13 replies to this topic

[Oreo931]

I've managed to completely confuse myself with wheel backspacing and offset when comparing between different width wheels. I'll explain what I want to do, and post some diagrams, and hopefully someone can help me figure out the end result.

My current wheels are OZ Record 17x7 ET42 (unsure of backspacing, maybe 5.7"?). In order to clear my brakes I am running a 10mm spacer. I also rolled both my front and rear fenders.

I want OZ Ultraleggeras, but NOT 18's. OZ no longer makes 17" ultraleggs in 5x108, so I have to buy another bolt pattern and use an adapter.

I found ultraleggeras in 17x8 ET48 (6.41" backspacing). I'd like to use 18mm adapters.

Tire size will remain the same (215/45/17)

I need to know a couple of things. First, will the ultraleggs clear my brakes with an 18mm adapter (by how many mm?). Second, how much further will the ultraleggs stick out compared to the current OZ record wheels (by how many mm?).


According to this diagram, the ultraleggs will stick out ~7mm more than my current wheels.




According to these diagrams, the wheel will only stick out ~2mm more???







Anyway, I'm clearly getting confused here. It's certainly possible my math is wrong. Are the calculations different between a 17x8 ET48 wheel using an 18mm adapter/spacer, and a 17x8 ET30 wheel?



Another option would be to buy an ultralegg in 17x8 ET35, 5x112, and have it redrilled - but that route is more expensive, and I still don't know if the wheel will clear my brakes w/o spacers.

[Black Betty]

Et is measured from the center of the barrel. So going from 7" to 8" with the same et is like adding 12.5mm to either side. (12.5 mm more poke, 12.5mm less clearance to struts). So then accounting that you'll be et30 vs et32 you'll gain an extra 14.5mm poke, and loose 10.5 mm strut clearance.

Someone else confirm also since I'm mobile I can't see your post when I reply and I might have gotten your ets mixed up...

Edited for 7" instead of the 7.5" I originally thought it was

[gilber33]

They'll poke ~15mm more and the inset increases by ~10.5mm

[NEU]

Adam, I know from the way my Ultraleggera are the spokes will clear, as they are bowed out a bit in the middle of the spoke. Mine are 38ET (I'm not running BBKs) But I know Gary (Yellow95) ran the same ones on his old Red T5 wagon w/BBK without an issue. I talked with him a couple times before I bought mine about clearance. My winter wheels are the only thing holding me back from getting the BBK setup.

If you add a 18mm spacer to the 48ET that will make it a final of 30ET and that should be more then enough spoke clearance. I could also check my other set of 18x8 Ultraleggeras which are 48ET for my Subaru to see how much clearance there is.

Also another option would be to get Superleggeras. IIRC they came in 17" and not 18", but I could be mistaken.

[Oreo931]

Black Betty, on 01 February 2012 - 11:40 AM, said:

Et is measured from the center of the barrel. So going from 7" to 8" with the same et is like adding 12.5mm to either side. (12.5 mm more poke, 12.5mm less clearance to struts). So then accounting that you'll be et30 vs et32 you'll gain an extra 14.5mm poke, and loose 10.5 mm strut clearance.

Someone else confirm also since I'm mobile I can't see your post when I reply and I might have gotten your ets mixed up...

Edited for 7" instead of the 7.5" I originally thought it was

gilber33, on 01 February 2012 - 12:47 PM, said:

They'll poke ~15mm more and the inset increases by ~10.5mm

Are you guys sure about this? Does wheel backspacing factor into the calculation at all?

If the above numbers are correct, why is the diagram below off by so much using the same figures?

[gilber33]

Yeah, I'm sure. Notice anything weird about your poke and inset numbers even with 100mm adapters? Hopefully you do.





That site does not take the adapter into account when it calculates inset/poke. Now, do it the better way and incorporate your adapters into your actual offsets:



Going from 8mm away from the fender to 6mm of poke, giving you the approximate 14-15mm of poke I posted earlier from willtheyfit.com

[Oreo931]

gilber33, on 01 February 2012 - 05:13 PM, said:

Yeah, I'm sure. Notice anything weird about your poke and inset numbers even with 100mm adapters? Hopefully you do.





That site does not take the adapter into account when it calculates inset/poke. Now, do it the better way and incorporate your adapters into your actual offsets:

Good call!

Thanks!

BTW, Is 78mm the correct hub --> fender distance?



I really don't think I can afford to push the wheels out another 15mm without running into huge rubbing issues.

Here are some pics for reference.






















I guess I'm gonna have to look into another wheel, or redrilling

[gilber33]

78mm is what I got when I measured my hub to fender. It's real hard to get an exact reading, but that's what I got.

Redrilling is possible, and is usually cheaper than adapters (I just bought adapters it was $305 shipped), only problem is that typically the backside of the wheel needs to be flat, unless you filling and drilling.

But yeah, you would be quite flush if you went with that. But FYI, Motorsport-Tech's smallest adapters they do are 15mm, so if that clears your BBK, then that's 3mm you shave off right there.

[Oreo931]

gilber33, on 01 February 2012 - 05:42 PM, said:

78mm is what I got when I measured my hub to fender. It's real hard to get an exact reading, but that's what I got.

Redrilling is possible, and is usually cheaper than adapters (I just bought adapters it was $305 shipped), only problem is that typically the backside of the wheel needs to be flat, unless you filling and drilling.

But yeah, you would be quite flush if you went with that. But FYI, Motorsport-Tech's smallest adapters they do are 15mm, so if that clears your BBK, then that's 3mm you shave off right there.

Closest place to me wants $110 per wheel (just called). http://www.wheelcollision.com/

[gilber33]

Oreo931, on 01 February 2012 - 05:54 PM, said:

Closest place to me wants $110 per wheel (just called). http://www.wheelcollision.com/

Holy smokes!

I was always told it was like $200-ish. Maybe they're all liars.

[Oreo931]

gilber33, on 01 February 2012 - 06:05 PM, said:

Holy smokes!

I was always told it was like $200-ish. Maybe they're all liars.

No I've seen those prices online too... But I cannot find anything within 2hrs driving distance that will do it for that cheap. If you have to ship the wheels then it kills the deal.

[JVC]

If you're going through the trouble of adapters and such. Why not hold out for sweeter wheels?

[Oreo931]

JVC, on 01 February 2012 - 07:19 PM, said:

If you're going through the trouble of adapters and such. Why not hold out for sweeter wheels?

There are very few 17" wheels that I like that clear my brakes and won't poke out too far, for under $1500.

[Oreo931]

Wanted to update this thread in case anyone found it in the future. I put on a spare peg yesterday to see how an 8" wheel would look. It's an OEM peg so it's 17x8 ET46 -- with the 10mm spacer final offset is ET36. Tire size is the same, 215/45. It fit fine and looked good. There was still room for the wheel to come out a couple more millimeters as well. Pics below.