CosmosMpower

Grabbed a set of 17X9.5 Enkei NT03+M's from a local evo owner for a good price and I'd like to run them on my RX-8 this upcoming season. I ran it the last half of the 06 season just to get a good feel for the car (was driving a S2000 the first half of the year).

Anyways, what size tire would you go with from a performance/price standpoint? Instinctively I would just opt for 275/40/17 since it's the widest that the wheels/fenders can probably accomodate. But is it really any better to run a 275 vs just a 245 or 255 on that width of a wheel? I was reading on the BMW autocross forums and it seems like those guys like to run a 245 on a 17X9 wheel, I'm not sure if that's to get the most tire on the ground or if that's just what is available. I believe it also requires extensive fender rolling past a 255 for a E36 M3.

There is a about a 100 dollar price difference per set on a 245/40/17 RT615 and 275/40/17 and I need to save some money for some Koni SA's and maybe MS springs as well. I WILL NOT be running in any SCCA classes so Bstock vs. STU etc is not a factor.

CRX Millennium

iTrader: (1)

Bridgestone RE-01R is on sale at TireRack. May worth a look if the price is right, since top drivers at '06 SCCA National Champ in Street Tire classes ran Yoko Advan or Bridgestone RE-01R. While you won't be running SCCA, the top dog tire is still applicable in your case.

CosmosMpower

I'm looking to spend no more than 150 or so a tire if possible, money is kind of tight. I was more or less asking about the benefits of various sizes since I know a 9.5" wheel can fit anything from a 255-275 realistically.

TeamRX8

iTrader: (25)

too bad you didn't get 18" instead, the 285/30-18 tire size is the one that works best WRT width/diameter

it doesn't really fit your budget constraints though, just stating it for posterity

Spin9k

Whatever tire brand you pick, check the manufacturer's wheel size recommendations. Obviously you know roughly what fits, but there is some variation among brands.

As an example, Falken's chart http://www.falkentire.com/rt615_sizes.html shows the 275/40R17 is optimum (and widest in 17") for 9.5" width wheel plus it has a higher load rating than stock indicating a stiffer sidewall. For ~$143 each it's hard to get better, cheaper for performance tires esp. compared to the same 18's which up the price like 50%! Likely price dif holds for other brands too. Good choice getting 17s!

TeamRX8

iTrader: (25)

true the cost is higher, but the performance advantage between a 285/30-18 Yoko Advan Neova on a 9.5 RPF1 and a 275/40-17 Falken RT-615 on a 9.5 NT03+M is as significant as the cost difference (and that's a fact, Jack) ... the only real advantage to 17" IMO is if you plan to stay with a 245 width tire and then you don't need such a wide wheel. In that case the 245/40-17's short diameter works to your advantage and has alower cost than the 245/35-18 aka OldDragger, but that's also the same diameter of the 285/30-18 tire so you pick up all that extra 285 width while maintaining the shorter OD advantage over any other 275 tire. The 285's are wider than the 275s by more than the 10mm stated width difference would suggest.

again, I'm not knocking the choice or the facts of a limited budget, this is the competition area so there should be no harm in stating the competition facts ...

Spin9k

We all know you want everyone to buy Advans Team, but Cosmos already has 17s... 18s are a not relevant here. The Advan 255/40 ZR17 size would, and is the best match for a 9.5" 17 wheel even providing a little performace boost because of its smaller diam than stock (3.6%), if he wanted advans. Unfortunately that's the biggest 17" size available in Advans.

But the other problem with them is price, he wants to save a bit for other mods. Price does count unless you're just flush with cash.

TeamRX8

iTrader: (25)

I could care less what tire anyone buys, I am not sponsored by Yokohama

again, this is the Comp area, just stating the Comp facts ... even if the brand was the same, say Kumho V710s, the 285/30-18 setup is going to be faster than the 275/40-17 setup on an RX-8 ...

turbosa22c

what would be faster? 275/40-17 or 275/35-18?

Razz1

I would use a 255 from Kumho.

Great tire and fits in budget.

CosmosMpower

Thank you, that's basically the info I was looking for. I know the 255's are a bit cheaper than the 275's and the whole point of the thread is for a the specific 17X9.5 wheel I ALREADY BOUGHT which tire is the best bang for the buck. AKA is the price of a 275/40/17 actually worth it over a 255/40/17.

I was thinking a 245 would be pretty streched on such a wide wheel and the 255 becomes within range of the wheel width (and might even allow for the most tire to hit the road). But the 275 is more rubber, but does that really translate to more true mechanical grip over a 255?

I'm not going to pay the prices for the Neova AD07's or RE-01R, the only 2 tires I am looking at right now are the Falken RT615 or Kumho MX and deciding which size I need.

CosmosMpower

Have you actually used a Kumho MX in that size on your RX8? I've used a set of 225/245 MX's on my M3 and I liked them but experiences with tires do vary based on the car. For instance miata guys LOVE the hankook RS2 but most S2000 guys hate that same tire.

CosmosMpower

Of course, you have a wider tire with a shorter stiffer sidewall which is advantageous in cornering and gearing.

But alas I got a great deal on the 17X9.5 wheels and I don't want to pay 18" tire prices so that's not really relevant for me and I'm not racing in STU so to me that little bit of extra speed is not justified for me. I'd rather spend the money on a few evolution and PCA autocross schools.

Spin9k

Being only $16/tire ($127 vs. $143 for RT-615s) I'd say it's a non-issue. We're only talking pocket change. Just get the one that works best.

All good questions, and difficult to answer. Some of my thoughts are that with the narrower tire the sidewalls are more stable as they are actually within the wheel width and can't flex/roll much. Also you may need to use less air than otherwise as the tire center will bow out compared to the edges of the tread. Less air will allow the carcass to relax and contact the road more evenly in the center tread area.


||^^^^^||<...wheel....>||^^^^^||
. \______/ <......tire.....>(__-----__)


Alternatively, the wider tire has more bowed sidewalls, allowing more flex/roll because the tire carcass is not as much within the wheel width. The center may tend to bend or bow up at the center due to the wider tread and need more pressure to flatten it out. Of course there's more rubber there, but...

My current idea of the optimal tire is more toward the 1st (slightly less than recommended) than the 2nd option (optimal or bigger than recommended), as track driving really tries to roll the tire, and this would combat this tendency. Still the other option has the extra inflation pressure to stabilize the carcass giving more direct (less slip angle) steering feel.

All in all, I still feel the 255 or 265 on 9.5 sound best to me.

(Full disclosure) I have Enkei 9.5x18s with 275/35/18 RT-615s, which are great, and better, more stable, than the 235s on OEM 8" wheels I had previously. Still if I buy another set, I think I'll go a tad smaller and see if the above proves out.

ULLLOSE

iTrader: (1)

If you already have a 17X9.5 and you are on a budget just go with the 275-40-17 Falken 615. The MX is no where near as fast as the 615 or Advan.

CosmosMpower

MX is slightly cheaper, I think 50 bucks or so a set which isn't really so much of a factor. I know the MX's wear well and do good in the TX heat, and a friend of mine ran a set of 245/40/17 RT615's on some 17X8 wheels this season and they did good for him so I guess I'll just stick with 275/40/17.

According to the Falken tire chart the optimal rim width is 9.5 for the 275/40/17. I also imagine that a larger/wider tire will probably disapate heat better than a narrower tire.

Spin9k

Found some expert advice on matching wheel sizes and tires sizes and even a host of tire brand recommendations from the EVO board, but applies to any car w/exception of offset issues re:Evo wheel size. Good read.

http://forums.evolutionm.net/showthread.php?t=200612

CosmosMpower

Good read, I wish there was a little more info on how different size tires perform on wheels of various widths. Looks like the RE-01R or Neova is the tire to have but if you don't have the money the RT615 should be the easy choice. I tried the Hankook RS2 on our 00 S2000 for a season and they were alright, sometimes unpredictable and easily overheated.

CosmosMpower

I was doing some thinking and it seems like a 255 on a 9.5" wheel might have a few advantages over a 275/40/17 such as a lighter overall wheel/tire combo, also might give some better sidewall stiffness and according to my calculations it should give some shorter gearing which helps the RX8.

Do any of you experts think the added sidewall stiffness and potential lighter rotating mass as well as shorter gearing would negate any advantage in the wider contact patch of a 275/40/17?

Spin9k

235/40r17 90w 8.5 / 8.0-9.5 ...24.4 9.6 836 8.7 8/32 .....24.3 51 1,323
255/40r17 94w 9.0 / 8.5-10.0 25.0 10.3 825 9.4 8/32 ....27.5 51 1,477

255/40 ZR17 94W 9 / 8.5-10 24.7 10.3 831 9.9 10/32 ....28.0 51 1477 <--ADVAN

275/40r17 98w 9.5 / 9.0-11.0 25.6 10.8 806 10.0 8/32 ..28.8 51 1653

It is possible the sidewall stability would negate the 'advantage' of a bit wider rubber i think. Above as an example is the RT-615 (3 different sizes) and the 1 size of Advan).

Notice the lighter weight - 1.3 lbs for the Falken, less for the Advan, of course the gearing advantage [doesn't affect cornering] is there, and the better sidewall stability for the smaller cross section - which probably would have the most positive effect overall. Note the Advan has deeper tread rubber, that might degrade handling initially unless shaved. The falken is already 'pre-shaved' in essence. Then there's the price Why not go for it and report back?

CosmosMpower

I'll probably end up going with the 255, should be about 600 for everything installed.

What is the 27.5, 28.0 and 28.8 number you have in bold?

Spin9k

weight of each tire

CosmosMpower

Ended up picking up a set of pre-shaved lightly used 255/40/17 falkens for 200 bucks and the MS springs/Konis are going in sat

Vrimmick

on 275 your wheel bearing would be really overloaded in cornering.

CosmosMpower

Explain further please. I went with 255 this time but may go to 275 next time. The 275/40/17 V710's were CONSIDERABLY wider than the 255 Falkens.