i prolly know the answer, but thought i'd p*** it through here for ***essment... the spindle:steering arm:steering knuckle ***embly is held together with four 7/16-20 bolts. from the factory they were decent grade 8. (on ford and chevy it's typically a single forging, but these are three piece.) given it's age (1961) and my relatively high demands (street, weekend rally, soon, autocross) i replaced them with AN type airframe bolts. installed by the book, shimmed correctly with appropriate thin washers, castle nuts, torqued, pinned. i just had the front end apart for some upgrades and upon re***embly, i torqued them to to 50 ft/lbs without thinking... old habit. as if they were the old factory grade 8 bolts. i realized my mistake now, two weeks later. i'm not worried about my wheels falling off, i'll sleep at night, etc. but the correct torque is 35 - 40 ft/lbs. 50 ft/lbs is 25% too much. it's the only place other than engine internals i have such fancy stuff, since it's a critical application, and it burns me i was dumb enough to do this. it's fifty bucks worth of bolts. so what would you do? never think about it again? rush right out and swap the bolts before morning's light? "when i get a round tuit?" i mean, if it was twice as much torque, ok, replace them would be reasonable. this is more of a general technical question than a 'will my wheels fall off' question, at what point is a bolt over-stretched?
I'm no expert but I'm sure you'll be fine - quality fasteners will have safety factors of at least 100%. I'd be interested in knowing what percentage of folks even bother with a torque wrench beyond mains, rods and heads and maybe a few other areas; which is a backhanded way of saying what are you worried about! Chris
often 7/16" wheel studs get torqued to 100 ft lbs or more. Buy some new bolts, Tom, the aircraft fastener industry needs the money.
I may be a bit of a backyard mechanic, but aren't torque ratings "recommended" and not necessarily "mandatory"? As mentioned above, I'm one of those guys that only uses a torque wrench on engine ***embly and never had a problem.
A bolt manuf's page gives a 70 ft-lb value, for dry, grade 8, 7/16 dia. ***umed co**** thread. Might check w/ARP page.
Since the bolts did not twist off when you tightened them, do not worry about it. Even if the applied torque has taken the bolts closer to yield than would normally be recommended they provide all the clamping force that comes with that preload. If you had taken them to yield, you would get the maximum clamping force available from that fastener.
Lubed, non lubed, new smooth slippery washers vs old ones- friction play a big part in what the torque wrench tells you about the bolts you are tightening.
Grade 5's will yield for some stretch, grade 8's are stronger, and less ductile. I tend to think of them as pre-tensioned.
Just think of how many times the Walmart monkeys have torqued wheel lugnuts to 200 ft/lbs because they don't know how to set the impact.............
In the auto industry, there was a revolutionary new discovery that eclipsed all previous SAE values. Angle Torquing! Don't know the 'reasoning' behind this, but it must have come from behind a closed-door meeting of geniuses that voted unanimously that "more is better!" I tended to prefer the measurable torque setting to the "just before the rubber band snaps" theory. Recalling 'bolt stretch', I was uncomfortable with a 45 degree 'pull' after reaching 60 foot lbs on a 10 mm. head bolt. (.030" less than 7/16") Imagine a novice service manager walking up after your final torqueing on a cylinder head...him grabbing the torque wrench and saying, "That's not enough...This is enough!" The stuff nightmares were made of.
Here is a good torque chart with lots of notes on variables. https://www.imperialsupplies.com/pdf/A_FastenerTorqueCharts.pdf
lol, i knew i was opening up a religious question... i'm not worried about it, four grade 8's were more than adequate, four AN rated bolts from Pegasus is aircraft-overkill. this is the only fastener in the car that got any special attention. (other than the usual engine internals, rod and head, etc). it's a funny application, four bolts in tension literally holding the wheels and brakes to the spindle. good grade 8's would have been fine. the problem is i don't trust hardware store grade 8, i've got some recently with visible swaging flaws in the head. i stock good hardware i get from MSC Direct but these were funny bolts, gotta online order anyhoo, so i said fcuk it, get ANs, done and done. i did momentarily forget that these are aircraft bolts, so the torque rating is stupid conservative, yeah, as pitman sez, they are 7/16-20's, for which 78 ft lbs is spec'd. you know what ****s? torque to yield! ugh! great i suppose for OEMs with giant robots. not so good for the rest of us.
money. less of it. i gotta ***ume that the newer torquing methods, which can be very precise and selected for each unique fastener, saves money and give fantastic performance -- iff (if and only if) you can precisely control the quality of the fastener, and very closely control it's installation. the former probable scales well for OEMs, yeah, the bolt costs a buck not 50 cents, but it replaces two, and the robot gets it to .00000000000000000001%, etc. too bad for repairs, mods, or the unlucky. i let me HOTROD mag lapse (too much cookie cutter) but the few articles modding late model stuff convinced me that i never want to have to mess with such nonsense. gimme two (or four) standardized fasteners over one specialized one, i can make it do non-OEM things.
Well, according to this chart (http://navyaviation.tpub.com/14018/css/Recommended-Torque-Values-Inch-Pounds-126.htm), the maximum torque rating for those bolts is 70 ft-lbs. The 'recommended' torque is 35-40, well below the maximum. The ratings are more dependent on the type of AN nut used. I'd be more concerned personally at the lower number if you're applying enough clamping force to the ***embly.
actually Steve, that's not Crazy at all. you're absolutely right -- the original bolt was 60 ft/lbs in that job, so that's what it gets -- not what the bolt needs, which is a crazy-conservative aircraft value anyway. it's a quality fastener (erm, i hope) of the correct size -- done and done. thanks!
Don't ***ume that AN fasteners are always better. The military rates the fasteners for particular applications and some don't require high strength but still carry AN certification.
yeah, once you go down this path... there is no end i bought these fasteners from Pegasus Auto Racing. i admit i'm relying on their reputation.
Had to do some research on that. The difference in he torque specs is due to the cad plating acting as a lubricant on the threads. https://www.askbob.aero/node/575 I don't remember them teaching us that in 1966 When I worked at Boeings and learned to safety wire those bolts.
It happens to all of us at one time or another,I snapped a bolt in a lower alternator bracket on my old roadster. After I removed part of the broken bolt with a easy out I realized someone had previously broken a bolt in the same place,hence two easy out's and two broken pieces of a bolt. HRP
oh man, not sure if hilarious is the right word here. it's stuff like this that reminds you that old car parts are old.
Just because I have too....torque to angle is far more accurate than traditional methods. Using traditional methods, 85-90% of the torque value is used to overcome the friction of the fastener turning and not actually tightening it, now imagine if we had dirty or damaged threads the number would change dramatically and on something like a cylinder head the clamping force would be all over the map. Torque to angle usually involves a small torque value and a set number of degrees after that, this takes friction out of the equation as say 90 degrees is 90 degrees no matter what, it’s a far more accurate method of tightening fasteners. Most modern stuff uses torque to yield fasteners which used torque to angle procedure but tightens the fasteners past the yield point into the plastic deformation stage which insures all bolts are stretched the same, therefore having the same clamping force, it’s also the reason most critical fasteners in modern applications need to be replaced after every use. Sent from my iPhone using H.A.M.B.
The Jalopy Journal
