Ford Focus ST Forum banner
1 - 16 of 16 Posts

·
Registered
Joined
·
1,955 Posts
Discussion Starter · #1 ·
I noticed on the sticker on Jay's car that it listed a different pressure recommendation, 44 psi vs 36 psi, for the 215 55 16 spare vs the 235 40 18 tires. I'm planning to go to either the 215 50 17 or 215 55 16 for winter tires. This would seem to indicate to me I'll need to run higher pressure with those smaller sizes. I just might contact the SVT line listed in the ST supplement in the winter tire section.

Can anyone who has a Focus with 17's comment on what the recommended pressure is?
 

·
Registered
Joined
·
617 Posts
Reason they run that high if pressure on spares is because typically nobody checks them or rarely uses them, and they over inflate so tire will be ready 3 years later when you need it. Doesn't really have to do with size. My wife's fusion has 215/50/17 and sticker says to run at 33psi. Also, your TPMS will be calibrated to a certain range, so you'll still need to run new tires within that range or recalobrate so you don't get a warning light.
 

·
Registered
Joined
·
1,955 Posts
Discussion Starter · #4 ·
I try to check the spare at least a couple times a year. I'll admit I don't do it every month like the rest though.

My VW has a full size spare and recommends the same pressure. The Fiesta has a donut which is 60 PSI. I was fairly certain the higher rating was because it's a donut. I do think 44 PSI seems kinda high considering that the spare for the ST isn't a donut but is in fact the size of tire that would go on a standard Focus. I'd be surprised to see it rated at 44 PSI so your logic may apply there.

The Tire Rack link is definitely good information but doesn't really tell me how to determine the right pressure. Is it really as simple as use the same pressure regardless of tire size......
 

·
Registered
Joined
·
338 Posts
The spare could have a different load rating if it's just a cheap disposable skin, which usually requires higher pressure. Not as much structure in the sidewalls, etc.
 

·
Registered
Joined
·
198 Posts
Similar to what Grabber523 said, it may run higher pressure to help compensate for the softer 55 series tire compared to the 40 series full time tires.

And the TPMS won't go off until the tires are underinflated by a certain percentage. That's what it's there for. Sometimes it may turn on the light if one tire is significantly overinflated compared to the rest but if they are all high then it won't do a thing.
 

·
Registered
Joined
·
1,955 Posts
Discussion Starter · #8 ·
I'll probably end up calling that SVT line that's in the supplement tire section. It's odd that they list the alternate sizes without listing appropriate pressure for each alternate size.


Sent from the jPhone using Tapatalk
 

·
Registered
Joined
·
1,533 Posts
I already ordered 17x8 PR 1.2 wheels and will be using 235/45R17 tires, so that is actually a bigger tire than stock. The wheel is smaller, but the tire is larger (almost identical outside dimensions). I have not previously considered a change in tire pressure. My thought was that at the same tire pressure, the larger wheels (which contain more air than stock at the same pressure) would provide more protection to the wheels (over pot holes) and a slightly smoother ride (over expansion joints and similar).
 

·
Registered
Joined
·
253 Posts
I haven't done this for a while, but you can check load inflation tables. Generally, as the tires aspect ratio goes up (i.e., going from a 40 to a 50 series tire), the pressure you need to run goes down.
 

·
Registered
Joined
·
1,955 Posts
Discussion Starter · #11 ·
So I called the SVT line listed in the insert. The guy said that the 44 PSI on the spare was in fact to make up for the difference in size vs the OEM tire. He said that I should consult with Tire Rack for specific PSI on the particular wheel tire combo I'm going with. He did say not to use the pressure listed on the tire as this is just the tires max rating and that the one on the placard only applies to the OEM wheel tire combo. Kinda dissapointed they didn't have a recomendation on PSI considering they have them on the tire size itself. I'll see what Tire Rack say's.

My *Guess* is that it's probably going to end up beingn around 34 or so.
 

·
Registered
Joined
·
1,955 Posts
Discussion Starter · #12 ·
WOW this is frustrating. So I just called Tire Rack and they say that they can't say anything about wheels until their engineers get ahold of an ST to try fitting things. Ford OEM wheels will fit according to Lisa's FB post but OEM wheels are going to be helluva expensive. When I called the SVT line the guy had a spec of the brake rotor but couldn't offer any dimensions on what kind of wheel I would need to fit.

And I've also yet to see ANY actual official package from Ford. I know some people are going to hate me for being negative and all. But seriously they could have provided a little bit more for us poor shmucks that have to come up with winter tire/wheels. I really think Ford should have an official sanctioned package.
 

·
Registered
Joined
·
283 Posts
I already ordered 17x8 PR 1.2 wheels and will be using 235/45R17 tires, so that is actually a bigger tire than stock. The wheel is smaller, but the tire is larger (almost identical outside dimensions). I have not previously considered a change in tire pressure. My thought was that at the same tire pressure, the larger wheels (which contain more air than stock at the same pressure) would provide more protection to the wheels (over pot holes) and a slightly smoother ride (over expansion joints and similar).
Post pics when you get them, because those are exactly what I want for my R-Comps.
 

·
Registered
Joined
·
288 Posts
I'm just using the tire pressure on the door sticker. Seems like I read something in the manual or supplement to use that pressure even on the different sizes but I may be wrong. I'll have to check it again when I have the manual in front of me.
As far as the TPMS goes I lowered the air pressure in one of the tires to see if the senors were synced with the car because I didn't have to use the tool to reprogram them. I had to lower the pressure from 36 to 20 before the light came on.
 

·
Registered
Joined
·
68 Posts
When I ordered my winters (215/55R16) from TireRack they gave me a call and told me that because my tire had a load rating of 93 instead of 95, I should not run them under 36psi. This all seems normal to me. It's always a good idea to run the pressure a little higher in the winter anyways.
 
1 - 16 of 16 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top