My last track day with the upgraded wheel and tire package showed that my alignment for the factory tires was not enough to handle the extra grip of the new Bridgestone Potenza RE-71RS tires. So, I went to add more camber using shims with the E-Motion Engineering control arm parts, but I ran into a snag. The rear toe links, which are NOT E-Motion Engineering parts, use a crappy 12-point fastener that stripped. At the time, E-Motion Engineering (which is now Paradox Performance), supplied a readily available aftermarket option which looks to be the same as the Tarett Engineering part. Because I couldn’t adjust the rear toe, I had to put the camber back to what it was and put off doing any more track days until I get this fixed. So, I tackled a few other items to improve performance, ease of maintenance, and reliability.
I was able to get the other three screws out (two screws per rear toe link). I bought some stainless steel T30 torx head fasteners and I used anti-seize on them. With the torx head, they can take all the torque and not strip. Proper fastener selection is critical. On Paradox Performance’s front toe links, they use a beefy hex head fastener instead of these fragile 12-point head fasteners.
The button head of the updated torx fastener just fits in the counterbore of the rear toe link. While I had the car up in the air, I decided to tackle a bunch of smaller mods and maintenance.
Often times, a drive up in the canyons results in a frontend covered in bugs. The Radiator Grill Store center grill does a good job of stopping many of them. The bugs that do get through have been significantly reduced in speed, so at least they are not rammed into the center radiator. If you recall, the center grill is held on by 3M tape.
I use a pick and a Fanttik vacuum to get the bugs out as my standard operating procedure.
3 comments
Dunno if I would have used stainless on a suspension bolt, they are like grade 2. 30-40% weaker than steel.
This depends on the grade of stainless – 80 grade stainless is roughly equivalent to grade 8 carbon steel.
Gr 8.8 carbon, yield @ 640MPa, min failure @ 800MPa
Grade 80 S/S, yield @ 600MPa, min failure @ 800MPa
Grade 70 S/S, yield @ 450MPa, min failure @ 700MPa
Most stainless fasteners we use (UK) are A2-70 by default, so yield ~75% and fail ~87% of equivalent load for Gr8.8 carbon steel.
80 grade yield ~93% and fail at 100% of Gr8.8 carbon steel load
The point is still valid, especially given the 12-point clearly state they’re 12.9 on the head
The fastener I got off of McMaster is 18-8 with a rated tensile strength of 100,000psi. So about 690Mpa. Where these M6-1.0 screws are used are as pinch-bolts to prevent the tie-rod from rotating, so they aren’t taking much load with suspension loading. The torque spec is 3-4 lb-ft, so basically 5Nm. That translates into about 300MPa stress on the bolt.
That 12-point head was crap. I used both a socket and closed-ended ratcheting 12-point wrench and they wanted to skip. I was lucky to get the three off as they all felt like they were about to skip. And of course, there was the one that did and I couldn’t get it off.