Wheel nut torque March 87C

[stownsen914]

I'd like to tap into the forum's wisdom about wheel nut torque for March 87C center lock wheels. The car is actually an old IMSA GTU car that uses March uprights and hubs (and wheel nuts). Wheels are BBS magnesium centers. I've recently completed re-assembling the car after it sat for many years after a wreck. After talking to a few people and doing some research, I decided to torque the wheel nuts to 350 ft-lbs, no lubrication. At Watkins Glen yesterday a rear wheel nut came loose. Fortunately it didn't fall completely off, and I managed to pull safely off track. I am not sure what I did wrong and do not want to experience this again! I'd like to get input on the torque value and the process I used to tighten them.

1. Snug wheel nuts while car is jacked up
2. Lower car, torque first to 150-200 ft-lbs [I'm guessing this step is unnecessary. Skip?]
3. Torque to 350 ft-lbs
3. Re-torque to 350 ft-lbs after first session

Thoughts? Thanks.

Scott

[J Leonard]

2 1/4 ish thread tapered face nuts? We use 350 and have not had problem. Do you have left and right hand threaded nuts? Left hand versions go on the right side of car.

[Joules5]

Recommended torque for Swift large nuts is 400#, I've never had a problem, but I do have safety pins to try and prevent total wheel loss just in case.

[john f]

Quote: " I've recently completed re-assembling the car after it sat for many years after a wreck."

350 lb-ft sounds fine. I would look very close at the flatness of both the wheel and axle flange. Just my $0.02.

john f

[EricP]

You gotta at least post a pic of the car!

[stownsen914]

Thanks guys for the replies. To answer questions that were asked - yes, around 2.25" diameter with tapered contact face on the wheel nuts, right hand threads on the left side of the car and left hand threads on the right side of the car.

Sounds like 350 ft-lbs is the right number, so something else must be going on. I've heard varying opinions about whether to lubricate the threads before torqueing. I did not. I've got one recommendation to use spray graphite on the threads and the contact face of the wheel nut. What do you guys do?

I'll check the mating surfaces for flatness as suggested.

Here's a pic of the car, since someone asked. Not painted yet obviously.

Scott

[Charles Warner]

Whatever you do, DO NOT spray anything on the contact face of the nut. This totally screws up any torque value. Clean with brakeclean. Apply a minimum amount of anti-seize to the threads. Assuming a calibrated, reversing torque wrench (hopefully a 3/4" drive minimum) 350 ft/lbs is adequate. However, do not retorque after a session. Allow the wheels/nuts to normalize before tightening. Of course, you can remove the wheels before they cool.

[stownsen914]

Whatever you do, DO NOT spray anything on the contact face of the nut. This totally screws up any torque value. Clean with brakeclean. Apply a minimum amount of anti-seize to the threads. Assuming a calibrated, reversing torque wrench (hopefully a 3/4" drive minimum) 350 ft/lbs is adequate. However, do not retorque after a session. Allow the wheels/nuts to normalize before tightening. Of course, you can remove the wheels before they cool.

Thanks. By normalize, I assume you mean to wait until they cool before re-checking torque?

[J Leonard]

We have been doing the dry mating surface with a little Kroil penetrating oil on the threads. We also have some nuts labeled Daytona that have been drilled for some sort of a set screw, possibly nylon. Someday I'm going to drill the spindles for safety pins.

[stownsen914]

Thanks again for the input on this.

Any suggestions how to deal with the damage to the wheel? Drive pins buggered their respective bores near the ends before exiting as the wheel nut came loose, and then spun and shaved the wheel center a little. Wheels are BBS magnesium centers. Pics attached. Damage appears to be in the .010-.040" deep range. It looks like I should plan to have the mating surface trued. Thoughts?

No damage was evident to the hub or wheel nut from quick inspection, but I will be checking those parts again very carefully.

I will also be more careful going forward about cleaning/checking the hub mating surface and threads, wheel nut mating surface and threads, and the wheel mating surfaces each time I put wheels on and torque.

[stownsen914]

...

[stonebridge20]

Old school method.

[stownsen914]

I hadn't noticed until now, but my hubs are drilled for safety pins. I plan to use them going forward. Doing a little searching, I see several styles of centerlock safety pins out there. I'm pasting some pics below. First the old school variety, and newer cars seem to either the second or third styles. Opinions on which is best / most reliable? Thanks ...

[J Leonard]

1 is probably what you had
2 might be tough to get in if nut is recessed
3 is what I have on the three point hitch on my tractor
If you find source for 1 let us know.

[stownsen914]

Found these ...

http://www.roadraceparts.com/t-a-wheel-nut-safety-pin/

It doesn't say what size spindle they're for, but under "related products" is a centerlock socket that's 2.75" which is almost the same size as the one I use (I think it's 2.625"). So maybe these pins would be a good fit.

[Pi_guy]

Found these ...

http://www.roadraceparts.com/t-a-wheel-nut-safety-pin/

It doesn't say what size spindle they're for, but under "related products" is a centerlock socket that's 2.75" which is almost the same size as the one I use (I think it's 2.625"). So maybe these pins would be a good fit.

1/8 stainless tig welding makes great wheel nut safety pins.
Made a few of them this way...

[romoman]

I've seen pins like this used on some of the current TA cars https://www.mcmaster.com/#safety-pins/=1ebx9yp

You might try one of the TA chassis builders (Ave, Weaver, Derhag, Meissen).

[stownsen914]

I've seen pins like this used on some of the current TA cars https://www.mcmaster.com/#safety-pins/=1ebx9yp

You might try one of the TA chassis builders (Ave, Weaver, Derhag, Meissen).

The McMaster link goes to a general page showing a few different kinds of pins. Do you mean this kind?

[romoman]

The McMaster link goes to a general page showing a few different kinds of pins. Do you mean this kind?

Sorry about that. Not like that image, like item 90026A110 https://www.mcmaster.com/#90026a110/=1ec4rdz

[stownsen914]

Sorry about that. Not like that image, like item 90026A110 https://www.mcmaster.com/#90026a110/=1ec4rdz

Thanks. I'm leaning toward that style. Somehow it feels more secure than the ones in the first pic in my first post above. The ones McMaster sells are 3/4" wide, which is just enough to clear the snout on the hub for 3 of my car's 4 corners. For some reason one corner has a longer snout, and the holes are a full inch in from the end. For that one I may buy a longer pin and bend it to get the extra clearance.

Scott

[romoman]

Thanks. I'm leaning toward that style. Somehow it feels more secure than the ones in the first pic in my first post above. The ones McMaster sells are 3/4" wide, which is just enough to clear the snout on the hub for 3 of my car's 4 corners. For some reason one corner has a longer snout, and the holes are a full inch in from the end. For that one I may buy a longer pin and bend it to get the extra clearance.

Scott

Look at 90174A116. Zinc plated, not stainless, but 1 1/8 clearance.

[stownsen914]

Look at 90174A116. Zinc plated, not stainless, but 1 1/8 clearance.

Good find - thanks for that!

[stownsen914]

I keep going back and forth about what type of centerlock safety pin to get. Is there any reason that this style is less effective?

[J Leonard]

Not there to keep nut tight, just to keep it from falling off.

[Charles Warner]

I keep going back and forth about what type of centerlock safety pin to get. Is there any reason that this style is less effective?

You are over-thinking this. That choice is as good as any of the others, and it the easiest to install. That's what all of the vintage F1 cars use.

[stownsen914]

Yeah, I was over-thinking it. I ordered the vintage style ones.

[J Leonard]

Did you get the ones from Road Race Parts? let us know how they fit.

[stownsen914]

Did you get the ones from Road Race Parts? let us know how they fit.

I did. They fit my car fine. The pins appear to be hand-made, but the quality is reasonably good. I did trim the ends a bit so I wouldn't have to compress them so much to install.

To give an update on my wheel nut loosening … I took a few steps to improve my discipline around fastening my wheels:

• I got feedback that I need to clean the wheel nuts and hubs before installing. I gave them a good cleaning and wiped down all the threads. There was some gunk in there that looked like anti-seize.
• I decided to remove the brake rotor on the rear corner that had the wheelnut come loose to make sure all surfaces were flat. I noticed two small surface imperfections on the hub under the rotor hat where two drillings hadn’t been deburred. There were corresponding marks on the rotor hat. So I deburred them. Checking the surfaces with a straightedge, they appeared flat otherwise.
• When installing the wheels before heading to the track, I give the threads on the hubs a quick wipedown with brake cleaner. I also clean the mating surfaces on the hub and wheel to ensure no debris, etc.
• I got suggestions all over the map about whether to use a lubricant on the wheelnut threads. I decided to use a light spray of graphite.
• I still used 350 ft-lbs on the front wheels. On the rears I decided to up it to 400.

After my first outing with the car after instituting the above, when I went to remove the rear wheelnuts, the other side was almost loose this time. I am wondering if the rear wheels are rocking slightly on the drive pins each time the car transitions back and forth from power to braking, and it’s gradually causing the nuts to loosen. I’ve noticed while installing the wheels that they are not really snug on the drive pins, and before I tighten the wheelnuts there is a little bit of rotation possible. Is this a problem?

I’m going to check the other rear hub to see if it needs deburring like the other side did (I should’ve done that before …).

Scott

[Charles Warner]

After my first outing with the car after instituting the above, when I went to remove the rear wheelnuts, the other side was almost loose this time. I am wondering if the rear wheels are rocking slightly on the drive pins each time the car transitions back and forth from power to braking, and it’s gradually causing the nuts to loosen. I’ve noticed while installing the wheels that they are not really snug on the drive pins, and before I tighten the wheelnuts there is a little bit of rotation possible. Is this a problem?


Scott

This is a common discussion on the forum. For some of us (me included) these are not "drive pins" but locating pins. They have nothing to do with the tightness (of lack thereof) of the wheel. (My 1987 March F1 cars only had 3 small - 6mm - pins to locate each wheel.) All of the clamping is done between the wheel center and the beveled part of the nut. You should have the smallest amount of graphite/anti-seize on the threads and none on the mating surfaces.

Possible areas of concern. What torque wrench are you using? A 1/2 drive probably won't give proper readings in those ranges. Get a 3/4" drive. Or, use a good air gun that is calibrated to what you want. Are the wheel nuts the proper ones? This may sound strange, but there are many different nuts out there that fit the same threads but have a slightly different bevel.

It sounds like you are not getting a proper fit between the wheel and the nut.

If the nuts are not matched to the wheels you will never get a good fit.

Make sure the wheels and nuts are not coated or painted. If either is coated/painted you will not get proper clamping force. The nuts may be anodized - that's ok. But, if the wheel center is painted you'll need to carefully remove all pain from the mating surfaces.

[J Leonard]

I'm with Charles on the nut profile. Maybe use some Prussian Blue to check the contact patch between nut and wheel.

[stownsen914]

Thanks Charles (and J Leonard). I'll check the wheelnut bevel compared to the wheel taper. I believe these to be the parts that were used on the car in the past, and per the previous owner he didn't have any issues. He did mention using what sounds like a higher torque than I am - he used body weight on a 4 foot longer breaker bar (no torque wrench).

There isn't paint on any contact surface - hub, rotor hat, inner wheel mating surface, wheel nut mating surface, or the wheel nut itself. And I cleaned all of those too before this last outing with the car.

I am using a 3/4" drive torque wrench. I don't recall the brand offhand. I guess I could have it calibrated to be confident in the torque values I'm getting.

So for the locating pins, it's OK that they allow a small amount of rotation of the wheel (only when the wheel nut is loose of course)?

[Joules5]

My wheels are fairly snug on the locating pins, your wheel photos would indicate your locating holes are oblong and I would assume that there is a limit to how much wear can be tolerated and still be safe as the wheel could move back and forth under successive acceleration / deceleration events impacting nut torque, albeit as stated it is the hub/wheel rear and nut/wheel outer mating faces that are critical.

It may be a silly question but you do have left and right had thread axles/nuts and they are on the correct side of the car right? Left hand on right hand side and vice versa to counteract the torque impact of forward motion.

Julian

[stownsen914]

It may be a silly question but you do have left and right had thread axles/nuts and they are on the correct side of the car right? Left hand on right hand side and vice versa to counteract the torque impact of forward motion.

On my car the RH threaded wheelnuts are on the left side of the car, and LH threaded wheelnuts are on the right side.

[stownsen914]

So I discovered that the holes drilled in the front hubs for the safety clips are a little too far inboard to allow the clips to fit with my wheels. See pic below - basically the holes are partially obscured by the wheelnut (obviously there isn't a wheel on in the pic, but it illustrates the issue). I see two choices to make the safety clips work:
1. Open the holes about 1/16" on one side with a Dremel or rotary file until the clips fit
2. Drill new holes in the hubs

I'm leaning toward #1. Any reason that wouldn't be advisable?

Scott

[Charles Warner]

So I discovered that the holes drilled in the front hubs for the safety clips are a little too far inboard to allow the clips to fit with my wheels. See pic below - basically the holes are partially obscured by the wheelnut (obviously there isn't a wheel on in the pic, but it illustrates the issue). I see two choices to make the safety clips work:
1. Open the holes about 1/16" on one side with a Dremel or rotary file until the clips fit
2. Drill new holes in the hubs

I'm leaning toward #1. Any reason that wouldn't be advisable?

Scott

Turn the nuts down until you can just insert pins. Do not drill hub.

[Jon Jeffords]

I recall going through a similar investigation for a centerlock wheel nut on a buddy's Formula Continental. We exhausted all the easy inspection / low cost items as mentioned in the previous comments above, but still kept loosening the left rear centerlock nut. It wasn't until we replaced the spindle and centerlock nut that we solved the problem. It was Doug Learned at Fast Forward that tipped us off that with enough on-off cycles, the external threads of the stub axle and internal threads of the nut can fatigue and no longer provide the neccessary clamp forces to prevent the joint from 'slipping', even at the proper nut installation torque.

Some related posts:
https://www.apexspeed.com/forums/sho...e-to-loosening
https://www.apexspeed.com/forums/sho...FC-Loose-wheel
https://www.apexspeed.com/forums/sho...er-spring-clip

[Dave Harmison]

The May 18, 1912 issue of Autocar has a very good article describing the Rudge Whitworth self tightening wheel nut design. The same design was still being used on the Ferrari 512 LeMans cars in 1971. You can find the article by googling "Autocar" Rudge Whitworth (Autocar in quotes).

Do the cone shaped nuts auto- tighten like the original?

[stownsen914]

It wasn't until we replaced the spindle and centerlock nut that we solved the problem. It was Doug Learned at Fast Forward that tipped us off that with enough on-off cycles, the external threads of the stub axle and internal threads of the nut can fatigue and no longer provide the neccessary clamp forces to prevent the joint from 'slipping', even at the proper nut installation torque.

Is there a way to inspect or test the threads on my hubs and wheelnuts to determine whether they are worn? They don't appear to be obviously damaged to my untrained eye. I noticed that there is some wobble when a wheelnut is loosely screwed onto the hub with no wheel. Is there a spec or rule of thumb to check this?

Scott

[cunn5]

I have a March 86A and have been told 125 lb torque for wheels?

[Garey Guzman]

I was having an issue with loosening centerlock nuts on my car (much lower HP, Swift FF, one rear only). After some conversations, I sent the uprights to Fast Forward for rebuilding and after Doug's work, haven't had a problem since. Bearing condition and location are critical for durability.