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Harder Ride on 17" Wheels

It appeared so, for the first 3 days I have driven the new Focus, but today I checked the tyre pressures and found 45 psi all round, instead of 31. I let 10 lbs out then drove around a 1 mile block, and the ride is transformed, so I need a word in the ear of whoever makes pre-delivery inspections. After that discovery I checked all levels under the bonnet...

This is the second time I have taken delivery of a new car and found tyre pressures of 45 psi, the last time being on a Viva HC in 1970.

Do they blast 'em up to 45 when the tyres are first fitted to ensure a seal, and then forget about them?

Reply to
Gordon H
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Entirely possible that they're inflated higher for transport, to reduce the risk of damage through pinching when the cars are strapped down.

But, yes, shonky PDI.

Reply to
Adrian

However, it is entirely possible that the 17" wheels need higher pressure than the 'standard' issue tires, or more than 31 psi. Although

45 seem too high. I find there is a lot of confusion at garages when low profile tyres are fitted, then just use standard tables for the model in standard trim.
Reply to
johannes

Why?

A quick look at Focus tyre pressures shows hardly any variation through the range, the only consistent factor seems to be vehicle weight, the diesel versions and C-max versions needing a couple of pounds more.

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Are you sure that it's them that are confused and not yourself?

Tim

Reply to
Tim+

2011-13 215/55R16 and 215/50R17 30 30 2.0 TDCi 33 30
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Reply to
Peter Hill

I have noticed that poor quality tyre places will pump the tyre up to the max. inflation pressure marked on the sidewall and leave it at that. I have also found owners that believe that is the correct pressure.

Reply to
Mrcheerful

:-) Like Henry Ford said: you can have any colour of tyre so long as it's at

31 psi.

I didn't trust my digital pressure gauge at first when I saw 45, so I hooked up the inflator which gave the same reading. I wish I could find the old-fashioned tyre gauge I inherited from Dad in

1959, it somehow disappeared after changing the clutter from the old car...
Reply to
Gordon H

The rating plate on my BM covers that single model's various tyre width combinations in sizes from 16" to 18". They're mostly around the

2.3(F)/2.5(R) mark apart from a notable dip to 2.1/2.5 for the 225/45/17(F) 245/40/17(R) combination which I'm currently running and it's wearing the tyres as evenly as the higher pressures ever did on 16s.

I put it down to the black magic of tyre specification.

OTOH, my old Jag S-Type had ridiculously low pressures specified. It wore the shoulders and didn't do the handling or economy any favours. Pumped up to something more appropriate and all was well. I could never decide whether they'd done it as a ride comfort thing (although, even on 'Sports' springs, it wafted very well) or simply that this was bog standard British car industry uselessness.

Reply to
Scott M

"Helps fuel economy, mate..."

Reply to
Adrian

The same sort of places that overtorque the wheel nuts!

Reply to
The Revd

From my Saab 9000 Owners Manual:

195/65 - 30 to 33 Max load 205/60 - 32 to 39 Max load 205/50 - 35 to 43 Max load

It also makes sense since the tyre is closer to the rim. Just look at wheels. I have 205/55 and use 35 psi; it looks and feels right.

Reply to
johannes

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