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Spare tyre under-trunk modification for Model Y?

DrTe$la

Member
Aug 23, 2021
19
10
Australia
Hi forum members.

I'm hoping to get my first Tesla Model Y in a few months but what irks me is that there is no spare tyre like an older S model. I have an idea of a possible modification to store a spare tyre in stead of the under-trunk well. However, I need to verify if this is possible with the help of this forum from someone who actually owns a Model Y and to hear your opinion.

I understand that the actual bin is too small to hold a tyre. In a post on this forum @halfricanguy shows pictures of the trunk after removing the mat and the attached under-trunk well. The space is much bigger than expected.

F512FA76-CCFC-4A77-84B2-A98E1ED14CA4.jpeg


Another youtube video posts how to lift the mat from the back (towards the bumber) which seems easy enough. Forget about him teraing apart the rest of the car in video.

In the Tesla Model Y manual it is stated that the loading in the undertrunk can take up to 130 kg. So this should definitely hold up

My thought is that if one cuts the undertrunk well away from the rest of the floor lining, would it be possible to put a spare tyre flat down in the hollowed out section and still be able to cover it up so the boot space is flush?

I doubt a normal 20 inch tyre with its 28 inch in rolling diameter would fit in that space, basically removing the option for an original Tesla tyre.
I don't think that a Modern Spare would fit either. Maybe it could be placed tilted and not fully flat?? 2020-2021 Tesla Model Y Spare Tire Kit Options

An option would be to put in a Vredestein Expandable/Collapsable tyre which should fit?
Two options I've found that have the same rolling diameter and space for callipers a
- Vredestein SpaceMaster 185/55-20 100P (rolling diameter 28, same as original tyre) - used in Mercedes Benz S class
- Vredestein SpaceMaster 195/55-20 102P (rolling diameter 28.4 inches, meaning+0,4 compared to original tyre) - used in Porsche Cayenne Turbo
- Vredestein SpaceMaster 185/65-19 104P (rolling diameter 28.5 inches, meaning +0.5 compared to orignal tyre) - used in Mercedes Benz ML AMG

I am no expert on tyre sizes, and there are a bunch of other Vredestein for Audi, VW etc which has a rolling diameter +1.5 or similar.

This is to be compared to Tesla Model Y Induction Tyres 20 inch rim: 255/40-20 XL 101W

So my question to anyone interested in this forum and who owns a Model Y, any possibility you could lift the lining from the back of the car and check the size available in the "box" the undertrunk forms? That would be greatly appreciated!


And last but not least, everyone has their own reasons for a spare. I fully understand why many auto manufacturers have opted to remove the spare. However, I do not agree with the fact that the engineers have taken away the possibility to have a spare for those who actually want or need one. I will always carry a tyre puncture kit, guck on spray. But, I will be driving along roads where there is 50-100 km gaps between towns and where there is absolutely no mobile coverage in between. Even if I carry a Thuraya sat phone for emergencies, it will put me far, far away from nearest truck to rescue me.

So for those who want to share how many years they have driven without a flat, managed to fix the car with guck, or stating the danger of changing a tyre because of driving by traffic... please refrain. This post is not about that.

I've had 6 punctures in 25 years. 5 of those happened on more or less deserted roads. 2 of those happened in the middle of winter at -15 or below without any cars passing by for half a day or more. The only danger was freezing to death as there was no network coverage. A tyre change fixed everthing. Now having relocated to a hotter climate, I don't want to die in 40 degrees weather because someone decided people don't need spares or the option to store them safely. I'm old enought to know how to change tyres.

I would appreciate any help in finding out if this mod works for the Tesla Model Y as I absolutely need a spare.

Cheers!
 

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Level 1

Member
Aug 10, 2021
62
50
Earth
If it helps, people have successfully put some 18" wheels on non-Performance Model Ys. Not a ton of caliper clearance, but enough.
So instead of 19 and 20", if you find an 18" space saver, that might make for a more compact spare that fits with less trunk clearancing.

I *believe* (please confirm for yourself, or correct me if I'm wrong) that a smaller overall inflated tire diameter would be OK too, as long as you remembered to turn off traction control so the car didn't try to fight the speed imbalance with selective braking on that wheel (thinking it was wheel slip). And obviously even if you DID cause "damage" (brake wear and computer faults) by driving with one improper tire size, that's still far preferable to being stranded in danger (your "-15 for half a day freezing to death" situation).
 
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DrTe$la

Member
Aug 23, 2021
19
10
Australia
Here’s a guy who did that, modified his sub-trunks to fit a “‘Modern spare” tire underneath:


So it can be done. I wish there was some aftermarket solution to make this look more clean.
Thanks SpaceShipDrvr.

I've seen this post and it is my last resort solution even though it isn't a pretty one. The Modern Spare can't go as far as the Vredestein which feels like a more robust tyre, but the negative is that it carries a much wider footprint.

I'm still hoping I can fit a Vredestein where the undertrunk well is located. Looks like a lot of space down there, especially when the Vredestein tyre is 20" rim + another 2" for the actual rubber when deflated / collapsed. One could possibly cut the undertrunk well nicely and place it ontop of the tire, giving a smaller less shallow underturnk bin. At least in theory.

Any chance you could measure the undertrunk space after flipping the lining mat away? ;)
 
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DrTe$la

Member
Aug 23, 2021
19
10
Australia
If it helps, people have successfully put some 18" wheels on non-Performance Model Ys. Not a ton of caliper clearance, but enough.
So instead of 19 and 20", if you find an 18" space saver, that might make for a more compact spare that fits with less trunk clearancing.

I *believe* (please confirm for yourself, or correct me if I'm wrong) that a smaller overall inflated tire diameter would be OK too, as long as you remembered to turn off traction control so the car didn't try to fight the speed imbalance with selective braking on that wheel (thinking it was wheel slip). And obviously even if you DID cause "damage" (brake wear and computer faults) by driving with one improper tire size, that's still far preferable to being stranded in danger (your "-15 for half a day freezing to death" situation).
Thanks. I'll definitely have to look into this.

I'm no expert on Tesla and the more advanced electronics in the car so I don't really know how much leeway the Tesla has for negative rolling diameter of say -0.5 o -1". A prehistoric car would barely complain. Newer cars, as you say, just kill traction control. But I understand Tesla is a special kind of breed.

Choosing an 18" rim with collapsible rubber of 2", taking it down to 20 inch in total storage diameter for Vredesteinr, gives a whopping 8" difference to the rolling diameter of the Modern Tyre. Looking at the subtrunk space, it feels like it should fit. Still need someone to measure it ;)
 

positiv

Member
Jul 20, 2021
45
25
Sydney
Here’s a guy who did that, modified his sub-trunks to fit a “‘Modern spare” tire underneath:

So it can be done. I wish there was some aftermarket solution to make this look more clean.

That is fascinating. Thanks for the link. He just had to cut away some foam and then the modern spare fit right in to the trunk!
It's frustrating to see that Tesla designed the car so that sub-trunk *almost* fits a space saver but not quite.

I cannot imagine why Tesla would have done this!?! It would have been so easy for Tesla to make this possible without any modification.
 

SpaceShipDrvr

Member
Aug 1, 2021
77
93
California
That is fascinating. Thanks for the link. He just had to cut away some foam and then the modern spare fit right in to the trunk!
It's frustrating to see that Tesla designed the car so that sub-trunk *almost* fits a space saver but not quite.

I cannot imagine why Tesla would have done this!?! It would have been so easy for Tesla to make this possible without any modification.
The reason is probably that 7 seater variant, and wanting to keep as much commonality between the 5 and 7 seater. This is why the sub-trunk is split into a front and rear one. But I agree… I ordered the 5 seater, and I would gladly sacrifice all the sub-trunk space for a spare tire space.
 
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Noflash

Member
Aug 11, 2020
189
124
Denver
The reason is probably that 7 seater variant, and wanting to keep as much commonality between the 5 and 7 seater. This is why the sub-trunk is split into a front and rear one. But I agree… I ordered the 5 seater, and I would gladly sacrifice all the sub-trunk space for a spare tire space.
Ditto
 

Pianewman

Active Member
Oct 28, 2020
1,480
1,059
Fort Worth
For sure, I wouldn't be modifying anything that couldn't be retrofitted back to OEM. I already looked once, and the structural beam between the wheel wells is the number one problem. Clearly, that can't be changed.
The other option I've thought: I'd like to find a Vredestein SpaceMaster (IIRC 22" diameter uninflated) and see if it would fit vertically right behind the bumper, or maybe behind the 2nd row seat back after modifying the shallow trunk well. It's as wide as a normal wheel/tire, though.
 

a2t2

Member
Jul 8, 2021
288
161
Atlanta
You would need to cut both the tray and the cargo bin but im not sure how much space there is forward before the rear motor assy
 

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Pianewman

Active Member
Oct 28, 2020
1,480
1,059
Fort Worth
I can't find the thread with the photo of a Modern Spare mounted vertically behind the 2nd row. The owner cut out enough trough for the wheel to sit a bit lower, but it still stuck up too much for my taste. That's why I thought the Vredestein would look a little neater. (The other issue is the bolt pattern of the Vredestein, but for temporary use, a spacer might work.)
 

positiv

Member
Jul 20, 2021
45
25
Sydney
Crazy Idea.... what about if the tub was removed and replaced with a flat piece of plywood?
Could the Tyre be suspended under that?
 

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patnshan

Member
Oct 7, 2020
217
179
Milwaukee, WI USA
If it helps, people have successfully put some 18" wheels on non-Performance Model Ys. Not a ton of caliper clearance, but enough.
So instead of 19 and 20", if you find an 18" space saver, that might make for a more compact spare that fits with less trunk clearancing.

I *believe* (please confirm for yourself, or correct me if I'm wrong) that a smaller overall inflated tire diameter would be OK too, as long as you remembered to turn off traction control so the car didn't try to fight the speed imbalance with selective braking on that wheel (thinking it was wheel slip). And obviously even if you DID cause "damage" (brake wear and computer faults) by driving with one improper tire size, that's still far preferable to being stranded in danger (your "-15 for half a day freezing to death" situation).
I run 18's on my MY LR in winter. Easily fits. Not sure about the spare, but the wheels fit the car easily.
 

ArtK

Member
Jun 1, 2020
214
189
NYS
I also wonder if the
Here’s a guy who did that, modified his sub-trunks to fit a “‘Modern spare” tire underneath:


So it can be done. I wish there was some aftermarket solution to make this look more clean.
I wonder if this YouTuber is working with Modern Spare's original Maxxis tire (found to trigger error messages and excessive unilateral braking due to a diameter mismatch) or the newer, larger Conti spare. Are we certain the Continental fits in the well at all? I personally still have the semi-useless Maxxis and am awaiting a swap from Modern Spare.
 

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