8 replies to this topic

[T Murray]

We recently upgradeed to a better car and as we were going through it found that the left rear swaybar had been disconneted and the link ty wrapped off. Is the bolt used to connect the link to the sway bar a particular type or can i purchase a replacement at the parts store.

Thanks TM

[dstevens]

I just measured the stock bolt that came off my car. It's a 10mm x 50mm long. The stock bolts have a hex washer head (Mazda calls them flange bolts)but you could do the same thing just s easy with washers. Personally when I replace OE bolts with non OE equivalents I use Grade 8 though a Grade 5 would work just as fine. The Mazda part number is 9978-41-045.

Dave

[Johnny D]

Grade 8.
http://www.saferacer...?productid=2393

J~

[T Murray]

Thanks for the info

TM

[dstevens]

Metric hardware would be classed as a 12.9 or 10.9. Depending on where you shop you could find them in the "Grade 5" or "Grade 8" section.

[Rob Gibson]

Two things. First, is it a stock end link? If so, OEM will work, but if it's aftermarket, measure the ID of the end link to make sure you're getting the right diameter bolt, otherwise you'll end up with slop which partially defeats the purpose of a sway bar. Our rod ends are 3/8" ID (one of the few SAE fasteners on the car) because I can get replacements locally and cheap.

Metric hardware would be classed as a 12.9 or 10.9. Depending on where you shop you could find them in the "Grade 5" or "Grade 8" section.

Second, Grade 5 is the rough equivalent of metric Class 8.8. Grade 8 is equivalent to Class 10.9. Class 12.9 is overkill for virtually ever fastener on a car, and for those fasteners where it's not overkill, I'd either use OEM or a purpose built aftermarket replacement (i.e. ARP fasteners).

[davew]

Depending upon what brand of link you have will determine what type of bolt you need.

My links use metric rod ends, so you need metric bolts. The oem bolts used from 90-97 work perfect. Some other brands use 3/8 bolts.

In theroy, you should not use a hardened bolt (grade 8 or metric 12.9) in a shear application. They are strong yet brittle. So when pushed, they are more suseptical to breakage. Probably not in this application as the shear forces are not that strong. Yet many people use the wrong fastener for the job. And pay too much money for them.

Over the last few years, I have changed my opinion on the use of factory bolts. I used to use whatever was convienent. When I have 15 cars at the track, uniformity is important. I try very hard to use factory hardware, so I can use the same size wrench on every car. Even the jam nuts on my sway bars are sourced to be 17mm, just like many bolts on a Miata.

Dave

[dstevens]

In theroy, you should not use a hardened bolt (grade 8 or metric 12.9) in a shear application. They are strong yet brittle. So when pushed, they are more suseptical to breakage. Probably not in this application as the shear forces are not that strong. Yet many people use the wrong fastener for the job. And pay too much money for them.

That is not supported by engineering data although many mistakenly think this. In most every application, specifically any app in which we would use said fasteners, a Grade 8 will have better shear, tension and yield strength. Shear is typical 60% of tensile. I'll spare everyone the math details but in cases of a like size fastener, a Grade 8 will always outperform a Grade 5. In fact, Grade 5 will likely fail tension before Grade 8 reaches it's yield. Fasteners below 180 ksi tensile are typically not considered "brittle".

For example using a nominal 1/4" fastener, Grade 5 has a 3683 lb shear strength. That same fastener in a Grade 8 would shear at 4468 lbs. The cost difference between the two is pretty nominal for the quantities we use is pretty minimal. I buy them from the local Grattan distributor for a lot less than I get cheapies at the big box. I do agree with the consistency of using the same hardware. I just spent about 500 bucks on Mazdaspeed hardware for the sub frames, suspension and misc other fasteners that I couldn't find suitable replacements for.

For those that want a more meaty explaintion, Marks’ Standard Handbook for Mechanical Engineers is good as is Machinery's Handbook

[ndrewoods]

We recently upgradeed to a better car and as we were going through it found that the left rear sway bar link had been disconneted and the link ty wrapped off. Is the bolt used to connect the link to the sway bar a particular type or can i purchase a replacement at the parts store.

Thanks TM

Personally I would go for Grade 8. However, Grade 8 isn't necessarily better either. It might have a higher tensile strength but it is more brittle. While the Grade 5 might bend before the Grade 8 does, I believe the Grade 8 will have a greater tendency to snap. That's how I've known it for the past couple years, but not sure if I'm correct though.