offset and BBK clearance

[jwmelvin]

So the brakes on my car are very wide and seem to present an issue for clearance. Right now there are ~10-15mm spacers on the front wheels, which I believe are Gram Lights 57s 17x8 and 18x9.5, but I don't know the offset. I suppose I could try to measure it. I'm interested in what I need to do should I want a new set of wheels.

I understand that an offset pushing the wheel out (less positive) may help with brake clearance. Is there any difference between that and using spacers? It seems like there are multiple ways that one could change the offset, but is it generally done by changing the axial dimension of the hub mount plate? In other words, do some manufacturers increase positive offset in a way other than milling the hub mount plate? If offset and brake clearance are directly related in a particular wheel, then it seems like spacers are as good an option as anything, along with picking a spoke design that maximizes clearance.

Also, I appreciate any recommendations that people may have for wheels with the maximum possible brake clearance. I know there is a huge range of prices but even understanding the styles better seems like it would help. For example, a concave wheel seems bad for clearance, since the spokes curve in to the hub mounting surface, whereas with a flatter wheel, they maintain more of a gap in the inner region (and yes I get that clearance is more an issue towards the outer diameter).

Thanks for any thoughts you may have. -Jason

 

[Hapa88]

BBK clearance is a factor of spoke/wheel design and "disk" and is generally NOT related to offset. There are certain custom Forged wheels where this is a factor, but on the Gram Lights, Volks, Rays, Work and most other wheels it is not.

What changes is the curvature of the spokes of the wheel (sometimes the hub thickness changes too as in SSR wheels). You can see it hightlighted here:


If you have have the Gram Lights 57S, you'll want to get the "High" disk wheels which have the most brake caliper clearance. The offset (and Disk type) is usually stamped on a sticker on the barrel of the wheel.


Here's the SSR wheel difference where HP = Hyper Disk or High Pad, MD = Medium Disk, NR = Normal Disk or Low disk, and SL = Super Low disk

 

[jwmelvin]

That's very helpful, thank you. I guess that as I look for new wheels, I need to consider the spoke-disk design more than anything.

Any thoughts on wheels that I should look at for the biggest BBK clearance? I'd love to hear any lower-cost options especially, but knowing of good forged wheels would help too. There are so many out there that it seems a bit overwhelming.

 

[asylum]

What are those so big calipers ? Are they more problematic than Stoptech ? If not, look on the forum what fits with a Stoptech BBK.

 

[Stephen@NCAutoUSA]

If I remember correctly they're some type of custom brembo brakes

 

[stuntman]

Advan RS-II and RG-III with +51 offsets have some of the most spoke clearance of any wheel I have researched (and has more clearance than most of the Rays Volk/advan/gram light line). Each of their offsets have differing spoke shapes and clearances, not just varying thickness of the center hub).

From there, use spacers for the offset that you want.

 

[jwmelvin]

Thanks for the thoughts all. That's exactly the type of thing I was looking for. The brakes are from a Porsche 997S, and are apparently wider than the Brembo Lotus calipers. They were adapted for the NSX by TitaniumDave.

 

[asylum]

The Enkei PF01 have big caliper clearance.

 

[RYU]

I like to maximize my offset for tire fitment. I like to maximize the wheel design for BBK fitment.

This might help.

 

[NSXAMG996TT]

FYI: Offset for Stoptech calipers clearance are +37 front, +35 rear.

 

[TURBO2GO]

If you start messing around too much with offset you're going to then have tire clearance issues. Find out what the offsets are on your current wheels. Lets start there. It's stamped on the back of the wheel.

If you want something inexpensive thats quality: enkei kojin

Billy is right on RSII and RGIII but some Volks do have more clearance at the same offset than RSii's. Volk RE30 with the "high clearance" version has more than even the RSII. Are you tracking? You may want to look to an even more wholesale solution to 18/19 setups with 225/40/18s up front. That opens up even more room inside the wheel barrel.

 

[NSXAMG996TT]

Yep! I'm running Advan RS (Hoosiers R6) and RZ (AD-08R) both in 17/18. No issues with tires or Stoptech clearance. But Advan model 5 et35 requires 3mm spacer up front.

 

[Stephen@NCAutoUSA]

Remember offset and also width determin things as well. The offset calculator online is good to look at. To compare your current setup to another setup.

Advan model 5's have the best chance if clearing with an 8 inch front and the 38 offset is great, the 30 def clears but is to aggressive for most. I know the 18x8 offset 38 barely clears and another member added a 3mm for extra protection for stoptechs.

 

[jwmelvin]

Find out what the offsets are on your current wheels. Lets start there. It's stamped on the back of the wheel.

Well after a long delay to get my engine rebuilt and the car back on the road, I remembered to look at my wheels.

Front: 17x8 +43 G/L 57maximum + 10 mm spacer
Rear: 18x9.5 +38 G/L 57maximum

I'm working on making a template for my brakes that I might convince some of you to test on your wheels. The biggest thing is that the caliper outer surface is about 50 mm from the mounting surface, versus 43.3 mm for Stoptech.

I'd really like to get wheels that have a higher effective offset but still clear the brakes. These are fairly brutal on my fender lines, on the outside top. With the new liners I put in, I used a heat gun to reshape as much as possible and it seems to have helped considerably.