How to install radiator

The longer ones are there so you can screw a fan and radiator in at the same time.

you can buy fan screws of different sizes

Take your radiator into your local hardware store...bring a fan as well so you know what length and what screw diameter/threading to get. There's also a screw threading guide in the sticky that illustrates the appropriate screw threads to use with many common radiator brands.

I've hauled all sorts of radiators, pumps, reservoirs, etc to the hardware store to find the exact matches I'm looking for. This is a lot simpler than trying to measure, write it down then drive home only to find out you got something a bit wrong.

Just make sure you don't buy screws that are too long or tread them into the radiator tubes behind the screw eyelets. Some rad designs are offset to avoid this, some are not, so make 100% sure you take the safe road here. If a screw is too long, you can always cut it- there are a couple ways to do this, but this is how I do it:

-Mark your screw/bolt with a sharpie marker where you need to cut.
-Thread 2 nuts onto the screw/bolt higher than the cut toward the head of the screw/bolt
-Make your cut with bolt cutters or cutoff wheel.
-Un-thread each nut one at a time to clean and cut the end threads and check by threading the nuts back on.

Best answer selected by the great hambino.

Glad to help man, get sorted ok?
Btw Rubix, Xspc rads have a 5mm gap from the frame to the fins, quite generous  
Thank you for B.a. Hambino  
Moto