is there another disc i could use with my s13 caliper on 310 struts ??

You have 310 struts on your B110? Datsun 310 is a FWD car.

Sorry i meant b310.i want to get my 13'' wheels to fit.with s13 caliper.

So is there another disc that can fit s13 caliper on B310 strut?

If you goal is to fit a smaller disk, how will that change things? Is'nt it the caliper that is hitting the wheel?

The answer is yes, other discs can be made to fit. Mainly larger discs that are cut down to the right diameter.

yeah its the calipers that are hitting the wheels but if i get 250mm disc will the clear my 13's ?

The disc will clear the wheel, but the caliper will still hit the wheel.

Yes, other discs can be made to fit. Mainly larger discs that are cut down to the same diameter.

Perhaps you could use a 280ZX rear 258 mm rotor which fits over the B310 hub (no machining needed) and use a custom bracket to mount the S13 caliper farther down. The 258 mm rotor fits under most 13" aluminum wheels when using the Pulsar caliper (see 280ZX Brake Upgrade).

Ok that looks like a great upgrade,Do you have any idea of how much inches the ca18 s13 rotor measures?

S13 with CA18DE used the smaller of the S13 brake rotors. 251mm (about 9.9 inch). However, it used a larger caliper than the one for the 280ZX swap.