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Old 05-29-2009, 07:17 AM   #21 (permalink)
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Quote:
Originally Posted by cfg83 View Post
Eddles -



Rats. I wish there were a "tyrerack.co.uk" for you.

I googled around, and I think the terminology would be "high pressure valve stems" :

SELECTING PROPER VALVE HARDWARE - May 6, 2002
http://www.techtirerepairs.com/tech_...0Issue%202.pdf


But, the above might not work if the *size* of the higher PSI valve stem is not compatible. I just don't know.

Let's wait for CapriRacer to chime in, he has the expert knowledge.

CarloSW2
Here's the problem from my perspective:

1) If you are planing on using more than 60 psi in a passenger car tire - well, I'm already on record as recommending against this.

2) But if you are still determined to do it, then I feel obligated to give you advice to do this safely: Please use high pressure valves as indicated above. The problem will be at the retail store end.

They are going to look at you kind of cross eyed, because the valves they use are appropriate for all uses - except high pressures, which is when they'll use valves for light trucks ( meaning LT metric tires) - and they might not be the correct size.

So I would suggest you buy and mount your own valves.

First take the assembly in and have the tires dismounted. Using a knife or razorblade, cut off the old valve (if it is an all rubber valve, which you will find out very quickly!). Then replace the valve with this:



You should be able to find it at any car parts place that has tire stuff. It's designed for chrome wheels and will accommodate both size valve holes. It's a screw-in, so you shouldn't have any trouble installing it.

Then return to the tire shop to mount your new tires. They won't mess with the new valves, because they'll be chrome - and of course you will have told them not to!

For those with TPMS's - and I recommend retaining the device as a good safety feature - this gets a bit more complicated - beyond my ability to know all the possibilities. Sorry.

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Old 05-29-2009, 09:21 AM   #22 (permalink)
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Not going to inflate my tires to 60 PSI - that's way beyond my personal comfort zone!

I've finally decided to get 44 PSI rated tires and not inflate it beyond 49 PSI maximum - I'll probably inflate it to 47 PSI which is 7% over maximum.

Thanks for your advice anyway!
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Last edited by Eddles; 05-29-2009 at 09:50 AM..
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Old 05-29-2009, 02:10 PM   #23 (permalink)
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try it for yourself. Inflate all your tires as much as you dare, get to a set speed, brake as hard and fast as possible, and measure your distance. Then try again with the pressure listed on the vehicle information label. Your stopping distance will be much less.
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Old 05-29-2009, 02:13 PM   #24 (permalink)
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Sure it would, if you overdid it. But most front wheel drive cars are nose heavy anyway, so a bit of oversteer added to the equation might help balance things out. But it could be taken too far and like you said, cause WAY too much oversteer.
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Old 05-29-2009, 02:26 PM   #25 (permalink)
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Here's the link to the wikipedia link on tires
Tire - Wikipedia, the free encyclopedia

follow the references. It is generally well known that overinflation puts less ruber on the road, hence the lower rolling resistance. But rolling resistance goes both ways. If there is less resistance in rolling, there is less resistance between the tire and the asphalt, giving your brakes less of an ability to stop the vehicle.
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Old 05-29-2009, 02:26 PM   #26 (permalink)
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I know the Goodyear Assurance "Fuel Max" tires are all rated to 51 psi. Since you're in the UK I would look at the "Efficient Grip". More than likely they are too.

Don
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Old 05-29-2009, 02:28 PM   #27 (permalink)
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Quote:
Originally Posted by ShadeTreeMech View Post
try it for yourself. Inflate all your tires as much as you dare, get to a set speed, brake as hard and fast as possible, and measure your distance. Then try again with the pressure listed on the vehicle information label. Your stopping distance will be much less.
Okay, let's look at my manual here. Feast your eyes on the unladen front tire pressures for the Y17DT engine on the leftmost column. It is all 35 PSI no matter what tire is used. The 61 PSI tire is just the "space saver" spare. Now look at Y17DT (ECO4). Now it says 41 PSI. Tell me why can't a Y17DT owner inflate his/her tire to 41 PSI? It's the exact same car. Also note the pressures for the ECO4 rear tires when fully loaded? It says 49 PSI. If it's really unsafe for me to run my tires at 49 PSI, why would a manufacturer of the 2nd most common car in the UK that weights only 2,500 lbs recommend this?
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Old 05-29-2009, 02:29 PM   #28 (permalink)
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Quote:
Originally Posted by DonR View Post
I know the Goodyear Assurance "Fuel Max" tires are all rated to 51 psi. Since you're in the UK I would look at the "Efficient Grip". More than likely they are too.

Don
Thanks for this,

Unfortunately the Efficient Grip doesn't come in 175/80/14 - which is a fairly rare size, annoyingly enough.
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Old 05-29-2009, 03:14 PM   #29 (permalink)
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Quote:
Originally Posted by Eddles View Post
Now look at Y17DT (ECO4). Now it says 41 PSI. Tell me why can't a Y17DT owner inflate his/her tire to 41 PSI? It's the exact same car. Also note the pressures for the ECO4 rear tires when fully loaded? It says 49 PSI. If it's really unsafe for me to run my tires at 49 PSI, why would a manufacturer of the 2nd most common car in the UK that weights only 2,500 lbs recommend this?
I've been wanting to know the same thing. It just reinforces my thoughts on traction vs pressure and i'd like to hear a professional opinion on this.
Thanks for posting the picture of your manual Eddles.

ollie
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Old 05-29-2009, 03:24 PM   #30 (permalink)
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CapriRacer -

Thank you for posting that. My information was vague. I was able to get tires rated at 51 PSI, so that's my max. Because passenger tire valve stems are rated at 65 PSI (according to that PDF I cite in my previous post), I should be fine.

For additional safety, the next time I get a set of (51 PSI rated) tires, I will make sure they install the valves you cite. If they don't have them, I will get some myself.

CarloSW2

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