Like some other '24 RX450h+ owners, I've been frustrated by the lack of a spare tire. The only flat I ever had in my 2006 RX330 was a sidewall blowout 500 miles from home on a family roadtrip, where the 2006's stock full-size spare really saved the day in terms of convenience. Any lesser spare (or no spare) would have been hugely problematic.

I bought the ModernSpare option for my '24 RX450h+ (https://modernspare.com/product/2023...e-kit-options/). It's great, and comes with all essential tools and a nice big padded storage bag, but now I'm frustrated by (A) how much space it takes up in the back and (B) that it's just *slightly* too big to be stowed under the panels unless I take out ALL the panel boxes.

I'm considering either (1) a smaller spare, (2) fashioning a custom recess and shelves out of plywood and 3D-printed parts, or (3) buying replacement plastic bin parts, cutting them to custom size, and filling in as needed with thin plywood and foam.

Unfortunately, I can't simply drop a full-size spare into any existing space in the back of the car. With most of the panels and boxes removed, it sticks up on the front-right quadrant.




With all of the panels and boxes removed, it lies flat -- but is resting right on what I believe is one high-voltage part (front-left quadrant), and right against another (front-right quadrant). This seems suboptimal, but it is low enough that I can put the back cover in place and it's only elevated about ½".



While I'm confident I can make solution 2 or 3 work, I wanted to first learn how others may have tackled this -- and if Lexus' own spare for a basic '24 RX350x might also work (and give me a bit more space to work with.

Thanks in advance for any insights, ideas, or recommendations. (Any criticisms of my purchase decisions or thinking will be cheerfully ignored.)

 

Thanks for starting this thread and discussion - now after compensating for the 12 V battery charging deficiencies, this is my next item to compensate for the RX450H+ - so highly appreciate your sharing your modern-spare endeavors. Yes, NX450H+ owners have also gotten the Modern Spare for themselves (@midcow3's thread/posts comes to mind), and have also ended up finding how much space it takes up in the NX450H+.

However, I find it highly encouraging that you were able to position it flat after removing all the panels, and sub-optimal points you point out - but I would like to glean whether those are really sub-optimal, in terms of any risk to the HV components (on this note, people can please not comment with speculation, and only comment with near-certain or certain knowledge).

The other point I also considered is whether getting the Lexus' own spare for the 21 inch wheels of their Premium-Plus Luxury trims of RX350 (or RX350H) ? Especially the question, if given that the Premium-Plus RX350H with 21 inch wheels also has the 12 V battery in rear, how does Lexus manage to still to place their OEM spare in those cars ? Or are those Premium Plus 350H also sold without spares ?

 

Hmmmm ... with only needing 1/2" of clearance, i wonder if just getting a smaller spare may be the easy fix action. I know that it will not look or ride the same BUT as a temp spare tire to get you home or to a garage to get your tire fixed it should work. This way you dont have to re-do, cut or fabricate parts.

Thanks

 

I don't this it is a good idea to have a much smaller tire as a spare. I guess one could just deflate the larger one to gain the 1/2" as long as you have an inflator when it is needed.

 

That may end up being part of the solution, but other challenges remain. The spare would still be resting right on top of some questionable electrical components (I'll get pictures later today). Plus, I'd like there to be some replacement compartmentalization so that other stuff I may put in the space won't rub against the spare, the 12V battery, etc. Ultimately I want to have something that's not only functional but looks decent, too.

I wouldn't go any smaller than Lexus' own 2024 RX spare, which I believe is smaller than the ModernSpare -- but still need to look into that. Deflating the modern spare a bit is an option, too. I'll play around with that later today.

 

I'd be concerned about "...I can put the back cover in place and it's only elevated about ½". "

It looks (can't be sure from the photo) like the tire weight really is resting on the box in the upper left corner, and anything you then add to the cargo area would be transferring more weight to the box.

Factor in shock/vibration from actually driving it (normal road stuff), which would transfer to the box as impacts, and it might lead to a box warping/failure.

 

Yes, I think this is a great direction to look - just deflate the Modern Spare (or even the Lexus spare) enough so that it fits even better than you already have in the second picture - without pressing against the HV parts. If that works well, that would be THE solution, methinks. In any case, at least I and perhaps most people carry a portable inflator - so that solves the problem.

 

I had some more time to mess around with this today. Deflating the Modern Spare to 0.0 psi (from the 53.5 psi that it shipped with) bought me ~¼" in diameter and height (while laying flat). Considering how long it would take to add the recommended 60 psi back in with the tiny little Lexus inflator, storing it deflated for a miniscule reduction in needed volume doesn't seem worth it to me. If Lexus' own spare is smaller, that's probably a better way to go.

The space is clearly designed (in part) to accommodate a spare -- you can see it in the curve of the compartment plastics — but the end result goes elsewhere.

Here are the panels and components that need to be worked around somehow. The part numbers are imprinted on the underside of each. (Note also the highlighted green curves, which seem to accommodate the placement of a spare.)



...and here are the two high-voltage components that I do not want to mess with, followed by their close-ups.







So... next I need to find the dimensions of the Lexus spare. If those high-voltage components are present only in the PHEV (RX450h+), then maybe Lexus' spare for any other '24 RX model would fit in the space that evidence seems to suggest was intended for a spare anyway?

Either way, I'm now leaning toward my original Solution #3, which would entail some kind of spacer/shield between the tire and high-voltage component 5, and replacement panels & compartments from Lexus that I can jigsaw & dremel as much as I want until the tire fits. This would mean the removal of section 1 and the trimming of sections 2, 3, and 4 (and possibly a notch from the small panel under the blue MagLight).

 

It appears that the HV component numbered 5 is the real problem for placing the ModernSpare on top of. Aside from the minimal reduction of size on deflating.

It really be great if there is someone who owns a RX Premium Plus or Luxury model can share their dimensions of the spare for their 21-inch wheels.

I had tried earlier looking for that spare's part number at parts.lexus.com - but had not conclusively found that spare's part number. Wonder if someone else has been more successful finding that spare's part #.

 

2024 RX 350 Premium here with 19in wheels. Not a plus. But, wouldn't tire size be the same with the difference being the wheel? If so:

 

I took delivery of a 2025 RX350h premium plus on 11 Jan 2025. It came with a space saver spare. Is that new to 2025?

 

This is very interesting - do you have 21 inch wheels ? Can you please share a picture of your space-saver spare ?

For us owning 2024 models, we can conceivably order this Lexus part, in case its reasonably smaller than the Modern-Spare, for 21 inch wheels.

 

My 2025 RX450h+ did not have a spare, so guessing not all 2025 RX models get one.

 

Can you possibly share the actual physical dimensions of that spare tire, in inches or cm, for both diameter and height while lying flat?

The challenge some of us are trying to solve is that there’s *almost* enough room in the back of a 2024 RX, if you remove three sub-panel compartments, to lay the Modern Spare emergency tire in there. If there’s a slightly smaller alternative spare available from Lexus, that may solve the problem.

 

The spare pictured is smaller, and is just provided to 'get you home' in event of a major blowout.


https://powerdog.com/tiresize.cgi




That is why a max speed of 50MPH is recommended: The handling characteristics of the smaller tire due to width and circumference is quite a bit different!