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another (my) '88 wheel question? by Tom Slick
Started on: 03-10-2014 07:22 PM
Replies: 5 (391 views)
Last post by: fieroguru on 03-11-2014 05:00 PM
Tom Slick
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Report this Post03-10-2014 07:22 PM Click Here to See the Profile for Tom SlickClick Here to Email Tom SlickSend a Private Message to Tom SlickEdit/Delete MessageReply w/QuoteDirect Link to This Post
I found a wheel I like.
the available sizes in 18" are:
18x8 with 35mm offset
18x8 with 45mm offset
18x8.5 with 45mm offset
18x9.5 with 45mm offset

my questions are:
1) will the 8" with the 45mm offset work on the front of an '88? without hitting the LCA on turns.
2) will the 8.5" with the 45mm offset work on the rear of '88 (with coilovers)?
3) will the 9.5" with the 45mm offset work on the rear of '88 (with coilovers)?

in case tires size matter I was thinking of either 225/40 for the front, and a 265/40 for the rear.
I know they are little taller than stock but i'd like to gain some ground clearance.

if anybody can give me a concrete "yes" or "no" to my questions i'd greatly appreciate it.
i'm wanting to order these ASAP.

thanks...
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Gall757
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Report this Post03-10-2014 07:26 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Have you seen the Joe Torma chart? It will answer most of your questions. The coilover will buy you more room on the inside, but it's not listed on the chart.....

Joe Torma chart

[This message has been edited by Gall757 (edited 03-10-2014).]

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Bloozberry
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Report this Post03-10-2014 08:53 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
In case no one with direct experience answers your questions, here's a bit of math to help you how to calculate your own answers:

The stock front '88 wheel is a 15 x 6 et 37. The best fitting wheel among the ones you've listed for the front is the 18 x 8 et 45. To figure out by how much these will stick further out than the stock front wheels, you go through this calculation:

First convert the stock width to metric: 6" x 25.4 mm/in = 152.4mm

Then figure out how far the stock outside rim is from the wheel mounting flange on the stock wheel (subtract the offset from half the width to find outer rim): (152.4mm / 2) - 37 mm = 39.2mm

Next convert the width of the 18 x 8 et 45 wheels to metric: 8" x 25.4 mm/in = 203.2mm

Then figure out how far the outside rim is from the wheel flange on the new wheel: (203.2mm / 2) - 45mm = 56.6mm

Finally, if the new wheel's outside rim is 56.6mm away from the flange, and the stock wheel's outside rim is 39.2mm away from the flange, then the new wheel's outer rim will be 56.6 - 39.2 = 17.4mm (11/16") further outboard than the stock wheel. Of course your new, lower profile tires will bulge out much less than the old stock tires simply because they have a shorter sidewall, so the difference won't appear as much as that.

Whether they rub on the control arms or not is a different story, but you can use the same methodology to figure out how much the new wheels will stick inboard as well and compare how much room you have to spare by looking at the clearances to the chassis parts using your stock wheels. There's a minor change to the formula for calculating the inside clearance (you add the offset to half the width rather than subtract it) so I'll run through one example.

The stock rear '88 wheels are 15 x 7 et 30. Your widest new rim choice is the 18 x 9.5 et 45mm.

So again, convert the stock width to metric: 7" x 25.4 mm/in = 177.8mm

Then figure out how far the stock inside rim is from the wheel mounting flange on the stock wheel (add the offset to half the width to find inner rim): (177.8mm / 2) + 45mm = 133.9mm

Next convert the width of the new wheel to metric: 9.5" x 25.4 mm/in = 241.3mm

Then figure out how far the inside rim is from the wheel flange on the new wheel: (203.2mm / 2) - 45mm = 165.7mm

Finally, if the new wheel's inside rim is 165.7mm away from the flange, and the stock wheel's inside rim is 133.9mm away from the flange, then the new wheel's inner rim will be 165.7 - 133.9 = 31mm (1-1/4") further inboard than the stock wheel. Once again, that's where the wheel rim will sit. The tire will bulge out somewhat further and needs to be taken into account.

Questions? Just ask.
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Tom Slick
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Report this Post03-11-2014 07:59 AM Click Here to See the Profile for Tom SlickClick Here to Email Tom SlickSend a Private Message to Tom SlickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:

Have you seen the Joe Torma chart? It will answer most of your questions. The coilover will buy you more room on the inside, but it's not listed on the chart.....

Joe Torma chart



I've study that chart until my head hurts and I don't believe to be 100% correct.
People post pics of there cars were the wheels should stick out past the fender's edge according to the chart but in the pics it looks just fine. Optical illusion I don't know.
If I were to believe the chart the 8" should work for the front except the unknown part about the LCA.
The 8.5 in the rear would definitely work and 9.5 might work but be very close to sticking out past rear fender's edge.

[This message has been edited by Tom Slick (edited 03-11-2014).]

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Tom Slick
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Report this Post03-11-2014 08:12 AM Click Here to See the Profile for Tom SlickClick Here to Email Tom SlickSend a Private Message to Tom SlickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Bloozberry:

In case no one with direct experience answers your questions, here's a bit of math to help you how to calculate your own answers:

The stock front '88 wheel is a 15 x 6 et 37. The best fitting wheel among the ones you've listed for the front is the 18 x 8 et 45. To figure out by how much these will stick further out than the stock front wheels, you go through this calculation:

First convert the stock width to metric: 6" x 25.4 mm/in = 152.4mm

Then figure out how far the stock outside rim is from the wheel mounting flange on the stock wheel (subtract the offset from half the width to find outer rim): (152.4mm / 2) - 37 mm = 39.2mm

Next convert the width of the 18 x 8 et 45 wheels to metric: 8" x 25.4 mm/in = 203.2mm

Then figure out how far the outside rim is from the wheel flange on the new wheel: (203.2mm / 2) - 45mm = 56.6mm

Finally, if the new wheel's outside rim is 56.6mm away from the flange, and the stock wheel's outside rim is 39.2mm away from the flange, then the new wheel's outer rim will be 56.6 - 39.2 = 17.4mm (11/16") further outboard than the stock wheel. Of course your new, lower profile tires will bulge out much less than the old stock tires simply because they have a shorter sidewall, so the difference won't appear as much as that.

Whether they rub on the control arms or not is a different story, but you can use the same methodology to figure out how much the new wheels will stick inboard as well and compare how much room you have to spare by looking at the clearances to the chassis parts using your stock wheels. There's a minor change to the formula for calculating the inside clearance (you add the offset to half the width rather than subtract it) so I'll run through one example.

The stock rear '88 wheels are 15 x 7 et 30. Your widest new rim choice is the 18 x 9.5 et 45mm.

So again, convert the stock width to metric: 7" x 25.4 mm/in = 177.8mm

Then figure out how far the stock inside rim is from the wheel mounting flange on the stock wheel (add the offset to half the width to find inner rim): (177.8mm / 2) + 45mm = 133.9mm

Next convert the width of the new wheel to metric: 9.5" x 25.4 mm/in = 241.3mm

Then figure out how far the inside rim is from the wheel flange on the new wheel: (203.2mm / 2) - 45mm = 165.7mm

Finally, if the new wheel's inside rim is 165.7mm away from the flange, and the stock wheel's inside rim is 133.9mm away from the flange, then the new wheel's inner rim will be 165.7 - 133.9 = 31mm (1-1/4") further inboard than the stock wheel. Once again, that's where the wheel rim will sit. The tire will bulge out somewhat further and needs to be taken into account.

Questions? Just ask.

Thanks Bloozberry...
think I need an engineering degree to fully understand that. Lol
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fieroguru
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Report this Post03-11-2014 05:00 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
18x8 with 45mm offset will likely work in the front, just stick out slightly. The 18" diameter gives you more clearance around the a-arms.

Steven Snyder is running 18x9 with 45mm offset on an 88. Might want to PM him and see how much clearance he has to the strut. It would need to be about 8mm or more for your 10x9.5 ET45 wheels to fit. It would also be important to know if his coil over sleeves go all the way down to the upright attachment flange or if they are siting on top of the weld bead on the strut (stock spring perch). If they sit on top of the weld bead, then you have more clearance on the rear (thickness of the spring and sleeve).
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