Go Back   986 Forum - for Porsche Boxster & Cayman Owners > Porsche Boxster & Cayman Forums > Performance and Technical chat

Reply
 
LinkBack Thread Tools Display Modes
Old 11-29-2010, 09:45 PM   #1
Registered User
 
Join Date: Jul 2010
Location: austin, tx
Posts: 64
rear offset 18x10

I know this is kind of an old subject but I just recieved my new wheels from forgestar, and I am disappointed to see that they don't have as much offset as I was hoping for. I am trying to get them to fix it because I want to run 275/35 tires and a lot of negative camber, which pushes the wheel outward. I am afraid I am going to cut the tires. I measured the offset to be just under 40mm, if my math is right. I used a straight edge to measure backset at 7.12 inches, and the wheel lip to be .50 inches, so 7.12-.50-5.00(distance from inside of lip to 0 offset)=1.62=39.xxmm. correct? There is no marking on the wheel that seems to correspond to offset. please let me know if I need to send theese wheeels back. I have to be able to run these tires to be competitive in my autocross class, and I don't want them to be rubbing, or sticking out even. seeing as porsche has a bulletin that states the rear camber should be adjusted less negative(within specification) to achieve proper tire clearance when the stock offset is 47mm and stock tires are 265/35/18 I am thinking I am going to definitely have clearance problems. anyone out ther had a rear wheel/tirre combination that would have similiar offset? do you have any issues with tires rubbing?
autodoctor911 is offline   Reply With Quote
Old 11-30-2010, 02:22 AM   #2
Registered User
 
Join Date: Aug 2007
Location: Virginia
Posts: 244
More neg cam pulls top of tire inward, which will reduce the chance of rubbing. I'm running 18"x10" with 265/35 and an offset of 43mm with no problem. Rear cam is at -2.0. Until you get camber set and wheels on I don't think you can be sure you will have a problem.
__________________
-- John
'00 Boxster S
'86 911 Carrera Coupe (Sold)
Lucky is offline   Reply With Quote
Old 11-30-2010, 03:39 AM   #3
JTP
Registered User
 
Join Date: Aug 2009
Location: MD
Posts: 628
Quote:
Originally Posted by autodoctor911
so 7.12-.50-5.00(distance from inside of lip to 0 offset)=1.62=39.xxmm. correct?
Your math is off. 1.62 inch = 41.1mm
JTP is offline   Reply With Quote
Old 11-30-2010, 08:37 AM   #4
Registered User
 
Johnny Danger's Avatar
 
Join Date: Nov 2008
Location: Massachusetts
Posts: 4,809
Garage
You should have no problems with that combination. I run a 19x10 +31 offset with a 275/30/19 tire with no problems.
__________________
Don't worry I've got the microfilm.
Johnny Danger is offline   Reply With Quote
Old 11-30-2010, 01:44 PM   #5
Registered User
 
Join Date: Sep 2006
Location: California
Posts: 713
I'm on 19x10 with 41mm offset in back with 265/35/19 right now with no rubbing issues... (not the same wheels in my sig)...

Might be a bit different with your wheel type/design and offset... mine are currently a 3 piece reverse lip..
__________________
http://farm4.static.flickr.com/3420/...90927559_o.jpg

Some stuff for sale: M030 S 24mm front sway bar, M030 base 19.6mm rear sway bar, 996 GT3 OEM Porsche Motorsport front strut mounts monoball "camber plates"

WTB: looking for some 5-7mm spacers with extended bolts
chaudanova is offline   Reply With Quote
Old 11-30-2010, 02:28 PM   #6
Registered User
 
Join Date: Jul 2010
Location: austin, tx
Posts: 64
no, more negative camber moves the whole wheel outward. the top of the strut is fixed, the control arm adjusts outward to increase negative camber, the top does not move out as much as the bottom, thus more negative camber is achieved. that is unless you have some kind of coilover setup that is adjustable at the top. are these available? would it work with a stock spring?

I am looking for some m030 USA springs and base rear sway bar, as well as a GT3 front bar, or other adjustable front bar. so I may be interested in the sway bar you mentioned.

johnny, I guess if 19x10 with 31mm offset is fine with the 275/30/19, I should be fine. my 275/35/18s are a bit taller. do your 31mm offset 19s stick out farenough to where they would hit the fender when compressed, but it just never gets that low? what is your ride hieght?

Last edited by autodoctor911; 11-30-2010 at 03:07 PM.
autodoctor911 is offline   Reply With Quote
Old 11-30-2010, 04:17 PM   #7
Registered User
 
Johnny Danger's Avatar
 
Join Date: Nov 2008
Location: Massachusetts
Posts: 4,809
Garage
Quote:
Originally Posted by autodoctor911
no, more negative camber moves the whole wheel outward. the top of the strut is fixed, the control arm adjusts outward to increase negative camber, the top does not move out as much as the bottom, thus more negative camber is achieved. that is unless you have some kind of coilover setup that is adjustable at the top. are these available? would it work with a stock spring?

I am looking for some m030 USA springs and base rear sway bar, as well as a GT3 front bar, or other adjustable front bar. so I may be interested in the sway bar you mentioned.

johnny, I guess if 19x10 with 31mm offset is fine with the 275/30/19, I should be fine. my 275/35/18s are a bit taller. do your 31mm offset 19s stick out farenough to where they would hit the fender when compressed, but it just never gets that low? what is your ride hieght?
Needless to say, I run a very aggressive set-up with my vehicle. However, before doing so, careful calculations were made with regard to clearance. Keep in mind, that my vehicle is not tracked or auto crossed. Nevertheless, its often driven aggressively on the road, and I have not had any issues with regard to rubbing . Although, I must admit the set-up is about as aggressive as one can go. I'll shamelessly post a photo so you can see the ride height.
Attached Images
 
__________________
Don't worry I've got the microfilm.
Johnny Danger is offline   Reply With Quote
Old 12-01-2010, 02:35 PM   #8
Registered User
 
Join Date: Nov 2009
Location: Winnipeg MB
Posts: 2,486
Damn, that's a sharp-looking car!
__________________
'99 black 986
Mark_T is offline   Reply With Quote
Reply


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
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -8. The time now is 09:40 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page