Didn't have a proper tool to measure the ball seat size tho...

 

I think there are a few of you out there using R13 bolts on R14 wheels. This is a McGard 28018 R13 locking lug bolt after 8k miles on an OE wheel. Look at the contact area - that narrow little ring - pretty scary IMO.

 

Here is a pic of a couple of R14 lug bolts for comparison. The one the left is a stock bolt and on the right a RAD 2 piece bolt 36mm shaft. The RAD bolt was installed on an aftermarket wheel so that might explain why the contact area is thinner but it is still in the middle of the arc and not at the bottom as the bolt above.

BH thanks for the idea of posting a pic of the bolt I think it really helps clarify the importance of proper sizing of the lug bolts R14 vs R13.

 

^ Interesting Mort, this is one of those things that you might never think about but whether it's the bolts, the wheels (most likely), or both, I'd expect better from the (higher end) aftermarket.

 

You guys are confusing the radius of the sphere (head) with the radius of the circle where the sphere is cut.

The R13 or R14 refers to the radius of the head sphere. If instead of a 17mm hex head you had the entire sphere (a ball), the first would be 26mm across at the widest point and the other 28mm across.

In either of the above two spheres, you can cut the sphere across at any place and end up with a circle of a different radius. If you cut the spheres exactly in the middle, you would indeed measure 26mm and 28mm diameters respectively, but if you cut them further down (or up for that matter), the actual diameter of the circle would be smaller. If instead of an R13 or R14 sphere you had one that had the radius of a basketball (which is 10" in diameter, so the radius is 127mm), you could cut a tiny slice of the basketball (say, 25mm across) but the radius of the sphere would still be R127. It would look almost flat if you viewed it sideways and you would only see a very slight curve, but the sphere would still be R127, not R25. So - what you guys are measuring is the actual diameter of the widest circle of the bolt head, NOT the radius of the ball itself.

With regard to the picture of the two different bolts showing different wear patters, the second bolt (with the scary thin wear mark)would also look like the one in the picture if it was used on an aftermarket wheel with a taper (60 deg conical) mounting holes. Yes, the radius of the seat on the bolt was different from the radius of the seat on the mounting hole, so the actual "thickness" of the wear pattern is due to deformation of the bolt and the bolt mounting hole on the wheel (it would only touch in a perfect circle if it had not been tightened which caused the bolt head and/or the wheel seat to deform).

 

I just installed spacers, H&R, F = 12 mm, R =10 mm using 40 mm H&R bolts. It looks good, but it is tight with the 245/265 tires, no rubbing but I haven't pushed it or loaded it up yet.

I was concerned about the rear bolts being too long but I could move the wheel no rubbing. I also measured the clearance with a depth mic and it is ~45 mm (conservative) from the bottom of the seat until you hit something (oem shank 26-27 mm and H&R is 40 mm). I also pulled the bolts after driving a bit, no marks/scoring. The H&R sheet does say to be careful with some MB models as there is as little as 2 mm clearance. Torqueq to 96 lb ft per manual. (actually 96 first pass, 98 second pass after driving a bit)


They do give the car more of a 'pitbull' like stance.

 

All good except for the bolt clearance in the hub. It may be 45mm where you measured, but it is only about 2-3mm beyond the length of the OEM bolt - which is 27mm - to the springs that hold the parking brake shoes together (so at that place you would measure approx. 30mm). If the wheels spin freely by hand while you still have the car jacked up, you are fine. Otherwise they will either 'tick' as they hit the parking brake shoe springs, or if they are deep enough to actually hit the edge of the shoe itself, the wheel won't spin at all.

 

I measured it in about 10 places while rotating the wheel.
Particularly at the top and bottom after looking at a parts diagram.
I could actually feel the spring

After driving 20 miles or so I pulled all the bolts (both sides) and no marks/mars/etc.

I'll probably do that again

 

No need to pull them out. If it's touching you would hear it right away.

I got a set of aftermarket wheels and bolts (with four locks) for mine. When I tested the bolts for clearance all was fine, but what I didn't test were the four bolt locks which were only 3mm longer than the rest of the bolts. Put the car down, torqued everything properly and heard a "tick-tick-tick" from the rear as I started to drive. The 3mm longer thread on the wheel locks was enough to hit something on the inside. Swapped the locks with regular bolts and no issue. Eventually ground down two of the locks by 3mm and put them back. So, yeah, it is pretty tight in terms of clearance in the rear.

 

does anyone know how many turns the stock bolts go into the hub? I am thinking if the stock bolts are 1 inch or 25.7mm and the back pad of the stock wheel is at least 1/2 inch or less, that leaves only around 1/2 inch of bolt that actually has threads going into the hub. Based on the number of threads that would leave at 12mm's we're only talking of around 7-8 turns.

The reason I am asking is because I got a set of new aftermarket wheels and the stock bolts are too short, so instead of focusing on how many turns are needed on the bolt to consider it safe and secure, I'm trying to compare how much bolt and threads should be into the hub to be considered as safe as the stock setup.

If stock setup only gets around 7-8 turns then we're on the border of what others consider the minimum amount of turns, and the bolt lengths have to be exact when changing the setup because too long and you damage the ebrake assembly in the rear.

so maybe someone can answer two questions for me if they know
1) what is the true safe minimum turns for bolts on this car
2) how many turns is the stock c63 lug bolts and I hear you can only do 1.5 additional turns more than stock because there's less than 3mm room to play with.

 

To be safe, you need a minimum of 7-8 threads (i.e. full turns) to be fully engaged. The OEM bolts - M14x1.5, R13 ball seat, 26.7mm shank - with OEM wheel pad thickness have about 8 turns as you mentioned (1.5mm thread pitch, so with 0.5" or 12 mm sticking out you get 8 full turns). Yes, you only have 2-3mm clearance in the rear - or 1.5 turns at most - until the bolts start touching the brake mechanism in the hub.

 

I can't answer how many turns is safe but try for a minimum of 7.

The stock bolt has a 27mm shank I believe and the stock number of turns is 7-8. 8 turns * 1.5mm pitch = 12 mm. Looks like your math is good. You should be good with bolts that protrude 12mm through the bolt holes without fear of fouling the e-brake mechanism on the rear. If you go any longer then test fit them and a 3mm allowance is about as far as you should go on the rear.

 

thanks for the feedback from you both. you mentioned my math is good, it is just because I've been trying to figure this out the past week and I've approached from all angles to get this right. I got a set of used carlsson wheels that didn't have the bolts with them so I've been dumbfounded since I tried to mount them and the stock bolts only had 2 turns when trying to bolt them to the car! I then got 40mm bolts and they hit the back of the brake assembly. I cut down to 33mm and now I only get 5-6 turns.

So between 40mm hitting the rear brake assembly and 33mm only being 5-6 turns I figured either the stock setup is exact or the 3mm clearance allowance you mentioned above stock tells me I'm 1mm a tad over and 37mm or 38mm is the proper length for my setup. To play it safe I got 35mm bolts, but that would put me only at around 6-7 turns.

 

this^

general rule of thumb
you want the bolt in as deep as it is wide (shank)
in this case 14 mm - 1 mm thread ~13 mm
pitch is 1.5 mm or it travels in 1.5 mm per turn
13/1.5 = 8.5 turns


H&R also has a not that tells you the same
d) Safety guidelines
(Minimum number of turns for wheel bolts / nuts):
M12 x 1.25 = 8.0 turns = approx. 10 mm of load bearing shaft length
M12 x 1.50 = 6.5 turns = approx. 10 mm of load bearing shaft length
M12 x 1.75 = 6.5 turns = approx. 12 mm of load bearing shaft length
M14 x 1.25 = 9.0 turns = approx. 12mm of load bearing shaft length
M14 x 1.50 = 7.5 turns = approx. 12 mm of load bearing shaft length
1/2" UNF = 8.0 turns = approx. 11 mm of load bearing shaft length

 

The stock setup is pretty exact, with very little extra room in the rear. If they are proper tempered steel (not cheap Chinese "look-at-me-aren't-I-pretty") bolts - look for a "10.9" marking on the heads - you should be OK with 6 full turns. Make sure that you buy the proper seat type for your specific wheels. I have found this to be the most overlooked issue when people buy aftermarket rims. An R13 head is not going to properly clamp and distribute the pressure in a wheel with an R12 or a conical seat, which can make the bolts snap.

 

would you happen to know whether this length applies and should match to the full amount of threads inside the hub to attach to? Because it looks like the threads inside the hub is less than 13mm, since the first 5mm looks to be without threads if you look in the hole.

going back and calculating the stock 1 inch 25.7mm shank bolts is about 10mm used for the wheel, 15.7mm left going into the hub, I wonder how much threads are in the hub for accepting the lug bolt. My reason in asking this now is whether the turns are more important or the number of threads holding onto the bolt. Because obviously excess threads that go beyond the hole inside is useless, since it is as good as chopping off the excess on the tip and will have no bearing on load distribution.

 

we have to assume the female threads have sufficient engagement
I'd be surprised if were less than 8 turns (12 mm), but who knows

the lugs also clamp the brake disc

looking at a couple of spindles they look at least 1/2" >12 mm
so a few turns past that should be more than enough
each bolt has ~10 kip clamping force

 

By turns I (and I suspect we all) mean fully engaged, load-bearing turns. One full thread is equal to one turn regardless of the thread pitch. What varies based on the thread pitch is the depth that the specific bolt will travel during that turn.


On the C63 there are about 7 full turns that are engaged at both the front and rear, so some 10.5 mm length-wise. I got a set of black wheel bolts to use with my wheels, and whenever I change the tires I can see the portion that is actually in contact with the threads on the hub as the black coating is partially worn out. There is only about 1 to 2 mm at the end of the bolts that is not engaged (i.e. floating in air) followed by about 10 mm of wear markings on a bolt that protrudes about 13 mm past the wheel mounting hub surface. That only leaves about 2-3 mm at most of unthreaded space in the bolt holes measured from the front of the hub.

 

i had some forgestar wheels on my car and bought the appropriate (i'm assuming anyway) conical bolts. i then bought a set of adv.1 wheels from someone and emailed adv.1. they said that i could use the oem lug bolts. i put them on yesterday and got about 6 turns total. is this safe? you guys are talking about like 8 turns and i'm not really close to that. anyway to verify that my wheels are on safely?

 

No one can verify that...I wouldn't do it. And by the way there seems to be recent reference to R13 ball seat as OE spec bolt. It's actually R14, big difference.

 

where can i find some black lug bolts?

as far as i can tell, i need:

m14x1.5 27mm shank r14 ball seat

can't seem to find black ones anywhere though.

 

actually I am surprised at how much clamping area of threads for the bolts on the female side of the hub are. I think there are less than 8 turns on the factory bolt, because I had 32mm bolts that turn 5 times, now I put 35mm bolts and it hits parts behind the hub.

Look at the pic and count the threads. Something is not right about this.

 

I got mine from ACG along with some black wheel locks.

 

To clarify: are the OEM Wheel Bolts R13 or R14 Ball Seat (for a 2012 C63 with OEM 19" Multispoke turbine style wheels)?

 

The definitive wheel bolt thread for the C63:

https://mbworld.org/forums/c63-amg-w...ze-length.html

(it gets interesting around post #7... my contributions are further down on page 2).

OEM bolts - for the OEM wheels - are M14x1.5, R13 ball seat, 26.7mm shank.