spyfish007

Just to bring up something from early on ... the stock revs count should be in the 830 to 840 range ... not 811 ... right?

SleepR1

No Text

nocab72

I've read this thread all the way through about 4 times now and I think I got all this wheel/tire stuff figured out EXCEPT offsets, so if I could get a bit of advice on offsets I'd be greatly appreciative.

As my street combo I'm looking at going with Borbet Type TD 18x9 all around with Toyo T1-S tires.

Toyo T1-S 255/35ZR18 gives me a over all diameter of 25.0", since this is just .2" over stock I should be good (please correct me if I am wrong).

I plan to install the Phase Three suspension package from TrueChoice which includes a modified to be double-adjustable Koni shock w/coil-over and Eibach springs (if anyone wants to recommend something better in the $2k range speak now or I order them tomorrow...

I am however completely baffled when it comes to calculating the required offset needed for the Borbets considering the above info.

any and all help is appreciated, I'll accept flames via PM if I should have already "caught on" and been able to determine the required offset(s)myself.

thanks!

SleepR1

See my responses in this thread:

https://www.rx7club.com/forum/showth...threadid=47113

Good suspension setup BTW. The folks at Tru-Choice do a great job with putting together systems for FD Rx7s. I believe the GC systems are over rated. You will be very happy with your new system. The great part is that Tru Choice will continue to work with you to ensure you have the right setup.

I'm somewhat envious that you're just "minutes" away from Mid Ohio (relative to the drive I have from Indy). IMO, Mid Ohio is probably one of the TWO BEST road racing courses in the mid west; the other one would be Road America! Personally, Mid Ohio is my favorite. I still haven't managed to leave my right foot on the floor through the "jump", turns, 9-10-11, into "Thunder Valley"

Borbets usually have an offset range that's available for the FD. Why don't you find out what that range is, and we could figure out which will work best for your application.

Generally for FD Rx7s, 255s on 9-inch wide wheels work very well at near stock offsets. With 2.5-inch diameter race springs, 50 to 51 mm will work very nicely for you.

You could push the wheels/tires outboard slightly by 0.25 inches and use 44 to 45 mm offsets all around, but you run the risk of very slight rubbing in the left-front position fender lip and fender lip bolt at full steering wheel lock left or right.

Good luck!

Probably will see you at Mid Ohio with Northern Ohio Chapter BMW CCA drivers ed and club race Memorial Day weekend. Look for a 24-ft long enclosed trailer in black, red pull vehicle--Dodge Ram dualie with Cummins diesel, and my red R1 shod with Hoosiers and SSR Competitions, and Indiana plates. There will be a windshield banner in red that reads, "Motorsports Driving Club".

If I were preparing your FD for dry track only, I'd go with a set of Forgeline RS Competitions in 9 x 17, 51 mm offset fronts; and 10 x 17, 45 mm offset rear. Tires would be Hoosier R3S03s in 245/45-17 fronts, and 275/40-17s rears. There's a bit of understeer dialed in for safety Well at least that's what I plan to do. The current SSR Comps will get shifted to wet racing setup--8.5 and 9.5 x 17s with 235/45-17 and 255/40-17 Bridgestone Potenza S-03s Pole Positions.

dclin

iTrader: (4)

The numerically largest offset number for the 18X9 5X114.3 Borbet TDs is +42. I, um, am somewhat familiar with them, heh heh. Do Toyo T1S 245/35/18s as you'll be happy - much closer to stock dia.

SleepR1

As requested...I put a sticky on the thread.

Manny Lozano
Motorsports Driving Club
www.autosportoutfitters.com/mdc/

RedR1

iTrader: (5)

Thanx SleepR1, much appreciated!

weaklink

I run these with volks and no rubbing.

1FAST7

i came up with the final decision of getting LE37s in 18x8.5(front) 18x9.5(rear) with 40 mm offset.
for tires: 245x35x18 (FRONT) 265x35x18 (REAR). I havent bought these yet, but when i do this will be the setup.

1FAST7

weaklink

Hey that's almost exactly what I run. Did you check my post?

1FAST7

wow, that is almost the same setup. cool!

1FAST7

ZoomZoom

iTrader: (2)

I'll tell you why. BFG is owned by Michelin. They discont the R compounds and are releasing the Pilot Cups to the Gen public now.

FavBandDMB

I like the 17" O.Z. F1 Racing II's with the Bridgestone Potenza S-03's.

ZoomZoom

iTrader: (2)

Well I ordered my Volk Te-37's a few weeks ago. I wont see them for another month or two but I went ahead and bought tires. I wetn ahead and bought the Bridgestone S-03's I have S-02's now and I like them alot better than any other tire I have ever used. So it was a no brainer. Like anything else. You get what you pay for. I work at a tire shop so I get a good break on tires. I have the Stock touring suspension and went with 18x8.5 in front and 18x9.5 in the rear. I am not sure of the offsets but I wetn by the Mackin industries fitment guide so the should fit. The tire size however I did push the limits. The front I went with 255/35/18 and the rears I got 285/30/18. I am pretty sure the rears will clear but the fronts I have heard from some people that they will fit and others they will rub. Hey if I gotta buy coilovers to fit I will. otherwise I will probably just buy some lowering springs. I like how the racing beat springs show less drop in the front 3/4 inch and over an inch in the rear. Its the rear that has the most gap. I will get some pics and post them as soon as I get the wheels on the car. Until then I wouldnt mind hearing from you who have the same set up as far as tire size vs both stock suspension and with the racing beat loweing springs.

Toy

ok. any of you pros out there want to help me? i would like to order asap. sleepr1?????

toy

SleepR1

Zoom Zoom...those tire sizes are pushing the limits of the wheel rim widths. It's better to have 9 to 9.5 x 18s for the 255/35-18s and 10 to 10.5 x 18s for the 285/30-18s. The wider rims give the wider tires better sidewall support. This is especially crucial if you have very low profile tires (35 and 30-series).

Convert 255 mm to inches and you have 10 inches; 285 mm converts to over 11 inches. It doesn't make sense (nore is it physically possible) to try to squash 10 inches of tire width onto an 8.5-inch wide rim; nor the 11.2-inch wide tire on a 9.5 -inch rim width!

If you have time to change your order, I'd go with a 225/40-18 for the 8.5 x 18 and 255/35-18 for the 9.5 x 18s. 225 mm converts 9 inches, and 255 mm converts to 10 inches, so you can see that an 8.5 and 9.5-inch wide rim wil provide superior sidewall support for the narrower tire widths...The overall diameters are nearly identical, and the narrower tire widths will ensure proper clearance from front fender lips and rear trailing arm links.

SleepR1

FWIW, the RB springs qre stiffer-riding on the public roads than progressive rate spring from Eibach or H&R.

I've had the RBs and the H&Rs, and the H&Rs are most comfortable on the roads. I do 90% of my driving on public roads, and the rest on high speed road courses...For me comfort was paramount, over stiffness.

Additionally, any aftermarket spring will require slightly stiffer shocks than the stock US spec Touring or Base FD shocks. I've used the stock Showa R1 shocks with both the RB and the H&R springs, and have had the best results with the H&R springs.

I also used the Tokicos with the RBs, and the results were less favorable than with the stock Showa R1 shocks. The Tokicos just aren't good shocks IMO. None of the 5 setting worked well with either spring combination.

It's better to get the R1 Showas or the Bilstein HD self-adjusting shocks.

SleepR1

Zoom Zoom,

FWIW, if you went with Volk and your rim widths were 8.5 and 9.5 x 18 fr/rr, then your offsets were 40-mm.

If that is the case, there will be NO WAY to run 255/35-18s and 285/30-18s on your tires anyway, as the clearance won't allow that UNLESS you roll the front and rear fender lips.

2.5-inch coil springs won't do anything for you unless your wheel offsets push the wheels further inboard, in which case your offsets would be 50 to 55 mm, NOT 40 or 45 mm...

Go with my recommendation of 225/40-18 and 255/35-18 for your 8.5 and 9.5 x 18 40-mm offset wheels, and you won't have ANY problems..

They'll look great too...

Trust me...

If you don't listen, all I can say is you've been WARNED!

Toy

SleepR1,

I'm using HKS hiper damper coilovers with M2 trailing arms and toelinks. I'd like to purchase a set of Fikse FM/10s in the next week. I will probably go with 18x10s in the rear and 18x9s up front. As for tires, probably 285/30s in the rear. What do you recommend for the front? 255/30s or 255/35s? Also what offsets will i need to get the wheels in to make this work? thanks for all the help.

Toy

SleepR1

You guys realize that you should be working with your wheel dealers for this kind of information...this information is what the wheel dealer is SUPPOSED to do for you as a paying customer...

I will provide this information, as a service to the FD Rx7 community, in hopes that some day you all will be able to help me out with something...

If you check Fikse's offset table you will find the following:

http://www.fikse.com/offsets.html

Assume the overall width of the wheel is 1 inch GREATER than nominal, because that's usually the case, plus or minus 0.5 inches.

With Fikse I'm confident the overall width is exactly 1 inch greater than nominal because Fikse provides backspace measurments and the numbers don't work out using the nominal widths.

When you see a Fikse 9 x 18, think 10 x 18; when you see Fikse 10 x 18, think 11 x 18 in overall width dimensions ok?

Assuming stock style coil springs (I'm not familiar with whether HKSes are 2.5-inch outer diameter coil springs), choose 44-mm offsets for your 9 (fr) AND 10 (rr) x 18s. This is based on Fikse's provided backspace measurements of 6.73 and 7.23 inches fr/rr, respectively. Choose 255/35 for the 9 x 18 fr; and 285/30-18 for the 10 x 18 rr fitments. You should have NO PROBLEMS at all with this setup, and they it will perform beautifully with only a very slight amount of understeer.

If you have 2.5-inch outer diameter coil springs, this buys you more clearance inboard, so you could actually go 0.5 inch wider--9.5 x 18 front and 10.5 x 18 rear with the same size tires, using 50.4-mm offsets, and 7.23 and 7.73 inches of backspace fr/rr, respectively.

The extra half-inch of rim width will provide better tire sidewall support, thus helping to increase steering and handling "feel", and eliminating tire sidewall flexion under severe lateral G loads.

If you intend to road race, and aren't bound by rim width rules, then I'd certainly go for the 9.5 and 10.5 x 18 fr/rr fitment to fit the widest possible slicks available!

Best of luck!

If my advice works out for you, and you are thankful, show your appreciation by telling your FD friends about my Motorsports Driving Club and supporting my track events at Putnam Park Road Course. Visit my webpage at http://www.autosportoutfitters.com/MDC/

Toy

will that set up give the wheels a deep dish look?

SleepR1

You shouldn't be concerned the deep dish look, you should be concerned with proper fitment, and clearance.

Only certain cars have offsets that allow that look...Porsche 930s in particular have low offsets for the rears allowing the rear outer lips to stickout and give that deep dish appearance.

Personally I don't care for the look.

Why don't consult further with your Fikse dealer. That's the place you should be getting your information from!

xph

I am curious SleepR1 why you wouldn’t go to 17x10 or 18x10 all the way round, but rather 9.5 on the front.. Is that above sizing just for Fiske's.. Wouldn’t the overall car balance and handling suffer from the resulting tire width and track width changes?

maxcooper

Here are some more data points for other wheels...

Volks seem to be 1 1/8" wider than the nominal width, based on my measurements for my SE37Ks.

CCWs seem wider still, perhaps 1.25" wider than the nominal width, but I didn't get a good measurement with the tires on. The 10" CCW rim is wider than the widest part of my 285/30-18 BFG R1A tires.

-Max

SleepR1

xph,

That's based on Fikse's backspace and offset limits.

I currently run asymmetric wheel/tire sizes with my track setup, and honestly, I'm just as fast with symmetric vs asymmetric. With wider tires in back, I can really flat foot the throttle, AS SOON AS I TURN THE CAR INTO the corner, without worrying about spinning the car's ***-end off backwards into the weekds...It's just a matter of becoming acclimated to how the car handles

Wow, the CCWs are really much wider than nominal! If I had 2.5-inch coil springs, I'd get the CCWs in 10 x 18 with 285/30-18 Hoosier R3S03s...