Juha G

I'm seriously thinking about widening my 993 during next winter.
The reason is we have quite "slow" tracks here in Finland so I want to fit the widest tire possible. As the speeds stay below 120mph, the additional parasitic losses play no role in the lap times.

Ideally I would like to have:

Front: 285/30/18 on a 18x11" rim
Rear: 315/30/18 on a 18x12" rim

Can this be achieved with NB fenders and RSR flares or do I need to get the Turbo rear quarters and GT2 flares?

I would like to buy the GT2 EVO 1 front bumber. I suppose I can use the GT2 front flares with it and I will be able to fit the 11" rim on there with 285 rubber on it.

What about the rear? If I get the GT2 flares, can they be mounted on the NB rear quarters or do I need to swap WB quarters?
Also, will the NB rear bumber stretch to GT2 dimensions or do I also need a WB rear bumber in that case?

I know there are several topics about this but I still cannot find factual information...

Thanks for the help!

Falcondrivr

I'd contact Thatcher. He built that gorgeous silver RSR on a NB.

Juha G

I did check his topic and actually based on that I am quite sure that I will not be able to fit the desired wheels/tires on with just the RSR flares:

Mark in Baltimore

bobt993 and ninjabones are good people to talk to, as is Premiermotorsp aka Chris Cervelli.

Flying Finn

+1

I've spoken with both of them and they have good info, Bob's car has a ton of engineering (he made the front wider etc.) and knows a lot.

But those tire sizes should fit with just putting the RSR flares on a narrow body fenders.

Getty says their kit adds 1.5" to the rear and 1" to the front so just from that, if you compare my track set-up which is 245 & 285 (rear fenders are rolled, fronts not) with about -2.5 camber on both ends. And my rear wheels have ET52 which sticks out more than they need to but still no rubbing.

Sooo... Your tire sizes of 285 & 315 would add 40 mm front and only 30 mm rear which is just over 1.57" front and 1.18" rear so rear surely shouldn't be a problem and since my front is not rolled (with those 245s), I'd say 285 will fit.

I'd start by measuring what kind of space you have now with the tires you have and adding whatever is needed when compared to 285 & 315 and then measuring the distance to the fender and inside body.
Rear is of course easier because the wheels don't turn but still you'll have a pretty good idea of what fits.

DALLWA

Juha,

Check out this information from Bill. Lots of great details and comparisons between models.

https://rennlist.com/forums/showthre...errerid=114301

Cheers,
Tony

trophy

Hey Juha,

I am planning the same thing at the moment and have been through every thread, looked at hundreds of photo's and have had a chance to look at both factory and clone GT2's and RSR's.

Front:

GT2 and RSR flares are the same, they each add 1" to each side. The shape of the inner lip of the flare is a different contour that the original steel fender, this does give some leeway to tire size.

The stock bumper will stretch to meet the contour of the new flares, fiberglass ones need to be purchased to match the width, some guys have made them stretch a bit but it is not always possible.

I would suggest you move the front side members to the outer mounting holes, to do this you will need to do some fiddling with spacers (Swaybar, booster mounts etc) This will ensure the geometry for the front end is right. Of course doing this will require some figuring on wheel offsets etc.

Wheels/Tires. Check some threads from spartan, scottmellor etc. These guys have GT2 conversions and have been through a bunch of different tire sizes. These guys have run 265's and 275's without too much problem. DM993tt has run 275's on the front of stock fenders with some rubbing so I would suggest 285's will be possible.

On a stock front end I have run 255's on a 9" rim with no rubbing etc. I would suspect with some aggressive alignment and wheels you should be able to fit a 285/30 One benefit is that tire is pretty short so gives you an additional room.

Rear:

GT2 flares will not work properly on the back end of a NB car, the contour of the original steel is very different. I don't think you could modify the flare enough to fit. To run the GT2 flares you will need to do the mod to WB steel first. As for the bumper the stock rear NB bumper will stretch to RSR flares but not to GT2. You wouldn't want the NB bumper anyway, its' only the top that stretches, the bottom of the bumper will still be narrow giving a 'V" look to the back end (The space between WB exhaust tips and NB are different)

The RSR flares will add 1.5" to the back end making it essentially the same width as a WB (little wider). Again there is a difference on the inside of the flare compared to the steel fender giving you a bunch more room. 315's will be a pretty easy fit on a 12" rim. I run a 295 on the back f mine now with no problems. I know of at least 1 NB RSCS race car in the US that runs 305 on the back of a NB, he had to modify the oil line a little but can work.

Hope this helps.....

Spartan

No 18X11's on the front if you use factory stuff. Well they will technically fit but you won't be able turn them. 10's fit great and they are still going rub at full lock (but who cares!).

You can always massage the factory flares to get some more room in there to stuff 11's if you really really want them. RSR and GT2 front flares are the same, rears are different.

I run a 265 up front and I don't find myself wishing for more front tire

bobt993

275fr /315 rear is a good combo. I have also run 255s front for practice tires I get from a GT3 buddy who also races. Club sport or GT2 flares will work. Full RSR flares are even wider, but the factory bumpers do not work well with them and fitment is poor. 10inch rims on the front with 12 rears.

You have a bit of work to do on the front of the car and it depends on the brake booster clearance as to how you have to do this. Also, don't just change the offset on the front rims to some extreme outer offset to widen the track. This is a bad move and alters the scrub radius too much. For a street 993 you can go the cheaper way, but if you want improved handling then:

All 993 chassis include the outer wheel carrier mounting holes in the tub to move the suspension out 30mm each side. (you also likely need to drill the back part of the mount spaced 30mm also. Brake lines need to be moved a bit / stretched carefully at the bend points. EVO uprights, choice of GT2 sway bars or modded links. GT2 tie rods are also needed. A good set of camber plates will help reduce the 9 degs of camber you are left with. Always start by maxing positive camber on the upright (factory camber), then go to the shock mounts. I was able to mod my camber plates and flip them in order to get down to 3.5 degs of camber in the front. Now for bumpers.............. If your not staying factory then there are a ton of options.

tcsracing1

What did the 993 Supercup use for fenders and tire size? Perhpas that would be the best choice for a narrow body.....

Flying Finn

Supercup had 245 & 285 and many of use that combo in narrowbody cars (as supercup) but if you put flares, you do that to stuff more rubber underneath...

Juha G

I found this very old post somewhere:

Is that true?

I have been thinking about the conversion and I think I will first go RSR and maybe after that GT2. The front will be the same in any case so going from RSR to GT2 will only require additional work in the rear (and only left over parts would be the rear rsr flares).

But, if FVD has GT2 width flares that fit NB, maybe that's the way to go?

Flying Finn

I'm pretty sure Getty also has flares for nb that are 1" more wider.

But remember then you also need to change the rear bumper, with RSR width, you keep the stock bumper.

Juha G

I have a turbo rear bumper in store for this...

bobt993

From my experience there are 3 different kits for the car and they are all different. (GT2 kit is different than the RSR flares)

Clubsport flares will fit on a NB car and you can stretch the existing fr/rear bumpers to fit with these.

GT2 will work but you are starting to push the fitment and the nose will not line up very well. A new front bumper and a turbo rear bumper help the fitment.
The RSR flares are much more aggressive and require a bit of work to get fitment. The EVO bumpers fit better with the GT2 and RSR front flares.

I used clubsport and had to modify the front bumper a bit to have it line up properly. Whichever flare you go with get the matching rocker panel for the side or it will look pretty bad. Easiest way to get good fitment is to mount the rocker panel first then align each flare starting at where it connects to the rocker. Other key point is you must upgrade to EVO uprights and widen the front track or the handling will suffer. Changing the front offset is not the way to push the wheels out. I have seen plenty of cars where this has been done and for street cruising you will not notice the difference, but for racing or heavy track use it is required.