Longer Diff bolts for BMS brace ?

[AusStinger]

Don't know why but I can't seems to search any more ( or upload pics ).

My question is, does anyone know what the bolt specs are for the 4 bolts that bolt the new thicker BMS diff brace to the diff ?

I'm going to install one for a person and I'd like to get some longer bolts.

TIA.

 

[socalvn]

I don't know the size but grade 8 is as strong as you can get

 

[BIG-D]

Hey Scott, mine came with bolts supplied bro?

 

[BIG-D]

Fixed!

 

[AusStinger]

The one I'm installing is 2nd hand but there were no bolts apart from the 4 big ones

Don't worry D. Just thought someone might know off hand.

I'll climb under and rip one out of mine and figure it out.

Cheers.

 

[Thomby]

I don't know the size but grade 8 is as strong as you can get

There are bolts above grade 8 in SAE, and metric equivalents like 10.9 and 12.9 (first number being tensile strength in hundreds of MPa, and second being yield strength in percentage of tensile, ie 80/90%).



In @BIG-D's pictures below, the ones on the car are marked with an 8, but the ones in the bracket on the desk look like they might have a double digit metric class marking...maybe he can confirm.

View attachment 89681

View attachment 89684

 

[BIG-D]

Here ya go brother, the bolts supplied are 1/2' longer in the shank the thread is the same count...

 

[Thomby]

Here ya go Scott the bolts supplied are 1/2' longer in the shank the thread is the same count...

And obviously grade 10.9, which after a quick browse is closer to SAE grade 8.

 

[BIG-D]

Decided to remove mine while I was under there... my diff bushes look like new haha.

 

[BIG-D]

I reused 2 of the original diff bolts to attach the rear bracket to the cradle I didn't trust the 2 shiny ones supplied with the kit would have been strong enough ?

Oh well

 

[Thomby]

I reused 2 of the original diff bolts to attach the rear bracket to the cradle I didn't trust the 2 shiny ones supplied with the kit would have been strong enough ?

I've noticed a bunch of the Kia's bolts have an 8 stamped on them. I don't think that's a standard marking for either SAE grade 8 (which it would be odd for them to use as Koreans), or a metric grade (which should be follow the #.# convention).

But I can't imagine what else it would be. If it's metric 8.8 then those 10.9s are something like 1/3 stronger, and if it's SAE grade 8 then your metric 10.9 is roughly equivalent, I think.

 

[95oRANGEcRUSH]

So what is the consensus, good and/or bad, on the diff brace for a stock AWD Stinger GT2? Mine is merely a daily driver, no drag strip or track use, with 27k in almost 4 years of ownership.

 

[BIG-D]

It eliminated wheelspin in my rwd for sure...

But I have fitted lighter wheels and wider tyres and just recently something hasn't felt right?

Can confirm she is back to her awesome self and spinning wheels again *sad face*

Can't post emoji's for some reason?!!!

 

[AusStinger]

Decided to remove mine while I was under there... my diff bushes look like new haha.

View attachment 89709

View attachment 89716

Thanks mate.

Disregard. Just read above.

 

[BIG-D]

It's a great mod for sure... I just am not racing my car anymore...

 

[BIG-D]

Day 3 not having the brace fitted... wheelspin is an issue so YES it works !!

Peace

 

[AusStinger]

I would have thought the brace would have made the wheels spin more ( but stop wheel tramp ). Oh well, learned something new today...

 

[Thomby]

I would have thought the brace would have made the wheels spin more ( but stop wheel tramp ). Oh well, learned something new today...

I understand the logic: more slack/flex in the drivetrain absorbing torque so it doesn't yank the tires so abruptly. In Top Fuel dragsters, the wrinkle wall tires "wind up" and soften power delivery.

But here I think the diff brace is more like cars with worn suspension bushings that experience wheel hop: as the tires slip and grip, the suspension or subframe shifts relative to the car, and the actual weight/force applied to the tires modulates.

When you install new bushings (or bolt the diff in place), you tie the drivetrain back to the chassis, and keep more even weight/downforce on the tires.