Making the centerlock safety pins fit

[stownsen914]

I’m putting safety pins on my front centerlock wheels (I have them on the rears already). Problem is that at the moment, when the center nuts are torqued on the wheels, they cover the holes in the spindles. To make the pins fit in the front, I’m going to have to either open the holes in the spindles by about 2 mm, or remove 2mm from the outboard edge of the center nuts. I had a suggestion to machine the nuts, but removing 2 mm would eliminate the entire outer face of the nut and will result in sun-optimal contact between the safety pins and the nuts. See pics of the spindles and nuts below.

I think I understand the suggestion to avoid modifying the spindles, but wouldn’t the outboard portion of the spindles be unstressed and low risk? Assuming I am careful and don’t make a mess of the job. If I go this route, I'd use a Dremel to open two holes on each spindle.

What say ye?

[Lotus7]

Can you drill two fresh holes further outboard and 90 degrees to the existing two?

[jrh3]

Can you drill two fresh holes further outboard and 90 degrees to the existing two?

Just my thought. Low stress area. Drill between and outboard of existing.
After see the pictures I would probably check the fit of all components, do the 2mm relief and go racing.

[Charles Warner]

Something has changed, or been changed. Verify those are the proper nuts. Try the rear nuts on the front to see if things change (and vice versa). The car should not have that type of mis-matching parts unless someone screwed with it or changed parts. Before chopping things up make sure of your problems.

[J Leonard]

I have never seen a brake caliper with mounting holes on the outboard side. It's like it was assembled with two inner halves.

[Charles Warner]

Well Spotted. Obviously an incorrect installation and will probably lead to other issues - disk location, etc.

[EACIII]

Have you change the wheels from what was original?

[stownsen914]

Thanks guys for the input as always. Responses below.

It's worth noting that the suspension parts in question are March 87C. The car is a GT car built in the 1990s using the 87C parts, which may well have been used at that time. So while they have been on this car a long time, it would not be surprising if the parts met each other for the first time on this car.

Something has changed, or been changed. Verify those are the proper nuts. Try the rear nuts on the front to see if things change (and vice versa). The car should not have that type of mis-matching parts unless someone screwed with it or changed parts. Before chopping things up make sure of your problems.

I have exchanged the front and rear wheel nuts. The nuts appear identical, the front and rear spindles do seem to have different dimensions. These parts are quite old of course - I'm sure the nuts are not the ones originally paired with the spindles. If someone can point me to a source of March 87C wheel nuts, I'd be interested in trying them.

Can you drill two fresh holes further outboard and 90 degrees to the existing two?

I realize it's not evident from the picture, but there are 3 pairs of holes already. Any reason that drilling new ones would be preferable to opening two of the existing holes about 2 mm to the outboard side?

I have never seen a brake caliper with mounting holes on the outboard side. It's like it was assembled with two inner halves.

I've wondered this as well. The outboard caliper halves aren't tapped for a brake line fitting. I've assumed a common casting was used and finished as needed when the calipers were built. They've been on the car since the 1990s as far as I can tell and no apparent issues with interference of parts.

Have you change the wheels from what was original?

These wheels are what came with the car, and to my knowledge are the ones that have been used on it for a long time. For sure the wheel is a critical dimension in determining the "stack" height and will influence where the nut sits on the spindle. The four front wheels that came with the car sit about the same on the car.

[Charles Warner]

"I have exchanged the front and rear wheel nuts. The nuts appear identical, the front and rear spindles do seem to have different dimensions. These parts are quite old of course - I'm sure the nuts are not the ones originally paired with the spindles. If someone can point me to a source of March 87C wheel nuts, I'd be interested in trying them."

IIRC the Indy Car nuts were the same as early 80s F1 nuts. I think I have a new pair in Sonoma that came off an Indy car and fit a 1981 March F1. Different colors for different sides. If you can get to the Masters race at the Glen next month I'll have the guys throw them in the trailer (if they haven't been sold already.) . . . . . .

[stownsen914]

IIRC the Indy Car nuts were the same as early 80s F1 nuts. I think I have a new pair in Sonoma that came off an Indy car and fit a 1981 March F1. Different colors for different sides. If you can get to the Masters race at the Glen next month I'll have the guys throw them in the trailer (if they haven't been sold already.) . . . . . .

I appreciate the offer! I hadn't planned on going, but now you've got me thinking ...

[stownsen914]

Can I get opinions on the following choices to make safety pins fit my front hubs (as a reminder the existing ones are mostly hidden by the nut on my car)?

Option 1 - turn down the outer face of the wheel nuts to remove enough material to expose existing holes in the spindle snout. ISSUE with this method in my opinion is that due to the nut design (see pic), it will leave the pins unsupported for about 1/4" between the snout and where it would contact the nut. I'd worry that if a nut were to come loose, it would bend the tips of the pins and let the nut loosen a few turns.
Option 2 - drill additional holes in the spindle snout at the right depth to use the safety pins . There are 6 holes already, so it doesn't feel optimal to drill more.
Option 3 - open 2 of the existing holes in the snout by about 2mm to allow installation of the pins

[tlracer]

Can we have a picture of the spindle, with wheel fitted and nut correctly torqued please.

Reading your posts, in the first one you say the nut partly covers the pin holes in the stub axle, but now you are saying if you machine the outer face of the nut, there will be a gap between it and the pin..?

As regards drilling holes further out, this would take you into the reduced wall thickness part of the stub axle which was never designed to have safety pins through it.

[stownsen914]

Can we have a picture of the spindle, with wheel fitted and nut correctly torqued please.

Here's the best pic I can offer now (not home at the moment) - see below. With a wheel in place the nut is another 1-2 turns further outboard and mostly covers the holes in on the front spindles. Only 1 mm of the hole is left exposed, so no room for pins to fit.

Reading your posts, in the first one you say the nut partly covers the pin holes in the stub axle, but now you are saying if you machine the outer face of the nut, there will be a gap between it and the pin..?

Have a look at the pic of the nut above, and imagine if 1/8" or so is removed from the outboard surface of the nut to make room laterally for safety pins. That would leave a gap (radially, not laterally) between the spindle and portion of the nut that the safety pin would contact. Seems like that would compromise the ability of the safety pin to do its job.

As regards drilling holes further out, this would take you into the reduced wall thickness part of the stub axle which was never designed to have safety pins through it.

Thanks, makes sense.

[tlracer]

Okay thanks, that makes much more sense now!

If the nut and stub axle are definitely correctly paired, then something must have changed to create the current misalignment.

That suggests either the disc bell or the wheel is thicker than the axle/nut were designed for?

In that case, could either of those be reasonably machined to allow the current (original?) safety pin holes to be used?

[stownsen914]

The items in the "stack" include only the hubs, rotor hats, and wheels. The rotor hats are probably 1/8" (3 mm) or so, so not enough meat to make up the 2 mm I need to shorten the stack and make the safety pins fit. I don't see any option to modify the hubs, so I guess that leaves the wheels.

It's very possible that the wheels that came with this car, while they appear to have been assembled for the car (a GT car), aren't intended for a March 87C. It's not a problem on the rear for some reason - the pins fit fine there. The front wheels all have the same fitment issue on the front. I hadn't considered the possibility that the front wheels might have different dimensions at the hub than the rear wheels do. I'll have to measure them.

[BeerBudgetRacing]

I looked but didn't see it asked....

How is the axle mounted to the hub? Has something been changed there so it doesn't stick out as much?

[J Leonard]

The wheels on this March are 1.5 inch from flat mounting face to the start of the taper. Front and rear are the same.

[stownsen914]

The wheels on this March are 1.5 inch from flat mounting face to the start of the taper. Front and rear are the same.

Thanks for that. I measured a few of my wheels, fronts and rears. All seem to be about the same as you mention, I got 1 7/16". Shaving the front wheel inner faces doesn't seem like the right option to make safety pins fit. And with the only other thing in the "stack" being the rotor hats (about 3/16"), I don't see any other options there to shorten the stack to move the center nuts inboard the 2 mm I need to uncover the safety pin holes.

I can only imagine that the front and rear spindles on my car came from different cars/teams that may have used center nuts of slightly different dimensions. Hard to say. I think that leaves me with the three options I listed earlier to get safety pins on the front of my car. All seem to be imperfect unfortunately. Perhaps the question is, which is least imperfect?
Option 1 - turn down the outer face of the wheel nuts to remove enough material to expose existing holes in the spindle snout. (Note the issue detailed a few posts above why I think this won't work well in my case.)
Option 2 - drill additional holes in the spindle snout at the right depth to use the safety pins . There are 6 holes already, so it doesn't feel optimal to drill more.
Option 3 - open 2 of the existing holes in the snout by about 2mm toward the outboard side, to allow installation of the pins.

[tlracer]

Are you sure your axles/nuts aren't designed for hairpin-type retainers, where they're fitted from inside of the axle bore, so the pins locate in the internal groove of the nut?

Similar to these:

https://www.hardmotorsport.com/centerlock-wheel-spring/

That would make much more sense as to why the existing holes are covered by the nuts and explain the internal groove in the latter, too.

[J Leonard]

Those 6 holes look to be larger than would be a nice fit for a retainer spring. Just put two new holes the proper size and distance from the nut. The spindle nose just guides the nut on for pit stops.

[J Leonard]

The set screw in the nut has a nylon type insert under it.

[stownsen914]

Are you sure your axles/nuts aren't designed for hairpin-type retainers, where they're fitted from inside of the axle bore, so the pins locate in the internal groove of the nut?

Similar to these:

https://www.hardmotorsport.com/centerlock-wheel-spring/

That would make much more sense as to why the existing holes are covered by the nuts and explain the internal groove in the latter, too.

Thank you for pointing that out. Looks like you are correct. I've been using exactly that style pin on the rear center nuts (outboard of the nut in that case). i did a test fit this evening, and they do indeed fit on the front and sit inside the recessed portion near the end of the nut and stop it after a few turns. I'd like it even better if the nut bottomed out on the pin sooner, but perhaps I can fashion some kind of insert to take up the slack. In any case, certainly better than what I've had up to this point!

The set screw in the nut has a nylon type insert under it.

Thanks for that. Is it a simple set screw with nylon under it to prevent marring the spindle/threads?

[tlracer]

Thanks for that. Is it a simple set screw with nylon under it to prevent marring the spindle/threads?

I've never seen those on centrelocks but something similar is used elsewhere, eg. spring collars on some shocks, to prevent loosening from vibration (instead of having a second collar working as a jam nut).

[Lee Johnson]

How about getting the outside face of the wheels machined where the nut seats? That will provide the desired clearance for the safety pin without changing internal wheel to caliper/upright clearances. Probably lots of "meat" in the wheel in this area.

Lee

[J Leonard]

I have lost track of or missed the type of pin your going to use. I was thinking it was the internal with ends poking out. We got a set of the set screw nuts with the Indy car. We also got a set with a GTP car that were labeled "Daytona".

[stownsen914]

I’m using the “vintage style” pins that install from the inner bore of the spindle. Here’s a pic using tlracer’s suggestion.

[Lee Johnson]

The link posted by tlracer

https://www.hardmotorsport.com/centerlock-wheel-spring/

has a picture of this outfit's safety spring installed:



To me it looks like the ends of their safety spring engage into the groove between the outer end of the nut and the outer end of the nut threads. It doesn't show that the ends of the safety spring extend over the outer end of the nut.

IF that is the correct way for the installation to be implemented, OP's last picture seems to show the wheel nut and safety spring properly installed. In this last of OP's pictures, the nut clearly doesn't thread onto the spindle/hub nearly as far as earlier pix without the wheel in place.

Close inspection of OP's actual installation would validate whether the safety spring end is really fully engaging in the interior groove near the outboard end of the nut.

[tlracer]

Lee - yep, that was my point about the pins locating into the internal groove of the nut.

Going by the latest picture, with the wheel fitted and nut in place, it all lines-up correctly and also explains why the groove may be there.

[Lee Johnson]

Tim --

Looks to me like you got it right, I just didn't follow your link right away & see the bright red nut photo illustrating how the parts are supposed to fit.

[tlracer]

Just a lucky guess - I did try to link to the second photo directly but couldn't figure how to do that!

[stownsen914]

Anyone have a source for the internal safety clips? I have a set of four, but wouldn't mind having a spare or two. The vendor I bought mine from is no longer in business. Figured I'd ask before I resort to making my own.

Seems the Hard Motorsport ones pictured above are for a smaller diameter application.

[J Leonard]

mcmaster carr has a request for quote for custom wound springs. Lots of stock springs listed but none that might be exactly what you want.

[psc85c]

Couple of thoughts -

I do not believe those are March Indy wheel nuts. The March 87C used the same wheel nut front and rear (85G-09-01 (LH) & 85G-09-02 (RH) as my 85C did and mine were aluminum and had Nylock inserts and a dimple on each flat. 3" socket, if I recall correctly.

You might want to contact Andy Gilberg at Marcharchives.com as he has the drawings for the wheel nuts. The 85C did not use lock springs. I do not know if the sports cars (85G) did.

The 85C AP caliper used a bridge pipe between the caliper halves. There are bleed screws on each half. AP told me the calipers were not meant to be split after they were made. The 85C had staggered piston sizes which made the calipers directional and not interchangeable.

I suspect that the front brake hat you have is from an 85C and not an 87C. I don't have the kit list to check the part numbers (Andy does) but you might want to download it and look at interchangeability. March reused parts between some of the cars but only the kit list will tell you for sure.



Watch the axle through bolts (86C-07-03) as March thought they had a less than 1000 mile life. (New for a 500 mile race). They were made of VascoJet1000 which is no longer available from ATI Alvac.

I hope this helps.

[tlracer]

Andy Gilbert's web address is: http://www.marchives.com/

...not as shown above.

[stownsen914]

Thanks psc85c and tlracer - hadn't seen your responses until now.

Entirely possible my car has some 85C parts on it. The rotor hats look a little different than the ones pictures above - the relief holes - not sure if that's a correct term, but I am referring to the 12 holes located halfway out from center - are closer to the center on mine. Otherwise they do look similar.

My brake calipers do appear to be different than standard ones, with the mounting holes on both sides. There's no tapping for a brake line visible on the outer half, suggesting it was never used as an inner on a prior assembled caliper, but who knows.

I don't know where the wheel nuts came from. They appear to be the correct thread diameter and pitch, and with correct taper to match the wheels.

Seeing as the car was built as a one-off almost 30 years ago, I am left to sort out some of these details as best I can. I'll check out marchives.com to see what I can find there.

Thanks to all for contributing the information you have, it's really helpful!

[stownsen914]

Watch the axle through bolts (86C-07-03) as March thought they had a less than 1000 mile life. (New for a 500 mile race). They were made of VascoJet1000 which is no longer available from ATI Alvac.

Wanted to comment on this as well. You're not the first one to mentioned the limited useful life of those bolts. Any information on a replacement since the original ones aren't available?

[tlracer]

VascoJet1000 is/was a trade name for AISI H11 tool steel (DIN 1.2343).

[stownsen914]

@J Leonard
@psc85c

It sounds like you both own / work on mid 80s March Indys. What do you do for replacement rear hub / CV bolts? The ones that go through the hubs and CVs, and have the drive/locating pins on the outboard end.

Scott

[psc85c]

Based on the Vasco Data Book (1965) there are some differences between H11 and Vascojet 1000:

Vascojet 1000 has:
more carbon (0.40% vs. 0.35%)
more Vanadium (0.50% vs. 0.45%) than H11 (at least Vasco's version)

I cannot imagine that March would have used this exotic (read: expensive) steel over H11 or SAE4340 if there wasn't some specific need.

Scott-

In the Vasco data book, they claim that Vascojet 1000 has a 10-35% gain in fatigue life compared to SAE4340 for a given tensile stress. That seems to be the point of this steel.

Before he died, Roger Mitchell had a somewhere around 200 of the rear CV thru bolts amongst all the other March stuff he had. I have no idea where all that stuff went to. Ken Petrie might know.

I suspect you are going to have to have them made. Andy has the drawing but there are differences between the years. The hex is broached and they were heat treated and shot peened as well as tested for hardness so they're not simple to make. I suspect you need access to someone that specializes in high quality fasteners to make them.

March was charging $44.96 each for them in 1985.