SpareTire

[L J]

Maybe should look into run flats. Had on my ATS and have Bridgestones on my GP. They do not ride as well as non run flats.
Should bring back the inflateable temp spare like they put in my 70 TA.

 

[Tdwpgtp]

Nope, I tried that. Even dead flat with the valve core out the tire was too thick to fit into the well.

Would you be able to squeeze anything bigger than the 125/70R17 in there by deflating it? Even a slightly taller tire might help prevent possible drivetrain damage.

 

[Idano]

T145/80D-18 is 27.1" in diameter. Problem is all the Mopar guys snap them up every time they're in stock.

 

[Tdwpgtp]

T145/80D-18 is 27.1" in diameter. Problem is all the Mopar guys snap them up every time they're in stock.

But those will not fit in the spare wheel well, correct?

 

[1500cc]

Would you be able to squeeze anything bigger than the 125/70R17 in there by deflating it? Even a slightly taller tire might help prevent possible drivetrain damage.

I wouldn't worry about drivetrain damage. Our cars come with spares in other markets, so they're obviously designed to detect when a spare has been installed and make the appropriate adjustments.

 

[Tdwpgtp]

I wouldn't worry about drivetrain damage. Our cars come with spares in other markets, so they're obviously designed to detect when a spare has been installed and make the appropriate adjustments.

The manual explicitly warns against using them for that very reason. Any car will experience excessive wear on clutches or differentials when there is a diameter difference between two or more driven wheels. I couldn't tell you how far is "safe" to drive on different sized wheels, though.

 

[FavaBean]

Does the Buick roadside assist allow you to tow the car to non - GM/Buick dealer?

 

[1500cc]

The manual explicitly warns against using them for that very reason.

The owner's manual paragraph you attached basically says exactly the opposite ... you absolutely can use a spare on these cars, because it's telling you how to use it. Obviously you have to be careful and limit your speed and distance, but that goes with any compact spare.

Any car will experience excessive wear on clutches or differentials when there is a diameter difference between two or more driven wheels.

Our cars' clutches are electronically engaged, so I would bet that when the car detects a spare is in use (from the difference in rotational speeds of the wheels), it simply does not allow engagement of the clutches, or at least very limited engagement. Hence the "reduced AWD performance" the manual states, and therefore probably not any additional wear if you drive carefully.

 

[Tdwpgtp]

The owner's manual paragraph you attached basically says exactly the opposite ... you absolutely can use a spare on these cars, because it's telling you how to use it. Obviously you have to be careful and limit your speed and distance, but that goes with any compact spare


Our cars' clutches are electronically engaged, so I would bet that when the car detects a spare is in use (from the difference in rotational speeds of the wheels), it simply does not allow engagement of the clutches, or at least very limited engagement. Hence the "reduced AWD performance" the manual states, and therefore probably not any additional wear if you drive carefully.

I think I will definitely disagree here. The manual is saying "sure, use a spare if you need to, but don't do it for long or risk excessive wear."

Regarding your second comment: I would hope that this is how it is programmed, but until I see it stated officially, I'm going to assume the worst case that it is going to read a diameter difference as a wheel speed difference and continue to engage the rear wheels, thinking there is slippage.

 

[ECM56]

You've seen those people that drive around for weeks with a doughnut spare on? The manual is telling you not to be that guy (or gal). If GM wants to hold you liable for damage due to using the doughnut, their language needs to state "Do not use a doughnut". I wouldn't sweat it but to each his own.

 

[Tdwpgtp]

You've seen those people that drive around for weeks with a doughnut spare on? The manual is telling you not to be that guy (or gal). If GM wants to hold you liable for damage due to using the doughnut, their language needs to state "Do not use a doughnut". I wouldn't sweat it but to each his own.

Many manufacturers that have AWD systems have explicit callouts for maximum allowable diameter (or rolling radius) difference to prevent drivetrain wear and damage. They are pretty small amounts, and mostly equate around 1/4 inch in rolling circumference, which is a miniscule difference in overall diameter. Buick does not call out a specific amount, but I'd venture to say that it probably isn't far off other manufacturers'.

Those people rolling around on donuts probably end up in the shop for transmission shop soon after, unless they move the donut to the non driven axle.

As you said "to each his own", but I certainly wouldn't risk driving on a significantly different sized wheel 1 foot or 1 mph more than I NEED to

 

[1500cc]

Many manufacturers that have AWD systems have explicit callouts for maximum allowable diameter (or rolling radius) difference to prevent drivetrain wear and damage. They are pretty small amounts, and mostly equate around 1/4 inch in rolling circumference, which is a miniscule difference in overall diameter. Buick does not call out a specific amount, but I'd venture to say that it probably isn't far off other manufacturers'.

This isn't a 'normal' AWD system though. You're probably thinking of normal diffs and lockup clutches kinda like a posi-trac, that isn't able to smartly adapt. In the GKN Twinster that's in our cars, the driveshafts are completely disconnected from drive torque (i.e. no mechanical connection whatsoever) until the clutches engage. So once the car recognizes a spare is put on, it simply needs to tell the clutches to stay disconnected (with perhaps the exception of an impending spin). Thus no additional wear, and the manual's warning of limited AWD capability when a spare is on.

 

[Idano]

But those will not fit in the spare wheel well, correct?

No, it won't fit in the donut hole. It's a full size spare that is half as wide as your stock tire/wheel combo. It just takes up less room in the cargo area. You can put it on and drive at speed without worry.

 

[ymerejmortsdnil]

Modern spare got back to me:
Thank you for reaching out to us. Yes, the spare should still fit in the tire well, However, the included mounting hardware that locks the wheel in place is not compatible. But jsut to make sure, I recommend that you get the diameter of your tier well. The spare has a T155/70R18 tire - 26.5" we have sold many for other Regal trims especially the GS and it fits well in their trunk well and we want to make sure it's the same. looking forward hearing from you soon.

Update:
Please disregard our previous email in regards to spare tire well fitment. Concerning the note, it has come to our attention that the Sportback and TourX models do not have a spare tire well that will accomodate a spare tire. Instead, they more or less have a storage compartment that is not big enough for a spare. As such, most of our customers that have the Sportback and TourX Models purchase the kit with the carrying case as this allows them to store everything neatly within the trunk of their vehice.

do you have the part # for the kit with carrying case that you mention? Thanks!

 

[MelsRegal]

here is the link to Modern Spare
search page - Modern Spare

 

[ymerejmortsdnil]

here is the link to Modern Spare
search page - Modern Spare

Thanks! I was looking at this as well. Have you or anyone else purchased this? Wondering if it takes up much space in the back since it likely won't fit under the floor. Looking for something to throw back there for longer drives that won't interfere too much with the other luggage etc. that I am taking along.

 

[Idano]

Thanks! I was looking at this as well. Have you or anyone else purchased this? Wondering if it takes up much space in the back since it likely won't fit under the floor. Looking for something to throw back there for longer drives that won't interfere too much with the other luggage etc. that I am taking along.

27" diameter, 5.5" wide. Won't fit in the donut hole and won't stand up on either side with the rear seats up. It will stand up against the rear seats and in the middle areas a little away from the rear windows.

 

[ymerejmortsdnil]

27" diameter, 5.5" wide. Won't fit in the donut hole and won't stand up on either side with the rear seats up. It will stand up against the rear seats and in the middle areas a little away from the rear windows.

Seems very small & should take up minimal space, I really like the idea of this kit & even more so after watching a YouTube review of the kit for a Camaro. Should provide peace of mind on longer road trips!

 

[GermyShoe]

Thanks! I was looking at this as well. Have you or anyone else purchased this? Wondering if it takes up much space in the back since it likely won't fit under the floor. Looking for something to throw back there for longer drives that won't interfere too much with the other luggage etc. that I am taking along.

Just get you a roof rack with KC lights and two Jerry Cans and throw it up there. Baja Wagon, baby!

 

[Charleetho]

I'm thinking of heading down to a local "Pick and Pull" with a tape measure and search the trunks of GMs for a spare donut. If I don't find anything I'll buy new.
Maybe runflats are the answer
The thought of my wife driving her often dark commute with only a can of fix a flat and a compressor is very concerning.