18" Wheel Fitment
01-31-2004, 10:20 PM
#1
Rennlist Member
Thread Starter
18" Wheel Fitment
I've done much searching on this topic and can't find any definite info on this topic.
Will
8.5 X 18 ET 56
10 X 18 ET 40
fit my '88 951??
Will
8.5 X 18 ET 56
10 X 18 ET 40
fit my '88 951??
02-01-2004, 01:16 AM
#3
Race Director
Ok, I'll be nice... 
Here's the specs you need for an '88 951:
18x8.5" will need offset of 60-65mm
18x10" will need offset of 55-60mm
You typically want to move the rim's centerline inwards to place most of the extra width on the inside where there's more room. This will allow to you run wider tyres than stock and place the outer-edge of tyre close to where the stock narrow tires are. You can keep offset close to stock or less if you want to use the same width or narrower tyres than stock.
Here's the specs you need for an '88 951:18x8.5" will need offset of 60-65mm
18x10" will need offset of 55-60mm
You typically want to move the rim's centerline inwards to place most of the extra width on the inside where there's more room. This will allow to you run wider tyres than stock and place the outer-edge of tyre close to where the stock narrow tires are. You can keep offset close to stock or less if you want to use the same width or narrower tyres than stock.
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02-01-2004, 02:34 PM
#8
Nordschleife Master
Yeah they would work on an 86....
you would just need to get the right sort of spacers, i'm sure danno would be able to come up with the exact size that you guys need.
you would just need to get the right sort of spacers, i'm sure danno would be able to come up with the exact size that you guys need.
02-01-2004, 10:35 PM
#9
Race Director
"What about those sizes on an 86?"
You'd use longer 66mm studs and 21mm spacers all around. Parts list and procedure on my RacerX website. But you'd want to not use the longer-studs and wider spacer on the rear (those are for fairly stock sizes). In this case, you'd use the parts for the front all around.
You'd use longer 66mm studs and 21mm spacers all around. Parts list and procedure on my RacerX website. But you'd want to not use the longer-studs and wider spacer on the rear (those are for fairly stock sizes). In this case, you'd use the parts for the front all around.
02-02-2004, 05:51 PM
#10
Instructor
Over and over and over again...
I guess there still exists this Porsche tech. bulletin that prohibits 18" rims for Porsche cars that are not equipped originally from the porsche factory.
So there must be some reason why they made this bulletin...
kind regards Frank
I guess there still exists this Porsche tech. bulletin that prohibits 18" rims for Porsche cars that are not equipped originally from the porsche factory.
So there must be some reason why they made this bulletin...
kind regards Frank
02-02-2004, 06:01 PM
#11
Nordschleife Master
Originally posted by turbinek
Over and over and over again...
I guess there still exists this Porsche tech. bulletin that prohibits 18" rims for Porsche cars that are not equipped originally from the porsche factory.
So there must be some reason why they made this bulletin...
kind regards Frank
Over and over and over again...
I guess there still exists this Porsche tech. bulletin that prohibits 18" rims for Porsche cars that are not equipped originally from the porsche factory.
So there must be some reason why they made this bulletin...
kind regards Frank
Yes there is.... After porsche makes a disclaimer like that they are no longer responsible for anything that happens to the car after it is fitted with 18s. So if there was excessive wear on items they would not have to replace them. Do 18's create that much more stress that one should worry about their car falling apart, well no. But one should make sure the suspension is up to the task, and has had all the proper updates....
02-02-2004, 06:44 PM
#12
Race Director
"Do 18's create that much more stress that one should worry about their car falling apart, well no."
Typically, you'd want to calibrate the dampers for the kinds of suspension & wheels you're using. So... 18" wheels would need a lower amount of high-velocity compression-damping; a lower blow-off valving. Not that big a deal really... Isn't there a guy running 19" wheels on a 951?
"So there must be some reason why they made this bulletin..."
It's the usual corporate CYA stuff... Here's the bulletin, could just be that the combination of 18" wheels on 944s were never tested to get TUV approval.
------------------------------------------------------------
ARTICLE BEGINNING
TECHNICAL SERVICE BULLETIN
INSTALLATION OF 18" WHEELS NOT APPROVED
Model All Porsche Models
Group 4
Bulletin No. 9305
Date April 15, 1993
Concern:
Retrofitting 18" wheels on Porsche vehicles which do not
have 18" wheels as original equipment is
NOT ALLOWED.
General Information:
Endurance tests have shown that equipping certain Porsche
vehicles with 18" wheels in an
application not already approved by Porsche Cars, N.A. may
result in loosened bolts and /or
threaded connections on the front wheel carriers. This, in
turn, may cause fractures in these
components. Fractures may also occur in the front strut
mounts and in the body in the area of the
rear suspension as a result of the installation of 18"
wheels not already approved for installation for
this specific application.
Such damage can occur without warning and the vehicle may
become very hard to control/steer
as a result of the improper installation.
Porsche dealer personnel coming in contact with a vehicle
that has been retrofitted with 18" wheels
in an application not approved by Porsche, should inform
the owner of the potential for damage
to their vehicle and loss of steering control. Porsche
Cars, N.A. should also be notified of any
vehicles retrofitted with 18" wheels.
END OF ARTICLE
-----------------------------------------------------------------
Typically, you'd want to calibrate the dampers for the kinds of suspension & wheels you're using. So... 18" wheels would need a lower amount of high-velocity compression-damping; a lower blow-off valving. Not that big a deal really... Isn't there a guy running 19" wheels on a 951?
"So there must be some reason why they made this bulletin..."
It's the usual corporate CYA stuff... Here's the bulletin, could just be that the combination of 18" wheels on 944s were never tested to get TUV approval.
------------------------------------------------------------
ARTICLE BEGINNING
TECHNICAL SERVICE BULLETIN
INSTALLATION OF 18" WHEELS NOT APPROVED
Model All Porsche Models
Group 4
Bulletin No. 9305
Date April 15, 1993
Concern:
Retrofitting 18" wheels on Porsche vehicles which do not
have 18" wheels as original equipment is
NOT ALLOWED.
General Information:
Endurance tests have shown that equipping certain Porsche
vehicles with 18" wheels in an
application not already approved by Porsche Cars, N.A. may
result in loosened bolts and /or
threaded connections on the front wheel carriers. This, in
turn, may cause fractures in these
components. Fractures may also occur in the front strut
mounts and in the body in the area of the
rear suspension as a result of the installation of 18"
wheels not already approved for installation for
this specific application.
Such damage can occur without warning and the vehicle may
become very hard to control/steer
as a result of the improper installation.
Porsche dealer personnel coming in contact with a vehicle
that has been retrofitted with 18" wheels
in an application not approved by Porsche, should inform
the owner of the potential for damage
to their vehicle and loss of steering control. Porsche
Cars, N.A. should also be notified of any
vehicles retrofitted with 18" wheels.
END OF ARTICLE
-----------------------------------------------------------------
