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06-23-2008, 10:48 PM | #1 |
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Road racers and HPDE participants, how are you dialing out the understeer?
I rented a 135i a few weeks ago at Autobahn Country Club and gave it a good solid whippin'. The motor and brakes are fantastic. I was even pleasantly surprised by the bitchstick - super quick shifts for an old school auto.
However, the suspension sucked. WAY too much understeer. Track exit was an exercise in frustration as the soft rear squatted so much there was no grip left up front. It's nice that the motor makes that much torque but too bad the car won't turn because of it. :-/ What's the plan to make this thing turn??? |
06-24-2008, 06:32 AM | #3 |
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06-24-2008, 09:53 AM | #4 |
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06-24-2008, 01:08 PM | #6 |
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Less pressure in the front? I thought it was more pressure in the front to counteract understeer... I must be wrong.
EDIT: Yeah, I'm stupid. Must have been the Wendy's burger I had.
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06-27-2008, 01:05 AM | #8 | |
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Quote:
That front wheel is pretty much straight up and already has zero clearnace with the shock. DARN strut type suspensions!! I'm trying to stuff a 255 up in the front for some more front grip. |
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06-27-2008, 07:01 AM | #9 |
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Well, first of all, there's a metal and plastic tab that connects the front fender to the bumper. You can feel it by sticking your hand in the wheel well, right where they intersect. This is a terrible design in my opinion.
Because of that tab, you get it gouging the tire on wider setups, and I needed to dremel most of it away. Even with the near removal of that tab, I needed to roll the fronts, and still did not like the amount of rub i was getting, and opted to lose the 255's in favor of 245s. That, in combination with increased camber, and I have no understeer at all, unless you dive ridiculously into a corner. |
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06-28-2008, 10:01 AM | #10 |
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Larryn also has H&R Sport springs which assist somewhat with understeer. I think the real big improvement in eliminating understeer will be adjustable front camber plates. This car needs -2.5 to -3.5 deg. front camber to maximize front grip, IMO. Then you can carry ridiculous speeds into corners.
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07-20-2008, 12:02 AM | #11 |
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how much negative camber with 135 OEM to get neutral tracking
How much negative camber is needed with 135 OEM springs,rft,etc. to get neutral handling on track days
(leaving rear suspension,tires stock) ? Can too much negative camber be a handling nightmare at the track with OEM 135 at high speeds? Must I reset back to zero camber for wife to safely drive on the highway? |
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07-20-2008, 07:24 AM | #12 |
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Can changing just front tires help understeer? Insane?
If I switch just the OEM front tires with say Bridgestone RE-01R
(400 V.S. 180 Wear rating) to defeat understeer on fast tracks, do you think the rear end will follow the front end,or will the front grip overwhelm the rear and cause an oversteer disaster? After 3 track days, I found that this car totally overwhelms the stock fronts at HI speed.Only a couple of hours track time nearly destroyed my front tire. |
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07-20-2008, 09:05 AM | #13 |
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The stock runflats have a UTQG 140 wear rating (not 400).
You may be able to mix tires, but if you're going with RE-01Rs, you're going to have to increase the fronts to 225's, which do fit your 7.5" front stock wheels. There is no 215mm 18" size in those tires. I don't think you'll be negatively affecting the car with that swap. Keep an eye on your tire pressures throughout the day too. Keep the tires under 40psi, and you should be fine. |
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07-20-2008, 09:53 AM | #14 |
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Better griping Potenza RE-01R
Read in Tire Rack that the Potenza RE-01R hold like full race slicks. Budds BMW says the runflats are far harder and can`t compare with ultimate grip.
Would this invite sudden uncontrollable oversteer with 225s RE-01R only on the front END? |
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07-20-2008, 10:10 AM | #15 |
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I have owned and driven the RE-01R's, Advan Neovas, and the Dunlop Direzza Star Specs. I've tracked and autocrossed all of them. They are all about equal in grip, wear, and feel. I've also had the RE-050A runflats on my last two cars, which I have tracked and autocrossed. I was giving real opinion when I responded.
In my opinion, a 215 RE-050A runflat and a 225 RE-01R are close to the same wear rating, and do not have a dramatic enough grip differential to cause "sudden uncontrollable oversteer". Stick a set of 245 Hoosiers up front, and you will. However, you may be better asking in the TireRack forum, since nobody has done what you are asking about though. |
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07-21-2008, 11:49 AM | #16 |
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burlington-track,
As with most things automotive evereything is a compromise and a matter of trial and error. if you start with information that others have tried and proven to their satisfaction it can save money and time. Since you are starting with the Vorshlag CPs you are on the right road to reducing understeer to a manageable level. Have you tried fitting 8" or 8.5" with front wheels with 235 or 245 tires? That should also help. Try and make one change at a time and evaluate the results. after tires and CPs if you still want more change try a larger front swaybar and perhaps both front and rear bars. Alignment is also critical to good street and track handling. Call Terry Fair at Vorshlag and talk to him about his suggestions for what you (and your wife) expect from the car's handling and then get the car aligned to what he recommends--he's the expert.
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07-22-2008, 01:34 AM | #17 |
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The only mods we're running suspension wise is KW V3 coilovers, Vorshlag camber plates, & H&R rear sway bar.
We were able to get about 2.1 deg of neg camber with the camber plates. We were hoping for 3.5 deg but it just won't happen with the Vorshlag plates. We're running a 255/35/18 Toyo R1R front & 255/40/18 Neova rear. |
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07-31-2008, 08:03 AM | #20 |
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Contact Terry Fair at Vorshlag to double check the install procedure.
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07-31-2008, 11:10 AM | #21 |
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camber plate
Terry found that a bolt on the plate is rubbing on the perch
on some applications causing a squeak(he can give the exact tech info). It will stop after it wears slightly.He is reducing the bolt lenght as a fix. |
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07-31-2008, 12:36 PM | #22 |
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I've read on e90post that his camber plates make noise like none other (link.) Hopefully it is just installation issues - I'm hoping to install camber plates in the future, but since this is my DD I don't want excessive noise all the time.
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