jps
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| posted on 22/10/18 at 12:56 PM |
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Why match donor tyre circumference on different diameter kit wheels?
Is there any specific reason for making sure that the overall circumference of the 15" wheels + tyres on my Haynes is as close as possible to
the circumference of the 13" wheels + tyres of my Sierra donor? Does it impact on the suspension effectiveness?
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nick205
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| posted on 22/10/18 at 01:27 PM |
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If you've already calibrated your speedomater then altering the outer (rolling) circumference of the tyre will make your speedometer read
incorrectly.
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Angel Acevedo
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| posted on 22/10/18 at 02:29 PM |
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If you adjust your suspension to maintain your Ride Height there may be an impact as you will be on a different point of your camber curves.
It may not be noticeable though.
Beware of what you wish.. for it may come true....
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SJ
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| posted on 22/10/18 at 03:44 PM |
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Why not just go with 13" wheels? The car will handle, ride and steer better.
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steve m
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| posted on 22/10/18 at 03:45 PM |
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"Why not just go with 13" wheels? The car will handle, ride and steer better."
And look better, imho
steve
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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voucht
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| posted on 22/10/18 at 04:26 PM |
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quote:
Originally posted by SJ
Why not just go with 13" wheels? The car will handle, ride and steer better.
Because rear lower wishbones on a Haynes Roadster (book specs, Sierra donor) do not fit in a 13'' wheel, it is too wide. I remember trying
to fit the the 14'' alloy wheels that where fitted on my Sierra donor, and the head of the bolt was touching the inside of the rim.
quote:
Originally posted by jps
Is there any specific reason for making sure that the overall circumference of the 15" wheels + tyres on my Haynes is as close as possible to
the circumference of the 13" wheels + tyres of my Sierra donor? Does it impact on the suspension effectiveness?
It is important only if you kept the original speedometer from your donor (assuming that you kept the same diff. and gearbox as well). I don't
see how it can affect the suspension.
https://vouchtroadster.blogspot.com/
https://cafrazx550.blogspot.com/
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ianhurley20
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| posted on 23/10/18 at 08:15 AM |
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On mine I was using an MX5 engine and gearbox driving a ford 3.92 diff and 15" rims so that they would fit the Haynes rear wishbones. I used an
MX5 loom and MX5 instruments. (I assumed they were accurate to start with). The MX5 uses a 4.1 diff on 185/60 x 14 tyres. I calculated that for the
prop to rotate at the same rpm for each speed then I would need 195/45 x 15 tyres. This worked out to be correct as at IVA the tester congratulated me
on having a speedo that was EXACTLY correct.
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jps
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| posted on 23/10/18 at 10:45 AM |
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Thanks chaps. Ideally I would fit the original steel wheels from my Sierra (13" i think) - but Voucht is correct - minimum of 15" needed
for clearance.
My speedo will be an aftermarket, so I expect to be able to program it as required.
I'll look at what common sizes are available in R15 and then go from there.
[Edited on 23/10/18 by jps]
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