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I am running 20 inch Michelins, 275/40s and was wondering what is the correct tire pressure to run on my C. Using the 'factory' tire pressures as reccommended for the 18 inch rims would seem to be too low. Any suggestions on what tire pressure I should run.
 

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tlim said:
I am running 20 inch Michelins, 275/40s and was wondering what is the correct tire pressure to run on my C. Using the 'factory' tire pressures as reccommended for the 18 inch rims would seem to be too low. Any suggestions on what tire pressure I should run.
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tlim said:
I am running 20 inch Michelins, 275/40s and was wondering what is the correct tire pressure to run on my C. Using the 'factory' tire pressures as reccommended for the 18 inch rims would seem to be too low. Any suggestions on what tire pressure I should run.
I would actually contact Michelin for their recommendation(s)? Also, have you possibly asked the facility (tire/wheel shop) which initially installed your tires/wheels how much air pressure they utilized, as well as how and on what documentation they in fact based their determination on in the first place? The maximum psi rating for my 20" Goodyear 'F1 Supercar' tires is 51psi, but I'm only running 40psi...which appears to be more than efficient. :dunno:
 

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Additional Note: 51psi would be appropriate for running my car on the track or being loaded to its capacity with passengers and luggage, but 40psi seems adequate for every day driving without affecting ride quality or tire treadwear. :cool2:
 

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tlim said:
I am running 20 inch Michelins, 275/40s and was wondering what is the correct tire pressure to run on my C. Using the 'factory' tire pressures as reccommended for the 18 inch rims would seem to be too low. Any suggestions on what tire pressure I should run.
I had this same question about my Hankook 275/40's. I emailed Hankook and they said that the tire load rating for my OEM and the 20's was almost the same. He suggested anywhere from 32-35 psi because I was on 8.5" wheels. So I chose 35. Pixel Pusher rides on pirelli 275/40's and runs 31 PSI and has not had a problem.
 

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I would suggest using 40-45psi all around! I've seen many cracked wheels (esp. cast wheels) because they were running oem press (35 or below) in a 20-22" wheel, with 35 and 40 series tires. Running below 40 psi, you can end up with small hairline cracks and a bent wheel due to impact, and also you can ruin the sidewall of the tires because it's underflated, which means new tires and they don't come cheap in 20's and 22's.. (btw, you cant fix the sidewall of any tire :wink1: ) Imagine a wheel barrow filled up with sand, and the front tire was at 5psi instead of the normal tire pressure, try pushing it!! It's freakin hard to push and manuevor, in most cases the wheel barrow tire will de-bead itself from the rim.. same thing with car tires..
 

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HEMMISSEY said:
I would suggest using 40-45psi all around! I've seen many cracked wheels (esp. cast wheels) because they were running oem press (35 or below) in a 20-22" wheel, with 35 and 40 series tires. Running below 40 psi, you can end up with small hairline cracks and a bent wheel due to impact, and also you can ruin the sidewall of the tires because it's underflated, which means new tires and they don't come cheap in 20's and 22's.. (btw, you cant fix the sidewall of any tire :wink1: ) Imagine a wheel barrow filled up with sand, and the front tire was at 5psi instead of the normal tire pressure, try pushing it!! It's freakin hard to push and manuevor, in most cases the wheel barrow tire will de-bead itself from the rim.. same thing with car tires..
I think you are right, I was driving on the highway yesterday and the car felt heavy like cars feel when they dont have enough air in the tires, like in winter driving and I could not get the car to avg over 21mpg's on the highway I usually get 26-27.5 mpg's. The first thing I thought was that my tires are under inflated and in the Hampton Roads area of Virginia which according to the local paper ranks 48 out of 50 in the worst road in the nation, I had better put a little more air in the tires.

SIDEBAR: Guys Im serious these roads suck. I came here 16 years ago and today they are still working on the same highways and it never stopped, there has always been construction on the same highways and they still have not gotten it right.
 
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