Street bumper mounts

[wkooiman]

I'm switching from quick jacks to street bumpers.

I have the street bumpers, but I don't have the mounts (bolts/sleeves). The quick jacks take larger threads.

What do you guys use for bolts/sleeves? Do I need to call a vendor, and if so, who has them?

My only alternative right now is all thread from Home Depot. I'd like something more solid.

[DanEC]

I would think that Finish Line or Acton industries would have a mounting kit for bumpers. I'm not sure how universal the bolt size is on all the various chassis makes.

His is a link to Finish Line that shows the tubes but not the all thread bolts.

Search - bumper

All thread can be sourced pretty easily at a hardware store.

[mickmate]

You can get a high tensile threaded rod from Mcmaster, do your over riders have the 7/16-14 thread? Then you just need to make the sleeve tubes the right length for the body standoff. Heavy wall aluminum tube works well in whatever finish you desire. Stainless tubes are available from our pals at Finishline Bumper Sleeves, Front Let me know if you need something special.

[wkooiman]

Thanks guys.

I think I can reuse the sleeves from the quick jacks.

The quick jacks had high carbon all-thread, but they are 7/16" (I think). They are larger than the over rider bumpers.

I can get all thread from Home Depot, which I will probably do while I wait on what I need from McMaster Carr. I feel weird using something soft for the bumpers. I suppose it doesn't really matter. The bumpers are mostly for looks anyway.

[DanEC]

I would go with something of medium strength (similar to grade 5 bolts). High strength - grade 8 stuff is more brittle and you want something that will take a hit and deform a little rather than shear off.

[mikeinatlanta]

Originally Posted by DanEC

I would go with something of medium strength (similar to grade 5 bolts). High strength - grade 8 stuff is more brittle and you want something that will take a hit and deform a little rather than shear off.

The above statement is 100% untrue and nothing but an internet myth, however, even an ungraded bolt will be stronger than your bumpers so I would worry more about fit than bolt grade. Mcmaster has a wide range of sleeve materials from aluminum to stainless and in a range of wall thicknesses to suit the look you want.

In the case of my bumpers, they are made from 18 gage cold rolled and the mounts are 18 gage hot rolled. The whole mess can be moved by hand and even an aluminum bolt is stronger than the bumper and mount.

[DanEC]

Originally Posted by mikeinatlanta

The above statement is 100% untrue and nothing but an internet myth, however, even an ungraded bolt will be stronger than your bumpers so I would worry more about fit than bolt grade. Mcmaster has a wide range of sleeve materials from aluminum to stainless and in a range of wall thicknesses to suit the look you want.

In the case of my bumpers, they are made from 18 gage cold rolled and the mounts are 18 gage hot rolled. The whole mess can be moved by hand and even an aluminum bolt is stronger than the bumper and mount.

I agree that an ungraded bolt (Home Depot all-tread) should be sufficient for this application. But since it was suggested that he go to Mcmaster for some "high tensile strength" rod - I felt there was no need to go overboard on high strength - grade 8 material. Yes, the issues of Grade 8 brittleness are primarily related to continuously stressed applications where work hardening can lead to brittleness versus where a Grade 5 will yield and deform instead. I'll give you that it isn't an issue with a bumper bolt that isn't exposed to cyclic loading.

[mikeinatlanta]

Originally Posted by DanEC

I agree that an ungraded bolt (Home Depot all-tread) should be sufficient for this application. But since it was suggested that he go to Mcmaster for some "high tensile strength" rod - I felt there was no need to go overboard on high strength - grade 8 material. Yes, the issues of Grade 8 brittleness are primarily related to continuously stressed applications where work hardening can lead to brittleness versus where a Grade 5 will yield and deform instead. I'll give you that it isn't an issue with a bumper bolt that isn't exposed to cyclic loading.

Once again, you statement regarding grade 8 vs grade 5 is completely false. Feel free to substantiate.

[brettco]

Well i know what he means. I have over 20 years in sprint car racing and have seen way more grade 8 bolt faliures where a bolt breaks and im not sure ive ever seen a grade 5 bolt break. Over analyze that statement all you want but ive lived it.

[DanEC]

Material Grade

" Harder bolts tend to be more brittle and may fail in specific applications."

Grade 8 bolts are treated to additional hardening processes. But it all depends on the application.

At least I think we agree that higher strength rods are unnecessary in this application.

And now my engineering degree and I have to catch a flight.

[mikeinatlanta]

Originally Posted by brettco

Well i know what he means. I have over 20 years in sprint car racing and have seen way more grade 8 bolt faliures where a bolt breaks and im not sure ive ever seen a grade 5 bolt break. Over analyze that statement all you want but ive lived it.

The number of years that you have gone in circles on dirt does not equal fastener knowledge.

Originally Posted by DanEC

Material Grade

" Harder bolts tend to be more brittle and may fail in specific applications."

Grade 8 bolts are treated to additional hardening processes. But it all depends on the application.

At least I think we agree that higher strength rods are unnecessary in this application.

And now my engineering degree and I have to catch a flight.

So your contention is that grade 5 and 8 use the same alloy with the only difference being hardness? Or is it that you are contending that a grade 8 has a lower shear strength? Or is it that you are contending a grade 8 bolt will break before it bends? Or is it that a grade 8 will fatigue and fail before a grade 5? Being an engineer, you should have no trouble producing a document to substantiate as opposed to waiving your degree. Were not talking about generic statements regarding heat treat and brittleness, specifically grade 8 vs grade 5.