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Downsizing to 17" wheels for track -- offset question
I bought 18x9.5 +45 RPF1's quite a while back as my daily driver wheels because i liked the way they looked and liked the price and performance figures. I've since bought a set of Advan RS 18x9 +28 to use as my street wheels with the plans of putting some r-comps on the Enkies for track days. I've ruled out ever getting a BBK so i dont really need the extra 1" diameter so i'm thinking about downsizing to a 17" RPF1 for a little less weight and cheaper tires. From what i've gathered there is a 17x9 +45 and a 17x9.5 +38 (please enlighten me if there are other options i should be considering).
I know the 17x9 +45 is a popular choice but is there any opposition to getting the 17x9.5 +38 considering this will be a track set-up? I'm worried about the offset being too much but i want the 9.5 width. I'm not worried about the offset for rubbing purposes but for general handling performance with a more aggressive offset.
Also, I'd like to buy these used so i can buy 17"s and sell my 18"s and not fork out a ton of money to do the swap. 17x9.5 +38 seem like they are a lot more common. A lot more people have them on Evo's, STI's, S200's etc so i could probably find a used set pretty easy. 17x9 +45's seem a littler harder to come by.
2c - the 9.5 width isn't needed or really preferable - 8s simply don't have the HP to utilize that. The extra tire width you would likely use on that wheel will slow you down, likely will wear less nicely, and cost more. Also getting the R-comp up to temp will be far harder on a wider tire.
2 more c - the offset difference would be uneventful on the street - but I'd be concerned (justified or not) that at the level of stress put on suspension components at track - the change in suspension geometry might cause some problems/wear/breakage that the closer to oem 45mm would not. But then I have a high self-preservation instinct others might not
At $250 for the 9" 17s, they are fairly cheap new.
I'd have to agree; the 9 or 9.5 will both work, but the 9 with a 265 tire would probably be the best for a track setup. The differences in offset are not quite negligable but wouldnt be noticable when driving.
If looks means anything to you, the 9.5 +38 would obviously fill out the fenders better. Even with a 265 you wont rub on stock fenders.
This can help you decide. Consider the sidewall height for response tuning, and the overall diameter difference for gearing tuning. The MPH delta isn't really critical on track, you should drive by your tach anyway. Don't forget friction which inreases with bigger tires, and they weigh more. Remember smaller diameter tire is lowering your car and cg. too.
IMO a naturally aspirated 8 has enough power to maybe utilize a 255 tire width at max, anything more than that is just added weight and will hurt acceleration and braking more than the benefits of added grip
also regarding offset, more aggressive offset wheels will change handling and will eventually end up hurting key parts like wheel bearings and put more stress on your suspension components, especially if your are planning on using stickier tires.
I'm using 5-Zigen Fnor1c 17x9 inch (can't recall if they were 9 or 9.5) with the 38 offset on 255-40-17 Rcomp NT01s at the track. I've got about 6-7 track days on them so far no problems, they work real nice. I use the stock wheels and 245-40-18 Dunlops Star Specs on the street.
Ok, i think i've been convinced on the 255's but i'm still not sure about the offset/width. I emailed Brian Goodwin at Goodwin Racing and he said he is faster on long courses with 255's but faster on tighter courses with 275's. I think my home course is in between fast and tight so i think a 255 will do just fine. He did, however, say the 17x9.5 +38 was probably the better option. I doubt he was thinking about wear and tear like some of you are but he mentioned the turn in response would be much better with the 9.5's with the same tire since the sidewall would be stiffer when mounted on a wider wheel. Makes me lean toward the 17x9.5's..
Some good input from Brian - 255s on 9.5 could be nearly perfect combo, stiff sidewalls, minimize friction. Did he mention what tires he's running? I've the 255/40/17 R1s on my 9"s and they are fine. Good wear, fairly even with my 2-3 deg camber, add 1/2" lowering. Next time I may get a bit smaller as I can't get enough heat into them easily. I have no lack of grip, more lack of nerves . Smaller may give better speed overall, heat up better so I can have even more stickiness.
There are many variables to consider, then take your shot!
7mm difference in offset from 9.5 +45mm will be negligible. 7mm is very small, some are forced to run this size in order to clear bigger brakes! Really, it won't be a big a deal as many are alluding to...
As Goodwin said, the same size tire on a wider wheel will give you better steering response due to a stiffer sidewall. You'll also maximize the mechanical grip of your tire as it will have the widest footprint possible, for that tire size. Furthermore, you'll also be saving a bit of weight on a 255 V 275.
The common misconception on rx8club is that it is required to fit the widest tire possible (within reason) on the widest wheel possible. If you post up pictures of a 255 on a 9.5 you'll get people asking, "Why the stretched tire?"
Get the 9.5 +38 as it will allow you to run a wider tire for tighter courses or autox, if you ever feel so inclined
I'm happy about Goodwin's response as it's counterintuitive to what so many believe here at 8club
I run a 255/40/17 on the exact same spec wheel as you mention (RPF1 right?) and it's not even close to looking stretched. Mind you, it's NT01s.. feels great.
I'm Running 17x10 +25 all around. With 245-45-r17 tires and this setup is the most amazing out of 4 different wheel setups I've had. And I'm running a BBK.
7mm difference in offset from 9.5 +45mm will be negligible. 7mm is very small, some are forced to run this size in order to clear bigger brakes! Really, it won't be a big a deal as many are alluding to...
As Goodwin said, the same size tire on a wider wheel will give you better steering response due to a stiffer sidewall. You'll also maximize the mechanical grip of your tire as it will have the widest footprint possible, for that tire size. Furthermore, you'll also be saving a bit of weight on a 255 V 275.
The common misconception on rx8club is that it is required to fit the widest tire possible (within reason) on the widest wheel possible. If you post up pictures of a 255 on a 9.5 you'll get people asking, "Why the stretched tire?"
Get the 9.5 +38 as it will allow you to run a wider tire for tighter courses or autox, if you ever feel so inclined
I'm happy about Goodwin's response as it's counterintuitive to what so many believe here at 8club
+1, also everyone keeps mentioning that the 8 doesn't have enough power to move x size wheel/tire combo without even knowing the actual weight of the wheels or the tires.
Here's my old combo, 17x9 +35 with 275/40s, 2 pounds lighter at each corner than stock wheel and 245 azenis, the difference is night and day.
^ not sure if you completely read the thread, but there was a consensus that
1) widest tire possible isnt necessary as you want to maximize footprint of the tire
2) turn in response with a stiffer sidewall on a slightly "stretched" tire is greatly improved
nothing about your wheel set up indicates this! but, your car does look great so i'll have to give you that. :D
Perhaps you failed to read the whole thread. Care to share your setup?????
Originally Posted by c0ldf1ame
IMO a naturally aspirated 8 has enough power to maybe utilize a 255 tire width at max, anything more than that is just added weight and will hurt acceleration and braking more than the benefits of added grip
also regarding offset, more aggressive offset wheels will change handling and will eventually end up hurting key parts like wheel bearings and put more stress on your suspension components, especially if your are planning on using stickier tires.
Originally Posted by JantzenRX-8
Ok, i think i've been convinced on the 255's but i'm still not sure about the offset/width. I emailed Brian Goodwin at Goodwin Racing and he said he is faster on long courses with 255's but faster on tighter courses with 275's. I think my home course is in between fast and tight so i think a 255 will do just fine. He did, however, say the 17x9.5 +38 was probably the better option. I doubt he was thinking about wear and tear like some of you are but he mentioned the turn in response would be much better with the 9.5's with the same tire since the sidewall would be stiffer when mounted on a wider wheel. Makes me lean toward the 17x9.5's..
you forgot to highlight that hes faster on long courses with 255s,
i feel while grip is important, running the lightest combo of rim with the maximum amount of tire to generate just enough grip will prove to be faster. And in general (i know its not true for all rims) but the less width usually means less material = less weight. People running 10-11 inch wide rims will generally feel better since they'll have enough grip to never break loose in a corner, but that doesn't mean they're actually faster because the car wont have enough hp to push the cornering speed to the point that utilizes the whole tire. (hope that makes sense)
for example if your coming out of offramp at say around 40mph, and your next corner is cotton corners, with a 275 tire you can take cotton corners at 80mph, but maybe you only have 160hp which will maybe take you up to about 70mph, then you have too much tire because you could have utilized the reduced weight from a skinnier rim size to shed some pounds and improve the acceleration and braking response.
275 maybe good on a autox course with short and fast turns but it wont be as fast on a faster course with longer 100mph+ sweepers, personally i feel perfectly adequate with my 18x8.5 rims and 245/40 tires on the local tracks around here. I know my setup has room too since i know someone who is at least 6-7 seconds faster than me in a stock rx8 on a similar rim & tire setup.
umm hope that makes sense, im not an expert or anything but thats how i got it figured in my head
(i wonder how many times i can edit this...)
so my friend mentioned that since wider tires can hold higher corner speed you probably dont need to brake as hard going into the corner, but coming out of the corner acceleration may be slower, and top speed on the straight will definately go down. I guess in the end it'll be a toss up and really depend on the track layout and the skill of the driver. I Still feel 245 and maybe 255 will be a good general all purpose track tire though. Plus cheaper tires = more track time
I know this post is past dead but wanted to throw a comment in here for those searching in the future. (As I couldn't seem to find the answer)
I recently purchased a 2009 R3 for track duty to get my FD off the track. I knew I wanted grippier tires but I also wanted weight savings. Everything on this forum and facebook pointed toward 17" wheels for multiple reasons. It was hard for me to find true weights and specific offsets etc. After diving through every thread I could find, I settled on Konig Hypergrams 17x9 +40 offset. For Tires, I chose Nitto NT05's at 255-40-17. (only because you see RPF1's on the majority of cars on track and I wanted something slightly different. RPF1's might have shaved a few more lbs)
Long story short, I had read R3 wheels were lighter than the factory S1 or S2 wheels but couldnt find any confirmation or weights. Hopefully the above and below will help someone on a similar journey.
Currently Factory R3 suspension (Ohlins DFV coming soon) zero rubbing/turning issues with factory fenders.
R3 Wheels and Tires weighed in at 47lbs on the head.
17in. Hypergrams weighed in at 44lbs even. (I was hoping for a bit less here but with the contact patch is evident so it's still a win/win)
06-21-2010, 10:56 AM
. Smaller may give better speed overall, heat up better so I can have even more stickiness.
but, your car does look great so i'll have to give you that. :D
now go catch your faster friend 
