I am about to attempt my first two-tier cake. The bottom tier will be three layers, and 8 inches round. The top tier will be three layers, and 6 inches round. Will milkshake straws in the bottom tier be sufficient to support the top tier? Any tips on how to do this would be appreciated. Thank  you!

Yes, it will. Just make sure to cut them all down to the SAME size and apply some BC or ganache under the second tier.

 I hear people sighing...screaming...no! Use a proper sps AND centre dowel!!!

LOL.

Thanks, Julia1812.

I should add that I will not be moving the cake. So I am not concerned about the top tier sliding off or shifting side to side. I just want to make sure the straws are strong enough to keep the weight of the top tier from sinking into the bottom tier.

Anyone else care to weigh in?

Absolutely fine.  Those straws are stronger than wooden dowels because hollow cylinders hold more weight than skinny sticks.

I've supported 4 tiers using large bore straws without any problems whatsoever.

That is very reassuring! Thank  you!

How many straws would  you recommend I put in the 8" tier to support the 6"?

And does the cake need to be chilled (or anything else special) when I insert the straws? 

The general rule is 1 large bore straws per 2" of cake being supported, so 3 would support the 6" just fine.  Mark where the cake will sit and then put  the 3 straws evenly spaced within that spot in a "V".

You don't have to insert them when the cake is chilled, but it can't hurt--the cake won't crumble around the holes that way.

To support a 6" cake I use just 3 straws in a triangle form.  Straws are *VERY! strong* and will hold the weight of much larger cakes than a 6"er :)  I used them in my bakery for years and never had problems.  Most 6" tiers are rather light in weight so the 3 straws is plenty :)