Just got off the phone with stoptech. The 897 golf kit will fit the 896 golf R but it won't be optimal. Piston sizing is 30,34 vs 32,34. He was asking the engineer who tested them on his personal golf R next to him. Piston size is different due to fwd vs awd & more weight per the engineer he brought on the phone.
So will it be better than stock, hell yes. Will it preform.as optimally as possibly, no it won't.
The difference is $1000 in the 897 vs 896 kit for me and I track 4-6 times a year. I feel like the $1000 savings is justified but I hope someone else can chime in.
So I happened to buy Teemy's used ST40 kit off of the forum the week before the OP created this thread. So I actually recevied the used kit from the forum member and the new kit at the same time.
With that said I just opened up both boxes this after noon and both calipers have larger pistons than the sizes you quoted above. The used kit that Teemy sold me has 36/38 pistons and the new kit I received has 34/36 pistons. Both are larger than what Stoptech told you.
Kinda odd?