C5 X7 19" wheel fitment

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n0stra
Posts: 21
Joined: 24 Nov 2015, 00:58

C5 X7 19" wheel fitment

Post by n0stra »

I know the OEM Adriatique wheels are 19x8 with ET33 but these are near impossible to get hands on over here. So i found some 19x8.5 Rays Engeneering ET37s instead but with a ET39.

The question is: would it be a problem with firment adding these with 19x225x35 tires? My calculations show that the wheels would widen 12mm towards the outside of the car and 26mm inwards with this setup.
Jay-Bruce
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Re: C5 X7 19" wheel fitment

Post by Jay-Bruce »

The correct tyre size for the adriatics is 245/40/19, but ours was running 235/45/19 when I bought it which is actually a smidgeon taller, and while the 245/40/19's I've put on it now don't look pinched, the book says they are at the upper end of the right width for that rim size.

My numbers suggest your new wheels are going to be 12mm more inset rather than poking out more, are you remembering that increasing offset pushes the wheel inboard, decreasing it pushes the wheels outboard, hence "stanced" JDM / euro cars running negative offset to get the wheels poking crazy far out?

Whether my sums on the offset are right or wrong, those tyres are FAR FAR too small for this vehicle, you're losing ~20mm of sidewall (top and bottom) so ~40mm off your diameter, ~6% smaller, 225/45/19 would be better. The 225 width is the minimum width for an 8.5J rim, better suited to a 235/245 width.
Jay-Bruce
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Re: C5 X7 19" wheel fitment

Post by Jay-Bruce »

Just a follow on thought, if you're willing to go with so little sidewall on your car in pursuit of looks, have you considered 20" rims?
n0stra
Posts: 21
Joined: 24 Nov 2015, 00:58

Re: C5 X7 19" wheel fitment

Post by n0stra »

20s are way more than i wish for esthetically + the cost of good tires in that size are high. The 225x35x19 tires came with the wheels. I got lucky, the owner had no clue he was selling a set of some of the sought after and high quality light wheels. I got them for 80 % below retail, tires included.

I used several offset calculators and all claim 12mm toward outside and 26mm toward inside because of the 1,5" wider wheels + 6mm change in offset? You sure about your calculations?

Also with 35 side i get about the exact same diameter as with the 225x55x17.
Jay-Bruce wrote: 18 Apr 2023, 19:47 Just a follow on thought, if you're willing to go with so little sidewall on your car in pursuit of looks, have you considered 20" rims?
Jay-Bruce
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Re: C5 X7 19" wheel fitment

Post by Jay-Bruce »

I totally agree that Rays are Gucci AF lightweight wheels, so you're off to a good start, now it's just a matter of tuning them to the car, between offset adjustments with spacers if needs be and getting the ideal tyre sizes, and that's what I tried to help you with. But I may have been confused as you initially said 19x8.5, now you say 1.5 wider than the stock 8.0, so are you running 9.5 or 8.5? Obviously, the extra inch of rim width changes the sums drastically.

It's late, so I'll resort to borrowing diagrams, but here's your offset visualised:
Image

By increasing the offset value from 33 to 39 you move the mounting flange of the wheel 6mm outboard, hence the inboard side of the rim moves 6mm inboard. 1" = 25.4mm so 0.5" = 12.7mm or 12mm amongst friendly car guys discussing wheel fitment. The extra 12mm from the wheels being 8.5j vs 8j is 6mm either side of the mounting flange, so there is 6mm "extra" rim sticking inboard past the mounting flange line, and 6mm sticking out past it. The 6mm outboard nicely counteracts the fact the whole wheel is now 6mm more inboard because of the change in offset, so your arch clearance will be roughly the same. The inboard 6mm from the aforementioned 0.5j adds onto the 6mm inward movement from the change in offset giving you a 12mm inward encroachment of the back of the rim towards suspension / inner arch. Can you see how I've arrived at 12mm inward movement now?

Tyre width isn't really much of a factor in these calculations as anything in the 225 to 245 range is going to be within the confines of the rims we are talking about or at the very worst pretty close to flush with the edges of the rim. However, if you are saying you've got 9.5j rims (1.5 wider than stock 8Js) then I'd be worried those tyres are stretched, especially with the lower aspect ratio as there isn't as much rubber sidewall to deflect and thus counter the distortion.

Google image of 225/35s on a 9.5j
Image

YOLO it, crack out the tools and see if they fit :-)

You can do a more thorough check for wheel clearances by using a laptop to depressurise the suspension, put the car on axle stands / vehicle lift, try the wheels on see if they fit, and try jacking up the depressurised suspension to see if the wheels clear the inner edges at full suspension articulation in both droop and compression.

Best of luck buddy.
n0stra
Posts: 21
Joined: 24 Nov 2015, 00:58

Re: C5 X7 19" wheel fitment

Post by n0stra »

I thought the oem 17s were 17x7 while the Reys are 8.5. Hence 1.5" wider?

Appreciate the thoughtful answers you have provided 👍 i really do! I was also considering going down the spacer solution but was originally concerned with fitment in the wheel arch since i have never used anything besides the oem 17s on these cars and dont want to take any chances that can be avoided 😊

I plan on replacing the tires with a better fitment for the c5 on a later stage when they are worn, but because of tight budgets i wont replace the ones that came with it since the cost of tires + fitment will be way more than i paid for everything so far.
Jay-Bruce wrote: 19 Apr 2023, 00:35 I totally agree that Rays are Gucci AF lightweight wheels, so you're off to a good start, now it's just a matter of tuning them to the car, between offset adjustments with spacers if needs be and getting the ideal tyre sizes, and that's what I tried to help you with. But I may have been confused as you initially said 19x8.5, now you say 1.5 wider than the stock 8.0, so are you running 9.5 or 8.5? Obviously, the extra inch of rim width changes the sums drastically.

It's late, so I'll resort to borrowing diagrams, but here's your offset visualised:
Image

By increasing the offset value from 33 to 39 you move the mounting flange of the wheel 6mm outboard, hence the inboard side of the rim moves 6mm inboard. 1" = 25.4mm so 0.5" = 12.7mm or 12mm amongst friendly car guys discussing wheel fitment. The extra 12mm from the wheels being 8.5j vs 8j is 6mm either side of the mounting flange, so there is 6mm "extra" rim sticking inboard past the mounting flange line, and 6mm sticking out past it. The 6mm outboard nicely counteracts the fact the whole wheel is now 6mm more inboard because of the change in offset, so your arch clearance will be roughly the same. The inboard 6mm from the aforementioned 0.5j adds onto the 6mm inward movement from the change in offset giving you a 12mm inward encroachment of the back of the rim towards suspension / inner arch. Can you see how I've arrived at 12mm inward movement now?

Tyre width isn't really much of a factor in these calculations as anything in the 225 to 245 range is going to be within the confines of the rims we are talking about or at the very worst pretty close to flush with the edges of the rim. However, if you are saying you've got 9.5j rims (1.5 wider than stock 8Js) then I'd be worried those tyres are stretched, especially with the lower aspect ratio as there isn't as much rubber sidewall to deflect and thus counter the distortion.

Google image of 225/35s on a 9.5j
Image

YOLO it, crack out the tools and see if they fit :-)

You can do a more thorough check for wheel clearances by using a laptop to depressurise the suspension, put the car on axle stands / vehicle lift, try the wheels on see if they fit, and try jacking up the depressurised suspension to see if the wheels clear the inner edges at full suspension articulation in both droop and compression.

Best of luck buddy.
Jay-Bruce
(Donor 2022)
Posts: 522
Joined: 20 Mar 2019, 01:30
x 251

Re: C5 X7 19" wheel fitment

Post by Jay-Bruce »

AH! I see what you mean now, I thought you meant 1.5" wider than the Adriatics.

I thought about using spacers to bring our adriatics hella-flush, until I seen how the wheels sit when the suspension is depressurised, and realised that if we had a suspension problem like a burst pipe, the wheels would be ripped off by the outer arches if I used spacers. I don't think there's anything inboard that would cause a problem with lowered / depressurised suspension with that extra 1/2" / 12mm sticking in. If your car has hydraulic suspension but if possible try and check it with a jack as discussed, if it's not hydraulic, fit them, then try and spin them while the vehicle is off the ground, then just listen for rubbing on for the first few miles, particularly rubbing noises from the front when turning and on the rear when going over bumps.

You'll need to post pics of your car when it's on it's new wheels :-)