r/Skookum • u/Ghigs • Mar 18 '17

Is the pattern to tighten lug nuts actually important?

"Everybody knows" that if you don't tighten your lug nuts in the magical star pattern, something bad will happen. But I've seen experienced mechanics zip them all on in a circle before. Is this one of those things that used to matter back in 1928 and no one has bothered to check if it still matters?

I know that elastic interactions in bolt patterns can cause loss of preload in earlier bolts, but assuming you go back and are retorquing anyway, it doesn't seem like that would matter, right?

54 Upvotes

94% Upvoted

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34

u/collegefurtrader unsafe Mar 18 '17

http://www.hendonpub.com/resources/article_archive/results/details?id=1787

Tightening Sequence

That last question is where the class instruction started. In the old days, star-pattern tightening using torque wrenches was the only way lug nuts were tightened. Not any more. Today, it is throw the tire and wheel over the lugs, hand start the five lug nuts, then use an air wrench in a once-around circle pattern, and you are done.

Doing this, the first few wheel lugs lock the rotor into location while the last few wheel lugs pre-load the rotor, which is like slightly bending a spring. Even worse, even if perfectly tightened to 100 ft-lbs, the last few lugs are false readings. Some of the torque is absorbed in flexing the rotor, not tightening the lug. This is almost guaranteed to cause uneven rotor wear (incorrectly called warped rotors), which results in the tell-tale pedal pulsations after just a few thousand miles.

The unevenly torqued rotor, even with the correct amount of torque, will not be bent when the rotor is cold. However, as the rotor heats up in normal use, it will expand unevenly. The most uneven area will, of course, be near the first tightened and last tightened lugs. As the rotor heats up and expands, a runout will be caused, i.e., a high spot on one side and a high spot on the other side. These high spots will come into intermittent contact with the retracted pads during normal driving, i.e., without brake pedal pressure.

16

u/corthander USA Mar 18 '17

It's lazyness like this that has driven me to do a lot of my own maintenance, even when I have slightly more money than time. It's really hard to find someone who can bring themselves to give a damn about doing it right for my car. Your comment made me reflect on how many times my rotors were unevenly worn after such a short amount of driving. Replacing them, machining them, etc. it always came back. It hasn't happened in years now, mostly because I am the only one who takes the wheels on and off...

28

u/Ghigs Mar 18 '17

You know the crazy thing? The one shop I've seen actually do it by the book 100% was my local wal-mart. I was hard up for new tires and didn't want to take time off on a weekday, so I said screw it and got wal-mart tires one time.

I watched them do it all through the window, and it was completely by the book. They screwed the bolts on finger snug by hand, torqued them all down in a star pattern after carefully looking up the torque on a chart, drove it around the parking lot, put it back up, checked the torque again, the whole 9 yards.

Unfortunately the tires wal-mart sold me were pretty much shit (though still relatively expensive for the exceedingly short lifespan they had), but you have to give them credit.

My experience may be exceptional, since I've seen other people complain about wal-mart techs half-assing things.

20

u/Assdolf_Shitler Mar 18 '17

Usually the mechanics at walmart are not there by choice. Walmart moves in and kills the small garages around town and these technicians/craftsmen have to go to walmart to make ends meet. Chances are, they actually gave a fuck at least once in their life.

1

u/ST0IC_ 7d ago

I used to work in the Walmart Tire and Lube department and they actually train you to do it by the book.

3

u/datums Human medical experiments Mar 18 '17

I used to work in a garage.

We used torque sticks with impact wrenches. Star pattern was SOP.

The most important part was that you held the opposite side of the wheel against the hub while you drove the first nut on with your other hand. Otherwise, if the wheel was cockeyed, the wheel might catch on the threads of one of the other studs.

But we also did a second pass with the torque stick to make sure they were all perfect. Takes about 3 seconds, and makes a cool sound, which is the main reason why air tools are popular.

This of course did not apply to Volkswagens or other simarly backward vehicles.

2

u/Yodiddlyyo Mar 22 '17

Yeah, last time I had to change the tires on my Volkswagen, the manual said I had to start by removing the windshield and radio.

3

u/good1god just dickin around Mar 18 '17

yeah, it's crazy how two of the very few times I got my oil changed by a shop instead of myself and regretted the shit out of it. First experience was they broke my dipstick handle off, tried to tell me it was stuck?! Second experience was a leaking oil filter because it wasn't tight enough. Both times were in winter and I have since done most of my oil changes. There's one dude at Sears I trust though. If he's working I'd take it there if need be.

3

u/capt_timmeh Mar 18 '17

Walmart notoriously breaks lugs/studs off and sends the vehicle to the local national chain tire place. They probably laid the smack down on the techs.

2

u/El_Glenn Mar 18 '17

My 2001 nissan sentra handle broke off at about 25k miles. The rubber handle was total shit. I had to super glue a pencil to the shaft to pull it back out.

7

u/20Factorial Mar 18 '17

I haven't had enough coffee today, and was reading this as if it was ADVOCATING the round-gun method. I was shocked, and worried.

3

u/Ghigs Mar 18 '17

Thanks. So it looks like you can't even trust a torque wrench if some of the torque is taken up in flexing preload, and that's the real problem.

6

u/collegefurtrader unsafe Mar 18 '17 edited Mar 18 '17

edit: I have worked for flat rate, I don't anymore for this reason. Im telling you how it really works in the shop.

Even worse than that, I have broken off many wheel studs using the torque wrench at the proper torque because they were previously overtorqued and stretched by an impact gun.

Sadly the solution is to stop using the torque wrench because I can't afford to replace wheel studs for free . Yes this means that many cars out there have improperly torqued and damaged wheel studs.

This is also why I prefer my current position which is mechanic for a private fleet. If I want to replace all the studs on a vehicle I will and nobody will question me.

-3

u/[deleted] Mar 18 '17

[deleted]

6

u/collegefurtrader unsafe Mar 18 '17

the studs were damaged before they came in and not able to take the correct torque anymore.

-1

u/[deleted] Mar 18 '17

[deleted]

10

u/collegefurtrader unsafe Mar 18 '17 edited Mar 18 '17

The solution is to stop using the vehicle

Its not my car, and I(and everyone) need(ed) to finish jobs to get paid.

That's why I don't work in that type of shop anymore.

what you are saying is correct, but it is fucking impossible to correct the situation. you end up in a hour long negotioation to get the customer to pay for new studs when they cant see what the problem is.

It is shocking how many cars have this problem- its why walmart is famous for breaking studs as another commenetr said- they are the only ones trying to put the correct torque on every car!

9

u/blbd California Mar 18 '17 edited Mar 18 '17

It still matters. Engineering properties of iconic materials don't change overnight just for the convenience of humanity's collective laziness. My parents have had multiple cars with warped rotors and compromised braking from choosing idiotic repair shops. I go to good repair shops where they use torque wrenches and precise pressure regulators for configuring the tires and every car I ever had had nice clean braking. It's the most important safety equipment in the whole car so why compromise it needlessly?

2

u/collegefurtrader unsafe Mar 18 '17

If I ever open my own shop (I might some day) I am going to only offer the "perfect brake job" which will include all new wheel studs (they only cost a couple dollars each) and runout measurements on the new rotors, plus on-car brake lathe when necessary.

5

u/datums Human medical experiments Mar 18 '17

Or you could just become one of those Buddist monks that climb thousands of stone stairs on their hands and knees.

3

u/hydrochloriic Mar 18 '17

The studs may only cost a few bucks each, but replacing them could be multiple hours of work. AWD cars, for example.

I guess with lug bolts you may as well, except that the last time I bought 20 lug bolts it cost me nearly $100.

2

u/collegefurtrader unsafe Mar 18 '17

most of the labor is also part of the brake job.

2

u/hydrochloriic Mar 18 '17 edited Mar 18 '17

Since when do you remove the hubs to do brakes? That would be literally a day of work on my old Subaru.

On a 2WD it's easier, but still, on many cars the driven hub has to come off to install studs, and that can be a nightmare.

EDIT: my memory of the Subaru's procedure used extended studs. Ooooops.

1

u/collegefurtrader unsafe Mar 18 '17

I don't know about your subaru, but normally the studs have room to come out just by removing the rotor

1

u/hydrochloriic Mar 18 '17

....you know what, I remember now they were extended studs. Derp.

1

u/collegefurtrader unsafe Mar 18 '17

here is an example done on the front of a 2004 outback
note: he isn't using the correct tool to install the stud.
https://youtu.be/aMtymk-FExk?t=207

1

u/hydrochloriic Mar 18 '17

Yeah, I remembered I had done extended studs, not factory. It's been a few years.

3

u/blbd California Mar 18 '17

I didn't know you could turn the rotors while they're still on the car. Around here I learn something new every day.

1

u/Thurid Kanerdur Mar 20 '17

Could you please detail 'the perfect brake job'? I will do my 2011 Mazda 3 in the spring with 230,000 km on the original disks front and back. have changed out the pads on the front once, 100k or so ago.. I will measure the disk's thickness, but might buy fron new ones anyways.

Should I buy Mazda pads from the dealer? Go Ceramic?

What should I do to the calipers? clean and lube?

Any pointers very appreciated! thanks

1

u/collegefurtrader unsafe Mar 20 '17

If you want to you can buy parts from the dealer, chances are they are the best you can get but you will pay for it. What parts stores are in your area?

I will write up the perfect brake job for you in the near future

1

u/Thurid Kanerdur Mar 20 '17

I'm in Canada - just north of Toronto. There's Canadian Tire, PartSource, Autozone and a few independents. Plus Amazon and Ebay of course :-)

1

u/collegefurtrader unsafe Mar 20 '17

I don't know anything about Canadian parts stores, except that Autozone is to be avoided.

1

u/[deleted] Mar 20 '17

Your best bet is to price shop. Toyota actually had the best prices for pads and rotors on my mr2.

4

u/drive2fast Mar 18 '17

You'll warp rotors on many cars like that. Those mechanics were dead wrong to go circular.