hi,

just looking for a definitive answer on whether a 7/32 inch spacer, or about 5.55 mm, will fit on the stock FC studs? i consider SIX turns of engagement to be the minimum, so does anyone know?


thanks

 

I would personally consider 7 turns as the min. But according to engineering text books 90% of the clamping force is produced by the first 3 threads of a bolt/nut combo on a purely theoretical stress analysis stand point. In practice things are different, in reality each thread is slightly different, meaning the stress on each thread isn't equal due to manufacturing tolerances and wear.

What happens when a bolt and nut start to fail is that the first thread will fail, then the 2nd and 3rd threads bear the loads. If the 2nd fails you are going into the wall.

In general if you can torque the nut/bolt combination to it's maximum rated torque allowed for that diameter bolt and thread it SHOULD not fail under normal operational conditions. Because the normal operational condition stress is a fraction of the stress due to the slight elongation of the nut/bolt during assembly to it's recommended torque (bolts stretch, ie preload, that is how they work).

As an engineer I almost always go with I want atleast 1 thread showing after the bolt/nut is torqued to spec. This ensures 100% that the bolt should not fail under normal operation unless I spec'd the class of nut/bolt/washer wrong.

 

I have read this too, but agree that in this instance - especially since the force is not static - that 3 threads isn't adequate.


I totally agree.

Could you not find some longer studs?

 

i also agree with you Cheers. i would prefer 7 threads, but 6 is the minimum i am considering.

now the thing is that i don't have a spacer around to test this out with, and time and money are a little short. i'm just looking to see if anyone has put this size of spacer on safely with the stock FC studs...

as for the studs, i would rather not get new studs if there is a safe amount of engagement. but if i must, then i must.

another thing i am wondering about is if anyone knows where to get a spacer that is smaller than 7/32 inches, or less than about 5.5 mm? a 4mm spacer would be perfect i think.

 

i have found some 3/16 inch spacers, or about 4.8mm.
anyone know if i will get 7 turns engagement with this size spacer? i have also heard the back studs are slightly shorter, i haven't checked that out yet.

 

You can calculate it can't you? the thread pitch of the bolt/stud is M12x1.50mm. Measure how much of the bolt you have with the stock tire on. subtract the thickness of the spacer from the depth you measured

The pitch determines/defines the distance between each major. so 7 turns is 10.5mm of stud. Do you have 10.5mm + 4.8 mm of stud showing when you have a tire on the wheel? don't forget to account for the thickness of the wheel (ie the part that contacts the brake hat).

so total stud needs to be 10.5 mm + 4.8mm + thickness of wheel.

good luck.

 

would i have asked this question here if i was just going to go and calculate it myself

anyways. i can't get a specific measurment on the wheel thickness because i don't have the proper lug nuts for them yet, and i don't know for sure where the lug nut will seat.
butmy measurments give me between 12 and 20 mm. so let's say the max total is 10.5+4.8+20 = 35.3 mm

now as for the exact length of the stock studs, i know the fronts are 2 inches, but all i have heard about the rears are that they are half an inch shorter.

so stud length in front = 50.8 mm
rear (if 1.5 inch) = 38.1 mm

now this SEEMS to make sense, but is the stud 2 inches from the hub or 2 inches total?
because what you said did not account for the part of the stud that is in the hub, so i am just curious...