flowrider

iTrader: (9)

I'm running 295/30/19 on the rear of my ISF



Lou

juliusdx

I think I'm going to bite the rubber and go for Michelin 4S but since the fronts still have about 40% tread left in them (they are stock 225s) I'm going to go get 275/30/19s for the rear for now.

is that recommended?? so front 225/40/19 falkens azenis (from previous owner), rear 275/30/19 michelin pilot sports 4s. Also, the roads in my area are considered horrendous, pot holes, undulating surfaces, are the 30 profile tyres cutting it too fine??

juliusdx

btw,i found this article: https://arstechnica.com/cars/2017/01...-at-cornering/
that says

"For the record, the PS4S is under warranty for 30,000 miles (48,280km) (300 treadwear rating) for square fitments (all four tires the same size) and for 15,000 miles (24,140km) for staggered fitments (different front/rear sizes). In fact, Michelin says the PS4S has significantly longer life on average than the PSS but hasn't yet provided a specific percentage improvement."

any cheapskates out there who might be thinking to go all 4 tyres same size to go for maximum mileage while sacrificing (some???) handling?

GunnyFitz

If it were me, I would most definitely do ALL Four tires at once with the 4S models. Keep those other stock ones as spares. But that's just me.

Since they don't make the Front Size I need for the new Wheels I have coming, I was pretty much forced to go with Conti or Bridgestone. (They look sick in person too!)

juliusdx

Ok, GunnyFitz, you're gonna say "I told you so!" but here's what went down:

because i still couldn't get the 245s for the front, i'm still running the 225s from the previous owner (with about 80% tread left btw) and the car is practically un-drivable! the turn in, stability at even 60mph, braking are PLAIN SCARY.

anyway, the tyre shop guy tells me he's had a few couple of M3s having the same experience when changing tire sizes but he can't remember the set ups and he couldn't prove it in numbers.

i then did some research and came up with this:

• The OE front versus rear diameter had a 3mm or 0.45% difference (compared to both front and rear diameter size).
• the recommended upgrade 245(f) 275(r) has a 7mm or 1.06% difference (compared to both front and rear diameter size)
• the UNSTABLE setup has a 15mm or 2.27% difference which is well over the acceptable tolerance when up (1.5% or downsizing (2%) ref: https://www.oponeo.co.uk/tyre-articl...sizes#changing

while still waiting for the 245s to come in, i've altered my ride front ride height be 5mm lower than the the rear to hopefully compensate for the difference with rear dropped by 5mm (so front drop 10mm, rear drop 5mm). The car is somewhat more stable at cruising........

Slowlane

So the strange handling is from height differences from OEM front to back, is this affecting the stability control angle sensors?

I've recently had new HKS coilovers fitted and traction control lights seem to flicker on a lot easier now than before with OEM suspension.

Initially had HKS out of the box settings and then I raised the front only by 10mm hoping to get it close to OEM differences, its still lower though, lights are still flickering quite easy through fast corners. I have PS4S 235/35 & 265/30 on 2012 ISF

Does anyone know whats going on here?

ChpEng

iTrader: (1)

Those PS4S sizes are smaller in diameter than OEM by 0.6in F and 0.7in R, which results in more revs/mile. More angular rotation of the Hall-effect ABS/TCS/etc wheel sensors than ECU calibration point would make it think wheelspin.

The HKS coilover kit probably has more rebound damping than factory. Technically rebound damping should be set to match the spring rate, but in practice it is a matter of taste and comfort. I can tell you from personal experience with FWD platforms that less rebound gives better traction to that axle. With FWD we were always trying to rotate nose-heavy cars, and ended up dialing in as much R rebound as we could tolerate for autocross, then dialing it out to avoid chipping our teeth on the street.

Just thinking aloud here, but it makes sense. Both factors go the same direction.

Slowlane

Great information, many thanks.

I currently have shock set from full hard out 39 clicks, front 9 and rear 15. Should I put them in the middle at say 19 or 20 clicks? They did come in the middle out of the box.

Interesting about the tire sizes, funny I thought they were larger in height as well. Is there other sizes that will work better?

Edit; Out of the box l've raised the front 10mm and left the rear were it was
Edit; I can't recall the stability control lights coming on same PS4S on OEM suspension, so it must be just the HKS's. What do you think?

lobuxracer

iTrader: (2)

If you're sold on those shocks, you'll need to experiment until they work well for you. Otherwise, you need to get shocks that actually work properly. I have many strong doubts about most shocks coming from Asian brands with Tein being one of the worst. I have them on my Supra and they're not long for this world for sure.

Slowlane

Might just do that.ChpEng makes sense, this is what he said.
"The HKS coilover kit probably has more rebound damping than factory. Technically rebound damping should be set to match the spring rate, but in practice it is a matter of taste and comfort. I can tell you from personal experience with FWD platforms that less rebound gives better traction to that axle."

I really do like how the HKS ride, soak up large bumps and seems quite planted but then again l haven't had a chance to really open it up as we're in COVID lockdown where l live can't drive my favourite roads.
l'll try it at different settings and see how it goes.

Slowlane

What shocks are you running lobuxracer?

lobuxracer

iTrader: (2)

I am ordering Ohlins TTX for mine. Still on the ancient and now quite dead OEM setup from '08. Been planning this for a long time, but the RR shock is for sure blown, so it's time, the wife can't say no anymore.

MileHIFcar

Nice! TTX I'm sure those will transform your car. When you getting those installed?

lobuxracer

iTrader: (2)

It's part of a major project. Lots of new suspension stuff to go with it. I should probably do a build thread when I do all this stuff.

MileHIFcar

For sure! sounds like your doing a major overhaul