Loose Wheel Stud(s)

fastsc92

Registered User
Long story short...

I machined my rear hubs to a 5 x 4.5" bolt pattern and a few of the studs don't seem to be fitting as tight as I'd like them to. They go in snug, but not too tight and generally can be tapped out with a hammer with little effort. I don't expect them to hold up to years of service and I'd rather address these now while everything is clean and out of the car.

These holes were machined, drilled with a 39/64" bit and then reamed to 0.620". Knurl dia. is 0.627" It's either these studs are soft, or the holes just arent as round as I expected them to be (which they should after I reamed them...). Short of starting over and machining new holes in another set of hubs, what's the best way to fix these? Granted I just pressed the hubs into the knuckles with new bearings. I'd like to avoid pressing them back out and destroying $100 worth of bearings.:rolleyes:

Any ideas?
 
Since these are already installed in the bearings/knuckles, I may just add a small tack weld with the tig. There is enough room on the backside that if I ever needed to get at them I could just grind the tack away and press these out like normal.

I went by ARP's recommendation for interference fit but I'm wondering if I should have gone tighter. The stock wheel studs look like they have a much heavier interference fit...something in the .013" range. I just banged out one of the studs that was "loose" and the hole is measuring in at exactly .620", giving a .007" interference fit. I'm thinking that these replacment studs just might be soft around the knurle area and are yielding rather than creating a tight fit. These are just Dorman replacement studs for 99-04 Cobras.
 
I'm guessing ARP's recommendation is for their studs and would be specific to the amount of knurl and type of material their studs are made from. Doesn't help now, but you probably needed more interference than that. Did you measure the old holes?

If you weld them, be sure to do more than just tack them in place and weld them with the lugs tight because if they do break loose later and spin - well that really sucks. I've had to deal with that before and it's no fun with the wheels on the car and a stud spinning in the hub.
 
I'm guessing ARP's recommendation is for their studs and would be specific to the amount of knurl and type of material their studs are made from. Doesn't help now, but you probably needed more interference than that. Did you measure the old holes?

If you weld them, be sure to do more than just tack them in place and weld them with the lugs tight because if they do break loose later and spin - well that really sucks. I've had to deal with that before and it's no fun with the wheels on the car and a stud spinning in the hub.

The old holes for the orignal studs measure in around .588"-.590", yielding a .017" interference fit. Dang, now I'm questioning whether it's worth it to machine a new set of hubs with a tighter fit. This would of course mean detroying these new bearings in the hubs and starting all over again...essentially tossing away $100:mad:

Weld em or start over?
 
The old holes for the orignal studs measure in around .588"-.590", yielding a .017" interference fit. Dang, now I'm questioning whether it's worth it to machine a new set of hubs with a tighter fit. This would of course mean detroying these new bearings in the hubs and starting all over again...essentially tossing away $100:mad:

Weld em or start over?

I'd get better studs. You are going to be changing tires/wheels often so the value of a better stud will pay for itself in time. Plus you can probably get them a bit longer.
 
I'd get better studs. You are going to be changing tires/wheels often so the value of a better stud will pay for itself in time. Plus you can probably get them a bit longer.

I can get ARP studs in 3" length w/ a .625" knurl, but I was worried that they would be too long to fit under closed-end lug nuts, which is why I opted for stock-length.
 
.017 interfernce is huge. I doubt yours are .007 if you can tap them out with a hammer, at work if we have just a .0003 we must use and arbor press to get it out ( our spec is <0.0005 clearance). Though I do suspect our shaft stock and bearings are significantly harder than hubs/studs.
 
.017 interfernce is huge. I doubt yours are .007 if you can tap them out with a hammer, at work if we have just a .0003 we must use and arbor press to get it out ( our spec is <0.0005 clearance). Though I do suspect our shaft stock and bearings are significantly harder than hubs/studs.

I'm quite certain that the stock interference fit is nominally .017" and that the fit that I developed is .007". I physically had to press out the stock studs with a 12 ton press to get them out. The fit that I generated requires a swift blow with a hammer to get them out. It takes some force but not nearly as much as the stockers which is why I questioned their integrity. Keep in mind that the interference fit between knurled surfaces is much different than that of a dowel pin/shaft. As a seasoned mechanical engineer, I'm well versed in precision fits on a wide variety of applications. I think the issue is that the stud material is softer that I expected. I followed what ARP recommend for their studs in steel, after I was having a hard time finding a spec with what I should be using for stock-style studs.

I wasn't happy with the shaft diameter bearing fit due to wear/fretting on one of the hubs so I'll be machining a replacement for that one anyhow and I'll adjust the tolerance for something tighter and closer to the stock fit. I wanted to avoid pressing out the hubs just to not trash these brand new bearings...but in the end....I guess machining another set of hubs may be my best bet. $60 in bearings is worth the savings in frustration if these were to work loose in the future
 
I would just purchase a stud with larger knurl. Like Dave said, its gonna suck if those spin. FTR, I've been using Moroso studs for a long time now and had no issues.
 
I would just purchase a stud with larger knurl. Like Dave said, its gonna suck if those spin. FTR, I've been using Moroso studs for a long time now and had no issues.

I haven't found another set of studs that would fit the bill. These have a .627" knurl. Most other either have a .625" or somewhere in the .680" range. Keep in mind that because these are redrilled hubs, there isn't much meat left and I'm hesitant going much larger than a .625" knurl.

I would go with a 3" ARP stud with a .625" knurl, which would satisfy the fitment condions that they prescribe, however they are only available in 3" length and I'm concerned that they wont be able to fit under closed-end lug nuts. I was hoping to get a stud length such that I can run closed and open lug nuts for the street and track respectively.

I've already started machining another hub (one for now). I've targeted a .017" interference fit, which replicates the stock fitment. I'll see how that goes before I machine the second set.
 
I think i would figure out the length of stud i want and then chuck up the ARP stud and cut it off.
 
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