18s + BBK: how close is too close?

['ringmeister]

I just installed a AP radi-cal BBK with a 372mm rotor. It JUST clears the barrel of my track wheels, 18x10 Enkei NT03s. The wheel rotates freely but there is only about the width of a credit card, a couple mms at best , between one point of the caliper and the wheel. I track the car and i know wheels do flex slightly under the stress of tracking, riding curbs etc. Should I be concerned? I know pebbles could get trapped between the wheel and caliper, but could the wheel flex enough to drag the caliper and damage both? TIA.

[roastbeef]

I'd say that is too close. You can be conscious of balancing weight placement, but as those things come off, I don't know how much time they spend moving around in the barrel...
Even without that, there is so much crap that the barrel of the wheel is exposed to, you will 100% get something jammed up in there.

Also, if you go off, you're going to get rocks in there for sure.

[kyippee]

I hear ~4mm at the least for clearance. Is yours closer than mine? 380mm 6 piston rotora fronts pictured with 18" TE37SL, Titan 7 T-S5, and APEX EC-7. Done about 14 track days with the BBK on, no problems with clearance so far. Are the NT03 wheels design to clear BBKs? That's an important factor. I know Brembo calipers are larger than most, so if your AP Racing ones are large.. maybe that's the issue too

[slicer]

I think 3mm of clearance is the rule of thumb. There is definitely the potential for stones to get lodged but I wouldn't expect the wheel to flex and make contact - unless it takes an impact. I always tape my wheel weights with high temp aluminum tape to prevent them from flying off. You can get the tape at any home improvement store. At the end of the day more clearance is better than less. I have the same brakes and use 18" E88's and BBS RIA's without any issues.

[pbonsalb]

I’d prefer the 4mm or even more. A wheel weight, pebble, failing wheel bearing could all cause trouble.

['ringmeister]

Thanks all! I am going to recheck clearance and make decision accordingly...really don't want to drop the cash on a new set of wheels, but that is the domino effect of mods & tracking...

[pbonsalb]

Would a spacer help? Depending on inside of wheel barrel contours, spacing could add clearance. I have to space my snow wheels on my E36M3 with ST40s, but not my summer wheels.

['ringmeister]

unfortunately not, the calipers are already in the "wide" portion of the barrel, and there is actually a ton of clearance to the spokes.

Originally Posted by pbonsalb

Would a spacer help? Depending on inside of wheel barrel contours, spacing could add clearance. I have to space my snow wheels on my E36M3 with ST40s, but not my summer wheels.

[bigjae1976]

I'd be more concerned with street driving. I've gotten to small stones lodged between the caliper and wheel twice. Not a huge deal as long as it pops out quickly.

Track...you'll get some rubber boogers in there.

ST60 and OEM rear 18s.

['ringmeister]

So I rechecked clearance with thin, plastic strips (brooks bros. collar stays ) as spacers taped to the inside of the wheel. I've got 3mm clearance so I think i'll be OK. Thanks again everybody.