Exidous

A long time ago I made the mistake of putting sumitomo 285/30-18 on my ccw sp500's plus they are 7 years old now.... It's just short of driving on rocks especially in cooler weather. I recently discovered that the Michelin tires are much cheaper over here(Netherlands). ~230€ each... Others are cheap too. Yokos, Bridgestone & Pirelli's. The PS2'S/Cup 2 are the most expensive so I figure better get them now before I return to the US. I really like the Michelin mileage guarantee(not available on the Cup 2).

Dunlops and hankook are not options over here at least locally.

Okay so I'm down to the AD08R, the Michelin Cup 2's and maybe the PS2s. Both 180 tread wear(220 for PS2).

AD08R available in: total cost with 255/295 is 870€
255/35 180€
265/35 ???
285/30 230€
295/30 250€

Cheap and 255/35-18 & 295/30-18 are the best size minus the stretch on the 10" wheel and no warranty.

Cup2 available in: total about 1200€
265/35 270€ each
285/30 280€
295/30 300€

Not thrilled about a 285/30(tram lining is pretty serious) or 265/35 (.3" taller than rear but better width for the 10") in the front. Still no warranty.

PS2 available in: total about 1000€ I got a little giddy about being able to buy PS2s and Cup2s for half what they are in the states...
255/35 230€ (run flat)
265/35 230€ each
285/30 250€
295/30 260€

Not thrilled about run flat for an "ideal" staggered fitment. The 20,000 mile warranty is pretty awesome for a square setup and 20k/10K F/R for staggered setups. Traction will probably be an issue. I'm at about 450rwhp

The AD08R looks like the best deal but the Michelin is just a better tire from what I can tell.

I've also got a question about under steer. Running the square setup with my other tires (ecsta XS 255/40-17) I found a good deal of under steer. Rear traction was great. I'm running the JIC FLT A2 10kg F and 8kg R (set to 7/7) which I think is what they came with. Can/should I swap the front and rear springs? Based on the math I've seen about the arm ratio between the front and rear we should generally be running a stiffer spring in the rear. Is this correct? I also have a tri-point front sway bar that is way to strong I think. Would I be better off just removing it?

My goal is for a safe few laps around the Nürburgring Nordschleife and SPA before I depart Europe late this year. I am NOT going to speed. Just a lot of fun without allowing my wife to collect life insurance. :-)

I'm open to other opinions as well. Thanks for looking.

LargeOrangeFont

iTrader: (7)

I'd say the Michelin is better but not that much better for the price difference.

Like I said on Nototors, don't waste your money on PS2s.

Swapping rear springs is probably too drastic. Those are really stiff front springs. I'd drop the front rate significantly, and the car will be better balanced.

BLUE TII

iTrader: (9)

I had the Tripoint front sway bar as well and hated the understeer.

I bought the thinnest tube available for the swaybar and the Tripoint told me it was less front swaybar than my car had stock.

I then went from stock springs/GAB SuperRs to 11K/11K Ohlins and loved the balance the equal rear spring rate provided (car is biased actually toward oversteer now).

BLUE TII

iTrader: (9)

Can you get the cheater street tires in Netherlands for a decent price?

Bridgestone Potenza RE-71R 285/30-18

Exidous

I asked about the 71Rs but no dice.

Seems like I'm weighted towards the AD08R. What do you guy think about the sizes. I know they run really wide for the given width. Should I just stick to the square setup and deal with the tram lining?

Maybe I should just go back to the stock front bar. The tri-point doesn't fit very well anyway with the samberg stuff.

BLUE TII

iTrader: (9)

The tramlining is more a function of putting too wide a tire on too narrow a wheel and in this case compounded by the tire construction (soft sidewall) of the Sumitomo tires.

I have 18x11 +45 and 295/30-18 that I run on my FD and RX-8 up front and they do not exhibit this behavior.

Another forum member who ran the above fitment also said he was surprised they did not exhibit tramlining.

I only notice mild camber thrust on the FD (-2.4deg front) which is when you drive across a surface where one side of the car has more grip than the other and the camber reaction pushes the car a bit toward the less grip side. This is not present on the RX-8 because it has limited front camber.

I have actually found the big wheels and tires with the right offset and fitment improve ride quality over poor roads and pot holes as the tire is so wide it doesn't easily fall into ruts or holes.

I would recommend a 255 or 265 max tire width on a 10" wide wheel to provide the best road manners.

BLUE TII

iTrader: (9)

The biggest draw back to driveability I have found with the wide wheels and tires is the car hydroplanes at a low vehicle speed.

If there is standing water I am the guy in the slow lane doing 45mph trying to stay in my lane while people blow past and/or cut me off spraying me with water making it hard to see.

Also, they can be very very hard on your paint.
I make some mud flaps that extend way up the fender arch and stick out as far as the tires and it worked great, but sure looks stupid if you put normal wheels/tires back on the car.

Exidous

Blue,

I must admit if surprised to hear you say too wide of a tire on too narrow a wheel. My CCW's run rather wide overall. About 10.5 at sidewall interface and 11" overall. I contacted CCW a long time ago and they said the SP500s run a little wide. Or they just gave me 10.5 anyway. In addition, The HTR Z III is a surprisingly narrow tire in both tread and section width. On my car they look like a VERY minor stretch. You can see it from the pictures in my gallery.

On the flip side, the AD08R runs rather wide and the specs on tirerack are:

..............RANGE....RIM...SECT....TREAD

HTR Z III
285/30. 9.5-10.5"...10".....11".......10.2"

AD08R
255/35...8.5-10".....9".....10.2"......9.9"
285/30..9.5-10.5"..10"....11.2"......11"
295/30...10-11"...10.5"...11.7".....11.5"

I cannot speak to the stiffness of the sidewall as I do not have another 18" tire for comparison. My ecsta XS ride MUCH softer but that's to be expected with a 255/40-17 tire.

I do know I had a minor issue with my alignment. I bought a front wheel hub from rock auto and the damned thing ended up having a LOT of run out. Enough to cause bad pulsing in the brakes which I thought was a warped rotor. Took it to a machinist and said it was fine. Measured the run out on the hub, mind you only 2-3" from center and was something like .02". You could see the wobble in the brake disk. Anyway that's fixed and so will be the alignment when I get the tires swapped over. The last time they were having issues with proper caster. They couldn't get the driver side over 4.5*. I'm hoping that's resolved.

BLUE TII

iTrader: (9)

That sounds normal to me for a 10" wide Aluminum wheel.

Nominal width +1" = actual width.

My 11" wide Forgestar F14 are 12" wide.

My experience is if you want the best behavior out of a tire run it at the widest recommended wheel width (10.5 for the 285/30-18 HTRZ III) or even a slight stretch.

The 265/30-18 and the 285/30-18 HTRZ show that as a 10.5" wheel width even though the 285 has .6" wider tread surface.

The HTRZ is a squirmy tire so a slight stretch will help its behavior.

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Anyways, hope you get your front suspension sorted out. Make sure the camber and castor adjusters are staying tight. If they loosen up the car wanders.

I bought the newer supersession bolts with finer pitch for more torque and they still loosened up, so I put thread locker under the eccentric washer and on the threads and it stays put now.

Exidous

Mazda RX-7 Picture by Exidous | 3435380 | RX7Club

Here's a link of what the HTR Z's look like on the SP500's.

I'll go for the 255/35-18 on the front. I think the 265/35-18 (25.3" dia) will be too tall.

For the rear do you suggest going all the way up to the 295/30 or just stick to the 285/30?

The alignment shop torqued them down TIGHT. I marked them with paint pen and it seems they have not budged at all.

I'm going to look for a little softer spring for the front and a smaller sway bar. Maybe I can trade the tri-point. :-)

Thanks again for the input!

Apparently the JIC's came with 12kg/9kg(not certain). Explains the rough ride lol. Maybe I should get another 9kg set for the front. If I could afford it right now I'd get a set of DFV's but my wife would have my hide.

BLUE TII

iTrader: (9)

For the rear do you suggest going all the way up to the 295/30 or just stick to the 285/30?


I would put whatever width tire you put in the front in the rear.

I don't like understeer and I don't like a vague rear where the sidewall winds up like a spring in the corner and the contact patch releases suddenly.

I like a rear that transitions smoothly in and out of slip angle without upsetting the chassis. Which is what you get with the widest wheel for a given tire width.

I understand not all drivers like that. Some want to feel the tire sidewall "take a set" so they know they are pushing the tire, but not far into slip angle.

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If you do go with the AD08R it is a precise tire (opposite of HTRZ) and it will behave fairly well even in wider widths on the same wheel width.

285/30-18 might not be as scalpel precise as 255/35-18 on 18x10, but it will worlds better than the 285 HTRZ.

Natey

iTrader: (19)

Don't forget that a square set up is rotatable and will most likely save you a few bucks on tires.

That was definitely a factor for me.

Exidous

I'd be a bit concerned about rear traction with a 255 in the back. Maybe I'll just suck it up and go 285/30 all round(again).

I've got the speedway pinto mounts for the steering and a laser point to get the bump steer down to a minimum. After that and the new alignment I should be in a better place.

Exidous

Well, I finally ordered the tires. AD08R's. 255/35-18 front and 295/30-18 rear. I'll get a pick up once they are mounted.

GoodfellaFD3S

iTrader: (213)

You're going to have grip for days, that's for sure. Make sure to weigh a front and rear wheel/tire combo.... I'm curious to see what the rears come in at in particular.

Even on 19 psi I have pretty good traction through second gear with 'only' 265/35 out back. I think the 295 will be very helpful for say 550+ rwhp, not sure it's needed for your current power output.

Exidous

That's what I'm hoping for! I've written off 1st for a long time but at 450whp having 2nd stick would be awesome. I also need to get the car corner balanced. I only just got the bump steer fixed up.

I'll make sure to get overall weights when the tires come in. I'm expecting around 45 in the rear and 40 for the front.

LargeOrangeFont

iTrader: (7)

Nice. Those will work nicely for you.