Aspect Ratio and Wheel Width

[cloudkid]

Hoping you guys can help me. I've looked over the Winter Wheels super-thread, and countless other posts here, but to no avail can I seem to piece together the information I need mostly. I only want to find a good set of winter rims and tires. This is due to so many variances when it comes to the Wheel & Tire selection process.

For this basis I want to keep my 2020 FK8 Type-R completely stock when it comes to suspension and do not want to have to bend/cut or do anything else to my wheel-wells and fenders. I would like to find some wheels and tires that will fit without modification. The only Mod I will consider is wheel-spacers, which is part of what's confusing me.

1) When it comes to Aspect Ratio, the higher the number, the better for Winter-Driving and the greater amount of treadlife, correct? Essentially higher Aspect Ratios = more rubber. What is the maximum aspect ratio one can have if they go with an 18" diameter rim? Could i get away with a AR of 50? Or do i really need to stay as close to the OEM 30 as possible? Does the reduction of wheel diameter make more room for more Aspect Ratio?

2) What is the maximum width that I can get on these rims and tires? 265 seems to be where it maxes out with stock fenders and housing? Is this accurate? Are there any requirements for spacers as long as its under 265mm? If so, how do i best determine the right spacers?

3) Spacers - are spacers dependent on offset or on tire width, or both? Can't seem to find the right answer in this regards.


These are just a few things I'm confused on. Thanks for sharing any insights or information to guide this total newb at buying aftermarket rims?

Sponsored

 

[arpypat]

For winter tires especially, I'd recommend you stay away from spacers and try to keep your track width and scrub radius as close as possible to OE spec.

As far as aspect ratio goes, the number derermines the sidewall height as a percentage of the tire width. So if you downsize on your wheel diameter, you'll need a higher aspect ratio to maintain the same rolling diameter

Eg: 245/30/R20 means
- 245mm tire width
- 0.3 x 245mm sidewall height (only one side; double for the rolling diameter.)
- 20" wheel diameter.

Your total rolling diameter for the example above is 20" + 2x(245mmx0.3) = 20" + 147mm = 25.79"

If you downsize to an 18" diameter wheel, you'll need to find a width/aspect ratio combination close that will give you rolling diameter close to 25.79"

245/40R18 is pretty damn close at 25.72"... This takes care of the tire.

For the wheel, I'd say look for an 18x8.5 or 18x8 wheel with PCD of 5x120 and offset between +40 and +60. (OE wheel is 20x8.5 5x120 +60)

 

[cloudkid]

Fantastic explanation and even gave me the equations to work on myself! Thank you kind stranger.

If i did want an 18" wheel, with a little more aggressive width what is the impact of that extra width (9"-9.5") I need to consider? Spacers? Higher or lower offset?

 

[zspeed]

Fantastic explanation and even gave me the equations to work on myself! Thank you kind stranger.

If i did want an 18" wheel, with a little more aggressive width what is the impact of that extra width (9"-9.5") I need to consider? Spacers? Higher or lower offset?

18x9.5 with a 38mm or 45mm offset will be right for you if you want it aggressive. No spacers required for that specs.

 

[cloudkid]

18x9.5 with a 38mm or 45mm offset will be right for you if you want it aggressive. No spacers required for that specs.

That's fantastic. Curious in regards to the Brembo calipers as that seems to be where many get caught up. Lets say that I do find a set of wheels that meets the 18x9.5 criteria with a 45mm offset, BUT my calipers touch. Is this when i would need spacers?

 

[arpypat]

Fantastic explanation and even gave me the equations to work on myself! Thank you kind stranger.

If i did want an 18" wheel, with a little more aggressive width what is the impact of that extra width (9"-9.5") I need to consider? Spacers? Higher or lower offset?

No problem! As you go wider in wheel size, you need to take offset into consideration for fitment. Offset is the distance between the center of the wheel and the wheel's hub mounting surface, in millimeters.

E.g., compared to your 8.5" +60 wheel, a 9" +60 wheel is 12.7mm wider, with 6.35mm of the width closer to the fender side and 6.35mm closer to the suspension side. A more negative offset shifts this towards the fender side. So a 9" +45 wheel would be 15mm closer to your fender and 2.3mm further away from the suspension.

Note that wider wheels/tires and aggressive offsets are not typically recommended for winter wheels.

 

[cloudkid]

I know we've all seen these JNC knock-offs, but for the price they'd be a great winter tire that has some style. The concern with these is if the calipers will fit. Anyone have any thoughts to share on these? They meet specs, but I've heard JNC rims often have clearance issues with calipers.

https://www.ebay.com/itm/18x8-5-5x1...0778&brand=JNC&_trksid=p2060778.c100290.m3507

 

[arpypat]

That's fantastic. Curious in regards to the Brembo calipers as that seems to be where many get caught up. Lets say that I do find a set of wheels that meets the 18x9.5 criteria with a 45mm offset, BUT my calipers touch. Is this when i would need spacers?

Yes, BBK clearance could be an issue. You have to look at wheels designs, not just widths and offsets, when considering wheels to fit over them...

 

[metal_driver]

As Arpan has already mentioned wider tires and more aggressive offsets (ie trying to get the tires to poke out towards the fenders more) is not a good idea at all for winter tires. Typically folks run narrower winter tires and inch down their rims to get more sidewall (depth) to their winter tires to get roughly the outside tire circumference.
Something like these Motegir 924's would work .. https://www.tirerack.com/wheels/Whe...Model=Civic+Type+R&autoYear=2017&autoModClar=

 

[cloudkid]

As Arpan has already mentioned wider tires and more aggressive offsets (ie trying to get the tires to poke out towards the fenders more) is not a good idea at all for winter tires. Typically folks run narrower winter tires and inch down their rims to get more sidewall (depth) to their winter tires to get roughly the outside tire circumference.
Something like these Motegir 924's would work .. https://www.tirerack.com/wheels/Whe...Model=Civic+Type+R&autoYear=2017&autoModClar=

Ohhh wow, those look great and seem functional, not too shabby on the price either. Funny too, I haven't seen an offset on any of the rims I"ve been looking at that are as close to OEM as this one is. That's a plus too. Thank you for sharing, and thanks for sharing your thoughts on winterization for the R. I was thinking it'd be nice to have a winter set AND a little different look, but I understand the point you're making in regards to snow/sleet/ice.

The Motegis are pretty cool looking...

Sponsored