have you ever worked on your rx7 around the suspension? have you noticed some bolt heads are staped with a number, say 8 or 10. What does that indicate? does it mean it's class 8.8 and class 10.9 respectively? Or does it mean grade 8 SAE and grade 10 SAE (note grade 10 sae doesn't exist).

 

I assumed it meant 8.8 or 10.9. I bought my 2nd gen when it was 9 years old, Carfax said it was owned by three different people before I bought it, I found sae grade bolts all over the car, most of which I upgraded to the 10.9 in metric.

 

std metric system says.



Metric convention is usually 10.9 wherein the 10 indicates 10x100MPA tensile strengh, and hte 9 right of hte decimal indicates yeild strength of .9 x(10x100MPA) is it's yeild strength

 

It's pretty imperative that this bolt be correct. I'm trying to replace the two bolts that hold the ball joint to the lower control arm, if that fails the ball joint seperates, and you would most likley crash. At this point you hope to hell that the steering knuckle can be held on by the shock, else the wheel will go flying.

 

If you need those bolts, I can pull them off my parts car. I you could yank some from a junk yard. I rather do that knowing they're for that specific part, rather then risk buying & installing the wrong bolts. Plus I'm cheap.

 

I would rather buy new bolts instead of re-using critical high strength bolts. Part of the process of installing critical bolts is to slightly stretch them so that the tension creates the correct clamping force. This action causes the bolt to weaken if it was re-used.

 

So how often are you supposed to change those bolts then, every time they're removed?

 

[quote name='Baldy' date='Apr 4 2005, 08:43 AM']So how often are you supposed to change those bolts then, every time they're removed?


[/quote]



Theroretically yes, all nuts, bolts, and washers that are critical are suppose to be replaced each time they are removed.



Spring washers should be subsituted with lock nuts that have a form of locking device such as nylock or oval locks. In areas where this is not possible loctite of sufficient grade shall be used.



When torque fasteners down, the applied torque should be done in stages to reach a final torque.

 

Those numbers are definitely referring to bolt hardnesses, there are 4 main metric grades - 4.8, 8.8, 10.9 and 12.9 where 4.8 is mild steel, 8.8 is heat treated and 10.9 is high tensile alloy. I don't know much about the 12.9's. If I was to walk into a shop to buy some bolts, 99% are 8.8 grade, and the high tensile hex head ones are usually 10.9 - I have no idea what way they work it in America, so that's the best way I can put it. HTH.



Mark

 

I wishes i had your brain powerses so i knew all that crap