renkenkyo

iTrader: (6)

I've done a bunch of reading and I can't seem to come up with a conclusive answer so I'm going ask the gurus here to chip in if they can.

Why I'm upgrading from stock rims:
I want to fit a BBK (Racing brake or Wilwood) and my stock 16" rims won't fit that kit.

What I'm using the car for:
Basically it's a track only car except driving to and from the track. My track usage is pretty varied but it's mostly consists of time trial or HPDE. I run Autoclub Speedway, Buttonwillow, Willow Springs (Big and streets), and Laguna Seca on occasion.

The Setup:
The car makes about 320 RWHP. I'm running Tein HA's right now but plan to upgrade those as well, but I'm doing one thing at a time. External mods are the Feed front bumper, F/R fenders, and 99 rear wing. I'll eventually get a full GT wing. I'm currently using Yokohama Advan AD08's all around. I have spacers on my wheels.

The Question:
Based on my initial finds, it seems I need to move up to at least 17" to fit the brakes. Is there any recommended wheel widths that people have for the track? I also am using spacers due to the wide fenders I have but I'd like to get rid of that rotational weight and use a proper offset. What kind of offset works with the Feed fenders?

Also if anyone has suggestions on brakes other than the ones mentioned, any feedback would be appreciated, thanks!

Mahjik

iTrader: (1)

Take a look at Enkei's racing selection:

Enkei Wheels - Racing Series Wheels

Something like the RPF1 would offer several options for 17's:

http://www.enkei.com/size_chart/RPF1.pdf

renkenkyo

iTrader: (6)

Those are nice light wheels, at ~16.5 lb for 17's and ~18 lb for 18's . Any recommendations on offset and width?

Thinking of running these wilwoods for the front brakes. I might need 18's for these.

BLUE TII

iTrader: (9)

RPF1 isn't big brake friendly, but the PF01 is.

On the Vorslag 2011 Mustang blog the owner went through this- using both those wheels.

I run Enkei PF01 18x10.5 +38 265/35-18 all around on stock fenders (front has lip rolled under). I am limited to this tire width in the rear unless I roll the fenders and I would have to make offset upper control arms to get more camber if I wanted to run more tire in the front.

It has full suspension articulation without rubbing with -2.4 deg camber in front and -2 deg in the rear.

I just ordered 18x11 +45 Forgestars so I can move to 295/30-18 all around. This puts the tire/wheel in the same spot on the outside, but goes inboard for the extra width.

I would just add a bolt on spacer in the front to flush the wheel/tire out with your wide fender. This way you can still rotate tires.

Mahjik

iTrader: (1)

It's only a problem in the higher offsets with 17's (i.e. stock/oem fitment). With his fenders, he can run a lower offset and still not be in the "fitment club" if that's not his desire. The only issue would be if he wanted to run 10" in the front which I don't believe will work with their offsets.

BLUE TII

iTrader: (9)

It's only a problem in the higher offsets with 17's (i.e. stock/oem fitment).

On the Mustang it was a problem with the 18x10 +38 RPF1 and the optional 14" Brembo brakes. It required a min 7mm spacer to get .04" clearance and I am sure will need a bit more for the flex you will get on the track.

I believe the Wilwood 14" brake kit has a lower profile caliper though, so it might clear without issue.

18x10 +38 RPF1 all around with a spacer to flush out his front fenders/clear big brakes is a good idea though as they are light at 18.5Lbs and relatively inexpensive and it would be easy to rotate the tires around to keep the wear even.

The only issue would be if he wanted to run 10" in the front which I don't believe will work with their offsets.

With the +38 offset you are limited to 265/35-18 up front on stock fenders with the lip rolled and -2.4 deg camber.

It should work with a spacer to clear big brakes and his fenders.

If you go wider than 265mm it would be nice to jump to the 18x10.5 +38 PF01 despite the heavier 22Lbs, though +38 and wider than 265mm will need to roll the rear fenders as well or run more than -2 deg camber out back.

I wouldn't sweat a couple of pounds of wheel weight especially if you are bolting up a heavy big brake kit.

The PF01 are a newer design that looks more rigid than the RPF1; which, if that were the case would help keep the suspension doing its job.

renkenkyo

iTrader: (6)

Would running that kind of camber mess up my cornering ablity? Wilwood calipers seem to be pretty light. If anyone knows the weight that'd be good to know.

I'd like 17's if that's what I can get away with, only moving up to 18's when I can't fit the calipers anymore.

BLUE TII

iTrader: (9)

Would running that kind of camber mess up my cornering ablity? Wilwood calipers seem to be pretty light. If anyone knows the weight that'd be good to know.


You make a good point that camber should be used in order to keep the tire in maximum contact with the surface and not a fitment tool.

I don't know how much you will need on the track as I autocross and drive the car on the street. Your really throwing the car into transitions for autocross which requires more camber.

Autocross and wheel rotation just kept the camber wear from street driving in check with my -2.4F/-2R alignment on 140 treadwear Federal 595RS-Rs, 11K/11K spring rate and Tripoint front bar (similar grip to your AD08, though no where near as refined).

17" wheels will definitely save you some money on tires and you can get the smaller diameter big brake kits.

Eventually you might want more width only available in streetable tires in 18s and that is why I mentioned starting with more a max fitment.

Just like I wanted more tire width only available from a custom offset...

Mahjik

iTrader: (1)

You mentioned Time Trials, what class are you planning to run and have you figured out your points (if it's NASA) as to what will happen for certain tire sizes?

The reason I ask is that depending on where you are trying to run, you may be limited on tire compound type and size. Finding that out will help us to help you pick your setup.

renkenkyo

iTrader: (6)

I believe I'm running TT3 right now. From the rule book "Tire and wheel size are unlimited, but non-DOT approved tires will be assessed via the “Adjusted Weight/Power Ratio”. Tire treatments and softeners are not permitted."

DeaconBlue

iTrader: (31)

Do a search on SSR type C. They were sold by TireRack and the 17x8.5 +42mm front and 17x9.5 +42mm rear work very well on an FD even with stock fenders. You can ran a 235 or 245 front and 275 rear tire. The 8.5" width rims are only 15.3 lbs - not sure about the weight on the 9.5" width rims.

I have made them work on an FC with the correct spacers.

https://www.rx7club.com/wheels-tires...tinued-991150/

https://www.rx7club.com/2nd-generati.../#post11000533

BLUE TII

iTrader: (9)

"Tire and wheel size are unlimited, but non-DOT approved tires will be assessed via the “Adjusted Weight/Power Ratio”. Tire treatments and softeners are not permitted."

So if you don't want to take the non-DOT adjustment you are in the same boat as I am in SCCA Solo 2 A Street Prepared.

I put in an order for 18x11 +45 offset ForgeStars because they are cheap and light. I will use 295/30-18 Toyo R888 because that size is cheapest at $244 and they work reasonably well on the street as well as on course.

18x12 was tempting, but I would have had to roll the rear fender with a lower offset or stick with +45 offset and use aftermarket rear trailing arms (not class legal) and offset rear shock bushing.

Anyways, I really really recommend keeping a square fitment (same size tire/wheel on all corners) as it will save you money by being able to rotate and keep understeer at bay.

lOOkatme

iTrader: (19)

I think wheel fitment and width is more important than weight. A couple of pounds per wheel is not going to be faster than a wider wheel with the right offset running the best tire.

I agree, tire rotation is huge. My car eats through the rear tires much faster than the fronts and the handling is better with a squared set up.

I would look for 18x9.5 or 18x10 wheel set up. On the 9.5 I would run a wide 245/35/18 or a narrow 255/35/18 tire and on the 10, run a middle to wide 255/35/18 tire.

renkenkyo

iTrader: (6)

Basically, if I can run a smaller wheel size and have the width I need that'd be ideal. If moving up to 18's is the only way that might be a better choice. Rotational weight is 3X roughly when considering acceleration.

Rotating the tires is a great benefit. Is there a width/offset I can use so I don't need spacers?

BLUE TII

iTrader: (9)

Rotating the tires is a great benefit. Is there a width/offset I can use so I don't need spacers?

I don't know exactly what you need since you have wide fenders front and rear.

Forgestar makes its wheels any offset you want; you just have to wait. I am told mine are taking 90 days.

You could easily fit up to their 18x12 front/rear and the F14 is only 21Lbs and ~$300 in that size.

I am not sure of their durability, though they are used mainly on larger heavier cars (BMWs, Audis) and one member here has used them last season for auto-x without a problem.

If you can tell me the size and offset of the wheels and camber you have on the car, the camber you want to run and exactly how far to the fender edge I can work out offsets for you.
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Rotational weight is 3X roughly when considering acceleration.

Rotational weight has a big effect on acceleration. Most important is where the weight is at. The further from the center of rotation the more effect it has.

I went from running 1/4mile in 13.4 to low 14 seconds (hard to launch with limited traction) with stock wheels (37Lb wheel/tire) to consistent 13.7 seconds with my larger wheel/tire package (50Lbs).

The tire weight is more important than the wheel weight. When Mazda was developing the FD they commissioned a lighter tire to be developed for the R1 model.

That said, my car is only ~270Rwhp and it doesn't feel slowed down much by the huge rotational weight difference, whereas the cornering grip is on a whole new level.

Another factor in wheel/tire weight is the higher rate of spring and damping you will have to run to control the wheel movement at higher velocities.

If the surface is very rough, this could counteract the added traction of the width because the tire is in contact with the ground less often.
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Basically, if I can run a smaller wheel size and have the width I need that'd be ideal

17x10 is going to be lighter and cheaper on tires, but 255mm the widest made in streetable tires as the 275/40-17 is too tall for the front.

You have to decide if 255 is enough or if you want to go wider.

Given stock body fits 295mm and you have a wide body it sure would be nice to go wider than 255mm.

Mahjik

iTrader: (1)

An option (not necessarily the lightest per say) is Diamond Racing wheels:

https://www.rx7club.com/suspension-w...2/#post8286360

They are inexpensive and you can get them custom made for your exact fitment. Unless you are at the point where you are getting the most out of your car, a little weight here or there isn't going to make that much difference. I personally plan to use the Diamond wheels since at their price, I can get several sets.