A little question I would appreciate some information on
My pre facelift mk1 focus ghia has 14'' alloys and one has become buckled. Early ghia alloys seem pretty rare and are v expensive new. So instead I have acquired a secondhand set of the later 15'' ghia wheels from a facelift car. These currently have 195/60X15 tyres which I see from the tyre calculator page will give me a 3% speedo error compared to the 185/65X14 originally fitted.
I have an option therefore of either changing the tyres to 195/55 which give an almost identical rolling radius to the originals or living with the error.
I notice from my focus handbook that 195/60X15 were an original option and my question is, how do ford deal with the slight differences in wheel/tyre sizes offered on new cars. Do they have different speed sensors or is it a matter of a software change to a constant in the speedo?
Many thanks
SR
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my focus mk1 ghia has 15" alloys (195/60r15v tyres) and the speedo over-reads by about 5.25% (against GPS). However if I use the "electronic" speedometer on the odometer LCD display, it is a much truer figure. the focus uses an electronic speed sensor in the gearbox that passes the speed signal to the ecu. i wouldn't bother trying to compensate for it personally.
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My pre facelift mk1 focus ghia has 14'' alloys .........
That's strange. I still have the 1999 brochure from when I bought my first Ghia and it says that 14" steel wheels were standard on the Ghia, excluding the 2.0 petrol which had 15" alloys. 15" alloys (together with metallic paint) were available (as part of the Styling Pack) on all Ghias except the 2.0 petrol. It just makes me wonder whether your 14" alloys are original. What year and engine is your car?
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L\'escargot.
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The Focus has a programmable cluster and engine managment. These are programmed at the dealership to conifure the two based on the wheel size fitted.
So to answer your question, yes it is a software change that allows the dealers to fit different size wheels.
Carse.
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It's a 52 reg 1.8 petrol which I bought as an ex demo from the local ford dealers. It must have been sitting in a field for a year as I have seen many a 51 reg facelift model. The 14'' alloys are of a fairly unusual design with six fairly evenly spaced spokes which I have only ever seen on two other ghias. They are definitely 'ford' wheels and I guess as my model was probably the last of the pre facelifts they loaded it with wheels and metallic paint to try and sell it.
SR
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It's a 52 reg 1.8 petrol which I bought as an ex demo from the local ford dealers.
I spoke too soon. I assumed it was earlier than a 52 plate.
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L\'escargot.
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I don't think you really have an issue here. My '02 Focus on 195/60/15 tyres reads fast by 3mph at each 10mph increment, compared to a gps, and all car speedos do in fact read fast. So a 3% reduction on your speedo reading will probably actually have the effect of maiking it more accurate.
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As above, a 3% increase in rolling radius will make the speedo more accurate - it'll also give an real improvement in fuel consumption of about 1.5% although it'll appear to decrease by 1.5%!
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These currently have 195/60X15 tyres which I see from the tyre calculator page will give me a 3% speedo error compared to the 185/65X14 originally fitted.
But does it matter? Under most circumstances I wouldn't think a 3% error is likely to swing the balance between getting caught for speeding and not getting caught.
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L\'escargot.
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