offset and backspace rear fender clearance question for 19x9 wheels

[brando1118]

Hello all,

My post on CF forum...
As the title of the thread states I'm looking for info from anyone that is running 19's on their C3 or are much more knowledgeable about wheel fitment on our C3's than I am. So here goes:
The wheel:
Concept 1 CSL 5.5. BMW bolt pattern 5x120mm
They do not make custom sizes. What they offer is what you get.

wheel measurements: 19x9 with 15mm +offset.

With no wheel adapters, the backspace of this wheel is ~5.6 inches.
I've never shopped or used spacers, but I'm assuming (dangerous) that they make 15mm spacers to bring my backspacing into a safer 5 inch range.

Now we get to my question: I LOVE wheels with a deeper dish. The choices of offsets from Concept 1 are +15mm (deeper dish) or +35mm (not as deep). Will the lower offset 15mm number plus 15mm adapter/spacer push my wheel outside of my stock fenders? I'm referring to the rear wheels here. Looking to run a 275/35 or 40 series tire. Whichever one is closest to stock wheel diameter.

As stated above I posted this question on the CF last night and this morning 3JsVette responded with some good info that got me thinking about the practicality of a 15mm spacer. It seems to me that if I run a 15mm spacer, I will either have to get longer wheels studs if it's a slip on type spacer or I will have to cut the wheels studs down so the bolt will sink deep enough into the spacer to mount the wheel. So if anybody has run a 19x9 wheel with a +15mm offset on our C3's, I'd love to hear about it.

Link to spacer..
http://www.livermoreperformance.com/gm_wheel_spacers.html#Eibach

Thanks!!

 

[mrvette]

Welcome to the motley crew....

I have '89 vette wheels on my '72 so 17x9.5 on all 4 corners....

I had to move the brake cables on the rear t-arms, picking up 3/4 inch clearance for tires, I use 2.5" thick wheel adapters....so to get to the brake rotor, I have ten lug nuts to remove....5 for the wheel, then another 5 for the adapter....over the years, I have seen too much bad crap from guys using mere spacers, broken studs/spacers....

edit....forgot to say how I measured for the adapter thickness....the stock steel wheels on my '72 were 15x8 the '89 wheels are obviously 3/4 inch per side wider...
I laid a straight edge against the FLAT part of the wheel/tire mounting flange, measured to the lug center face inside....note the differences, keeping same center line, did a quick calculation, came up with 2.5" in my case,

:hi:

 

[MYBAD79]

Ok, here's some more info on spacers/adapters:

http://www.vettemod.com/forum/showthread.php?t=7112&highlight=adapter

H&R have a good reputation, their products are usually top notch quality. I have a set of their spacers in 1" thickness on my Mustang, no complaints. Powertech is another good brand, thay make 20mm as well (3/4")

Some are running 10" rims under the stock fender so that 9" rim will fit with a spacer .... however: will the backside of the spokes clear the calipers ??? That's one of the bigger issues with fitting rims on the C3 .....