ground clearance measurement?

[smoothound]

Hi folks,

A cheeky one... I can't get to my dealer for a few weeks... and I can't find any drawings on line....

Please could someone kindly measure (and post) - In lift mode and low mode - the height above ground at lowest part of CT 'chin' (spoiler/splitter) - and the distance to that point from the front wheel centre? (ie the overhang).

also on which size wheels please?

I have a steep drive - The front street approaches my drive (end of cul-de-sac) at around 8:1 (12.5%) and then my drive goes up from there at around 3:1 (33%) - roughly

My A7 has a front spoiler clearance of 145mm (5.75") at 750mm (29.5") in front of centre of wheel.

99.99% of time it's fine, but I did once gently scrape the front chin spoiler when I had an undetected slow puncture in a front tyre........ Not much leeway.

Luckily the A7 chin spoiler is just plain black plastic, hidden from view and sacrificial

cheers and many thanks

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[Bry5on]

Keep in mind that 20” wheels and tires will provide an extra 10mm of ground clearance over 21” wheels and tires due to overall tire diameter. If you need the clearance, go 20”!

 

[smoothound]

Keep in mind that 20” wheels and tires will provide an extra 10mm of ground clearance over 21” wheels and tires due to overall tire diameter. If you need the clearance, go 20”!

Thanks Bry - that is useful info - could come in handy if it's tight - hopefully there is sufficient clearance to allow a free choice of wheel.

The auto-lift memory function could be useful - but I don't like to rely on tech - wouldn't like to have to leave my car on street if the lift function fails and it won't fit on low setting.

Or worse - bottom out because the memory function forgets to lift.

 

[lcarron]

Keep in mind that 20” wheels and tires will provide an extra 10mm of ground clearance over 21” wheels and tires due to overall tire diameter. If you need the clearance, go 20”!

The diameter for the 20" on the front is 729 mm and 719 mm for the 21". it is only 5 mm extra clearance not 10mm. But yes the clearance is better with the 20".

 

[smoothound]

The diameter for the 20" on the front is 729 mm and 719 mm for the 21". it is only 5 mm extra clearance not 10mm. But yes the clearance is better with the 20".

I guess tyres wear around 6mm or so too.

But I just hope it's not that tight - or even too-fast an approach could bottom out.

cheers

 

[cometguy]

The diameter for the 20" on the front is 729 mm and 719 mm for the 21". it is only 5 mm extra clearance not 10mm. But yes the clearance is better with the 20".

Where do you find these data? Is the 19-inch wheel even larger, with even more ground clearance as a result?

 

[lcarron]

Where do you find these data? Is the 19-inch wheel even larger, with even more ground clearance as a result?

You have to take in account the height of each tires size.

20 inches
front is 245/45 R 20
rear is 285/40 R 20

21 inches
front is 265/35 ZR 21
rear is 305/30 ZR 21

Here Is the link to calculate it.
Tire Size Calculator

 

[Bry5on]

You’re right - 5mm more clearance in front and 10mm more in rear. I had only run the rear numbers previously. Good call!

 

[Y1BDB1]

If the lift fails then the air suspension has failed and it will settle down so low you won’t likely be able to drive it. It’s not like the lift on a 911. If your drive is steep you probably won’t forget. You could probable buy some lowering links and raise the car if you wanted extra clearance.

 

[cometguy]

At tiresize.com, I confirmed that tires for the both 19-inch wheels (standard Aero) and 20-inch (Offroad Design) wheels have diameter 28.7 inches. So you're just getting added sidewall on the 19-inch wheels.

 

[smoothound]

Thanks guys - I will wait and measure at the dealer -

thanks anyways

 

[ptilley42]

dont all wheel size and tyre combs end up the same diameter , other wise the speedo would be out

 

[smoothound]

dont all wheel size and tyre combs end up the same diameter , other wise the speedo would be out

Gps speedo? not sure - but its the clearance measurements that are important to the OP (trust me I know) - it's now a thread on wheels/tyre dia. enjoy.

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