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Old 06-15-2009, 12:56 PM   #1
Aaron B
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Default Wheel spacers - STX WRX

Who else here has done testing with wheel spacers?

I tried a set of 20mm spacers on the front this weekend. Ran the whole event with them on, then after the event we had some time for fun runs so I did some testing with and without after the event. Did one run with them on, 1 run with them off, followed by another run with them on.

Best run for the event 35.3xx (wasn't crazy about any of my runs throughout the day)

Test run 1 WITH spacers 35.1xx
Test run 2 WITHOUT 34.8xx
Test run 3 WITH again 35.1xx

It was a short, 2 lap course, on a very tiny lot. Top speed was 38mph (in the slalom!) low end was about 20, avg about 30. Not a WRX friendly course, too fast for first, not fast enough for 2nd.

Wasn't exactly sure what the actual effect (time) of the spacers was going to be, actually, I guess I was expecting faster with them. Wider front track -> less weight transfer -> more grip was what I was expecting. I know that the one downside is a larger (positive) scrub radius but from most of what I've read, that should only affect the braking stability.

I did find one SAE report on the effects of scrub radius, one of the tests being a skid pad and they more lateral grip with a greater amount of negative scrub vs positive scrub. The vehicle used for that test was an SUV, offsets ranging from ~55ish mm+ to ~20ish mm-

Just going off the seat of the pants feel, I would have sworn it was faster WITH the spacers. Felt much more stable and planted. Onlookers said that the rear wheel lift was also less on the runs with the spacers.

The clock doesn't lie though.

Has anyone else tested this? If so, what results did you have?
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Old 06-15-2009, 04:05 PM   #2
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very interesting results Aaron.

I've never tried w/ or w/o. I've usually not had room to play around with that much.

did you take tire temps across the tires? I wonder if your widen track will need other tweaks in your setup to be truly optimized.
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Old 06-15-2009, 09:10 PM   #3
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Actually had the chance to do a little testing last weekend, didn't test with and without spacers then, just pressures. Had the spacers on though. Temps came up with about a nice 15 degree spread from outside to inside.

I did consider the possibility of the need for another setup change with the spacers on vs off. Would like another chance to just test the spacers v no spacer back to back again.

The front sway is already on it's stiff setting, could try to stiffen the front shocks to adjust for the lower motion ratio. The rear was reported to be more planted but was still lifting so I don't think I want to go any stiffer there. Hate to drop money on MORE springs to try stiffer front springs. Not sure. May just try the shocks.
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Old 06-17-2009, 02:58 PM   #4
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aaron : ygm
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Old 06-17-2009, 07:21 PM   #5
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I ditched my spacers becasue the extended lenth lug studs I put on my car made so much noise they distracted me so much I was slower on course. They were 23 mm custom made spacers.
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Old 06-17-2009, 08:56 PM   #6
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What wheels or setup are you running that you can use spacers w/o rubbing?

You think the extra weight would have an effect too?
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Old 06-18-2009, 12:36 AM   #7
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17x8 Rota Torques, 48mm offset with 245/40 Kumho XS'. Only had the spacers on the front, plenty of room there.

I used hub centric spacers, so no extra noise (that I could hear over the exhaust anyway)
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Old 06-18-2009, 12:04 PM   #8
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I'm trying to figure out how extended studs can cause a noise... I've had ARP long studs on all 4 for quite a while now. I run et 44 wheels with 10mm spacers up front.
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Old 06-18-2009, 12:26 PM   #9
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Quote:
Originally Posted by Splash View Post
I'm trying to figure out how extended studs can cause a noise... I've had ARP long studs on all 4 for quite a while now. I run et 44 wheels with 10mm spacers up front.
Loose wheels or wrong studs?


I was always a proponent of my wheel spacers. I ran 20mm up front and had the rears pushed out as far as I could with the lateral links. 17x8's +45 and +48's


It always made me feel faster, and got rid of that nasty wrx tucked in tire look.
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Old 06-18-2009, 01:08 PM   #10
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Hey, the wider it is, the less it leans. Anything to reduce the amount of bar you need... Mine are about as far apart as I want without making them cone-catchers... <grin>
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Old 06-18-2009, 04:42 PM   #11
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Nothing was loose. I couldnt figure it out either but when we replaced them with the stocker's the noise went away.
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Old 06-18-2009, 06:30 PM   #12
Aaron B
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Quote:
Originally Posted by mccanixx View Post
It always made me feel faster, and got rid of that nasty wrx tucked in tire look.
That's the thing, it definitely FELT faster with the spacers on. Had we not timed the runs I would have sworn it was faster. Didn't appear to be the case though.

Quote:
Originally Posted by Splash
Hey, the wider it is, the less it leans. Anything to reduce the amount of bar you need...
Well, pushing the wheels out DOES move the motion ratio further away from ~1 on the springs, the motion ratio on the sway bar is already at something like .6 without the spacers, so technically, just throwing that into the equation the effective spring and sway bar rates are being lowered.

There's a lot of variables that get mixed around with a change like this, motion ratio being one, roll stiffness, track width (obviously), weight transfer, scrub radius, etc. It's entirely possible that what's lost in one aspect could outweigh what's gained in another.

This was just the result from one testing opportunity though, on one course and one surface. Who's to say that what didn't work on in this scenario won't work in another, only more opportunities to test will decide that :shrug:
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Old 06-18-2009, 07:45 PM   #13
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Quote:
Originally Posted by Aaron B View Post
Who else here has done testing with wheel spacers?

I tried a set of 20mm spacers on the front this weekend. Ran the whole event with them on, then after the event we had some time for fun runs so I did some testing with and without after the event. Did one run with them on, 1 run with them off, followed by another run with them on.

Best run for the event 35.3xx (wasn't crazy about any of my runs throughout the day)

Test run 1 WITH spacers 35.1xx
Test run 2 WITHOUT 34.8xx
Test run 3 WITH again 35.1xx

It was a short, 2 lap course, on a very tiny lot. Top speed was 38mph (in the slalom!) low end was about 20, avg about 30. Not a WRX friendly course, too fast for first, not fast enough for 2nd.

Wasn't exactly sure what the actual effect (time) of the spacers was going to be, actually, I guess I was expecting faster with them. Wider front track -> less weight transfer -> more grip was what I was expecting. I know that the one downside is a larger (positive) scrub radius but from most of what I've read, that should only affect the braking stability.

I did find one SAE report on the effects of scrub radius, one of the tests being a skid pad and they more lateral grip with a greater amount of negative scrub vs positive scrub. The vehicle used for that test was an SUV, offsets ranging from ~55ish mm+ to ~20ish mm-

Just going off the seat of the pants feel, I would have sworn it was faster WITH the spacers. Felt much more stable and planted. Onlookers said that the rear wheel lift was also less on the runs with the spacers.

The clock doesn't lie though.

Has anyone else tested this? If so, what results did you have?
20mm spacers, with no other suspension adjustments, should cause some wonderful understeer. If you understeer more on corner exit you will lose time quickly.

I also don't know how consistent you are, but .3s is within a margin of error for many drivers.

Last edited by stimpy; 06-18-2009 at 08:51 PM.
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Old 06-19-2009, 08:03 AM   #14
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Quote:
Onlookers said that the rear wheel lift was also less on the runs with the spacers.
This is why I run spacers up front... I don't want to use a big front bar to fix it. It's either widen the front a touch, or use even stiffer front springs (they're already pretty stiff). I was close enough, both on lift and front grip, that I didn't want a big change.
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Old 06-19-2009, 01:07 PM   #15
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Quote:
Originally Posted by Splash View Post
This is why I run spacers up front... I don't want to use a big front bar to fix it. It's either widen the front a touch, or use even stiffer front springs (they're already pretty stiff). I was close enough, both on lift and front grip, that I didn't want a big change.
A wider track increase roll control, just as you've said. If the car pitches less, the opposite corner is going to come up less. Problem comes about if you have tuned the car to rotate with one wheel in the air. With the spacers, the car will have both rear wheels on the ground more often.
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Old 06-19-2009, 04:46 PM   #16
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Exactly.

I can have the inside rear up on entry only. Anywhere near the apex and it will spin it, ruining the exit. The car is tuned to rotate as best as possible with at least some pressure on the inside rear.
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Old 06-21-2009, 08:13 AM   #17
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Plus, I don't think just one timed run is enough to back up the data. May'be run your 3-4 compitition runs with them and when you get time for fun runs run without. Of course that also depends on the ambient temps along with the surface temps. If the course is too hot your street tires will suffer with grip level anyway.
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Old 06-22-2009, 07:14 AM   #18
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Buy/beg/borrow a datalogger and try to isolate it using specific tests, maybe at a test and tune day or something. Otherwise it is going to be hard to tell where you are losing/gaining time.
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Old 06-22-2009, 01:19 PM   #19
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Quote:
Originally Posted by ButtDyno View Post
Buy/beg/borrow a datalogger and try to isolate it using specific tests, maybe at a test and tune day or something. Otherwise it is going to be hard to tell where you are losing/gaining time.
We rented a paddock at Miller Motorsports park back in February and set a traction circle, some offsets, and a slalom. It was readily apparent when we juggled 4mm front to back. We saw changes in both throttle steer and segment time around the traction circle. We were able to quantify the felt changes with times through our datalogger.
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Old 06-22-2009, 10:59 PM   #20
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Quote:
Originally Posted by stimpy View Post
We rented a paddock at Miller Motorsports park back in February and set a traction circle, some offsets, and a slalom. It was readily apparent when we juggled 4mm front to back. We saw changes in both throttle steer and segment time around the traction circle. We were able to quantify the felt changes with times through our datalogger.
Apparent how? What was faster where?
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Old 06-23-2009, 05:17 PM   #21
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Originally Posted by ButtDyno View Post
Apparent how? What was faster where?
It was on the wrong car for it to apply directly but I'll offer the information anyhow.

We did the testing on a 2003 M3. We had 10mm front spacers and 12mm rear spacers. On the traction circle it would understeer and require waiting for the front to tuck in properly. The spacer selection was originally done a few suspension iterations before to solve a snap oversteer trait that occurred in slaloms. By switching to 12mm/10mm the car tucked in quicker faster on lift and was much easier to steer with the right foot (traction circles are supposed to be done with constant steering input). The change showed a cool .200s on a 9 second lap. This was a 150' traction circle on racetrack grade asphalt.

It may be that 12/10 is the right combination or the car was simply matched better to 12/10, but the slight spacer change was pretty profound. Just swapping spacers and saying one was faster than another isn't enough. Both spacer configurations ought to be tuned and then compared. With realistic timelines, that can't exactly happen.
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Old 06-24-2009, 02:28 PM   #22
Aaron B
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Quote:
Originally Posted by planetarygear View Post
Plus, I don't think just one timed run is enough to back up the data. May'be run your 3-4 compitition runs with them and when you get time for fun runs run without. Of course that also depends on the ambient temps along with the surface temps. If the course is too hot your street tires will suffer with grip level anyway.
That was a thought of mine as well, more runs would have been nice. I was in the first run group, however, and had to wait through FJ and the 2nd run group so I decided to do a baseline run with them on to start the fun run tests. The co-driver (aka the guy that bought the car from me at the end of last season) then decided he wanted to try it also after my first run with them off. He took his sweet time getting back in line so time was limited and I made the decision to stick with an A:B:A test instead of A:B:B:A (or more)

FWIW, his 2 runs were, if I remember correctly, ~36.6 without and ~36.3 with
during the testing runs. His fastest run of the event was, I believe, a 35.9 with most of his runs in the 36's. So, not much to be gained from him testing.

*edit

This weekend's event is on airport concrete, that last event was on a small asphalt lot. Should be some good info from this one. Still haven't investigated the data logs too much from the last event, the course was so small it's been hard to read too much from it.

Last edited by Aaron B; 06-24-2009 at 02:35 PM.
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Old 06-24-2009, 11:35 PM   #23
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I could feel a difference w/ 5mm spacers (front only), 20mm spacers should certainly provide a felt difference in handling- wider front track will dial some understeer out- as pointed out above it could have some negative effectives as well

not a lick of scientific data to offer though

I am going to run them again, this time on my D Stock car
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