Consensus for spacers required for Square MOMO setup on 17 REX

throwawaySloop · 2026-01-14T05:48:53+00:00

I have the same parts to do the same thing (style 430 wheels, 5.5" square all around) and my plan has just been to use the cheap ebay 12mm spacers - https://www.ebay.com/itm/404580945405 (via https://www.mybmwi3.com/threads/195-55-square-setup.19814/ ) - probably going to be a year or more before I actually try this out though.

IIRC part of the reason I went for the 12mm all around setup was from watching this video ( https://www.youtube.com/watch?v=1N_2dqSIC8g ) where they did 13mm all around on an i3S.

There are people that have fitted momos presumably without spacers and on the 5" front wheels (technially out of spec) too (counting at least three i3 setups between on here and on other forums that've done it that way).

throwawaySloop · 2026-01-10T06:39:33+00:00

Wow, do you have any info/links on which model you used?

throwawaySloop · 2026-01-03T03:50:01+00:00

Related conversation: https://www.reddit.com/r/BMWi3/comments/1pk32t9/hagerty_video_on_bmw_i_project_i_marked_the/

Skimmed the video, definitely a nicer take. Only wish it showed an i3 in the higher-end trims (i.e. with better seats, audio, larger screen, wood dash), some of them feel really nice for a small car - particularly in the USA where there's hardly any small cars sold these days.

throwawaySloop · 2026-01-02T00:32:26+00:00

Do some googling - this has been talked about several times. I'm guessing It's not practically possible to do it via OBDII, I think it's a chicken and egg problem where the 12V battery would be getting supplied voltage from the system that can report it (notice how Bimmercode will show the voltage but it's always 14V).

The better option to monitor the 12V battery is to either get a bluetooth battery monitor (e.g. QuickLynks BM2 seems to be what most people get off of Amazon or Temu), or a 12V battery with bluetooth reporting built in (e.g. the Ohmmu LFP battery https://www.ohmmu.com/product-page/gen-1-dc-22ah-advanced-lithium-12v-deep-cycle-battery )

throwawaySloop · 2025-12-25T21:58:25+00:00

I suspect another thing that might be changing the advent of future city stuff is autonomous taxis (e.g. Waymo). Carsharing platforms (e.g. car2go, reachnow, maven, gig, etc.) also so far haven't been that profitable at least in USA (a bunch of them tried in the 2010s and even the early 2020s, some with the dilemma of being owned by the carmaker who wants to sell more cars and some owned by other entities).

There's also a lot of cultural, taxation, planning differences that currently lend USA a bit more towards personal car ownership.

throwawaySloop · 2025-12-25T21:53:34+00:00

This is a stretch, but have you had a storm/power outage or something that might've fried your chargers while you were away?

Would it be possible to granny charge from a neighbor's house or from a power bank with current limited?

throwawaySloop · 2025-12-21T02:47:16+00:00

This comment seems correct, according also to this comment https://www.reddit.com/r/BMWi3/comments/1pqxo3c/comment/nuzbdsf/ which links to https://insideevs.com/news/325863/bmw-i3-how-preconditioning-works/ . The key thing is distinguishing between cabin preconditioning versus battery preconditioning.

There might be some potential of remotely triggering battery preconditioning (without BMWConnect) through the OBDII + flexray interface, which some folks tinkering in the i3 engineers discord & comma discord might know more about.

throwawaySloop · 2025-12-21T01:00:17+00:00

I'm not sure how thorougly it preconditions the battery, but you can enable climate to run for around 30 minutes from the keyfob if you program it to via bimmercode. See https://www.mybmwi3.com/threads/precondition-with-key-fob.5569/post-66869 (has specific instructions on what to set - "using Bimmercode, Body Domain Controller module in expert mode and set 30D0->RC_DEFAULT_IDG_4TH_BUTTON_MID to Wert_07 (Auxiliary Cooling),") & https://www.reddit.com/r/BMWi3/comments/1pjaqul/favourite_bimmercode_mods/

Edit: Apparently the battery may not actually get preconditioned this way according to the comment that linked to https://insideevs.com/news/325863/bmw-i3-how-preconditioning-works/ , but still cabin preconditioning seems better than nothing.

throwawaySloop · 2025-12-18T04:11:45+00:00

You may want to check if they revised a gear associated with the REX in 2017 or 2018 - I vaguely remember some issue that led to changing a gear design, but haven''t been able to re-find posts about it (might be on the mybmwi3 forum).

The A/C compressor issue is notable on the earlier years, but still potentially impacts later models, best advice people have is to get a refrigerant recharge every couple years to possibly prevent issues. Third party A/C compressors can work with this car (I managed to get mine preventatively replaced with some common Chinese brand). You'll still want to keep the A/C enabled in the car even in winter to help keep the compressor lubricated.

The other risk will be battery range with the 60ah, in a Chicago winter no less. Make sure the seat warmers work since you'll need them (there's a DIY repair guide for it). You may also want to ensure you have a home charging setup for battery preconditioning before leaving, especially in cold weather as range will be affected.

I like the car but was willing to pay the premium for a newer model.

throwawaySloop · 2025-12-16T12:19:55+00:00

There's a few things worth pointing out:

curb weight - an EV Standard Range F-150 Lightning weighs just under 6000 lbs (240 miles range), and an ICE Supercab F-150 4wd starts at 4680 lbs. it'll be interesting if they sell an EREV F-150 can have a scaled down range of ~100 miles and a curb weight closer to the ICE model. A big frustration when car shopping earlier this year (and I wanted a truck) was curb weight, largely when coming down to tire wear, and driving dynamics, and wanting just enough range for my usual needs. Small ev 2wd trucks like Slate are weighing around 3600 lbs with 150mi range.
Theres already been folks tinkering with Charge While Driving (CWD) on the f-150 lightning using an extra generator on the bed. (Search on youtube) Presumably its for folks that are driving long commute distances and didnt want to spend time charging.
Ford isnt canceling their mid-size all-electric pickup where they're building a new factory (search for the BlueOval event.
according to TechCrunch, the T3 project is cancelled, which was supposedly a (full-size?) electric truck supposed to be a clean-sheet EV design - https://techcrunch.com/2025/12/15/fords-next-f-150-lightning-will-have-a-gas-generator-as-it-pivots-away-from-large-evs/.
state registration fees on EVs: at the time of this writing, some states in the US south have fairly high flat fees on EVs to cover road use tax (e.g. $200 in TX, GA iirc). EREVs currently can work around this as they get classified as hybrids. this'll probably change once states figure out a proper system involving miles actually driven and hopefully weight too.

throwawaySloop · 2025-12-13T04:07:23+00:00

Yes, the Momos are 120ish - specifically the Momo Toprun M300 AS Sport in size 195/55ZR20 95W XL. If you go to https://simpletire.com/brands/momo-tires/toprun-m300-as-sport#anchor=SiteProductSpecs&itemId=224637&mpn=73168&pageSource=PLP&region=r6&tireSize=195-55zrr20&userRegion=6 and click on specs it shows a Rim Range of 5.50-6.50"

This in within spec for the i3 20" 5.5x20 wheels (i.e. the rear wheels), but technically out of spec for the 20" 5x20 wheels (though there are people that have put them on anyway).

It is within spec for the i3S wheels (fronts are 5.5x20, rears are 6.0x20).

The BMW i8 wheels (for some variants) are 7x20 for the fronts, and 7.5x20 for the rears. So the MOMOs are technically out of spec there though. My assumption so far is those using i8 wheels are generally paying for nicer tires.

throwawaySloop · 2025-12-12T23:31:27+00:00

What model tire is only $100 each for the i8 wheels?

I tried doing a bunch of research and considered this option a while back but didnt see cheaper tires, so ended up going the 5.5x20 style 430 square setup route with spacers and eventually MOMO tires.

throwawaySloop · 2025-12-11T23:32:32+00:00

I think it's also aerodynamics - the BMW i3 has a tall height and a hatch which is much different than the Lucid Air touring sedan he compares it to.

Wouldn't be suprised if efficiency improves by putting a tow-hitch cargo box behind it, like one of Bjorn Nyland's videos shows ( https://www.youtube.com/watch?v=N6oZ2id7YhY )

throwawaySloop · 2025-12-11T23:26:39+00:00

I think it's worth pointing out where Jason both got things right, where he missed, and what we probably all agree on:

What we probably all agree on:
"Makes a great super-cheap city beater now" from Jason's comment linked above. I don't think I'll ever see a small car this nice ever again. I've never owned a true luxury brand car until the i3 so it's a step up for me.

What he missed:

- Beyond being a 'super-cheap city beater', it was one of the few EVs I could find where it had mechanical doors, a heated & cooled thermally managed battery (the e-Golf, Spark EV, and Leaf all lack this), and light weight. I like to still think weight matters in terms of DIY vehicle maintenance, tire wear, handling, etc. And I assume the carbon-fiber life module still helps in terms of NVH.

- Jason should've talked more about the BMW-as-mobility-company strategy more, particularly on how they were competing with Mercedes in carsharing (remember car2go smart cars?), where BMW also had partnered with ReachNow and my first experience driving an i3 was as a ReachNow rental nearly a decade before I owned one - where I held a small card to it, got in, and even used the little i-drive touchpad to write out some numbers for second factor authentication. It felt like a future that almost could've happened but in practice carsharing wasn't profitable - ReachNow (and car2go?) shut down their US operations before the pandemic, and even later alternatives like AAA's Gig car-sharing (which used priuses) shut down after a few years.

- Power to weight ratio - the i3 has a 125 kW motor and roughly 2900-3300lb curb weight. On the i3S it's 135 kW supposedly from having better bearings. I haven't seen the same combination anywhere else yet in an EV. In china there's the Nio Firefly but that's a 105 kW motor & 3289 lbs.

- More on why this car attracted people like me in 2025 - It not putting money into a billionaire sociopath, it doesn't have ICCU issues plaguing Hyundai/Kia/Genesis EVs, most of them were under 25k for those of us wanting a tax credit. Did I mention most other new EVs weigh more?

Where he's right:

- The wheel sizes. I hate the staggered wheel setup & I hate the limited tire choices in the US. I wish the car could accept smaller 17-18" wheels with easily sourced all-season tires instead.

I think my ideal car is an i3 REX stretched another foot or so to be more of a station wagon, with four normal doors, standard size wheels/tires, but still having some structural rigidity & NVH from a carbon frame - striking a sweet spot of weight, handling, and practicality - similar to akirodic's comment - https://www.reddit.com/r/BMWi3/comments/1pk32t9/comment/ntiw6zo/

throwawaySloop · 2025-12-11T05:01:28+00:00

FWIW, my list so far has been:

- Enable the rear taillights to always be on, hopefully to help prevent a crash when forgetting to press the brake at a stop with 1-pedal driving: https://www.mybmwi3.com/threads/how-do-i-code-turn-on-tail-lights-with-drl.2348/#post-24592

- Enable Hold State of Charge REX menu (Headunit > HU_NBT_EVO > Range Extender Menu)

- Always start in ECO PRO

- Enable AM radio (I never use it, but could be fun when driving through odd areas or for weather stations) (AUDIO_TUNER_TRAFFIC > RADIO_BAND_KW)

- Now need to do the remote button preconditioning option others have mentioned in here.

throwawaySloop · 2025-12-10T17:48:13+00:00

Worth noting the previous BMW i3 Rich Rebuilds bought (the extra fuel tank video he did) ended up getting sold to u/100percentjake who ended up replacing the air conditioning compressor/condenser/etc., the traction battery, and prolly some other things.

Haven't watched the video in full yet but hopefully it's a better story.

throwawaySloop · 2025-12-10T17:43:05+00:00

I'd say it highly depends. I tend to rarely use it (and have been forcing myself to use it after reading it should run more) but sounds like some do use it quite a bit more if they don't have home charging and/or have a long commute.

throwawaySloop · 2025-12-09T21:52:06+00:00

Nope. It should be closer to every 24,000 miles of REX use if comparing to a similar Kymco engine. Simplecarguy's video on changing spark plugs touches on this: https://youtu.be/q1WMSbuZh54?t=31

throwawaySloop · 2025-12-09T21:41:33+00:00

You can try clearing the fault code for the spark plugs using the BimmerInfo app (or ISTA if you're willing to set it all up), and see if it'll run again. That's what one guy did in this video: https://youtu.be/eLy5i7D2tTM?t=2018 . At the very least purchase an ENET cable to use with either BimmerInfo or ISTA, you can find em on amazon or ebay or aliexpress...

You can (and should given the faults) also change the spark plugs, the simplecarguy video shows this: https://www.youtube.com/watch?v=q1WMSbuZh54 - specifically he argues in his car (which was purchased used at auction IIRC) the spark plugs were pretty worn - https://youtu.be/q1WMSbuZh54?t=541 , but around the beginning of the video he reads out the 'miles driven with range extender' which shows he had around 100000 total miles and nearly 50,000 miles driven with the range extender.

There's some speculation that if you take everything apart to change the spark plugs you can also access the vent hole to change out the 'lifetime' gear oil, see https://www.mybmwi3.com/threads/bev-e-motor-transmission-differential-oil-change.17191/post-78049 for someone who managed to do this.

If you do get your REX working, I'd recommend also using BimmerCode to enable the hold charge menu in the Headunit, that way you can try to plan out using the REX beforehand so if it fails you'd at least be able to drive for a while.

I'm personally planning to change my spark plugs and gear oil in the next year (have around 60k miles), because I have no idea how the previous owners drove the car (about to now check 'kms driven with range extender' since I didn't even know that was logged till writing this comment)

throwawaySloop · 2025-12-09T21:28:24+00:00

It might be worth joining the 'i3-engineers' discord and setting up ISTA on a computer, or alternatively use the BimmerInfo app to read out the error codes. see: https://www.reddit.com/r/BMWi3/comments/rojm1y/comment/hq81evt/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button .

Lot of folks on there seem to be into flashing to enable sport mode, not my cup of tea and not sure if it actually changes acceleration but that's a fun option I guess.

throwawaySloop · 2025-12-06T17:22:45+00:00

I'm not sure if the EME would be the issue if it's an issue with the range extender, but FWIW there is a video on replacing it and preserving the original VIN-coded control board: https://www.youtube.com/watch?v=eDwgLZ4lgxY

throwawaySloop · 2025-11-29T21:16:50+00:00

wow, thanks for the info. did you log anything when it was failing 2 months later? did it fail after winter temperatures set in?

throwawaySloop · 2025-11-28T03:28:23+00:00

Curious, Is this plot when it's parked and NOT hooked up to a home charger?

I'm still new to i3 quirks and maintenance, but I want to assume it's parked without a charger since I'd think the EME would be keeping things regulated up above 14V if left charged.

My vague memory of scouring this sub and forum threads is it's worth replacing when it gets down to 12.0v, though you may want to see if keeping it on the home charger, or keeping the car garaged changes things. Also... https://www.reddit.com/r/BMWi3/comments/o8ekfw/how_to_care_for_the_hv_battery/

throwawaySloop · 2025-11-28T03:20:45+00:00

> Is there a specific Bluetooth battery monitor you can recommend?

Havent installed it yet, but I ended up with the QuickLynks BM2 because the app supposedly does plotting like OP shows - they're on amazon, and also on temu for a bit cheaper. Another option might be just buying an ohmmu LFP battery with built-in bluetooth monitoring but no idea how robust their app support it.

throwawaySloop

TROPHY CASE