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Mud tyres vs Powertrain

971 views 3 replies 2 participants last post by  THEmailman 
#1 ·
Hi, i have searched the forum but i could not find.
I am putting a new set up on my 3.6 06; 18" and Muds 365/60R18.
Does that cause an extra effort to gearbox, transmission?
Experiences , recommendations?
Thanks in advance
 
#2 · (Edited)
Edit: Looking again, I see you said 365/60/18 but I think you meant 265/60/18? I don't know what the stock tire size is outside of the US, but using the 255/55/19 as a baseline, the difference in those sizes isn't great (half-inch) and there won't be a significant weight difference either unless you are going LT tires (which MT tires likely are). Even with that, since you aren't crazy up-sizing, the below really isn't as applicable since it isn't a huge departure from the norm.

Is there some effect, likely yes. In the same way that car manufacturers design engines and transmission for certain power levels, the same can likely be said of wheel and tire modifications. The extent though, as with those power mods, is always a bit of a grey area. The main issue is the increased weight of the tires, which means extra effort to move for the same power. Is this a huge added stress on the driveline, in my opinion, no, but it isn't nothing either. Tires/wheels come at the end of the powertrain so I think there are other factors in play there. I would say more of the strain would be put on wheel bearings and suspension hardware that was designed to support much lighter wheels/tires. Again, is it something that is going to kill your car in 1,000 miles...likely not. But they will probably wear faster and will be something to watch for maintenance.

The one thing I can say you should do is code in the tire size change to the vehicle. It will fix your speedometer and, as far as I know, the car's computer will use that as a factor for shift points. If the car thinks you're on smaller tires than you are, it's going to want to behave differently than if it knows it is rotating more mass and diameter/circumference. You will have less effecive torque at the wheels, which is usally solved with differential re-gearing, but that is probably not as easy of an option as it is with Jeeps.

Unfortunately, at the end of the day I don't know if anyone has ever taken the time to actually study the effects of these things, but you're certainly not the first person to put larger wheels/tires on a car (see Jeeps) so if there were larger issues, they would be more easily found. I would suggest searching the Jeep forums though and see what info you can find there, as there will be a lot of topics on this subject.
 
#3 ·
Thanks THEmailman .

The original set i have is 225/50R20 . I will change to 265/60R18 ( a rim downsize) in order to have a litlle bigger sidewall and be able to remove pressure when offroading ( specially sand). Whithout lifting the car or any other changes.
In fact the new tyre is 8Kg plus ... but i think the difference will be reduced by the smaller wheel
Also thanks for the tip of "code in the tire size change to the vehicle ": i hadn`t though about that...
 
#4 · (Edited)
Yeah, an almost 2 inch bigger tire will be a good increase in tire weight, but depending on the wheels you go with, a 2 inch drop in wheel size should net out a good chunk of that tire weight, so net-net, you shouldn't be too bad (again in comparison to jeepers that go from 33s to 37s or 40s).

My stock size was 255/55/19 and the new tires in 255/65/19 add about 5 lbs (2.3 kg) to each wheel, which is pretty reasonable to me.

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