I'm about to pull the trigger on a set of custom wheels and want to confirm backspacing and center bore for hub centric ring on a 1974 car. I will be running fat 205/50/15 Hoosiers on the wheels.

I will be having 15x7" wheels made with 4 lug 4x130mm bolt pattern.

Back spacing specs: I have heard everything from 4.25" to 5" for backspacing for 15x7 wheels. I'm not afraid of bending my fenders a bit to make things fit and I like the idea of a little wider track. Would 4 1/2" back spacing be enough for somone who has rolled fenders? I have lots of room now with rolled fenders and my 205/50/15 tires on 5.5" Fuchs - easily 2 to 3 inches

I do have centering ring on my front hub. Mueller provided dimensions of 78.60 mm x 15 mm which looks about right using my tape measurer. If I make an error I want to make sure its making this bore too big.

I appreciate everyones feedback.

I'll be watching for the answer, as well.

What do the rims look like? I may want to piggyback on the order

KT

All cars are a little different, so there isn't a single right answer. But the general rule of thumb on 7" wide wheels, is that a 5.00" backspace will very closely center the wheel between the inner wheel well and fenders which have been rolled and/or tugged out a bit.

The right thing to do is to take measurements on your current wheel/tire combo. measure the clearance between the tire and inner wheel well (hard to do), and the clearance between the tire and fender. Do this on both sides of the car as they will be different. From there, some simple math will tell you the proper backspace or offset you will require to center the wheel between the inner and outer fenders (if you have 4 bolt Fuchs, your current backspace is about 4.7" - you will need this info in your calculation). There won't be much room for error, but you will want to err on the side of having the wheels closer to the outer fenders than the inner fenders (a little less backspace) because it is much easier to massage the outer fenders to get the wheel/tire combo to fit. The inner fenders or wheelwells will be much more difficult.

Demick

I've had 2 sets of 15 x 7 Revolutions with 5" BS. The spacing was just about perfect. I did have to roll the lip in one side only.

Go with 5" BS.

Paul

QUOTE (trekkor @ May 25 2005, 06:21 AM)

I'll be watching for the answer, as well. What do the rims look like? I may want to piggyback on the order KT

You may want me to test this out before you spring for same specs. I'm still negotiating with a couple of providers.

QUOTE (Demick @ May 25 2005, 06:44 AM)

All cars are a little different, so there isn't a single right answer. But the general rule of thumb on 7" wide wheels, is that a 5.00" backspace will very closely center the wheel between the inner wheel well and fenders which have been rolled and/or tugged out a bit. The right thing to do is to take measurements on your current wheel/tire combo. measure the clearance between the tire and inner wheel well (hard to do), and the clearance between the tire and fender. Do this on both sides of the car as they will be different. From there, some simple math will tell you the proper backspace or offset you will require to center the wheel between the inner and outer fenders (if you have 4 bolt Fuchs, your current backspace is about 4.7" - you will need this info in your calculation). There won't be much room for error, but you will want to err on the side of having the wheels closer to the outer fenders than the inner fenders (a little less backspace) because it is much easier to massage the outer fenders to get the wheel/tire combo to fit. The inner fenders or wheelwells will be much more difficult. Demick

Thanks Demick, So looking at my car currently (205/50/15 Yoko's mounted on 2.0 Fuchs) I have about an inch of clearnce on the inside and about 1 1/2" of clearence on the outside fender. If the Fuch 2.0 wheels have 4.7" of spacing I may need to keep that or even go for less?

So maybe 4 1/2 backspacing if I'm not shy about pulling on my fenders?

I definitely dont want and issue with tires rubbing on inside of fender wells or to fool around with spacers in the rear.

QUOTE (URY914 @ May 25 2005, 10:21 AM)

I've had 2 sets of 15 x 7 Revolutions with 5" BS. The spacing was just about perfect. I did have to roll the lip in one side only. Go with 5" BS. Paul

I've heard that the Revolution wheels were a little on the heavy side. Just surprised they were on the lightest 914 on the planet if that is the case...

QUOTE (grantsfo @ May 25 2005, 08:59 AM)

Thanks Demick, So looking at my car currently (205/50/15 Yoko's mounted on 2.0 Fuchs) I have about an inch of clearnce on the inside and about 1 1/2" of clearence on the outside fender. If the Fuch 2.0 wheels have 4.7" of spacing I may need to keep that or even go for less? So maybe 4 1/2 backspacing if I'm not shy about pulling on my fenders?

Highly unlikely that you would want your current 4.7" backspace, and definitely don't want less!!

Your measurements are obviously balllpark - and you should try and measure as accurately as possible (and try to take into account what happens when the suspension gets depressed). But just generally from what you have provided: You currently have 1.5" clearance on the outside, and 1" on the inside. This means that your wheel is sitting about 1/4" off-center toward the center of the car. Now assume you retain your backspace and add 1.5" of wheel width to the outside of the car. Your wheel will now be about 1/2" off-center toward the outside of the car (centerline of the wheel moved 3/4"). I would probably target something around 1/4" off-center toward the outside of the car. This would put your desired backspace at 4.95".

But like I said, you need to carefully measure. 1.5" sounds like an awful lot. Remember, the place your tire will touch the fender is not at the center point of the wheel well opening - it is toward the rear of the car - so be sure and measure for the minimum clearance you find.

Demick

QUOTE (Demick @ May 25 2005, 09:44 AM)

But like I said, you need to carefully measure.  1.5" sounds like an awful lot.  Remember, the place your tire will touch the fender is not at the center point of the wheel well opening - it is toward the rear of the car - so be sure and measure for the minimum clearance you find. Demick

Think I forgot to mention I ran a rolling pin in between my tire and my fender to flare things a bit a couple of months ago for another set of wheels that didnt work out. I remeasured across the entire rear fender and clearence ranges from almost 2 inches to just a little over an inch towards the rear of the fender. So I think 5" may be the ticket especially since the 15x7" Revolutions use that offset.

I'm going to have the wheel guys talk me through the measurement process too as I dont want to screw this up! If we come up with anything other than 5" I'll probably come back for more input.

15 x 7 Cookie or Fuchs have back spacing of 120mm (4.725") and will/may not fit standard bodywork. Min backspacing required is 125mm (4.92") to fit without any dramas. I had my first set made with 135mm (5.31") because I wasn't sure how everything would work out and run spacers to put the wheel where I want it.

QUOTE (don9146 @ May 25 2005, 08:46 AM)

QUOTE (URY914 @ May 25 2005, 10:21 AM) I've had 2 sets of 15 x 7 Revolutions with 5" BS. The spacing was just about perfect. I did have to roll the lip in one side only. Go with 5" BS. Paul I've heard that the Revolution wheels were a little on the heavy side. Just surprised they were on the lightest 914 on the planet if that is the case...

Their not on the "World's Lightest 914" anymore.

I did say "had".

And they are a bit heavy.

Paul

My Panasports have a 4 and 7/8" backspacing I think... Had to massage the fender lip a bit, but not by much

here's a pic. The rear has since been lowered

Hmm, IIRC my 15x7 cookies are like 4 5/8" and the correct backspacing is the 4 7/8. Whatever the RSR wheels is correct.

Grant,

as long as I get it back in timely manner, you can test fit one of my wheels.....17x7 with a 205/45...if you are going to the breakfast, and bring your car, we can test fit it right there.....

47mm offset as is, but I can also bring you a 1/2" spacer that brings the offset to 34.3mm (normal revolutions are 35mm offset)

4x130mm bolt pattern

QUOTE (Mueller @ May 25 2005, 09:52 PM)

Grant, as long as I get it back in timely manner, you can test fit one of my wheels.....17x7 with a 205/45...if you are going to the breakfast, and bring your car, we can test fit it right there..... 47mm offset as is, but I can also bring you a 1/2" spacer that brings the offset to 34.3mm (normal revolutions are 35mm offset) 4x130mm bolt pattern

Thanks! If I can make it I'd love to see how it fits. My sense is I wont have much of a problem since I got some 15x6 American racing wheels under my fenders with tires.

I forgot, I also have one 15x7 steel wheel (no tire) that fits under the stock fenders (it's one of the rims that Jenny has on her car now).....this way you could mount the specific tire you have in mind to get a better fitment idea......

QUOTE (URY914 @ May 25 2005, 07:21 AM)

I've had 2 sets of 15 x 7 Revolutions with 5" BS. The spacing was just about perfect. I did have to roll the lip in one side only. Go with 5" BS. Paul

I agree with Paul. Go with at least a 5" backspace.

I have a set of 15 x 6.5" Revolutions with 5-1/8" backspacing with 205/60 tires. At the rear there is 1/4" or so clearance to the outer stock fender lip.

Thanks for everyones input. I have ordered custom 15x7 wheels with 5" back spacing.

Cool

What do they look like and how much are they?

KT

QUOTE (trekkor @ May 26 2005, 05:34 PM)

Cool What do they look like and how much are they? KT

Keizer wheels ...about $1300 for all 4 including shipping to California. 10.85 lbs per wheel!

Wow, Grant


Kinda expensive. Nice though.
I look foward to seeing them on the car.

Gonna do any freaky race car paint work. I might.

Thanks for pioneering this.

KT

QUOTE (trekkor @ May 26 2005, 07:14 PM)

Wow, Grant Kinda expensive. Nice though. I look foward to seeing them on the car. Gonna do any freaky race car paint work. I might. Thanks for pioneering this. KT

Carbon fiber hood/trunk and black fiberglass bumpers are next. I'm staying with Olympic blue with lots of black. Wheels will have black centers.

very cool grant


my 'phase II' plans for the car might involve custom wheels .... nice to see how these will work. 1300 really ain't bad. and <11 lbs!! damn!!