MX5 NA/NB torque specs

MX5 NA/NB torque specs

Miata torque specs

The Factory Service Manual is a great resource for the appropriate torque specs for your car; however, sometimes it is not really handy as you need to go through a lot of pages just to find a number. Since I started working on mine, I have created a spreadsheet with the required torque per car area. Keep in mind that this is only for “service items”, if you want to tear in your engine or differential you NEED to refer to the FSM, as you need to respect the correct sequence and torque-down steps.

In addition to the FSM, I follow a rule of thumb approach based on bolt sizes whenever I cannot reference anything. You may find this additional table at the end of this post.

I usually have this list on my phone, and run through it when doing some work, so I thought it would be useful to post it! You may also download this in an xls form, in case there’s no internet access in your garage (like in mine). Enjoy!

ITEM	TORQUE SPECIFICATION (NM)		NOTES	TOLERANCE
	MIN	MAX
Typical service items
Spark plugs	15	23		35%
Engine oil drain plug (19mm)	31	41		24%
Gearbox drain plug (24mm)	39	59		34%
Gearbox fill plug (square)	25	39		36%
Differential drain plug (24mm)	39	54		28%
Differential fill plug (23mm)	39	54		28%
Wheel lug nuts	89	117		24%
Suspension
Swaybar bushing bolts F	18	26		31%
Swaybar bushing bolts R	20	28		29%
Swaybar end link bolts, both ends	36	54		33%
Axle lock nut	167	216		23%
Wheel lug nuts	89	117		24%
ABS wheel speed sensor	19	25		24%
Upper shock mount plate bolts	29	36		19%
Upper shock nuts	31	46		33%
Lower shock bolt	73	93		22%
Lower control arm bolt, front	73	93		22%
Spindle (vertical) bolt	73	93		22%
Camber adjustment bolts, (D or H-style) F	94	112		16%
Camber adjustment bolts, (D or H-style) R	73	95		23%
Brakes
Front/rear bracket bolts	49	69		29%
Caliper bolts F	78	88		11%
Caliper bolts R	34	39		13%
Front/rear banjo bolts	22	29		24%
Rear adjuster plug bolt	12	16		25%
Engine & Cooling
Crank pulley main bolt (late 1991 - present)	157	165	Plus Loctite 242/blue	5%
Crank pulley bolts - 4	12	17		29%
Cam cover bolts	5	9		44%
Alternator mounting bolt	37	52		29%
Alternator tension adjustment bolt	19	25		24%
Water pump - 4 bolts to block	19	25		24%
Water pump pulley - 3 bolts	8	17		53%
Water inlet pipe - 2 bolts to water pump	19	25		24%
Radiator - upper bolts	19	25		24%
Thermostat cover - 2 bolts	19	25		24%
Timing belt tensioner bolt & idler pulley bolt	38	52		27%
Timing belt cover bolts	8	10		20%
Cylinder head bolts (must be done in stages and in correct order.)	76	81		6%
Fuel Rail	19	25		24%
Intake / Exhaust
Airflow meter bolts	8	10		20%
Intake manifold bracket	36	54		33%
O2 sensor	30	49	By feel	39%
Exhaust pipe clamp bolt (to bell housing)	21	27		22%
Bell housing bolts	65	88		26%
Exhaust header nuts	38	46		17%
Cat converter nuts (both ends)	40	55		27%
Clutch
Transmission front cover bolts	19	24		21%
Flywheel bolts	96	102	Plus sealant	6%
Pressure plate bolts	19	25		24%
Bell housing bolts	65	88		26%
Prop shaft nuts	27	30		10%
Power plant frame bolts	104	123		15%
Starter motor bolts	38	51		25%
Starter motor mounting bracket bolts	38	51		25%
Slave cylinder fluid tube	13	21		38%
Slave cylinder mounting bolts	16	22		27%

Now, a bit more insight into how torque works and what you should keep in mind. Bolts (and bolted joints) operate in tension/compression only. The way for a bolt to pass loads from one part to the other is by clamping the respective parts together tightly. The way a bolt achieves that is by “translating” torque to clamping force via the thread pitch. Think of the thread as a wedge wrapped around a cylinder; this is exactly how this works. This is also precisely why you should keep in mind the pitch of the bolt in your calculations. A characteristic example of this is when people switch to ARP head studs, which have a different pitch on the section the nut threads on when compared with the section that threads into the engine block. Due to this difference in pitch, less torque is required to achieve the same bolt tension (clamping force) when compared to the stock head bolts.

An important thing to keep in mind is if the torque values correspond to dry or lubricated torque. Typically lubricated torque is lower for the same amount of axial bolt tension, due to the way bolts work. Lubricated torque might be 30-55% lower than dry torque for the same bolt tension (depending on the lube). The FSM always assumes dry torque, unless otherwise specified (usually there is a previous step calling for applying the correct type of lubricant or sealant for the application). These remarks can be found on the xls as well.

Some additional info regarding torque wrenches. For maintenance work, you do not really need very fancy/expensive torque wrenches (although they do not hurt!). I prefer to keep the fancy/very accurate ones for engine work and have a set of cheaper ones for the generic stuff.

You will notice that I have included a percentage next to the min/max torque values; this represents the acceptable percentage “error” (the difference between the lowest and highest allowable torque for a certain bolt) according to Mazda. As you see most of these allow for a quite wide range; the “tightest” one on the list is 5%. This was done to help with the selection of the appropriate tools for the job. Even the cheapest torque wrenches come with calibration sheets and are calibrated within 5% (and most of them within 3%), however, do your research on what is considered decent given your budget. Always ALWAYS remember to fully loosen the adjustment knob when done, as leaving it tightened causes the spring to creep which in turn leads to inaccurate measurement.

The typical torque wrench ranges (at least in Europe) are as following:

1)      6-30 Nm

2)      10-100 Nm

3)      20-110 Nm

4)      40-210 Nm

You can probably get away without purchasing (1) if you have a good feel on how tight is tight for small bolt sizes, although if your budget allows it (or if you have doubts), go for it. No (2) does not make much sense to me, but I like (3) a lot, as it covers all items on the aforementioned list sans the axle lock nuts, and the main crank bolt. You can always opt for (4) instead of (3), but since the torque range it covers is much wider, the resolution you get is much lower. (1) and (3) and (1) and (4) make good combinations, covering practically everything you will ever need. If your budget allows only for one, go for (3).

There’s also the option of purchasing these fairly new electronic torque adapters. They are quite affordable, and their operation is based on a strain element (an electronic element with variable resistance based on its’ deformation), so they “should” be fairly accurate given they come from a reputable/trustworthy source. I have never used one, but I must admit I am tempted, especially in jobs that do not require the highest accuracy.

NOTE: All information provided in this blog is purely informative. Work in your car is your sole responsibility, and you should always do your own research!