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2G Mismatched tires.

spyderdrifter

Supporting Member
5,104
615
Jul 11, 2009
Some where, Colorado
I'm just looking to find out how screwed I may be after doing this. So I had to replace my clutch recently, and during the time my car was down, my rear passenger tire somehow went flat. So after the clutch replacement I had another tire I had in storage put on. I usually have 225/55/16's on and the replacement is a 205/55/16. I have noticed that the 205 looks shorter in overall height than my 225's. However I need to get new tires anyway and don't want to waste money getting a new 225 that'll end up being worn more when I can afford to get the rest. I have decided not to drive my car unless absolutely necessary, like tonight. My wife needs her car in the morning before I get off work, so I drove my car to work, 5-6 miles distance tops, and haven't gone over about 40mph. How much damage could I be looking at if tonight's drive, and the drive home in the morning are the only times I drive it with this one mismatched tire? And spyder is AWD which is why I'm asking. If it were still fwd, I would already know answers.
 

dgdsm

Supporting Member
164
4
Aug 24, 2008
Tarzana, California
I'm no sort of authority on tires, but the bottom line is that you're putting stress on the entire structural and suspension systems. But I can't imagine how 40mph for 5-6 miles in your scenario would make much of a difference. Try and imagine the stress that would go into a car by someone driving 40 miles on the freeway with a spare on one wheel. Anyways this is the gist of what a AAA tow-truck driver told me the one time I put a spare on my Spyder.
 

ThunderChild

Supporting VIP
3,764
1,116
Jan 5, 2012
Rathdrum, Idaho
It's not so much the suspension, but the awd components (rear diff, tcase, center diff and mostly, the viscous coupler).

The 205 is definitely shorter, 3.2% roughly in height and diameter. You will definitely put some heat into the VC when driving it at anything over parking lot speeds. Personally, I would limit driving as much as possible, it's hard to gauge the damage you're doing.

Quick and dirty way would be a VCE, but unless you have one or can sacrifice a spare VC, take out the t-case and D/S, youre kinda stuck. Continue at your own risk.

Does your car have a rear LSD?
 

spyderdrifter

Supporting Member
5,104
615
Jul 11, 2009
Some where, Colorado
What's a VCE? Eliminator to the VC? I do have LSD in the rear.

Here's another thought, since my mismatched tire is on the rear, would it do more harm to the rear diff, or the center diff?
 
Last edited:

turboglenn

Proven Member
6,379
104
Nov 5, 2007
RIpley, West_Virginia
If anything, out the odd you're in the front where it's an open diff so you won't be stressing the rear LSD if so equipped. I'm interested in hearing any proven data aboutthis myself though
 

spyderdrifter

Supporting Member
5,104
615
Jul 11, 2009
Some where, Colorado
Since I need new tires in a month or two, I went and got a used tire of the proper size with 50% tread left so I don't have to worry. Still curious though for future knowledge.
 

gofer

Moderator
8,076
1,177
Feb 18, 2006
South Gilbert, Arizona
The standard rule of tolerance is .25" from tire diameter to tire diameter, since you don't know the exact brand and model (just the size) the only way you can really know if you potentially damaged something is to physically measure them around the outside of the tire.

Again, should be within 0.25" (which is what the majority of our members gap their spark plugs too LOL)


Some back story though, I did some research on those generic tire brand/sizes you provided above and IIRC the Uniroyals were ~ 24.9" and the Starfires were ~ 25.75". But, without knowing the exact models it's just me shotgunning the numbers. If they're accurate though, just hope the Uniroyal had 41psi of air in it and the Starfires were in the mid 20's so their diameters were a bit closer and nothing was damaged.
 

spyderdrifter

Supporting Member
5,104
615
Jul 11, 2009
Some where, Colorado
Wow, that's quite a difference in tire pressure. I did another matching size tire, but I think I did do some damage.
 

boostdawd

Supporting Member
1,450
326
Apr 6, 2010
phoenix, Arizona
It's not so much the suspension, but the awd components (rear diff, tcase, center diff and mostly, the viscous coupler).

The 205 is definitely shorter, 3.2% roughly in height and diameter. You will definitely put some heat into the VC when driving it at anything over parking lot speeds. Personally, I would limit driving as much as possible, it's hard to gauge the damage you're doing.

Quick and dirty way would be a VCE, but unless you have one or can sacrifice a spare VC, take out the t-case and D/S, youre kinda stuck. Continue at your own risk.

Does your car have a rear LSD?
For give me if I'm incorrect but wouldn't 205 be the width? The 55 should be the height.
 

spyderdrifter

Supporting Member
5,104
615
Jul 11, 2009
Some where, Colorado
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