13x7 with a +7 offset

Discussion in 'Discussion Forum' started by Chris in Canada, Mar 16, 2019.

  1. Chris in Canada

    Chris in Canada True Classic

    Location:
    Ontario, canada
    will these fit a stock x suspension? Plus offset brings the rim inward and a negative offset is outward, correct?
     
  2. stingray250

    stingray250 True Classic

    Location:
    Oz
    wheel-offset.jpg
     
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  3. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    Another factor to use to gauge the wheel fitment on an X is backspace as shown in stringray's graphic. Many Fiat of the "stock" alloy wheels for the X1/9 have around 102mm or 4.7" of backspace. There are exceptions, for example, the CD30 (13x5.5) has only approximately 90mm or 3.5" of backspace. Lots of folks run CD30s, so they must fit fine. (I have never owned a set.) The CD31 (13x5.5) have an offset of 18mm, so the backspacing on those is 3.96" or 100.6mm. I do have CD31s and they fit really well.

    You can figure out the backspace on a wheel using the width and offset.

    Backspace in inches = ( (width in inches +1 ) / 2 ) + ( offset in mm / 25.4 )

    For your example of 13x7 wheels with a +7 offset, the math would be:

    ((7+1)/2) + (7mm/25.4) = ( 4 ) + ( 0.27559 ) = 4.28" or 108.7mm of backspace (results rounded)

    So the 13x7 wheels you are looking at have a backspace measurement of 108.7mm, not too far off of the "stock" alloys that have backspace of 102mm. The issue that you run into with 7" wide wheels is that most of the "stock" X alloys were 5.5". That extra 1.5" in width has to extend either inward toward the suspension or outward toward the fender lip. With a positive offset of 7mm, I think most of that added width will project toward the fender.

    This extra effort is just the price of going for a deep dish look. You can see in stingray's graphic that negative offset produces the best dish. You won't find many Fiat specific wheels with a negative offset. If you do find them, they will more than likely be wider than typical and intended for cars with wide body kits or flares.

    MWB has a 77 K20 car for sale that is wearing 15x7 wheels. The info on the car says the all the fender lips were massaged to get the proper clearance. The front tires are 195/45/15 keeping the diameter at 22", which is pretty much the space limitation of a stock wheel well. Even these wheels aren't terribly dishy, but they look business like on this car.
     
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  4. carl

    carl True Classic

    Location:
    Virginia
    I have found over the years that anytime you use non stock Fiat wheels there is a good chance you will have to do a little trimming of the front fender for full lock. Rears have never been a problem. Also, the ready availability of stock wheel spacers gives you some latitude on pushing wheels further out. On my rat, I used iron cross wheels but had three spacers to help push them out. Using long studs allows easy playing with all this. The massive 13x8 wheels I have on Fatrat clear the stock strut springs with no spacers but I will have to do a lot of trimming of the fiberglass wheel flares (the stock fender lips were cut off front and rear to take full advantage of the flares). Adjustable coilovers obviously allow for height adjustment but not sure if that will help with front fender clearance. It's all very fiddly and can be frustrating. I gather most folks here have stock Fiat alloys with 185/60/13 tires and have no clearance issues.
     
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  5. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Front fender clearance is always the more difficult end to deal with when going to wider wheels...for pretty much any car. The fact they turn ('steer') in addition to the usual up and down movement has a lot to do with that. Plus front suspensions/steering mechanisms are typically more complex and therefore more crowded than rear's. Adding spacers or using wheels that sit further outboard (more negative offset) complicates this more by increasing the 'swing' (steering) distance. It causes the wheel to move further forward and rearward as it moves through the steering arc.

    However on the X it is even worse than most cars due to the front suspension design. If you look at the wheel to fender relationship, you see the wheel isn't centered in the wheel well (it sits further forward). So the front lower corner of the front fender lip is the biggest offender. The wheel could be relocated further back to center it (and give much more clearance) by extending the position of the suspension arm on the trailing/radius rod, but that will screw up the castor setting and handling will suffer. By the way, installing new bushings on the trailing/radius arm will help assure proper geometry and assure the wheel is located in the original position. Likewise, making sure all bushings are in good shape and a proper front end alignment is critical.

    A fender lip "roller" (see below) works great to add clearance. It will bend the inner fender lip flat against the fender panel, adding about 1/2" more room. It can also be used to "pull" the fender out a little. This stretches the fender a bit wider to give a tad more space, especially at the points that need it most. Trimming that front lower corner might be still necessary with the X (depending on the choice of wheel/tire). If you install a full front "air dam" that extends to the fender wells, then it might allow you to trim the forward lip more without being noticable (the dam covers that area). Obviously flares also allow for that. Oddly, many flares for the X do not really widen the actual fender dimension by much (if at all). The stock fender shape has a lot of extension toward the top, so it is very wide at that point. However flares bring that extended width all the way around the fender lip arch to give a more universal width. The real benefit to adding flares is the ability to trim the stick lip off and hide the modification.

    On the rear of the X there is a lot more room. For one thing the fender sits about 40mm wider (relative to the hub) than the front. So if you use the same size wheel/tire combination for all four wheels, then you will need to add more spacer to achieve the same overall width as the fronts (relative to the fender lip). Also there is less stuff in the way in the rear. The rear strut locates the bottom of the spring (the lower perch) higher up on the strut body. That offers more clearance on the inner side, between the tire and strut assembly. So a much wider wheel (with the right offset) could be mounted on the rear by having additional width on both sides of the hub.

    Sizing custom wheels and tires for maximum width is complicated. Every aspect of width, offset, diameter, etc changes all of the geometry which affects the outcome. Careful measurement of several dimension is required, but in the front it is very difficult to calculate for the steering motion. A mock-up wheel measuring device (see below) makes this much easier than trial and error.

    Fender roller:
    p31158.jpg

    Wheel/tire measuring tool:
    s-l300.jpg 760-01201chartsmall.jpg
     
    Last edited: Mar 17, 2019
    kmead likes this.
  6. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    I like those wheels. The size fits the X very well. The description does not say too much other than the brand/model and 15x7. According to the manufacturer's site they are available in several offsets, I'd like to learn what these are. Also it does not show them available in a 98mm bolt pattern, so I'm assuming these are 4x100? If so, how were they mounted? There's no indication of adapters.
     
  7. kmead

    kmead Old enough to know better

    Location:
    Michigan
    The Shakotan wheels were indeed 4 x 98. Mark Allison was the first to offer them. He has sold through on the ones he had. I believe they were also sold by Autoricambi but I may be mistaken.
     
  8. Chris in Canada

    Chris in Canada True Classic

    Location:
    Ontario, canada
    I asked Matt details on those. They are 4x98 but he said there was a lot of work involved to fit them. Coilovers, rolled lips and a couple of other tricks, but the end result is beautiful!! I just want some period correct, 13” rims with a little depth to give it that aggressive look. I have some aluminum slots on her now. I like the look on the front, but not so much on the rear. You answered a question I had about the wheel stance(rear lips stick out farther!!) I’m gonna fit some spacers on the rear and see if that looks better. I really liked the look of those bwa’s oldrascal had on his. Those are 8” rims with no flares!! Don’t want to cut my car(yet!!!) i’ll Just have to be patient and see what comes up. Again, you guys are awesome with all your knowledge and help!! Thanks so much!!!
     
  9. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Interesting, the maker does not offer that bolt pattern. Maybe they did a limited run at one time. I still woner what the offset is though.



    It will make a big difference. The actual width of spacer you will need could depend on a couple of factors. So you'll need to do some measurements. For starters, mount the wheels and check the distance on the fronts to a good reference point (like the top center of the fender lip). Use a plumb bob to measure from that point down to a good reference on the tire/wheel (the rim lip for example). Then do the same on the rears for the same reference points there. The difference between those will give an estimate of the spacer thickness needed to make the rears match the fronts, as far as appearance goes. here are other ways to measure but this is a simple method to get a good idea. If you want to get a test fit before buying spacers, try making some 'dummys' out of wood planks to bolt up behind the wheels and see how it goes.
     
  10. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    I was wondering what the Shakotans would look like on my 85X, so I stole Matt's photo and Photoshopped his car orange. They look OK. My efforts made it look like fall at MWB as some of the grass and leaves changed color too. :)

    ROTA wheels.jpg ROTA wheels orig.JPG
    I am still undecided on 15" wheels in general. I think I would go with 15x6 rather than the headaches of fitting 15x7, even though I would most likely lose some of dishiness with the 15x6.
     
  11. Chris in Canada

    Chris in Canada True Classic

    Location:
    Ontario, canada
    66420683-F88A-434E-9CC7-0DB6210BD939.jpeg BD1AB251-7949-4754-9DE0-859B7827269B.jpeg Just took a couple of pics. I think it’s more of a camber issue rather than spacing! Tires are 185’s on aluminum slots(4x98!) think 6”?? No numbers, off set unknown, running one factory spacer. Crusty lip is the rear.
     
  12. Chris in Canada

    Chris in Canada True Classic

    Location:
    Ontario, canada
    7B21ED87-AAB9-4A78-A321-B6DA52486F82.jpeg E754EC86-078A-46E6-B554-F30283B3CE39.jpeg This is a pic with 205’s on the rear. I’ve just lowered the front end (one coil) and was thinking of dropping the rear we well?
     
  13. Daniel Forest

    Daniel Forest True Classic

    Location:
    Montreal,Canada
    All tires are not created equal. While on my way for the canadian autoslalom championship, I went thru the stated and stopped at the Tire rack to buy some new Hoosiers. I was running toyo ra-1 185-60 13 in front and 205-60 13 in the rear. I bought the same size inHoosier R6 (if I remember well, it was the tire of the time). They were so large, they were rubbing everywhere. At the race, I had to fit wider spacers and raise my coil-over (adjustable) to avoid scrapping the tires on the (hammered inward) lips.

    Yours certainly don't look like 205.
     
    Last edited: Mar 18, 2019
  14. Those wheels look very similar to my 13 x 6 Shelby mags. They also made a 7" and a 5.5" with 4 x 98 bolt patterns for Fiats. The rears look a little skinny for 205s.
     
  15. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Granted it is a personal choice, but I really prefer 15" on the X. To me 13" look way too small for the big fender arches on the car.

    And I think that Rota style is a good design for the era of these cars.
     
    Last edited: Mar 18, 2019
  16. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Chris, looking at your pictures. I am guessing those wheels have a much different offset/backspacing than the stock wheels, moving yours further outward than stock. Yours seem to fill up the wheel wells nicely. If you want to retain 13" wheels, I would not replace them (assuming you like the style). Either use the wider tire on the rears or add a little spacer on the rears to increase their width relative to the fender. The camber will affect how they appear to fit in the fender lip. But the camber should be set for overall handling and driving, not looks. So maybe have the alignment (all four wheels) checked/adjusted. Then add spacers as needed to get the look you want (eg. wider in the rear).
     
  17. carl

    carl True Classic

    Location:
    Virginia
    From the rear/side picture, it looks like you are running a bunch of positive camber with the top tipping further out than the bottom. Those slotted wheels look great on your car and they seem to have a lot of offset to push the tires out that far.
     
  18. bpimm

    bpimm Brian Pimm

    Location:
    Washougal, WA
    Hoosiers are known to be oversized compared to most if not all others, have seen a lot of people face the same challenge you did with them.
     
  19. Chris in Canada

    Chris in Canada True Classic

    Location:
    Ontario, canada
    Picture is deceiving!! The top of the wheel actually leans inward!! I have had a 4 wheel alignment done by a high end shop and he told me the camber was a little off. I think I saw some bolts to solve this?? I’ve also replaced all struts, bushings, basically every mechanical part on the car!! Interior is almost completed, just deciding on a paint colour! She was originally blue. She looks a little rough, but mechanically A1!!!
     
  20. Kevin B (Asheville NC)

    Kevin B (Asheville NC) Administrator Moderator

    Location:
    Asheville, NC
    You want a little negative camber in the rear (and likely the front) on an x. when the suspension loads up, the wheels do straighten up some (on the loaded up side). I have camber bolts top and bottom, front and rear on my x and can get just about any camber I want, within reason.
     
    Cratecruncher likes this.

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