Stainless Bolts in Aluminum - Crankcase

[Sam 78 GS750]

Can anyone help me interpret this web page here? https://alloyboltz.com/conditions-of-use-torque-information/

About to tackle reassembling crankcase halves. I bought all stainless allen head bolts from AlloyBoltz. I've found all kinds of info on the web, and a few posts on the forum here... It seems there's a lot of heated debate about this, with some even saying that you should just torque to spec.

Not trying to start a thing here. I just want to follow the bolt manufacturer's recommendations. I could call, but they're closed now and I don't want to wait til Monday (really that would mean waiting until next weekend for me).

The manual calls for 14.5 ft/lbs for the 8mm bolts, and 7.2 ft/lbs for the 6mm bolts on the crankcase halves. From the chart in the link above, it looks like I would use 0.7 ft/lbs on the 8mm and 4.4 ft/lbs on the 6mm bolts

OR I would use 20 ft/lbs on the 8mm and 8 ft/lbs on the 6mm.

Neither of those seem right to me...

 

[fastbysuzuki]

Well good luck with interpreting that chart it's about as good as saying if you bugger up threads don't complain to us.

 

[Nessism]

I think the reason they recommend less torque is because they recommend lubrication on the threads, which provides a higher effective torque.

That .7 recommendation for the M8 looks wrong. Not sure what they are referencing since 7 (ft-lbs) is too low and 17 too high.

The 4.4 number for the M6 bolts seems about right. Be sure to convert the torque values to in-lbs and use small in-lb torque wrench.

Oh and BTW, A2 bolts are weaker than the OEM Suzuki bolts. The OEM bolts have a "7" number on them which is similar to SAE Grade 5 and/or Metric 8.8

 

[Steve]

Personally, I think the 0.7 number for the M8 bolts is a mis-print, it should probably be 17.0. :-k

Not sure whether I would use stainless bolts to hold the crankcase together, though. Yeah, it's not as stressed an application as the brakes or suspension systems, as they warn against, but I think that I would use OEM bolts on the structural parts and just use stainless to hold on the covers.

The torque numbers might be OK for the slightly stronger bolts, but they are still going into threads cut into the relatively soft aluminum, so I would stick with OEM torque specs.

.

 

[Agemax]

Stainless bolts work just fine on crankcases, torque to manufacturers spec.
Had s/s bolts on my crankcases and almost everywher else on my GS and hasn't caused an issue in years.
Just be sure to smear a dab of anti sieze on the threads before installation.

 

[Guest]

Not trying to start a thing here. I just want to follow the bolt manufacturer's recommendations.

You should be following the Suzuki specs exclusively. Suzuki engineers chose the bolt size and preload (torque) that was required for the application. It doesn't matter what the bolt manufacturer recommends, if their bolts won't survive the necessary preload as per Suzuki then you need different bolts that will.

I think that I would use OEM bolts on the structural parts and just use stainless to hold on the covers.

That seems the most practical to me as well.

Just be sure to smear a dab of anti sieze on the threads before installation.

The problem with using anti-seize is it renders the Suzuki torque specs invalid and will result in a much higher preload force on the connection. Whether that causes a problem or not I can't say, but I guarantee all of your bolts were stressed much more than Suzuki intended.


Mark

 

[Nessism]

It's not possible to follow the Suzuki torque specs because stainless hardware must have antiseize on the threads which increases torque. You have to knock down the numbers a little.

 

[Sam 78 GS750]

It's not possible to follow the Suzuki torque specs because stainless hardware must have antiseize on the threads which increases torque. You have to knock down the numbers a little.

This makes sense...

I ended up torquing the 8mm bolts to 150 in/lbs and the 6mm bolts to 75 in/lbs. That's about a 15% reduction in the specs from Suzuki, which should account for the anti sieze. I'm pretty confident about it.

I'm just hoping it doesn't leak on me... this is the first time I've assembled a crankcase. Pretty sure I did a good job with the sealant though. Guess I'll see when I pour the oil in and fire it up for the first time. ray:

This is pretty big for me. Up until tonight, my bike was pretty much in as many pieces as it possibly could be... This was the first step in reassembly. I'm pretty ecstatic right now!:triumphant::dancing:

 

[Guest]

It's not possible to follow the Suzuki torque specs because stainless hardware must have antiseize on the threads which increases torque. You have to knock down the numbers a little.

Yes, I understand that. Stainless in aluminum without the anti-seize is a recipe for disaster, especially in the areas of the world where corrosion is a big problem. The biggest problem is how much to reduce the torques to achieve the desired level of preload. That's why I agreed with Steve that using the factory spec'd fasteners on the case connections and stainless fasteners on the covers is a better way to go.

I ended up torquing the 8mm bolts to 150 in/lbs and the 6mm bolts to 75 in/lbs. That's about a 15% reduction in the specs from Suzuki, which should account for the anti sieze.

Torque charts I have seen specify from 20% to 30+% reduction in torque when going from dry to lubed threads, depending on bolt grade, size and thread pitch. You are probably a bit on the high side with your 15% reduction but at least in the ballpark.


Mark

 

[Guest]

Why not install a bolt dry and mark it's resting place with a fine line marker. Then lube it with whatever you're using and see what torque is required to match the marks again.

I've used this method on bicycle suspension pivot bolts and it not only works well, but acts as a quick visual check method on bolts that have a habit of walking out.

 

[rapidray]

Do NOT put stainless fasteners into aluminum threads without using ANTISEIZE on the threads!!!!!
Ray.

 

[Dogma]

Do NOT put stainless fasteners into aluminum threads without using ANTISEIZE on the threads!!!!!
Ray.

Is there a danger of galling during installation?

 

[Sam 78 GS750]

Definitely used anti seize. I actually just found this article here (after the fact), which cleared up the whole situation a lot for me...

https://www.boltdepot.com/fastener-information/materials-and-grades/Thread-galling.aspx