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Generation 5 235/45/18 versus 245/45/18

  #1  
Old 11-07-2014, 11:54 PM
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Default Generation 5 235/45/18 versus 245/45/18

I just purchased a 2000 Monte Carlo SS and have already purchased the 06-07 SS wheels. Is there are superior tire choice between the 2 mentioned in the title or another size I should chose? My biggest concern is rubbing, so I know I cannot use the O.E. size 235/50/18. Any input or advice would be appreciated.
 
  #2  
Old 11-08-2014, 04:30 AM
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To answer your question:
235/45/18 = 235mm wide x 45% of the width, high sidewall x 18" dia.
the rolling circumference is 2016.75mm
245/45/18 = 245mm wide x 45% of the width sidewall height x 18"dia
the rolling circumference is 2043.89mm


the difference is 27.14mm bigger circumference on the 245 tire which calculates to a 1.35% error at 70 mph. So if the 235 was the original tire size on your car then by going to the 245 tire you would be doing 70.94mph when showing 70 on your speedo.


Now here is the kicker, you want to put these ss 18"rims on your earlier car. The rubbing that you should be concerned about is at the lower spring perch on the rear struts. The 06 and above use a different strut which has the higher from the ground perch welded up a 1/2" higher than earlier models to allow the 18" wheels with the 235`s and as you see in the calculations above the 245`s will most likely bring the tire closer to the perch base an rub. There is only a 1/4"- 3/8" clearance on the factory 18" setup for the ss 06+ models.
 

Last edited by Ill_Born_ss; 11-08-2014 at 04:34 AM.
  #3  
Old 11-08-2014, 09:18 AM
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Which I agree with the above mentioned calculations...
In other words... Either youll eventually ruin the tires with the rubbing (Not recommended)
Or you may relieve the problem by using Spacers..(Also not recommended)

Theres a price to be paid by trying/looking cool..

Hope this answers your question!

By the way...
Your 2000 Monte Carlo is a 6th Generation (Not a 5th) like you mentioned in your post title..

Which one looks like yours?
 

Last edited by STUMPMI; 11-08-2014 at 09:23 AM.
  #4  
Old 11-08-2014, 02:38 PM
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So there is no way of doing this clean?

If I use spacers, what size is needed for the rear?

I assume the fronts clear.
 
  #5  
Old 11-09-2014, 07:09 AM
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Originally Posted by fo44rd View Post
So there is no way of doing this clean?

If I use spacers, what size is needed for the rear?

I assume the fronts clear.


Doing it clean would mean...
New rear struts for a 06+ W18" wheels
New springs and isolators and top plates
New (recommended: camberbolt kit , installed in the upper hole)
New four wheel alignment


Due to the limited clearance from the proper/factory design it would also be recommended to stick with the factory 235/45/18 tires as there is also possible tire sidewall to trailing arm clearance issues. So by going wider on the tire also puts the inner sidewall closer to the trailing arm thus creating another danger zone.


The fact that your car is a 2000 that makes it 14 yrs old and the struts/ springs/isolators/top plates are most likely overdue anyway.
 

Last edited by Ill_Born_ss; 11-09-2014 at 07:13 AM.
  #6  
Old 11-09-2014, 10:23 PM
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Thanks for the input guys. I lurked on the Impala forums and RYD SLO is running factory tire size on his 2001 Impala using 1/4" spacers. So if I go down to 245/45/18s I should clear and if not use 1/4" spacers, but I guess that is doing it "dirty". LOL
 
  #7  
Old 11-10-2014, 06:10 AM
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Originally Posted by fo44rd View Post
Thanks for the input guys. I lurked on the Impala forums and RYD SLO is running factory tire size on his 2001 Impala using 1/4" spacers. So if I go down to 245/45/18s I should clear and if not use 1/4" spacers, but I guess that is doing it "dirty". LOL

The term you use, "So if I go down to 245/45/18s I should clear" If you re-read my first response it clearly shows that the 245`s are larger/higher/bigger.
as far as spacers go you would also have to change out all your studs for longer units and this alone is expensive and the amount of work involved.. besides the possibility of getting it all done only to find you damaged the hub after it is all assembled.


Here is an example of "doing it DIRTY"


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