just like the title states...is there any detrimental effect if i switch?

 

275/35 has a diameter of 26.6in and 275/30 is 25.5 which is more than an inch off = NO NO.
My coupe came with OEM 19s which are 245/40 out back. 275/35 or 285/35 are both essentially near perfect matches for that size.

When you run a 275/30 your speedometer will be off by more than 4%, almost 5%. This will throw off your VDC and your odometer pretty severely. 30 spec tires can be run with 295 or 305, anything below that is far too small a tire for the original calibration.

As always check http://www.miata.net/garage/tirecalc.html
Put in your OEM size, put in a size to check, try to keep it less than an inch difference in diameter or less than 3% difference in speedo effects. I personally like staying as close to OEM rolling size as possible (1-2% at most), but thats just me.

 

you have a long way of just saying 'yes'

 

It will throw off your speedo/odo, and may cause some VDC issues too.

 

Look at the specific diameters for the tires you are looking at, they very greatly between manufacturers.

 

Newbie question. Not befitting for a 3 year member.

 

trying to be helpful and explain WHY it's detrimental so he might be able to answer the same type of question himself without creating a thread for it.

Sorry about that, if I would have known it would have bothered you so much, I'd have just put the letter Y to save you some trouble of actually having to read the word yes...thanks for your input though!
You have a very brief way of contributing nothing useful to a thread.

 

^lol

yes but i have 295/30/19. its good. i put both rims (the other was stock) and tires next to eachother and they were the same height. and ive seen the 275/30 and they were a small 'bit' off. but not anuf to mess anything up i think