Shims question
09-30-2008, 07:45 PM
#1
Shims question
For those of you who run shims up front to get more camber, does everyone have rubbing on the inner wheel well liner? Any long term consequences or problems from this? Any tips to avoid or fix it?
I previously had rotated the struts to get more negative camber but my alignment guy thought there would be more benefit from the shims so I went that route this time and as others have said, I do have rubbing. Camber is set at -2.4. Thanks.
-John
I previously had rotated the struts to get more negative camber but my alignment guy thought there would be more benefit from the shims so I went that route this time and as others have said, I do have rubbing. Camber is set at -2.4. Thanks.
-John
09-30-2008, 08:00 PM
#2
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For those of you who run shims up front to get more camber, does everyone have rubbing on the inner wheel well liner? Any long term consequences or problems from this? Any tips to avoid or fix it?
I previously had rotated the struts to get more negative camber but my alignment guy thought there would be more benefit from the shims so I went that route this time and as others have said, I do have rubbing. Camber is set at -2.4. Thanks.
-John
I previously had rotated the struts to get more negative camber but my alignment guy thought there would be more benefit from the shims so I went that route this time and as others have said, I do have rubbing. Camber is set at -2.4. Thanks.
-John
09-30-2008, 08:41 PM
#3
Yes, seems to be most during steering (can't tell yet during compression as I haven't driven it too hard yet). Starts to rub about 1/2 to 2/3 of the way to full lock and by full lock, tire is pretty firmly against the wheelwell.
09-30-2008, 08:45 PM
#4
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What size wheel and tire combo are you running? When is the rub? At full lock?
I ran rotated my strut mounts AND ran shims (perfect balance between the two) and got run at full lock with 245/40/18 tires.
I ran rotated my strut mounts AND ran shims (perfect balance between the two) and got run at full lock with 245/40/18 tires.
09-30-2008, 10:41 PM
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John,
Dell is really good at this too, can you tell us where the rubbing is occurring within the wheel well, and what tire/wheel combo you're on? Also, ride height if you have it please.
Dell is really good at this too, can you tell us where the rubbing is occurring within the wheel well, and what tire/wheel combo you're on? Also, ride height if you have it please.
09-30-2008, 10:56 PM
#6
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If you put 6mm or more on shims, the stock tires (235/40R18) will rub the inner fender liner in the front section (right behind the radiator).
Running wider tires without enough caster will rub the back section of the fender liner.
I personally consider these fender liners as disposable as the front lip. I took out the rear ones, but the front ones need to stay to protect the coolant and brake lines.
I put custom camber plates with more caster, and took out the shims.
Running wider tires without enough caster will rub the back section of the fender liner.
I personally consider these fender liners as disposable as the front lip. I took out the rear ones, but the front ones need to stay to protect the coolant and brake lines.
I put custom camber plates with more caster, and took out the shims.
09-30-2008, 11:24 PM
#7
Okay, to answer some questions, stock tire on stock wheel, I assume stock ride height as I didn't change it (I noticed on the last corner balance sheet 25 1/8 for the rear and while the ride height for the front is blank, they filled in 25 5/16 for "Spring").
I've attached pictures for the location of the rubbing. You can see in one area it is actually rubbing the metal for the retainer clip and the tire is indented against the liner (full lock).
Interesting thought about shims and rotating the strut. I just found out that they used some shims to move the whole wheel out first, then added more shims to get the desired camber. Do you think this is making it worse?
Rad, thanks for your input. If they are disposable too, no big deal, just don't want to blow out a tire or cause an unsafe situation. I wonder how much the hoosiers will rub as I had rubbing with those before the shims (and without the struts rotated) and those have a nylon belt so they're even more delicate.
I've attached pictures for the location of the rubbing. You can see in one area it is actually rubbing the metal for the retainer clip and the tire is indented against the liner (full lock).
Interesting thought about shims and rotating the strut. I just found out that they used some shims to move the whole wheel out first, then added more shims to get the desired camber. Do you think this is making it worse?
Rad, thanks for your input. If they are disposable too, no big deal, just don't want to blow out a tire or cause an unsafe situation. I wonder how much the hoosiers will rub as I had rubbing with those before the shims (and without the struts rotated) and those have a nylon belt so they're even more delicate.
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09-30-2008, 11:45 PM
#8
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I actually put 11mm of shims one time and I could not even turn the steering wheel beyond a half turn.
Shims need to be combined with a custom control arm bushing like the one from ERP Racing, as it allows fine tuning of caster through rotation of the bushing (bringing the wheel back).
The 996 and 997 GT3 RS use these same control arms at the back. That's why the 997 GT3 RS has a slightly longer wheelbase, adding shims at the back increases wheelbase but the tires rub the metal bracket that retains the rear bumper. I had to removed the rear shims as well, as my ERP Racing solid bushings were not adjustable.
The Manthey Racing camber plates are quite nice, they are side dependent (not like the stock ones). You get the desired camber, more caster, and the wheel stays where it should. They're not cheap though.
Shims push the front wheels way too much forward.
Shims need to be combined with a custom control arm bushing like the one from ERP Racing, as it allows fine tuning of caster through rotation of the bushing (bringing the wheel back).
The 996 and 997 GT3 RS use these same control arms at the back. That's why the 997 GT3 RS has a slightly longer wheelbase, adding shims at the back increases wheelbase but the tires rub the metal bracket that retains the rear bumper. I had to removed the rear shims as well, as my ERP Racing solid bushings were not adjustable.
The Manthey Racing camber plates are quite nice, they are side dependent (not like the stock ones). You get the desired camber, more caster, and the wheel stays where it should. They're not cheap though.
Shims push the front wheels way too much forward.
10-01-2008, 09:53 AM
#9
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John,
I had the same experience. I didn't rub when the camber plates were rotated, but now that I am using shims (all other front parts stock except Motons and #800 front springs), I rub when turning 3/4 rotation or greater. This only happens at very low speeds, like when parking. No damage to tires after 10+ track days, but this is dependent on wheel offset and tire type. Also, my fenders are rolled, which is very important. I did slice a RF Nitto when I first started, with incompletely rolled fender.
I had the same experience. I didn't rub when the camber plates were rotated, but now that I am using shims (all other front parts stock except Motons and #800 front springs), I rub when turning 3/4 rotation or greater. This only happens at very low speeds, like when parking. No damage to tires after 10+ track days, but this is dependent on wheel offset and tire type. Also, my fenders are rolled, which is very important. I did slice a RF Nitto when I first started, with incompletely rolled fender.
10-08-2008, 11:02 PM
#11
So, I talked to my alignment guy. He said that he purposefully pushed out the the strut top and then put extra shims on the bottom so there would be a wider front track to aid turn in. Car is going back so that it will just be shimmed the amount necessary to get the camber without pushing the wheel further out. We'll see if that decreases the rubbing. Any other suggestions while the car is there are appreciated.
Austin, in moderate street driving today, definitely noticed rubbing on compression. It would be pretty bad with any real turns.
-John
Austin, in moderate street driving today, definitely noticed rubbing on compression. It would be pretty bad with any real turns.
-John
10-08-2008, 11:32 PM
#12
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So, I talked to my alignment guy. He said that he purposefully pushed out the the strut top and then put extra shims on the bottom so there would be a wider front track to aid turn in. Car is going back so that it will just be shimmed the amount necessary to get the camber without pushing the wheel further out. We'll see if that decreases the rubbing. Any other suggestions while the car is there are appreciated.
Austin, in moderate street driving today, definitely noticed rubbing on compression. It would be pretty bad with any real turns.
-John
Austin, in moderate street driving today, definitely noticed rubbing on compression. It would be pretty bad with any real turns.
-John
The increase on track is driven by the shims themselves. 7mm of shims per side are increasing your front track by 14mm, a good thing. A bad thing also, once the tires push out a lot at the bottom, you will be driving a brick at high speeds, your drag coefficient goes to the roof. Good for autoX, bad for the track and gas mileage.
The Solo National Champion 996 GT3 last year ran 245/35 and 295/30 Hoosier A6. They tested the 315 and the times were slower. The National Champion this year: 245/285 V710.
The lower profile 245/35 gets better response to steering inputs. The smaller diameter 295 improves gearing and rear end response on transitions.
10-09-2008, 10:26 PM
#14
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Push in the struts as much as possible, then dial back the side with the most negative camber until both sides are even, then add shims to get to your desired camber limit. I would not go beyond -2.4 to -2.6.
The increase on track is driven by the shims themselves. 7mm of shims per side are increasing your front track by 14mm, a good thing. A bad thing also, once the tires push out a lot at the bottom, you will be driving a brick at high speeds, your drag coefficient goes to the roof. Good for autoX, bad for the track and gas mileage.
The Solo National Champion 996 GT3 last year ran 245/35 and 295/30 Hoosier A6. They tested the 315 and the times were slower. The National Champion this year: 245/285 V710.
The lower profile 245/35 gets better response to steering inputs. The smaller diameter 295 improves gearing and rear end response on transitions.
The increase on track is driven by the shims themselves. 7mm of shims per side are increasing your front track by 14mm, a good thing. A bad thing also, once the tires push out a lot at the bottom, you will be driving a brick at high speeds, your drag coefficient goes to the roof. Good for autoX, bad for the track and gas mileage.
The Solo National Champion 996 GT3 last year ran 245/35 and 295/30 Hoosier A6. They tested the 315 and the times were slower. The National Champion this year: 245/285 V710.
The lower profile 245/35 gets better response to steering inputs. The smaller diameter 295 improves gearing and rear end response on transitions.
285/30 18's not 295/30 18's
Peter
10-10-2008, 10:58 PM
#15
Thank you all for your help. Car came back MUCH better. Now I get just a hint of rubbing full lock but before I couldn't even turn out of the garage or make a sharp right turn without it rubbing. Car feels great, I am quite pleased. So far haven't felt any rubbing on compression. Will give it a good workout this weekend on Hoosiers to try it for real.