I am currently running 265/35/18 in the rear and would like to add pettit's widebody flares. They say it can occomadate an extra 2" I believe. Would it be okay for me to run 1" or 2" wheel spacers until more $$$ comes in for me to afford wider wheels? And... what would I need to do about the stock fenders? Cut, roll, or what?
Thanks

 

A 1" spacer is too big and 2" is totally out of the question. Spacers significantly increase the load on the wheel studs. It would be much better to get different (wider and/or different offset) wheels. There isn't much need for flares unless you want to run huge rubber.

A wider rear track will reduce weight transfer at the rear, increasing understeer. Cars that understeer a lot are no fun to drive fast, and it can even be quite scary when you turn the wheel and the fronts just slide. Be sure to consider some changes to counteract this effect if you go wide in back. A stiffer rear sway bar or stiffer rear springs will help bring the car back in balance.

If you could just roll the fenders to get the tire clearance you need, there is no need for flares. I would assume that everyone cuts the fender when installing flares.

-Max

 

Well, for one thing the flares would be, in a way, just for looks. I realize that you do not need to get flares if just stepping up in wheel width and that there are guys on the forum running 10.5"/11" in the rear. I do have an m2 coilover suspension setup with eibach springs and I have yet to upgrade the swaybars. So, for the mean time, can a 1" spacer be used to keep me from spending way too much money at the moment? I dont normally track the car, I have taken a 2 lessons at VIR with a neighbor of mine who owns a pure track fd and has been very helpful. I asked him about this and he mentioned to me that there are many porsche owners that use spacers for wider wheel bases. Thanks. I was hoping somebody would answer my question.

 

 

So then what? I shouldnt do it at all? Exactly how bad is it?

 

See what Rishie has. 1" is a huge spacer, though. Rishie, what size spacers can you supply tookwik?

You will need to get longer studs of the highest quality you can find. Spacers themselves are surprisingly expensive, too.

This just doesn't make sense to me unless you are going to get some 11"+ wheels.

-Max

 

I agree that spacers of that size are a horrible choice, but as far as load on the studs wouldn't it be the same whether the offset is created by spacer or wheel?

 

So what kind of spacers are EVER used? What would be the point if nobody should use them?

 

Bearing load is the same with spacer or offset, but wheel stud stress is very different.

-#WWW SSSS HH# is harder on a wheel stud than:

-#WWW HH#

where:
- end of stud
# lug nut or head of stud
W wheel
S spacer
H hub

-Max

 

Thin ones, usually. They do widen the track reducing weight transfer, so they can be useful with stock (or other) wheels in a competition situation. People use them to avoid rubbing also. They are always a last resort, however.

Good spacers are expensive and you need to get longer wheel studs to use them. Considering the costs, it seems like you could spend roughly the same money on a much better solution by selling your current wheels and buying new ones with the offset that you need.

-Max

 

well, what if i feel I could only get maybe $1500 for my wheels. I bought them for $900 including my stockers with very nice rubber. The buy was great, new the wheels are $2000 something.link to some pics of wheels (large size)

 

ok, then for just spacers to accomodate the wheels in order to fit right in the widened body, what would you do. Keep in mind, i have a limited budget. This may sound like the bad idea, but.... whats the cheapest way to do it.

 

If the wheel offset is correct for your car, there's no need for fender flares and spacers. The265/35-18 is a conservative fitment, and can be run up front (with 50 to 51-m offset). Now if you were widening to 295/30-18 on 11 x 18 (7.5-inch back pace, 38-mm offset), in back, then perhaps...but even then, you could roll the rear fender lips, and dial in 1.5 degrees of negative camber to tuck the tires under the rear fender lips. I would not consider the Pettit flares. The only reason you'd need them is if you were running rear tires Cam Worth does on his Pettit race car (315s I think?). Dude, save your money

 

Not intending to sound argumentative, but even if the wheels are hub centric?

 

You know your proabably right, but i kinda just want to add some extra subtle look to my car because i thing body kits are rediculous for an FD. Do you think I should even do the spacers? How do you think it would look with just the flares. Thats what troubles me

 

If the wheels AND spacers are hub-centric, it would help to reduce the load on the studs, but it will still be more than it would with wheels that had an equivalent offset because the studs are longer.

I would think that most of the time a number of things are not as good as they could be when using spacers:
- spacer is not hub-centric to hub
- wheel is not hub-centric to spacer
- lugs are not long enough
- lugs are threaded through the spacer (they should not be)
- spacer has its own studs (weak design)

-Max

 

If you are planning to do any high stress to your vehicle (IE Road Racing) I would not suggest spacers, unless as previously pointed out, you have significantly longer studs, as the pressure becomes greater as the moment of friction is moved farther and farther from the contact point of the stud.

I would get larger wheels in the correct offset, its safer.. Personally, I wouldn't sacrifice safety because of cost.

 

so i guess untill i can get different wheels... dont worry about it?

 

How about if I am going to add a 2" flare on both the front and back and I want to run 18x10 for the front and 18x13 in the back. I have a coil cover suspension with 2.5" Diameter springs. I will add the trailing arms if I need to. I want to leave a 0.5" gap between the fender flare and the edge of the rim so I don't crack them. What kind of offset will I need?

+37mm for the front and +25mm for the back?

Chuck

 

Chuck,

18x10" fits under the stock fenders in front. With a +51mm offset, the rim and fender are roughly equal looking from the top (though obviously it depends on the camber setting). You probably want them tucked under a bit (say 15mm), so you could have and offset of like +15mm or something for the front. That sure will screw up the scrub radius, though, and may lead to fender rub when you turn the wheel since they will be sticking out so far. It would be cool to have new (longer) upper and lower suspension arms, tie rods, sway bar, to widen the track without messing all that stuff up. How about 18x10" fronts under stock fender with flares and huge tires only in the rear?

You can have up to about 7.5" of backspacing in the rear with 18" wheels. I was just looking for the Fikse page that had all their fitments, but I can't find it. The offset-to-backpsacing calculation depends a little bit on the particular wheel maker anyway. My 18x10 CCWs have 7.5" backspacing (measured) and +51 offset (educated guess), so the same backspacing on an 18x13" wheel would be -25 or so.

That brings up a point I am kind of curious about. Fred Puhn's book How to Make Your Car Handle inverts the offset numbers we commonly throw around here. He is the inventor of monocoque wheels, so it seems like he probably knows his stuff. By his convention, my 18x10 wheels would have a negative offset (-51mm), but I/we always seem to indicate it as a positive offset. His convention makes more sense to me, but I wonder why we don't use it. Anyone know why? Or maybe its only me that has been writing it this way and I'm an idiot.

-Max

 

Thanks Max. Do you know the back space for the front? Just to make sure we are talking about the same thing. The backspace is the distance between the hub mounting surface and the back edge of the rim, right?

Chuck

 

you are correct re backspacing. How did the dyno session go? Sorry I couldn't make it. Car is on jackstands, and my widebody conversion has begun... Carl Byck

 

My wheels are all the same all around with 7.5" of backspacing.

When converting between backspacing and offset, remember that the nominal wheel size (mine are "10 inches" wide) is for the tire bead. The actual wheel will be 0.5 - 1.25" wider than the nominal size. I think my 18x10" CCWs are 11.125" to 11.25" wide (haven't had a chance to measure width that closely). Backspacing is measured to the actual rim width, so converting using the nominal width will give you erroneous results.

-Max

 

The dyno run didn't go as planned because the Power FC boost controller cannot control boost accurately. The boost was spiking to 1.3 kg/cm2. After we install another independent boost controller, we are going to go again. Should be sometime in March. You want to come?

Chuck

 

Thank you Max. You have provided great help. I hope Volk Racing can give me some info on that but I doubt it. Maybe I will just go with 18x12 just to be safe.

Chuck