06-25-2004, 05:56 PM
I was told by my service manager that if I put low profile tires on my E that it would cause problems with the engine performance, not just the speedometer reading. Has anyone experienced any problems after putting low profile tires on? If so, what did you notice? Is there a cure for the problem other than going back to the original tire diameter.
Thanks a lot,
06-25-2004, 06:13 PM
I have had no problems in 7,000 miles. Of course you would have to go to a larger wheel to maintain the proper overall diameter.
A good size is 235/50R18. It is almost exactly the same as the 215/70R16 in diameter. I am running 245/45R18 which is 1" less in diameter and still have no problems.
When my speedometer reads 75 mph I am actually doing 72 mph.
06-25-2004, 06:30 PM
I haven't had any problems, in fact they are quieter and I get a bit better gas mileage. I am running 235/60r17 though.
06-25-2004, 08:55 PM
[quote:00884ab581=" "]I was told by my service manager that if I put low profile tires on my E that it would cause problems with the engine performance, not just the speedometer reading. Has anyone experienced any problems after putting low profile tires on? If so, what did you notice? Is there a cure for the problem other than going back to the original tire diameter.
Thanks a lot,[/quote:00884ab581]
I think "problems" is the wrong term. If the diameter/circumference isn't the same, it will give you different engine performance. For instance, I have oversized tires on my Nissan pickup. Not only is the speedometer off by 5-8 mph at highway speeds, acceleration is slower and top speed is compromised. With luck, MikeQBF will pick up this thread and give you a more comprehensive explanation.
06-27-2004, 10:43 PM
I think the dealer was poorly explaining that with a smaller final diameter that your engine will be running at higher RPMs to get to the equivalent speed with the stock tires. I think he/she was assuming that you would be going low-profile with the stock wheels.
However, I'm assuming that you're changing wheels, and the objective is to go with a larger wheel like the 18's that Wolfmeat suggested. The 235/50R18's he mentioned only differ in rolling diameter by 2% - no difference that you'll notice in either engine speed or speedometer reading.
Low-profile itself isn't any problem (other than ride... :wink:), it's the final rolling diameter that's important.
06-28-2004, 07:17 AM
Let's assume you are able to maintain the exact same rolling diameter of the tire as you upgrade.
By installing tires which have mass concentrated further out on the wheel, even though they weigh the same they can eazily sap 10 hp from your dynamometer performance. This is due to rotational dynamics.
For instance, a figure skater will pull her arms in and spin very fast. When she puts her arms out, she slows down. This is because the rotational energy stayed constant while the mass was moved outward from the center of rotation.
Typically going +1 can improve your 0-60 performance slightly, simply because of increased grip and less wheelspin. However, going +2 almost always slows acceleration (and deceleration) performance due to increased rotational inertia.
If you go up in wheel size, do it for one of three reasons:
(1) Being able to install high performance tires,
(2) Being able to install bling bling rims,
(3) Better cornering at the likely expense of straight line performance.