so you want buy a new ESC and motor,
after reading some of the questions on the Hobby King web site ESC section i do wonder what some people are doing with their cars, one kid wants to run a 3s li-po with a 3.5t motor in a 1:10 scale tourer!! , i think the biggest problem he will have is keeping the car in one piece , not to mention his tyre bill ,
this post will assume that you want to drive your rc car rather than launch it into another dimension.
rule 1 ,
know what you will be needing .
if you are going to use a 13.5t motor dont choose an esc that can take 13.5t motor at the most, choose one that can take a 10.5t or more , over spec the ESC every time and you wont be one of those guys that has the marshals running in with a fire extinguisher .
 i am not gonna name names here but i have tried many ESC's from the big US and German brands and they have all failed , badly!!! smoke and flames despite being used well within their respective tolerances!!! , over the last 5 years i have been using hobby wing, yeah racing and turnigy branded ESC's in all conditions including torrential rain and they have been flawless . this has led me to the conclusion that Novak, and LRP use the lowest spec components they can get away with , that or i am the unluckiest guy ever , i am not talking one or two here , 4 Novaks and 6 LRP's have all died or gone up in smoke , sometimes they have given me replacements under warranty but i simply dont trust them any more , try searching youtube for ESC's going up in flames or smoke and see what brands die the most.
 my mate got a hobby king esc for around £20 and it kept up with a novak gtb until the gtb went up in smoke ! the HK is still going to this day.
 gearing , keep it as low as you can while being competitive , if you cant touch the esc or motor after a run you are geared too high , if you are geared correctly and the motor is well within the limits of the esc then the whole system should not get beyond touch hot (you can touch it for several seconds without any discomfort) , use a fan on the esc if you can as they can extend the life of the fets in the esc .
my yeah racing 60a esc can run with a 7.5t motor in my off road 2wd buggy all day and never gets more than luke warm .
sensored or sensorless?
sensored systems give far better low speed control and virtually no cogging( cogging is when the motor stutters ) , the sensor constantly monitors the motors phase position and thus ensures the correct phase or pole of the motor is being powered , this is a slightly simplified view though and its actually a little more complicated , the more phases a motor has the smoother and potentially efficient it will be, most motors are three phase 2 pole but newer systems are going to 4 pole motors mostly for the SCT market where the extra pole can make the truck more drivable out of the turns especially on slicker tracks where traction and grip are low ,
 the biggest drawback of the sensored system is that the sensor cable or circuit can fail , although most manufacturers have realised this and designed their ESC's to switch to sensorless mode in the event of a failure ,
i only use sensorless systems these days but may try one of the new systems such as the turnigy 1 cell for my 1/12th scale car , my reason is, i had a sensored system from Novak and it sucked , just my experience though and there are those that swear by them , i mostly swore at them!!

i have decided to use this post to list the ESC's i have and give some brief comments ,good or bad!

i will start with the hobbywing brand ,
i have a 35A and a 60A ,they have both been soaked many times and get very dirty on a regular basis ,
the 35 amp has been flawless from day one , its easy to programme thanks to the programme card and is tiny , i use it in one of my Mchassis cars with a team powers 15.5t motor and 2s lipo , i cant fault it in any way.
the 60A too has worked as it should from day one ,it gets used in a 1/10 2wd buggy with a 7.5t trinity epic duo2 and a 2s lipo .
yeah racing 60A
its the same as the hobbywing and many others apart from a black heatsink , again flawless regardless of treatment , it gets used with a turnigy trackstart 8.5 motor (silver sensored version with slotted can )and 2s lipo,
novak goat crawler with 17.5 motor , works well but always goes to default setting when switched on after the transmitter , although it goes to my custom setting when i switch it on before the transmitter !!! sent it back 3 times and it got a clean Bill of health every time , i even tried it with 5 different radio systems and still it does the same thing , it also runs very hot ,esc and motor despite only being run on 2s in a crawler with a 10t pinion and 96t spur ,

novak gtb , up in smoke within a year while running a stock motor!!!

novak rooster x2 , up in smoke just after a year while running a stock motor!! ,

lrp runner's 6 of em , died , just stopped , kaput, all within six months

castle sidewinder sv2 , first one was getting hot and kept shutting down with a flashing orange led , got a replacement under warranty , its perfect with brushless motors but wont work with brushed motors!!! keeps stopping and starting , more American garbage , wont be buying any more stuff that has anything to do with America or Europe .all their claims are hyperbole , what good is having the fastest esc on the market if it catches fire and you dont finish the race ?
made in china is where its at , , novak , lrp, stick your products up your respective arses or each others if you are that way inclined , 100%failure rate is not world class , its shit .

tamiya TEU101 or 104 ,
awesome esc's for beginners , they even work with 4 cell 1/12 scale cars , they have a 25 turn limit i am told , i have been using all 6 of mine with 21t ansmann clash motors for over a year and they only get warm with 2s lipo , very smooth throttle response and fast with the 21t motor in many of my Mchassis cars and considering they come free with a tamiya kit i cannot fault them , in fact i rate them as one of my favourite ESC's.
more as i test them
;-)