Welcome to Bimmerfest -- The #1 Online Community for BMW related information! Please enjoy the discussion forums below and share your experiences with the 200,000 current, new and past BMW owners. The forums are broken out by car model and into other special interest sections such as BMW European Delivery and a special forum to voice your questions to the many BMW dealers on the site to assist our members!

Please follow the links below to help get you started!

Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > Z Series > E36/7 Z3 (1996-2002)

E36/7 Z3 (1996-2002)
E36/7 Z3 Roadster, Z3 coupe, Z3 M Roadster and Z3 M Coupe talk with our gurus here.

Reply
 
Thread Tools Display Modes
  #1  
Old 06-20-2011, 02:19 AM
michael_retired michael_retired is offline
Registered User
Location: Baguio City
 
Join Date: Jun 2011
Posts: 25
Mein Auto: 2003 Z4 3.0i
2003 Z4 - larger tire to prevent bottoming out

Hi all, first post, love this site

I have low profile 235 ZR19/35/84W tires (I believe these numbers are more or less correct).
I'm concerned that the car bottoms out occassionally on speedbumps.

What is recommended size wise as far as a less low-profile tire so as to give more clearance ?
I think I would increase the '35' number but what would be the safe max so it doesn't
hit the wheel well ?

Thanks

Michael, Baguio City, Philippines

Last edited by michael_retired; 06-20-2011 at 04:19 AM.
Reply With Quote
Advertisement
  #2  
Old 06-20-2011, 11:07 AM
Living Dead Living Dead is offline
ZEDHEAD
Location: New York
 
Join Date: May 2011
Posts: 129
Mein Auto: 2006 Z4 3.0i
The profile of a tire will not raise or lower the height of the bottom of the car from the ground and prevent the car from bottoming enough without causing clearence problems (with the wheelwell) and handling issues. The aspect ratio or profile, 35 in the case you mentioned represents the height of the sidewall in relation to the width (the 235 on your example). The thickness of the side wall is 35% the width of the tire (sidewall to sidewall) in this case about 82mm. You can increase the height of the car by increasing the rolling diameter of the tire but you will have to greatly increase that diameter to make a difference so as to not bottom out going over speedbumps and in so doing you will drastically change how the car handles plus the spedometer will also have to be recalibrated to compensate for the larger diameter tire. I would suggest you either avoid known speedbumps that are too high or drive slower over them. Since you mention your car is a 2003 I would guess if the car is riding too low the springs may be sagging a bit.

Last edited by Living Dead; 06-20-2011 at 12:03 PM.
Reply With Quote
  #3  
Old 06-20-2011, 05:15 PM
michael_retired michael_retired is offline
Registered User
Location: Baguio City
 
Join Date: Jun 2011
Posts: 25
Mein Auto: 2003 Z4 3.0i
Great info, thanks. I'll look into the springs.

Michael Labrador
Reply With Quote
  #4  
Old 06-20-2011, 05:23 PM
michael_retired michael_retired is offline
Registered User
Location: Baguio City
 
Join Date: Jun 2011
Posts: 25
Mein Auto: 2003 Z4 3.0i
1 inch ?

I would think increasing the 'rolling diameter' by say an inch would help greatly.
I don't bottom out often, just once in a while and if I go a bit too fast.

The lowest point of the car (the skirt) is about 4 or 4.5 inches.
I do go very slow now when going over speed bumps.

Michael
Reply With Quote
  #5  
Old 06-21-2011, 04:34 AM
Z3Papa Z3Papa is offline
Officially Welcomed to the 'Fest
Location: Bloomington
 
Join Date: Dec 2004
Posts: 612
Mein Auto: 2002 Z3 3.0
You need to differentiate between scraping and bottoming out. Scraping would entail the bottom of the car (front, middle or back) coming in contact with surface due to insufficient clearance. Bottoming out relates to a lack of suspension travel which means you hit the bump stops. You can have both -- ie the car scraps because you "bottom out" but that would be exceptionally rare on stock suspension car. Regarding the 19" wheels and 35 aspect, realistically speaking, you may be hard pressed to jump to a 40 aspect and still fit that wheel into the well without serious rubbing on lock. The problem with our cars going to 35 or even worse 30 aspect tires is the tire is a factor into how the car absorbs bumps. May look cool to have very low aspect tires, but that doesn't make it ideal for comfort handling. It's possible your OE springs are sagging, but highly unlikely. Were you the original buyer of this car because it sound like someone put aftermarket springs on which have lowered the car and reduced shock travel.
__________________
SS braces, AST 4200's coilovers, Vorshlag camber plates, GC RSM, H&R Front sway, Conforti CAI, Magnaflow exhaust, Recaro seats, and Apex ARC-8 with RS3's and Style 32's with Pilot SS for autocross
Reply With Quote
  #6  
Old 06-21-2011, 07:22 AM
michael_retired michael_retired is offline
Registered User
Location: Baguio City
 
Join Date: Jun 2011
Posts: 25
Mein Auto: 2003 Z4 3.0i
No, I'm not the original buyer..

I guess the accurate description is it's 'scraping'. It's just a very brief and slight
contact but it still bothers me.

I'll try to ask the previous owner if he changed the original shocks. The car only has
40000 kms. Yes I trust this person, he has several other high end cars (rich family) and
this isn't the only car he drives.

Anyway, thanks for the tips.
Michael
Reply With Quote
  #7  
Old 06-21-2011, 09:10 AM
dougmcintyre dougmcintyre is offline
formerly updmst
Location: Chapel Hill, NC
 
Join Date: Sep 2009
Posts: 681
Mein Auto: 2000 M Coupe, 1997 318ti
Why not just measure the ride height? See http://www.bimmerfest.com/forums/sho...z4+ride+height, especially posts 8 and 30.
Reply With Quote
  #8  
Old 06-25-2011, 12:19 AM
bimmerlike bimmerlike is offline
Registered User
Location: Hong Kong
 
Join Date: Jun 2011
Posts: 21
Mein Auto: 2006 Z4 roadster
good sharing~!
Reply With Quote
Reply

Bookmarks


Forum Navigation
Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > Z Series > E36/7 Z3 (1996-2002)
Today's Posts Search
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On



Forum Jump


All times are GMT -7. The time now is 02:38 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
© 2001-2011 performanceIX, Inc. All Rights Reserved .: guidelines .:. privacy .:. terms