wheels are straight.
    • Make sure your droop is even on both sides of your car.
    • Are you running something much more heavy on one side than another?
    • Are your differentials acting smooth and free?
    • Disconnect your tires from the differentials. Try spinning them to see if they move freely. If they don't, then disassemble the knuckle
      and clean or replace the bearings as needed.
    • Try taking off your tires and suspension. Your a-arms should free fall under their own weight. If they do not, then try loosening your screws on the pivot balls slightly. If this doesn't help, then replace any pivot balls that are binding.
    Q: I cant get the stock rims off the hub?

    A: Grab the back edges of the tire, hold the car, and then slowly and gently pull in your direction away from the center of the car in a rocking motion. It may take some force to do this. If this fails to work, you can drill a small hole in the rim to access the inner hub screw and take the whole assembly off.
    Q: What do the different slots on the rims do?

    A: It allows you to widen and narrow your track base a little for another tuning option. A Narrow base will react faster, but could traction roll easier. While a wide base will react slightly slower, but then could traction roll less.
    Q: I bought the optional servo saver for my M18, and now I cant turn right all the way?

    A: With the stock 12 degree caster front upper arms, the servo saver will slightly hit the knuckle. Slightly cut away the excess material to allow free movement. See this notice.
    Q: My Pivot Balls are binding up up my suspension travel.

    For dusty conditions use the following:
    -387541 M18 Nickel Coated Pivot Ball 4.2mm Type C (8)
    -387561 M18 Nickel Coated Pivot Ball 5.8mm Type A (8)
    -387562 M18 Nickel Coated Pivot Ball 5.8mm Type B (8)

M18T Running

As noted above, if you would like something added or corrected, PM me. Do not add to this thread.


Last edited on 06/21/2008

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