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8 & 10 cyl Bristol cars Type 407 onwards - restoration, repair, maintenance etc

409 Wheel and tyre size changes

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Old 24-04-09, 06:41 AM
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Location: Ardrossan South Australia
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Default 409 Wheel and tyre size changes

My 409 came with a collection of 15inch x 6J loose steel wheels, reckoned to be ex Mercedes Benz. The previous owner, Dale Allen, had been thinking of changing the wheels to 15 inch from 16, due to tyre availability. Current tyres are 175 x 16 which I would say are on a rim width of 4.5 J.
Is there any benefit of changing the tyres to the wider 185 size, I wonder?
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Old 24-04-09, 07:20 AM
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Default 409 Wheel and tyre size changes

I suggest you try a set of 205 70 or 75 on the MB rims it should transform
the handling and ride .
But check out the clearance of the tyre on the rear guards & the calipers
and steering ball joints on the rims.
There are various offset to those MB rims depending on model & year . The
offset will be stamped near the wheel stud holes .

The 175 x 16 are OK for a lighter 2 litre model , depending on brand .
Regards
Geoff
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Old 24-04-09, 07:50 AM
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Join Date: May 2008
Location: Nr Oxford, UK
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Default 409 Wheel and tyre size changes

Just in case you haven't seen one before I have attached the gear
ratio/speed/tyre size calculator I use for my option checks on the
406 project. As you can see I have decided on 15x205x65 tyres, but
there again, I might end up with 16x205x60 to keep the mph / 1000rpm
roughly the same in any gear. Any questions on use please contact me
off-line.

Kevin, this can stay on the site as a download if you want.

Clyde
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Old 25-04-09, 01:19 AM
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Default

Quote:
Originally Posted by MYTA21 View Post
My 409 came with a collection of 15inch x 6J loose steel wheels, reckoned to be ex Mercedes Benz. The previous owner, Dale Allen, had been thinking of changing the wheels to 15 inch from 16, due to tyre availability. Current tyres are 175 x 16 which I would say are on a rim width of 4.5 J.
Is there any benefit of changing the tyres to the wider 185 size, I wonder?
I don't think there is any doubt that there would be a benefit in using a wider tyre.

It is worth noting that Setright drove a 409 with 205/70VR15 tyres on 6" or 6.5" Minilite rims and said that they transformed the handling of the car but they also fouled the wheel arch in certain circumstances when fully laden. Maybe you could prevent this by altering the bump stops.

Alternatively, if you can get them, 195/75HR15 may be a safer bet, these will also be a slightly larger tyre diameter than the 205/70VR15, although still smaller than your current tyre diameter.

BUT you need to first consider any offset on the Merc wheels.

PS. Typical disclaimers apply!
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Old 25-04-09, 04:01 AM
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Default 409 Tyres

Thank you Kevin.
The bump stop issue is one that can be used to my advantage by suggesting to my wife that she really does need to go on a diet, without telling her of the change!
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