Koni Oranges + 275's in front

[Moonchopper]

Has anyone had clearance issues with the Koni Oranges and 275/40R20s in the front? I just put my Koni's on, and thee front tires have been clearly rubbing the spring perchs on both sides. I could hear them rubbing under braking and when I turned the wheels (what I originally thought was regular tire noise due to needing an alignment after changing them).

Will 5mm spacers help fix this problem? My brother got the exact same shocks for his Camaro and has no issues - he has the stock 245/40R20s, though.

Does anyone have any suggestions?

[Norm Peterson]

I think you need to post a picture showing where the rubbing is occurring, along with a picture showing how much clearance is there between the tires and the struts.

Are your 275/40's mounted on original front wheels (8" wide) or on a separate set of 9" wide rear wheels?


Norm

[Moonchopper]

20x9 wheels in the front, so completely square all the way around. It's also possible that I didn't set the camber back up properly, so perhaps the camber is too extreme - I'm not confident that is the problem, however.

Here is the best picture I could get (drove the car to work this morning - didn't drive it at all prior to, which is my own damn fault) - you can see where some of the paint has already been rubbed off.



I've made an appointment with my shop to have it checked out and to get their recommendation - I've already got some spacers and longer studs picked out so I can order them ASAP. My primary concern is with getting my car ready for Autocross this weekend (and track the following weekend). Just figured I would come here for some advice while I was waiting to get it looked at by the shop.

[Burt]

Are you running the factory rear 9" wheels up front, of after market wheels? Also, do you remember what your camber is set at?

[Norm Peterson]

I'm not entirely surprised. Your car's front tire inner sidewall is nearly 3/4" further inboard than your brother's. 5mm of that (0.2") is coming from the difference in wheel offset, but about 1/2" is coming from the extra width of your 275 tire. The left side in the plots is the strut side.

Camber that's a little less negative might be enough to eliminate the rub, or possibly a thin spacer will let you keep your camber where it's at if it's going to be better for your autocross and track time, though if this ends up being the way you go I'd rather see you running the thinnest possible spacers that would permit adequate clearance.

Can you measure the clearances that you have with the car sitting with its weight fully on its tires, using feeler gauge blades?


On edit, a 275-wide tire mounted on a 9" wide rim will distort laterally more than either 255 tires on 9.5" wide rims or 285's on 11", so I'm afraid that I don't know how much static clearance will be the minimum you can live with.


Norm

[Destructo09]

I'm the brother, I think it's mostly just too much camber from bolting the knuckle back up.

This is one of the things nobody mentions when they say oh yeah you can totally run 20x9 +40 wheels all around, lol.

I'm guessing that side probably has as much camber as it'll take most likely, so probably at least -1.8 currently.

I have -2.1 on my car, but of course am on the staggered setup, I planned to run 275's on OEM 20x9s in front but i'm guessing i'll need either different wheels or a 5-10mm spacer. My math tells me a 5mm might work since a 5mm spacer would make the wheel a 20x9 +35 which is the same backspacing as the 1LE 20x10 +23 wheel, and i'm assuming a 1LE can run max camber without rubbing.

Here's a picture comparing 20x10 +23 and 20x9 +35 (+40 with 5mm spacer).

[Norm Peterson]

D - I think you need to use something a little fussier than that particular wheel and tire page with respect to evaluating tire clearance if the tires are what's rubbing. Tire section width also varies with wheel width, and I don't think that one accounts for it (my plots above do). Most of the time it's not as critical as it is here, and to get it really right when it's this tight you'd need to use actual tire dimensions rather than dimensions computed from the nominal tire size.

If it's the wheel that's rubbing, almost any clearance at all should be sufficient unless there is some play in the wheel bearings. My track wheels have just over 1.0 mm clearance to the struts and don't rub under even the heaviest lateral loads I've been able to put on them. OE Camaro wheels should not be enough more flexible to matter; as OE they should probably be stiffer.


Norm

[bannonm]

I'd go with camber plates before spacers. I had the same kind of clearance issue with Pfadt feather lights and 20x10-35 up front. I'm lowered as well which made it even worse. Originally I had Pfadt camber plates but lost a plate due to a track mishap. I replaced them with FMT camber plates which are an improved design.

http://www.camaro5.com/forums/showthread.php?t=379874

[Norm Peterson]

Originally Posted by bannonm

I'd go with camber plates before spacers. I had the same kind of clearance issue with Pfadt feather lights and 20x10-35 up front. I'm lowered as well which made it even worse. Originally I had Pfadt camber plates but lost a plate due to a track mishap. I replaced them with FMT camber plates which are an improved design.

http://www.camaro5.com/forums/showthread.php?t=379874

Sounds like you must have used the OE camber adjustment to take some of the negative camber out (giving you strut clearance) and then used the camber plates to put at least some of the negative camber back in without affecting strut clearance. That's really a better option, the question being whether the plates are available on a timely enough basis.

A really thin aluminum spacer - 1mm or thinner - I wouldn't worry about as it isn't going to compromise engaged thread length or joint stiffness enough to matter.


Norm

[bannonm]

Originally Posted by Norm Peterson

Sounds like you must have used the OE camber adjustment to take some of the negative camber out (giving you strut clearance) and then used the camber plates to put at least some of the negative camber back in without affecting strut clearance. That's really a better option, the question being whether the plates are available on a timely enough basis.

A really thin aluminum spacer - 1mm or thinner - I wouldn't worry about as it isn't going to compromise engaged thread length or joint stiffness enough to matter.


Norm

Yes exactly. I'm still a fan of camber plates since it allows you to compensate for tire/wheel changes without having to mess with spacers. And you can add more camber for track days and put it back to a street setting when you're done.

[Moonchopper]

Just heard back from the shop - they aligned the car to about -1.2 camber (where it was before I swapped out shocks), and they're saying it just barely clears the strut. This is what I ran when I last ran track and autocross, so it might not be a problem at all. In any case, I am going to consider running some camber plates or maybe go with wheel spacers in the meantime (which I know I can get a hold of before autox this weekend [spacers, that is]).

Do either of you have experience with small wheel spacers on track/autox? (5mm max)

[Norm Peterson]

It's really too close to call without having feeler-gauge level measurements before and after available, as different struts may well have slightly different dimensions. Even nominally identical struts have dimensional tolerances (think strut to knuckle bolt hole diameter and location).

I need to run an 0.025" (0.6mm) spacer on my right front with one of my front track tires (285/35). That gives me just over 1.0 mm there. Half a mm static clearance without the spacer was enough room for the wheel but not quite enough for the tire. Six track days on three different tracks with two personal best lap times (and one spin) later, still no rubbing.

Some day if I get really, really bored I may make a matching spacer for the driver side front.


Norm

[Moonchopper]

I appreciate the help and information - I'll need to decide if I'm going to use spacers or just go ahead and drop the cash for the camber plates (which may be the better option in the long run, since this is also my DD).

[Moonchopper]

Question, for anyone who's still reading:

I was under the impression that the issue with rubbing was normally from the sidewall rubbing the strut cylinder -- not the spring perch. Are the two essentially the same, or is it possible there might be something else wrong? I'm concerned that a spacer won't fix the issue, primarily, because the rubbing is happening on the spring perch, not the shock cylinder itself.