PSA: Replace/upgrade your spindle and driveshaft bolts for $25!
12-21-2013, 05:04 PM
#1
PSA: Replace/upgrade your spindle and driveshaft bolts for $25! All,
I just measured the stock driveshaft bolts and spindle-to-upper control arm bolts. These bolts have been bothering me for some time, because their threads tend to flatten if you remove them frequently. Here's what I found:
For small (10-20 piece), high-end fastener orders, I've been using (and like) The Bolt Barn on eBay. In general, it's not a good idea to reuse the nuts if the bolt threads have stripped or flattened, so I'd take this opportunity to switch to more common, Grade 10.9 flanged bolts and nuts. Compared to the Grade 8.8 bolts included with the driveshaft, Grade 10.9 bolts have 42% greater yield strength (940 MPa vs. 660 MPa).
When torqued properly, the spindle bolts have 5 threads to spare (see pictures below), meaning that you can use a 50mm bolt if you want (you'll have one or two spare threads). Because there is no practical limit on the length of these bolts, you can order a common bolt for both applications. Since there is no 65mm size that I could find at an economical price, and 60mm is a little bit short for the driveshaft, you could try 10 M12x1.75x70 bolts and 10 M12x1.75 nuts for the entire car, which will give you two spare bolts and nuts (a spare set for the spindles for later). Or you can do like I did and cope with knowing that you're missing 1-2 threads on the driveshaft bolts (mitigated by the higher yield rating of the bolt, IMHO).
Hope this helps!
Above, Bolt Barn M12x1.75x60 and below, GM OEM M12x1.75x55 (both Grade 10.9)
Alternate shot of the bolts. Both have 18mm heads.
GM OEM 55mm bolt, passenger's side. Fully torqued. 5 spare threads.
Bolt Barn 60mm bolt, driver's side. Hand torqued. 8 spare threads.
Slightly different angle.
Simulated thread engagement of 60mm bolt in driveshaft application. 4 threads engaged (2 threads not engaged).
My fingernail marks where the base of the flanged nut is.
Slightly off-angle shot of the same 60mm bolt. This is why I recommend 70mm bolts for the driveshaft, since 65mm bolts are not available. If you want perfect bolt lengths everywhere, you'll want a set of 50mm bolts and a set of 70mm bolts. Here's a sample of what they've got in M12-1.75.
I just measured the stock driveshaft bolts and spindle-to-upper control arm bolts. These bolts have been bothering me for some time, because their threads tend to flatten if you remove them frequently. Here's what I found:
- Spindle/Control Arm bolts: M12x1.75x55 Grade 10.9 (flanged hex)
- Driveshaft bolts: M12x1.75x65 Grade 8.8 (standard hex with washers)
For small (10-20 piece), high-end fastener orders, I've been using (and like) The Bolt Barn on eBay. In general, it's not a good idea to reuse the nuts if the bolt threads have stripped or flattened, so I'd take this opportunity to switch to more common, Grade 10.9 flanged bolts and nuts. Compared to the Grade 8.8 bolts included with the driveshaft, Grade 10.9 bolts have 42% greater yield strength (940 MPa vs. 660 MPa).
When torqued properly, the spindle bolts have 5 threads to spare (see pictures below), meaning that you can use a 50mm bolt if you want (you'll have one or two spare threads). Because there is no practical limit on the length of these bolts, you can order a common bolt for both applications. Since there is no 65mm size that I could find at an economical price, and 60mm is a little bit short for the driveshaft, you could try 10 M12x1.75x70 bolts and 10 M12x1.75 nuts for the entire car, which will give you two spare bolts and nuts (a spare set for the spindles for later). Or you can do like I did and cope with knowing that you're missing 1-2 threads on the driveshaft bolts (mitigated by the higher yield rating of the bolt, IMHO).
Hope this helps!
Above, Bolt Barn M12x1.75x60 and below, GM OEM M12x1.75x55 (both Grade 10.9)
Alternate shot of the bolts. Both have 18mm heads.
GM OEM 55mm bolt, passenger's side. Fully torqued. 5 spare threads.
Bolt Barn 60mm bolt, driver's side. Hand torqued. 8 spare threads.
Slightly different angle.
Simulated thread engagement of 60mm bolt in driveshaft application. 4 threads engaged (2 threads not engaged).
My fingernail marks where the base of the flanged nut is.
Slightly off-angle shot of the same 60mm bolt. This is why I recommend 70mm bolts for the driveshaft, since 65mm bolts are not available. If you want perfect bolt lengths everywhere, you'll want a set of 50mm bolts and a set of 70mm bolts. Here's a sample of what they've got in M12-1.75.
Last edited by FuzzyLog1c; 12-21-2013 at 05:17 PM.
12-22-2013, 12:44 AM
#6
I would recommend getting the longer bolts though as it is best to fully engage the nut. it looks like you have ~3+ FULL threads engaged so the stress distribution should be the same, but still it is not a good practice (as you have already mentioned) there could be a greater opportunity for the nut to rock under vibration (with some Loctite though this probably not going to happen)
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12-31-2013, 04:15 PM
#8
A couple of days ago, I pulled the rear calipers in preparation for my brake system overhaul. Today, my new bolts arrived. Class 10.9 for the upper rear bolt position, and Class 10.9 (same bolt as the previous post) for the lower rear.
The stock bolts are 5mm shorter, but do not go all the way through the caliper. Pics:
The stock bolts are 5mm shorter, but do not go all the way through the caliper. Pics:
Last edited by FuzzyLog1c; 12-31-2013 at 04:22 PM.
