Smaller diameter on front tires.

jsavvy

I tried to search around and didn't find a completely definitive answer.

Right now on my 18s I am running
Front 245/45
Rear 275/40
Which is great but I want more lows on the front and happen to have some extra tires laying around, which brings me to my question-

If I swapped my front tires to 255/35 (which I realize is less diameter) will my traction control/VDC go completely out of whack???

This would lower the front of my car by .8in but would have like 1.4in smaller diameter in the front vs the rear. I'm cool with it if my traction control is...

BGTV8

My calcs show 255/30R18 are 610mm in diameter and 275/40R18 are 677mm so your differences are 66mm (about 2.65 inches) which is massive !!

Your TC/VDC will likely be FUBAR'd (and I'm not sure you can purchase a 255/30R18 without checking).

Did you mean 255/40R18 which is 661 mm dia?

Even so, you are 16mm out which is 2.5% difference and on the cusp of acceptable differences .... it might be OK, if might give you trouble.

Google "site: the370z.com tire size VDC" and review the results .... if you are going be this far, be aware you might have a problem.

Check the threads thrown up by Google and make your own decision but if you have 255/30R18, you will definitely have a problem..

If you want more "rake", then lower the front with your existing tyres - plenty of lowering springs available, but I'd also be wary of camber/caster/toe changes with a 1.5" change in rake - especially lowered at the front, because you will also affect the roll centre

Tread your own path dude.

madwi

You can use this calculator if you want to see the size differences.
https://tiresize.com/calculator/

TreeSemdyZee

Front tires, not back, but the 245/40 are about the same.

OP, you're looking at 2.7" less diameter and 8.4" less circumference. You're better off with a 255/40.

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jsavvy

Oops goofed the original post. I said 255/30 when I meant 255/35 - 1.4" less diameter than my rear. Should be about a 7% difference in size from the rear. But I assume same results with VDC and traction control

OptionZero

wait . . . are you trying to lower your car by changing the tire size?

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MaysEffect

ikr

jsavvy

I have swift springs but I just wanted the front a tad lower; and yes I realize I should just get Coilovers. I just happen to have a free pair of 255/35s sitting in my garage that would drop my front end .8inches granted no traction control issues.

MaysEffect

It will also reduce your rolling diameter and subsequently increase revs per mile to about 830+ from 780ish. Your steering will be erratic and the rake of the car will ruin the caster alignment.

Please let us know how it turns out.

OptionZero

one of the "reasons" for lowering would be to decrease the wheel gap from tire to fender

smaller diameter actually increases wheel gap

but hey

do whats free

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Rusty

Before the lights on the dash come on. It's a little less then 3% difference or about 1" in height. You go over that. It's on you.

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jsavvy

thank you for the concise answer. I'll be grabbing some coilovers sooner than later.

/thread

madwi

That is a wise decision. There are other spring setups out there that go lower than the swifts, if cash is tight.

madwi

Lowering Springs Comparisons

jsavvy

Thank you for this info. I had given it some thought but I'm just thinking damn I'm already 250 deep on the swifts another 300 on some ARK and I'd be more than half the price of most coil options. Might as well get it done right and stop playing myself.