Last modified: 2026-01-23 22:20:40
< 2026-01-22If one front wheel has the entire weight of the car on it (cornering hard while braking in a dip in the road?) and you are full on the brakes and it's a particularly grippy day and everything is aligned and we're decelerating at 1g. And the car has 2 heavy occupants so weighs 450 kg in total.
Then our braking force is 4500 N.
And if the wheel outer diameter is 660 mm then the torque on the front wheel is 1500 Nm.
And if our bolts are at 80mm PCD then the bending force on the 6 bolts is 37.5 kN, or 6.25 kN per bolt.
The yield strength of a grade 8.8 M8 bolt is 640 MPa. And the Young's modulus of steel is maybe 200 GPa.
If the bolt spans a gap of 100mm, how much does the bolt bend? And does it break?
So we have a (let's say) 7.5mm diameter steel rod, 100mm long, with 625 kg hanging off the end of it.
Without doing the calculation: yeah I think it breaks. So we definitely want the spacers.
I've cut these out:
I've stopped short of welding them because I don't want to weld them at the wrong angle and I don't have a good way to set the angle.
I think the plan is to 3d-print a jig that I can clamp to the tube to hold it at the right angle and then use it to tack them all, compare them, and then weld properly if they look good.
< 2026-01-22