Wayne, that 205/50/15 tire size might be a little small for anyone's Spyder, especially when you consider that it is the ONLY tire you have to provide drive &/or contact with the ground up the back end!! Plus, it might pay check with your tire supplier to make sure that it is safe to fit a tire that narrow (205 instead of 225!) on the rim - it may not even be a legal fitting size on the Spyder rear rim here in Aus, it is certainly close to automatic disqualification, but I haven't checked that & would need to do that in order to confirm!! :sour:
Those changing from 225 to 215 are usually upping the profile size at the same time as they are dropping the width, but because of the way different manufacturers size their tires, they generally end up running a tire that has very much the same rolling diameter & contact patch - but that's probably not the case if you go that small/narrow! :lecturef_smilie:
Regardless, running a tire that much narrower than specification is likely to bring some degredation in traction & wear rates, & therefore also probably introduce lesser braking &/or cornering abilities as well!! :shocked: