Tyre profile 18"

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Vendee
Posts: 53
Joined: Sun Sep 19, 2021 5:56 pm

Post by Vendee » Tue Nov 23, 2021 7:09 pm

MagneticGrey wrote:
Tue Nov 23, 2021 6:52 pm
Vendee wrote:
Tue Nov 23, 2021 6:46 pm
DesertIslandBlue wrote:
Tue Nov 23, 2021 5:17 pm


Apologies for that, mistakenly attached the wrong image, that’ll teach me to post whilst on the move (not driving though!).
Interestingly it would seem the profile for all 18” wheels have been reduced - wonder why they did that?
No idea. The 40 profiles seem to be 30% more expensive than the 50's.

I might be tempted to go back to 50 profile when the original tyres need replacing in a few years time.
There is a significant difference in the rolling diameter (nearly 7%) so you probably won't be able to do that without making other changes to avoid messing up the effective gearing and the speedometer / odometer readings.
Yeah I know the speedo reading will be affected but I wonder if the factory actually allow for the gearing when they change the tyre profile? The speedo is electronic so it can be programmed quickly and easily but the gearing is costlier to change.

MagneticGrey
Posts: 52
Joined: Tue Aug 24, 2021 9:37 pm
Location: Denbighshire

Post by MagneticGrey » Tue Nov 23, 2021 11:22 pm

Vendee wrote:
Tue Nov 23, 2021 7:09 pm
MagneticGrey wrote:
Tue Nov 23, 2021 6:52 pm
Vendee wrote:
Tue Nov 23, 2021 6:46 pm


No idea. The 40 profiles seem to be 30% more expensive than the 50's.

I might be tempted to go back to 50 profile when the original tyres need replacing in a few years time.
There is a significant difference in the rolling diameter (nearly 7%) so you probably won't be able to do that without making other changes to avoid messing up the effective gearing and the speedometer / odometer readings.
Yeah I know the speedo reading will be affected but I wonder if the factory actually allow for the gearing when they change the tyre profile? The speedo is electronic so it can be programmed quickly and easily but the gearing is costlier to change.
Maybe they changed the final drive ratio when they changed the tyre profile, but I don't actually know. I've often wondered what they do with the straight ST-Line model (not the ST-Line X) where the buyer can order standard 17 inch rims or optional 19 inch, with a different rolling diameter.
Puma ST-Line X 155 Magnetic

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Sparks
Posts: 1708
Joined: Fri Aug 07, 2020 5:40 pm
Location: Warwickshire

Post by Sparks » Wed Nov 24, 2021 9:18 am

This is handy for calculating speedo inaccuracies... http://www.autopartuk.com/tyre-calculator/
Ford Puma ST-Line X First Edition (Manual 125)...Frozen White.

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