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Rubbing issue on track (FD)

Old 02-04-07, 07:57 PM
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Rubbing issue on track (FD)

Anyone seen this issue before?

For the record, I'm running 18x10 CCWs. As you can see, I have the M2 lower links. (Yes, I installed the spacers in the right direction.) The wheels do not rub under normal street driving. I am running zero toe and camber in the rear. The tire pressures were a little low--a few psi--due to cold ambient temps. I'm running 285/30 Michelin PS Cups. They are new and have been heat cycled.

The car is lowered on Zeal coilovers, but I'm not running nearly as low as some FDs.

You can see that there was rubbing on both the well and the trailing arm.

The wear pattern was nearly identical on both sides of the car. The car is straight and has never been in a wreck.

-ch
Attached Thumbnails Rubbing issue on track (FD)-img_0952.jpg   Rubbing issue on track (FD)-img_0953.jpg  
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Old 02-04-07, 08:35 PM
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Those rub marks seems to come from the tires.
During hard cornering, tire deflects. And these deflection could go up to .3-.5 inch. Check out these photos at the Bay Area Autocross forum: http://www.baautox.com/forum/index.p...&start=0&rid=0


haven't seen you at the autocross for a while now.
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Old 02-04-07, 08:59 PM
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Well, I was surprised to see rubbing from the CCW setup. Is this common among FDs?

Reza, I haven't been to an autoX for about 1.5 years because that's how long it took me to do my LS1 conversion!

Are you still running your FD in the bay area?

-ch
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Old 02-05-07, 12:07 AM
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If you got that set of wheels of Alex, then yes that wheel was on my car, and at Atwater those Kumho V710 rubs the inner fender.
We did a test with masking tape, and it rubs due to the tire deflection. Did you see the link to baautox?

Oh yea, the CCW did not rub, if its the CCW that rub, then you will have very thin marks, the rubbing definitely off the tires.

Yes, I am still running. They have a new class now, XP = it is X-whatever Prepared..... something like that.... you should be able to put your LS1 FD in there.
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Old 02-05-07, 12:28 AM
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Hah! I bought those wheels from Jason who I think got them from Alex. They've been on quite a few bay area FDs!...

I haven't measured them, but I'm assuming they are the +50mm offset that John at CCW uses for all FDs? (In other words, this happens often with the 285/30/18 combo?)

I'm planning on bringing the car out but running it on street tires--the PS Cups take about 1-2 laps to heat up so they'll be useless at the AutoX.

-ch
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Old 02-05-07, 08:36 AM
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My 10 +50's rub a bit in back like that too. It's very close (a compromise for the front really).... in fact, it's down to alignment. You're running 0 camber, and that's the problem. Put a degree or so in, and it won't rub anymore. I actually snagged a 5 mm spacer (apparently made by CCW) from Fritz to help out.
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Old 02-05-07, 09:27 AM
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Are you absolutely certain of the rear toe? With 18x10's the wheel wells get very tight.
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Old 02-05-07, 11:23 AM
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Glad to see it's not totally unusual. I'm going to call CCW about some spacers for the rear.

Does anyone have a recommendation on how best to cover up the exposed steel in the fender well? My inclination is to mask off a 1" border and spray it with Krylon, but if there is a better approach I'd like to hear it.

I'm also going to re-verify the toe settings with my toe gauge. I'm pretty sure the alignment shop got it right, but you never know.

-ch
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Old 02-05-07, 11:50 AM
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Just ordered a set of 0.190" spacers from CCW. $20 each. Thanks for the tip!

-ch
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Old 02-05-07, 11:56 AM
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Originally Posted by hyperion
Does anyone have a recommendation on how best to cover up the exposed steel in the fender well?
A can of spray on undercoating.
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Old 02-05-07, 12:21 PM
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Old 02-05-07, 12:28 PM
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would massaging/banging in the wheel well solve the issue?
shouldn't you have like -1.5 neg camber in the rear? you said you run zero camber; doesn't that contribute to massive oversteer especially with your power?
your car is hot as hell
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Old 02-05-07, 02:33 PM
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Thanks for the kind words on the car! Great to see another LS1 conversion--and running 10s! That's fast. I really like your oil cooler setup. I have that LG adapter but haven't gotten around to installing it because I can't decide if I'm going to stay with an wet sump (and add an Accusump) or just bite the bullet and go with and LS7.

Back to tire issues: I'm still working out the setup and am running only -1 deg in the front. It's a street alignment; anything more and the car hunts like a 19-year-old at Panama Beach. If I were track only I'd go -2 in the front and -1 in the rear with a bit of toe in on the front.

At Laguna--where my tire pressures were wrong and it was cold as hell--my water temps never went above 180 F the whole session. I was getting a bit of turn-in understeer but you could manage the attitude with throttle/brake pretty well. On power the T-2R diff was very progressive but in 2nd or 3rd it wasn't too hard to get wheelspin if you really provoked it. You could make turn 11 look fun to the observers.

My brakes were shot too, do I didn't push too hard. I'm going to run it again in the Spring when it gets a little warmer.

As far as hamming out the wheel well, I could definitely make room with the 5lb persuader but I'm also rubbing on the M2 trailing arm as well which is already offset inboard.

-ch
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Old 02-05-07, 02:48 PM
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I recently spoke to a fabricator about hammering out the wheel wells. He said the most problematic area is tied into the end of the frame rails and will not move. I believe that is where the scuff marks are in the pictures above.

I wonder how difficult it would be to cut it back a bit and seam weld it. The trailing arms could be curved around the tire to provide more clearance. Obviously it would be a lot of work, but if it would provide enough room for 315s without doing any exterior sheet metal work it might be worth it.

Hyperion. What's the meaning behind your name? Any relation to structured finance?
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Old 02-05-07, 03:13 PM
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Originally Posted by CMonakar
Hyperion. What's the meaning behind your name? Any relation to structured finance?
Heh, no, it's a reference to a Keats poem if you can believe that.

-ch
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Old 02-05-07, 05:43 PM
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so you run -1 camber in front and you get hunting? what is your caster? mine was too hight at 7 and would hunt like crazy. i put it to 6 and all is good now. FWIW this was with the looped rack.
i have -2 camber in front currently and its great for street. you said you get understeer; i would bet its because you ain't running enough neg camber up front.

in the rear, you have zero camber. did you do any slaloms? i would think the transitions would be really difficult because of oversteer if you had enough speed with the zero camber. but also keep the rear shocks set to softest setting, and put -1.5 camber in the rear. and don't use high psi. in my v700's in back, i was running 25 psi. never ran michelin PS so can't advise.

re: oil cooler. not necessary for autocross, but if you open track the car, i'd do it. even with accusump. getting LS7 is not a bullet to bite, its more like a cannonball. i personally think thats way overkill in the HP and tq dept's and damn, its dangerous on a road course with that much power. especially on stiffly sprung FD. keep the shiny side up
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Old 02-06-07, 12:09 AM
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No wonder you guys have suspension problems, you've got big heavy V8s in your RX7s!

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Old 02-06-07, 02:42 AM
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LMAO!

Yeah, it ruins the handling and makes the car Xp10d!!11!!



-ch
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Old 02-06-07, 08:14 AM
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Hunting is almost inevitable with 285/30/18 front tires, particularly R's like sport cups.... that's why I went 255/35/18 for the street (front).

You're going to have to live with it to get the most out of them
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Old 02-06-07, 11:21 AM
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Yeah, I run 265/35/18 PS2s on 9.5 SSRs for the street...but even those can get a bit nervous over uneven pavement.

I'm very curious to understand what people like Chevrolet do to make such wide tires work predictably on the 'Vette.

-ch
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Old 02-06-07, 12:16 PM
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Probably a combination of less-than-ideal alignment and isolation/complient bushings.

Thoe cars are also heavier, so they'll not be as sensitive.



Originally Posted by hyperion
Yeah, I run 265/35/18 PS2s on 9.5 SSRs for the street...but even those can get a bit nervous over uneven pavement.

I'm very curious to understand what people like Chevrolet do to make such wide tires work predictably on the 'Vette.

-ch
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Old 02-06-07, 12:47 PM
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Originally Posted by hyperion
Yeah, I run 265/35/18 PS2s on 9.5 SSRs for the street...but even those can get a bit nervous over uneven pavement.
I'm very curious to understand what people like Chevrolet do to make such wide tires work predictably on the 'Vette.
Does wheel offset also play a part?

Yeah, I run 265/35/18 PS2s on 9.5 SSRs for the street...but even those can get a bit nervous over uneven pavement.
Why did you select that size? The overall diameter is 25.3. A 255 or a 285 seems like it would be closer to ideal. I know the PS2s aren't available in 285 (which sucks), but they do come in 255.

Last edited by CMonakar; 02-06-07 at 12:53 PM.
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Old 02-06-07, 02:51 PM
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Originally Posted by hyperion
I'm very curious to understand what people like Chevrolet do to make such wide tires work predictably on the 'Vette.
I haven't driven a C6, but the C4's and C5's groove hunt on streets like nobody's business! The C5 steering isn't has heavy as the C4's so it's not quite as bad.
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Old 02-06-07, 03:06 PM
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Cmonakar, I'm not sure what you mean...I'm pretty sure the 265 is the ideal tire for the 9.5" rim.

Mahjik, I drove a C6 Z51 recently and I didn't notice much hunting, even on the ultra-crappy California freeways. But then again, I wasn't paying much attention to it...

-ch

Last edited by hyperion; 02-06-07 at 03:30 PM.
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Old 02-06-07, 03:28 PM
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My only point was that the 255 with an overall diameter of 25" is closer to the stock overall diameter of ~24.8 than the 265 which is .5" larger than stock. As far as being ideal for a 9.5" rim, they're both within .25" of the middle of the range.

255 8.5-10" (9.25 mid point)
265 9-10.5" (9.75 mid point)

If a choice is going to be made based on width, isn't it better to be on the upper end of the rim size spectrum?

-Chris
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