|
|
SUPPORT ZPOST BY DOING YOUR TIRERACK SHOPPING FROM THIS BANNER, THANKS! |
Post Reply |
|
Thread Tools | Search this Thread |
04-25-2011, 11:38 AM | #23 |
Lieutenant
19
Rep 409
Posts |
__________________
| v3.0si | | '08 Z4Coupe 3.0si | BMW Aero | BMW Performance |
|
Appreciate
0
|
04-25-2011, 11:59 AM | #24 |
Captain
56
Rep 815
Posts |
I'm curious. Do you guys recommend the E9X rims (34, 37mm offset) just for the flush look, or because you find that the 1" increase in overall track width has a beneficial effect on handling?
|
Appreciate
0
|
04-25-2011, 12:12 PM | #25 |
Lieutenant
19
Rep 409
Posts |
i'm not tracking the car, so i cannot speak for that.
however, the theory of increased handling due to increased track is sound, otherwise the guys on this forum that are tracking their cars wouldn't bother with super aggressive offsets. i certainly don't see how increased track in the rear of the car could be detrimental. the rear wheels are not pivoting like the front, so only verticle movement is considered. as long as the toe angles are proper for the width and offset of the wheel, increased track should theoretically always be better. the front is a bit different. by changing the offset (and probably the track), the scrub radius that was originally defined by the engineers is changed, hence my afore mentioned issues with bumpsteer and tramlining. increasing track is good for grip; however, a change in scrub radius is bad for steering feedback and may also contribute to understeer or oversteer. racers chime in, and let me know if i'm way off base.
__________________
| v3.0si | | '08 Z4Coupe 3.0si | BMW Aero | BMW Performance |
|
Appreciate
0
|
04-25-2011, 02:22 PM | #26 |
Private First Class
16
Rep 176
Posts
Drives: 2006 Z4 3.0si Coupe
Join Date: Jan 2011
Location: Bulgaria
|
Thing is, I actually do like the 269 way better than the 313. That is just my opinion. I think it suits the car better, I don't like the huge space between the spokes of the 313, otherwise it is a great rim.
I am running run flat Potenza RA050As and I used to get a lot of bumpsteer until I got the whole car realigned and the tires rebalanced again. Now even at 200km/h I can let go of the steering wheel and it does not bumpsteer any more. I like the harsher ride that the run flats provide and they are also a lot safer if you blow a tire at high speeds (happens often here since there is a lot of trash on the road). Next summer I will get the 269s and will wrap them in either PS3 or PSS. Those tires are not run flat but rather they have a strengthened board (they are used on the M vehicles because normal run flats can't handle the stress if you decide to really "drive" the car). So they should ride a bit softer, although I am going up an inch so we will see the results, they have way more traction than my current tires and are quieter. And ofc I will realign the whole car again when I get the new rims. |
Appreciate
0
|
04-25-2011, 02:34 PM | #27 |
Lieutenant
19
Rep 409
Posts |
no criticism from me. the 269 is a beautiful wheel!
you mentioned that the tires will be an inch taller... remember that will effectively change your overall gearing and will cause slower accelleration. it will also change your speedo, tach, odometer, and fuel economy.
__________________
| v3.0si | | '08 Z4Coupe 3.0si | BMW Aero | BMW Performance |
|
Appreciate
0
|
04-25-2011, 03:19 PM | #28 | |
Private First Class
16
Rep 176
Posts
Drives: 2006 Z4 3.0si Coupe
Join Date: Jan 2011
Location: Bulgaria
|
Quote:
|
|
Appreciate
0
|
04-25-2011, 03:28 PM | #29 | |
Lieutenant General
2387
Rep 12,635
Posts
Drives: Z4 M, X5, GX460
Join Date: Apr 2008
Location: CT
iTrader: (100)
Garage List E86 Z4 M [10.00]
F15 X5 xDrive35i [9.17] F10 550i (Retired) [9.17] F25 X3 xDrive35i (R ... [9.43] E82 135is (Retired) [9.53] E85 Z4 M (Retired) [9.41] E90 328i xDrive (Re ... [9.25] E86 Z4 3.0si (Retired) [8.93] |
Quote:
v3.0si was confused (as was I) because your previous post mentioned 1" gain in the context of tires. You should be fine on 225/40 - those are the oem recommended specs. I ran 225/45-17 on my winter setup and the ride was definitely more comfortable but it didn't look nearly as good as the car sitting on 18s. |
|
Appreciate
0
|
04-25-2011, 03:54 PM | #30 | |
Private First Class
16
Rep 176
Posts
Drives: 2006 Z4 3.0si Coupe
Join Date: Jan 2011
Location: Bulgaria
|
Quote:
|
|
Appreciate
0
|
04-25-2011, 04:27 PM | #31 | |
Midlife Crises Racing Silent but Deadly Class
1827
Rep 5,337
Posts
Drives: 2006 MZ4C, 2021 Tesla Model 3
Join Date: Oct 2007
Location: Welcome to Jamaica have a nice day
|
Quote:
Wider than, or significantly wider than stock offset numbers, results in unfavorable suspension geometry that puts extra and unnecessary stress on the suspension components that leads to premature wear.
__________________
Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
|
|
Appreciate
0
|
04-25-2011, 04:50 PM | #32 | |
Private First Class
16
Rep 176
Posts
Drives: 2006 Z4 3.0si Coupe
Join Date: Jan 2011
Location: Bulgaria
|
Quote:
|
|
Appreciate
0
|
04-25-2011, 05:09 PM | #33 | |
Lieutenant
19
Rep 409
Posts |
Quote:
help me out though, if track guys aren't using the aggressive offsets, why are these guys... crfine88 F360C GothM Colatkitty Shereef_Osman ... all using wheel and tire combos that push the limit? is it that they want both function and looks? why do places like Turner sell suspension and brake upgrades that do not work with factory wheel specs? i am NOT trying to start anything, I just like to know so I don't give out bad info.
__________________
| v3.0si | | '08 Z4Coupe 3.0si | BMW Aero | BMW Performance |
|
|
Appreciate
0
|
04-25-2011, 05:12 PM | #34 |
Colonel
190
Rep 2,138
Posts
Drives: Me
Join Date: Oct 2007
Location: Virginia Beach
|
This is going to get interesting...
|
Appreciate
0
|
04-25-2011, 05:29 PM | #35 | |
Midlife Crises Racing Silent but Deadly Class
1827
Rep 5,337
Posts
Drives: 2006 MZ4C, 2021 Tesla Model 3
Join Date: Oct 2007
Location: Welcome to Jamaica have a nice day
|
Quote:
For example, a friend of mine campaigns a very successful H-Prepared E46 M3 with a 34mm front offset, but only because in order to STUFF 275mm wide R-Comps under the front fender, he needed a set of rims wide enough that pushes the wheel out far enough not to rub. IF he were to run a 245mm wide tire he would have done so with a 38-42mm offset on a reasonable rim. His rear rims are 25mm offset (1mm shy of stock E46 M3 offset) on 275mm R-comps. His H-Stock 135i runs with factory offset rims. You'll have to ask the people on that list you provided, individually, why they specifically run with super aggressive offset. As for Turner, I also can't speak for him but I know he runs a business, and part of running a business is you have to know what your customers buy. I'm willing to bet, that if his business is anywhere like our own, it is comprised of 1% racers and track junkies, and 99% your normal, run of the mill customers that never sniff the hot side of the pit. And for those guys, a "flush" look will likely sell better than a properly designed/engineered product.
__________________
Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
|
|
Appreciate
0
|
04-25-2011, 05:37 PM | #36 |
Lieutenant
19
Rep 409
Posts |
good call on all accounts. like i said above, i'm not a racer, and any reasonable input from track hounds is very appreciated. HACK, thank you again!
any other racers out there willing to spill their thoughts? DUBBEDOWN, i know you're a auto-x guy, what about you?
__________________
| v3.0si | | '08 Z4Coupe 3.0si | BMW Aero | BMW Performance |
|
Appreciate
0
|
04-25-2011, 05:54 PM | #37 |
Colonel
190
Rep 2,138
Posts
Drives: Me
Join Date: Oct 2007
Location: Virginia Beach
|
I track on Stock wheels and have one set of 12mm spacers and one set of 10mm spacers. I have had these for a while but I will not put them on the car for the reasons Hack has stated. I bought them before I received an education on suspension geometry at the track from some Grand-AM mechanics.
I find that every older and wiser instructor that I have had in the Z4M Coupe (I can only talk about this car on the track), has remarked that with only some suspension alignment changes (camber, toe) that the basic car is phenomenal, and they love being in the car. Since I have not switched to R-Comp tires or have installed coil-overs (yet), it will only get better. |
Appreciate
0
|
04-25-2011, 06:06 PM | #38 | |
Midlife Crises Racing Silent but Deadly Class
1827
Rep 5,337
Posts
Drives: 2006 MZ4C, 2021 Tesla Model 3
Join Date: Oct 2007
Location: Welcome to Jamaica have a nice day
|
In an effort to re-affirm my side of the discussion, I found this VERY informative post about the relationship between steering angle inclination vs. scrub radius on a MacPherson Strut. The diagram is very helpful in visualizing how increased or decreased OFFSET from factory can affect a car's handling characteristics.
http://forums.rennlist.com/rennforum...768-post6.html If none of what is discussed here make any sense, don't worry. THIS is the most important part of the discussion: Quote:
I don't know. Maybe those guys you referenced, crfine88, F360C, GothM, Colatkitty, and Shereef_Osman knows a lot more about chassis dynamics than I do. I'm merely going by what I know and what those that have taught me what I know knows. I'm by no means an expert on this topic, I just pretend to be one. Do keep in mind, that the steering angle inclination discussion is SECONDARY to the amount of grip you can add by going with a wider tire...The amount of grip you can add up front with MOAR tire is going to easily offset the drawbacks of altering the scrub radius. And you can always INCREASE CAMBER to bring that scrub radius back in line. Or you can do a combination of everything, increase tire width, increase offset, increase camber to retain scrub radius. But to blindly add offset without knowing what your scrub radius based on current tire size, IMO, is counterproductive. EDIT: Nevermind, it appears you are well aware of scrub radius and SAI and its effect on steering feel.
__________________
Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
Last edited by The HACK; 04-25-2011 at 06:19 PM.. |
|
Appreciate
0
|
04-25-2011, 06:32 PM | #39 |
Lieutenant
19
Rep 409
Posts |
so... i should apologize to the OP, Arxangel, for kinda sorta stealing his thread. sorry, man.
i am extremely interested in these topics as i would love to get into auto-x with my z4c. if there's interest from others here, i would like to start a new thread that contains some of the theory and the math behind opinions reflected in setups found in track hound cars, auto-x cars, and straight up tuner cars. this would be a near one-stop shop for all willing to fill their heads to the brim with crazy talk like scrub radius, arc trajectory, and overall suspension geometry. it probably would not go into detail about power upgrades, instead focus on getting the power to the pavement. so what say you? how about this, if three others reading this are interested, let me know, i'll start a new thread linked from here. takers?
__________________
| v3.0si | | '08 Z4Coupe 3.0si | BMW Aero | BMW Performance |
|
Appreciate
0
|
04-26-2011, 02:59 AM | #40 | |
Private First Class
16
Rep 176
Posts
Drives: 2006 Z4 3.0si Coupe
Join Date: Jan 2011
Location: Bulgaria
|
Quote:
As for your idea, it sounds cool. In any case it would be beneficial since there isn't a lot of ready info on our cars in this forum anyway. The M's have taken over. :P I am not planning on ever setting up my car for track use or auto-x or any other competition, but you never know, it would be good to have a thread where you can go and have a look, if only to educate yourself. |
|
Appreciate
0
|
04-27-2011, 08:31 PM | #41 |
Captain
56
Rep 815
Posts |
Well, despite my skepticism about increased track width, it looks like I've found a good deal on some style 189's (with decent tires for around my cost to replace tires alone). So I'll be jumping on the 34/37 offset bandwagon. I suppose if I really don't like it I can always sell them to an E9x-er...
FWIW I wasn't particularly sold on E9x wheels, but did want lower aspect ratio tires since I can feel an objectionable degree of sidewall softness on my current 235/45/17s. So I was looking for a good deal on 18's of some OEM flavor. I had a line on some decent style 135's with the stock offset, but could get the 189's for a couple hundred less and decided to try 'em. I'll end up with a real Frankenstein suspension hodgepodge on my non-M coupe that would probably make the HACK barf (or worse, tsk in derision): Style 189 wheels, H&R sways (currently front full stiff and mid setting on the rear, Koni yellows which I'll be putting on in another few weeks, and... stock non-sport-package springs). It'll be "interesting". Last edited by vachss; 04-27-2011 at 11:26 PM.. |
Appreciate
0
|
04-28-2011, 03:37 AM | #42 | |
Private First Class
16
Rep 176
Posts
Drives: 2006 Z4 3.0si Coupe
Join Date: Jan 2011
Location: Bulgaria
|
Quote:
Last edited by Arxangel; 04-28-2011 at 03:46 AM.. |
|
Appreciate
0
|
04-28-2011, 12:18 PM | #43 |
Private First Class
5
Rep 174
Posts |
Pity, it looks like those 269's are not for the M's. At least the Dutch BMW website says so explicitly.
Such a shame, one of the few wheels that I really liked... |
Appreciate
0
|
04-28-2011, 12:32 PM | #44 | |
Midlife Crises Racing Silent but Deadly Class
1827
Rep 5,337
Posts
Drives: 2006 MZ4C, 2021 Tesla Model 3
Join Date: Oct 2007
Location: Welcome to Jamaica have a nice day
|
Quote:
IT IS A VOODOO science. Actually calling it science would be too kind. There are so many variables involved here that sometimes, what will make a specific set-up work won't work for another set-up. And I don't claim to be any sort of expert on these matters. All I know is, a lot of times when I get advice from other racer or instructor friends when it comes to suspension (and that includes wheels and tires) they can sometimes seem counter-intuitive...But for some reason, counter-intuitive or not, they work. THERE REALLY IS NO RULE OF THUMB. Despite the fact that none of my racer and instructor friends use anything more than 5mm off from OEM offset (or the equivalent based on width of wheel), it doesn't mean that so-called "aggressive offset" won't work for someone else with a different set of compromises on their suspension. And I've seen Frankenstein suspension systems work and work well. Granted they were put together by someone who knows a lot more than what I know, but it CAN work. There are some basic guidelines you can follow, but at the end of the day... The only way for you to know for sure if a certain setup works or not, is by TESTING. Go do as many laps as you can, eliminate the variables, and systematically test your adjustments to find out what works and does not work for you. That is the ONLY thing any of you should take away from anything I say on this topic.
__________________
Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
|
|
Appreciate
0
|
Post Reply |
Bookmarks |
|
|