mustanghammer

iTrader: (3)

A couple of shots of my car from an autox last weekend

Those are HUGE!

On the front I am running the adapters (25mm thick) plus a 10mm spacer to get my wheel to a zero offset. This gives me about .5-.75" away from the struts on the inside and about 3/8" on the outside between the tire and fender. This is with a 205 Kumho V710 on an 8" wheel.

In the rear I have a 5mm spacer to push the tires out a little more but everything is tucked up inside the fender.

What I have noticed is that as the body rolls the panhard bar pulls the loaded tire closer to the center of the car. So you pick up some clearance. Next time you are behind a first gen with a panhard bar watch the rear tires in relation to the body. You'll see what I mean.

Freeskier7791

Looks good, your build gives me lots of good ideas

mustanghammer

iTrader: (3)

Thanks!

toyzforme

Hey Mustanghammer I have a 80 RX7 that I run here in the southeast. When I got the car ($1500) all I needed to do was drop my 1991 high compression rotor 13B EFI motor with a haltech ecu in. The car also has 13" wheels 13x7 to be exact, running 225/45-13. How much of a difference is this going to be if I move up to 15x7 rims. I still have the stock rotors but have upgraded to drilled and slotted. With motul 600 it stops on dime so not sure what going to 15" rims is going to do to stopping power. The car has been run in SPU in SCCA and running in TTD in NASA due to power to weight ratio. The last SCCA regional race I did I was told that I should be running in EP but they want me to add too much weight. So I will just stay where I am at and have fun.

Next question, I have noticed that my oil temps have gotten to 230 during a race and I don't like that. I have another oil cooler, and could do like you did, but I am afraid that it would block too much air going to the radiator. What do you think.

3rd Question is about how much camber are you running? I would have to change my lower control arm to get more as my camber plates are maxed out and I don't think it is enough. Oh well I just read through all 13 pages of this build and I love what ya did and wished I enough money to what you did. I am retired from the Air Force and my job now helps me race but not as much as I would like LOL. Isn't that always the case.

mustanghammer

iTrader: (3)

Hello Toyz!


I went to 15" wheels out of necessity so that I could fit 11" brakes because I think bigger brakes become necessary when HP numbers get up around 200. Also, at 2300lbs (STU weight with a street ported 13B) my car is a few hundred pounds heavier than an EP car with the same engine.


From a performance standpoint, a tire with a larger diameter will tend to have a larger - longer foot print. Also, a 15x7 wheel gives you the option to fit a very popular tire size - 205 50 15. I have been able to get great deal on used and new racing tires in this size. I ran 13" tires from 03-09 and never scored any great deals on tires...


There is a downside to 15" wheels however. First, larger wheels and tires are heavier so when you shop for wheels you need to find the lightest ones you can afford. Next, you will be changing tire diameter which will have an effect on gearing and on the ride height of your car. For the later, I have spent allot of time getting my car back to the same ride height it had on 13" wheels while also keeping the suspension in proper geometry.


Regarding braking, the GSL brakes are allot better than most people think. You are making the right choice on brake fluid. You didn't mention the brake pads you are running - I ran Hawk Blues. As far as rotors are concerned, I was not allowed to run drilled/slotted rotors in SCCA Improved Touring. However, I would not have ran them anyway. Drilled/slotted rotors are prone to cracking in racing conditions. Brake rotors on a race car are a consumable item. Buy the cheapest ones you can find and replace often. Also, make sure that you have brake cooling ducts that provide cool air to the back side of the rotors-pointed to the center of the rotor. It is extremely important that you keep the wheel bearing cool - they are tiny.


My oil cooler/radiator setup nets 210F for both oil and water in racing conditions. Adding the second oil cooler did raise my water temps but it made such a huge difference in oil temps that I think it is worth doing. All of the club racing RX7s in town are set up that way. Keep in mind that if you measure oil temps at the oil filter you are seeing the temperature of the oil coming BACK into the engine from the coolers. Can you imagine how hot the oil is when it leaves the engine?? Pretty scary. By the way, you should only use proper stainless steel braided hoses to plumb your oil coolers. The push-lock stuff cannot handle the heat.


I run around 3 degrees of negative camber.


Thanks for the props! Good luck with your car. Oh, and in racing you have never have enough HP, Tire or Money......

mhr650

Got the new wheels and tires on my car, 15X9 Jongbloed wheels with Maxxis 245-40-15 tires. I ended up making adapters for all 4 wheels, I was going to have to use really thick spacers anyway on the front if I redrilled so it made more sense to just make adapters. I made my own so I could upgrade from what you normally se, if they mention it at all adapters are made at best from 6061 which is good aluminum but I used 7075 which is almost twice as strong. I used ARP studs listed for late Camaros and to hold the adapters on I used 35mm wheel bolts listed for a Mercedes. I had to make my front adapters 40mm thick for the tires to clear my struts, due to some silly rules I am limited to a single spacer/adapter per wheel so I had to get it exactly right on the first try. The rear adapters are 20mm thick and I could maybe go down as thin as 15 but that leaves less material under the studs and bolts.



Since I took these pics I have rolled the lip in on the rear fenders and flared out the fronts a good bit, I think I will be good for clearance, but I am keeping my angle grinder handy at the first race…

mustanghammer

iTrader: (3)

Look great!


Is your car's build documented? If so, start a build thread and share what you have done in detail. We would all benefit from that!

RGHTBrainDesign

Fukkkyaaaass! So glad that Phil's Tire Service could help you guys out. They've been good to me so far. My wheels look GOOD on the FB!

mhr650

I know I need to do my own build thread and stop butting into your thread LOL. ChumpCar has a rather bizarre rules enforcement procedure where the tech does safety and basic value inspections and the main enforcement of performance modifications are supposed to be handled by other racers protesting at post race impound. In reality tech takes a fairly liberal positon on how highly modified a car with a low starting value like an FB can be, but there are always internet tough guys, generally who race high starting value cars and who can’t do many modifications to their cars that want to nickel and dime you by charging for every nut and washer. I am a bit concerned to give them more ammunition than they already have…

Right now I am going full bore getting ready for the 24hr at VIR, I think I have a good enough team of drivers to end up on the podium if we run clean, of course running clean for 24hrs is way easier said than done.

mustanghammer

iTrader: (3)

Okay, I can completely relate to that! Many times I have questioned myself for doing this thread.


Actually SCCA rules enforcement is not allot different in the non-spec classes, by the way. SCCA Tech workers don't do allot of non-safety rules enforcement until the Runoffs. Until that time, drivers are expected to hang protest paper on racers they feel are out of compliance.


Good luck with your race!

82transam

iTrader: (18)

I'm glad you did make this thread Scott, it's inspired a ton of the work on my current and recently finished builds (which ironically I have not made threads for yet lol)

mhr650 - would love to see more details of your build as well

Gian

iTrader: (3)

I know I'm being lazy. But I did take a quick look and couldn't find what your running for spring rates?

I know my car came with 350lbs F & 175lbs rear. But doing the math. I think I need much more.

I have to keep the rear suspension (Watts & 4 link) stock but the front is & tires are about equal to what your running.

I'd really like to know what your running.

mustanghammer

iTrader: (3)

Current setup - subject to change


500 Front
275 Rear

Gian

iTrader: (3)

Thanks a lot MH!
That's about what I was guessing.

Running NASA PTE with a 2350lbs car.
I was going to start. at:
450 front.
300 rear.

I was second guessing myself. This helps me a lot.
You have done a lot of really cool stuff on this project. There is a wealth of info here.

Freeskier7791

Glad I am about the same for my car at 2500 lbs, 450 front, 350 rear

mustanghammer

iTrader: (3)

Not so fast guys. Spring rate is not necessarily a function of the cars weight. It is a number that needs to be considered but if is not the end all be all.

I think you have to take into consideration the kind of rear suspension you are running. My car has a three link with a panhard bar with everything in spherical bearings. So, unlike the factory four link/watts setup there is no bind in my suspension. So spring rates are more actual. I also have allot more cage in my car so springs are compressed consistently. With an OE style rear suspension that has inherent bind, you would not run as stiff a spring in my opinion.

"Spring rate" is comprised of a number of factors like tire brand, grip, sidewall height, rear suspension design and whether or not you are running a rear sway bar. For example, spring rates are going to be different on a car running Hoosier R7s vs Toyo RA1, or a 200 UTOG tire.

Don't forget driver preference. I like a car that pushes at the limit because it is safer. Also I feel like an RX7 is an easy car to get to rotate on demand so I don't need a loose car helping me out. The late Tom Thrash - Champion E production racer - had really radical spring rates compared to other drivers. But they suited his driving style.

For an additional data point, when I ran my car in IT7/ITA it had 400 Front and 200-225 rear springs. At that time I had a Tri-Link and all suspension bushings were spherical as well. But that suspension set up did not have great geometry compared to what I have now. Also the cage that I had in the car didn't add as much stiffness so the unibody flexed more. Especially up front.

Also, the kind of shocks/struts you run as a bearing on this too. Most of my ITA/IT7 competitors were not managing weight transfer under braking very well. This made them easy to pick off in fast to slow corners. Don't skimp here.

Freeskier7791

Good points, also intended use will vary the correct rate, since mine is a drift car I am running stiffer spring rates in the rear to basically minimize roll and force the tires to break loose. Good point on the flexing as well

Carl

iTrader: (2)

I just (yesterday) went with 450-275 on my ITA w/ tri-link panhard. Also have Bilstein non-adjustable shocks front and rear. Tokicos are probably too soft in the front. I haven't tested it yet. Changed from 400-225. It worked well, just wanted to try stiffer. To be honest, the PRO7 set-up you had is pretty fast with the stock watts/ 4- link steup. Mike Chiapetta has 400-225 with the stock rear set-up. He thought it was fine. Mike almost had a conniption when he tried to run 350-275 at Willow Springs. Could barely keep the car on track through 8-9. I think 350 is way to much for the rear with 450 in front. If you already have it though, it can't hurt to try.

Gian

iTrader: (3)

All things concentered, I've always just done what others have said that works. And it has worked ok. I finally decided to get some real shocks. To try and manage the rear a little bit better. I need just a little more off my lap times (don't we all..lol).

I defiantly understand the uni-body is part of the spring rate (takes more spring to compensate). So is the 4 link bind (need less spring to compensate). But as long as you have the shock to manage your spring rates. This should work, on paper anyways. It's just when you putting out the $$$$$$. I would like to think it's going in the right direction.

I'll be testing this in the next month or so. I know things will change. Just wanted an Idea if I was in the ball park.

MH, I too like a car that pushes. It seem I'm faster when I have to drive harder and deeper to get the turn to rotate the car.Thanks Carl. I'll be talking with you guys in the next few weeks.

mustanghammer

iTrader: (3)

I should add that the springs I have on my car were selected as a result of an E-WAG.....Educated Wild *** Guess. I am woefully short of on track development with the car right now. At this point, these spring rates have proven to be functional and seem to be in the ball park but are subject to change.

Freeskier7791

I have been wondering the same thing, PAC racing springs relocated 5 mins from my house so I might pay them a visit.

Carl

iTrader: (2)

You might try looking for rear springs at Blue Coil Springs. Their springs are about 1/2 the price of PAC. You can also get them in 8" length, which is about right for a lowered 1st gen. It is nice to be able to just drop in and talk to someone though.

Freeskier7791

Thanks for the info, PAC only makes 9.5" length like most other circle track springs. I think I am going to try 250 in the rear for now.

Carl

iTrader: (2)

You can also "customize" your own size and length by using a spring calculator (Blue Coil Springs has on their website). Buy one longer and weaker than you want and cut it to give you the exact length and strength. You need to know the number of coils and diameter of the wire. Kind of a pain if you can get what you need right off the shelf, but a possibility anyway.

Freeskier7791

Ended up getting some 8" tall springs from Lafrum in 250 lb rate. Also ordered Fox Body mustang KYB Gas-A-Just rear shocks, I hope this set up works. Scott have you used these shocks before?