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Currently running 235/60/16 on stock Alloy rim.
In an effort to reduce rpms at cruise (and increase gas mileage) I am looking at going up in tire size to a 235/70/16
diameter 27.1 28.9 (there is about 1.25 clearance so this will work)
tread width 8.1 7.1 I lose an inch on the ground. Will I notice?
THe larger tire weighs about 2 lbs more.
Last question, the 70's seem to be more of a truck tire. Is the ride going to be that much rougher
I would think the strength of the sidewall would determine if the ride is rougher or not.
Increasing your profile will reduce engine RPM, and the excel calculator I made shows about a 250rpm decrease at 100km/h (62.5mph - hey I am metric). Your speedo will be off though, but if you have a GPS, monitoring speed should be OK.
Ride and handling will be shot. Decrease in engine speed at 60MPH will only be 135RPM.
Will it be legal? You are talking about a 6% change; most I've done (while it was legal) was 3%, and that made the speedo just about spot-on (odo. was out, however).
Sounds like you need an extra gear, although the differenced will still be small. One of my cars used 8.0 litres/100km in 6th and 8.4 litres/100km in 5th. That was with a ratio difference of 20%, so even with your planned 6%, you will need to be careful to see the difference. Cost? -That's up to you.
thanks for the replys!
Yes, I figure about 1k drop in rpms.....but I was guessing!!!
Fortunately, in the USA it's not illeagal to raise tire size.
I need to buy at least 2 tires pretty soon so I'm going to give it a shoot w/ a couple of slightly used tires.
I bumped the tire size on my Q45 from 245/45/18 to 245/50/18 and picked up a couple of mpgs.
Cant 'add' a gear.
have another post about the tranny issue.
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