Too wide! 993 widebody on early chassis wheel survey.

[MotoSook]

So I am building a 1973 race car with a 993 widebody kit on it.

The rear suspension has non-turbo trailing arms which means the rear hubs are more inboard than with turbo trailing arms. Never mind the pros and cons of one or the other, I'm stuck with the non-turbo arms.

The problem is the rear wheels. To fill the rear wheel wells with 11" wheels I'm gonna need approximately 3.5" backspacing. Pretty shallow. (ETA: I actually will need 4.0 to 4.5" BS)

So those with a wide body kit and narrow trailing arms, what have you done for rear wheels?

[MotoSook]

It's widddddde!

[Kevin Stewart]

10.5 wheels on my none turbo with turbo fenders is 3.3/4 back spacing, by the way looks great, Kevin

[RarlyL8]

You put 11" wheels in the front. Something like 14's would fit the rear. Waste of a widebody to put on skinny wheels.

[MotoSook]

Originally Posted by RarlyL8

You put 11" wheels in the front. Something like 14's would fit the rear. Waste of a widebody to put on skinny wheels.

Not really.

A Hoosier 345/35R18 R6 tire, the widest in 18", is designed for rim widths 11'-13" and optimal rim width is 12". I don't intend to use a 345 tire as my 2100 lbs car will (and perhaps 2300 lbs with fuel and me) with a normally aspirated engine, will likely be too light to build and maintain heat in that much rubber.

A 295 tire is my target width for the rear, and it is designed for 9.5'-11" with an optimal 10" rim width.

So a 14" is pretty much for show in my case. Could you stretch a 335 or 345 tire on a 14" rim, sure...but why. What does one gain?

[kinein]

12 inch wheel would be the way to go with 335's or a 315

[MotoSook]

I bought the tub with the widebody kit. If I were to start from scratch I would go with a Turbo width. This wide body kit adds 3" in the rear and 2" in the front fenders.

For show, I have another 993 wide body car I'm building. If the "widddde" doesn't do it...it's also in full carbon fiber

[kinein]

[kinein]

I bought my wheels from Jae lee at mirage international . Contact him

[Bill Verburg]

Originally Posted by MotoSook

Not really.

A Hoosier 345/35R18 R6 tire, the widest in 18", is designed for rim widths 11'-13" and optimal rim width is 12". I don't intend to use a 345 tire as my 2100 lbs car will (and perhaps 2300 lbs with fuel and me) with a normally aspirated engine, will likely be too light to build and maintain heat in that much rubber.

A 295 tire is my target width for the rear, and it is designed for 9.5'-11" with an optimal 10" rim width.

So a 14" is pretty much for show in my case. Could you stretch a 335 or 345 tire on a 14" rim, sure...but why. What does one gain?

optimal rim width is 12"

no, that is the measuring rim. The best performance would come from using the widest wheel, 13"

for a 295/30 x18 RS you would want to use an 11" wheel, the max it is spec'ed for.

[MotoSook]

Originally Posted by Bill Verburg

no, that is the measuring rim. The best performance would come from using the widest wheel, 13"

for a 295/30 x18 RS you would want to use an 11" wheel, the max it is spec'ed for.

I am corrected on the "optimal" vs "meas." I am intending to use a 295 tire, with 11" rims.

[MotoSook]

Originally Posted by kinein

I bought my wheels from Jae lee at mirage international . Contact him

Thanks. Jae and I have discussed this and he thought the BS might be too shallow for parts he has on hand. I will see if CCW can make me a set or two.

I really just wanted to see what you wide body guys are running, and to determine if I missed something. I have spent a lot of time in the shop staring at the car. Some of you may know what I mean by that.

[pkracer21j]

Our wheels are made by Forgeline, for our project Mjølner and our K3(rear), they shipped us a test fit wheel so we could make sure the offsets we're spot on. they have no trouble accommodating our low offsets.

[YermanCars]

I've been down this path to many times. What works is you have to run inner barrels as outer lips and vice versus. Going wide cost to much money, just think of the extra $$$ your going to spend in tires.

[ted]

I've had CCW and Jongbloed wheels in those sizes.
Jongbloed Racing Wheels - Contact/Service

I have run 17 and 18 CCW rims similar width with R rated tires on my 993 race car.
The 18s were just too tall and heavy, the 17s were fine.


Currently 74 RSR flares with 15x12 and 15x14 with 23.5 tall front and 25 tall rear Avon bias ply slicks.
My current Jongbloed 15 diameter rims and the bias ply slicks saved 10+lbs per wheel and tire.
Jamie Lipman's photos.



PS don't bother with the American Racer slicks, cheap slicks that start off crappy and get worse.

[kinein]

Originally Posted by YermanCars

I've been down this path to many times. What works is you have to run inner barrels as outer lips and vice versus. Going wide cost to much money, just think of the extra $$$ your going to spend in tires.

+1 tires is a huge cost if you are wanting a street tire there isnt much of selection above 315 and up. there is plenty in drag radials

[gsxrken]

Wow that car looks great! Every kid should be issued a poster of that for their bedroom wall.

Originally Posted by ted

Jamie Lipman's photos.



PS don't bother with the American Racer slicks, cheap slicks that start off crappy and get worse.

[Mahler9th]

That appears to be Getty Design bodywork. We have quite a few 911s in our area that have run that bodywork (as many as 20 cars or more) in recent years. Some have turbo trailing arms, many do not. Weights range between ~1850 - 2350 without drivers.

Sixteen inch wheels are popular in our area. We have a special GT class that requires them, but a number of GT1, GT2 and GT3 cars elect to run 16s. There are a number of benefits of 16s.

The Goodyear bias ply tires have been popular for over a decade, and have proven fast enough to beat heavier factory cars on modern radials.

Goodyear is no longer committed to the 11.5 and 13 wide tires that have been popular, so a number of folks have moved to Hoosier 16 inch bias ply tires in similar sizes. Avon has bias ply tires in this size range that can be very fast. But the new hot ticket appears to be Hoosier 16 inch radials, with pretty big sizes (12 and 14).

My car has that bodywork and SC trailing arms. I will likely change my set up to run the 16 inch Hoosier radials in 12 and 14 inch widths.

Quite a few of use have been using the Bogart wheels for over a decade and are very, very happy with them. Sizes we run are typically 10-11 x 16 and 12-13 x 16. Strong, light and fairly priced.

These are race cars, not street cars, although some are licensed and registered for occasional street driving.

[Cory M]

I'm running 18x12 rears with a 1" spacer and long studs. I could fit 13" easily but the 12" give me more tire choices, it's in the recommended range for 315 & 335 rcomps as well as several slicks. I race on a budget and want to have a lot of options in case I can score a deal on used tires. I also want to be able to run long lasting tires (NT01) for lapping days. You have to look at tire height as well as width.

To be really competitive you need to pick the tire you plan to race on and buy the wheels accordingly. Are you going to be on slicks or R-comp? Are there rules that limit or penalize wheel size? How much does the car weigh (with driver) and how much power will it have? How low can you get it in the rear with a tall tire?

Everyone loves big tires but the fastest cars I've seen with a set-up like yours are running slicks in cup car widths (240/280). With lighter cars and medium power you may not get the heat into the big tires, especially the fronts. If you aren't racing for wins in a competitive series you can go wide and get a longer life out of your tire, you'll be sacrificing some speed though.

Lets see some more pics of your project too, looks cool!

[MotoSook]

Originally Posted by Cory M

I'm running 18x12 rears with a 1" spacer and long studs. I could fit 13" easily but the 12" give me more tire choices, it's in the recommended range for 315 & 335 rcomps as well as several slicks. I race on a budget and want to have a lot of options in case I can score a deal on used tires. I also want to be able to run long lasting tires (NT01) for lapping days. You have to look at tire height as well as width.

To be really competitive you need to pick the tire you plan to race on and buy the wheels accordingly. Are you going to be on slicks or R-comp? Are there rules that limit or penalize wheel size? How much does the car weigh (with driver) and how much power will it have? How low can you get it in the rear with a tall tire?

Everyone loves big tires but the fastest cars I've seen with a set-up like yours are running slicks in cup car widths (240/280). With lighter cars and medium power you may not get the heat into the big tires, especially the fronts. If you aren't racing for wins in a competitive series you can go wide and get a longer life out of your tire, you'll be sacrificing some speed though.

Lets see some more pics of your project too, looks cool!

You just highlighted the major factors that are influencing my rim choices. Heat, tire choices and budget.

I am not going to spend bags of money chasing a plastic trophy. So that sets the tone for my budget. I also have the benefit of feedback from a couple guys who run in NASA GTS3 and GTS4 as to how their tire choices worked out. So I'm pretty much set on 245x18 in front and 295x18 in rear. Any bigger and I will have heat issues. I expect it to be approximately 2100 lbs without my fat arse in it.