Downsized to 18 inch wheels

turbobeagle · 10-26-2020, 04:23 PM

Just wanted to post another data point for folks that are considering wheel size changes.

I switched from OEM 20" w/ RFT to OEM 18" w/ RFT on my 540i M Sport (no DHP/DDC). I couldn't decide whether to go with RFT, but felt I wanted the security of being able to drive a bit further upon getting a flat, particularly since I have my children in the car.

My goal was to improve comfort, and while there is definitely a noticeable difference, it's not a simple home run. It seems to help in some cases, and have marginal benefit in others.

For small bumps, it definitely makes things smoother. There's a certain set of bumps that I don't think I even feel anymore.
For large bumps, it seems to still crash a bit in a way that I wish I could tune out. I'm really curious to know if non-RFTs would solve that.
Road noise is improved significantly on certain surfaces. On the highway, it's not a big difference, but in 40MPH driving on rough pavement, it's much quieter.
Handling seems fine. I did get the tires to squeal, which never happened before. So I definitely lost some capability there, but I'm ok with that. I assume that's more about switching from Summer to All-Season rubber compound rather than size.

I'm really tempted to swap the 18" OEM RFT (Goodyear Eagle Sport) with something like a Conti DWS 06 to see how it feels. I figure I can throw one of the 20" front wheels into the trunk as a full size spare. But honestly, the car feels so good already. In fact, it felt great even with the 20s. If anything, it's remarkable how good the sport suspension is with the barely-there sidewall of the 20s.

So it's hard to justify further expense. Just love tweaking

mffarrell · 10-26-2020, 04:43 PM

Quote:

Originally Posted by turbobeagle

Just wanted to post another data point for folks that are considering wheel size changes.

I switched from OEM 20" w/ RFT to OEM 18" w/ RFT on my 540i M Sport (no DHP/DDC). I couldn't decide whether to go with RFT, but felt I wanted the security of being able to drive a bit further upon getting a flat, particularly since I have my children in the car.

My goal was to improve comfort, and while there is definitely a noticeable difference, it's not a simple home run. It seems to help in some cases, and have marginal benefit in others.

For small bumps, it definitely makes things smoother. There's a certain set of bumps that I don't think I even feel anymore.
For large bumps, it seems to still crash a bit in a way that I wish I could tune out. I'm really curious to know if non-RFTs would solve that.
Road noise is improved significantly on certain surfaces. On the highway, it's not a big difference, but in 40MPH driving on rough pavement, it's much quieter.
Handling seems fine. I did get the tires to squeal, which never happened before. So I definitely lost some capability there, but I'm ok with that. I assume that's more about switching from Summer to All-Season rubber compound rather than size.

I'm really tempted to swap the 18" OEM RFT (Goodyear Eagle Sport) with something like a Conti DWS 06 to see how it feels. I figure I can throw one of the 20" front wheels into the trunk as a full size spare. But honestly, the car feels so good already. In fact, it felt great even with the 20s. If anything, it's remarkable how good the sport suspension is with the barely-there sidewall of the 20s.

So it's hard to justify further expense. Just love tweaking

Why didn’t you go with 19” wheels? They are not bad, and the ride is smooth. When I ordered my car, I really wanted 20”, but after hearing about blowouts and Ben rims I went with the 19”.

turbobeagle · 10-26-2020, 06:06 PM

I normally custom order, but this time I had time requirements that forced me to go with something on the lot. I knew ahead of time that I didn't want 20s, but the dealer really wanted to do the deal and discounted it further (took off the price of the wheels) to make it worthwhile. Once I had a choice of any wheel size, I figured I'd go for more sidewall.

LuvMyE92 · 11-17-2020, 09:19 AM

My car has the 19" and I would have preferred the 18" for the better ride quality, but I was working a good deal and decided not to wait. I immediately took off the runflats and replaced them with Pirelli all seasons. RFTs have gotten much better than they used to be, and the difference was not as noticeable as before (I do this with nearly every car I buy). The conventional tire does remove that "crashing" feel that the OP describes, as big bumps are absorbed better by the softer sidewalls.

I suspect that the difference in road noise that he noticed is largely due to going from summer to all season. Less aggressive tread means a quieter ride, typically.

Half of my rationale for doing this was that the car is a lease, so at turn-in time, I figured I could just put the original tires back on and all would be good. I did not figure on Covid and me working from home for 4 months, plus no travel, means that I'll be turning in this car (if I decide not to keep it) with about half of the expected mileage on it.

turbobeagle · 11-19-2020, 03:32 PM

Quote:

Originally Posted by LuvMyE92

I immediately took off the runflats and replaced them with Pirelli all seasons. RFTs have gotten much better than they used to be, and the difference was not as noticeable as before (I do this with nearly every car I buy)

Thanks for chiming in. I have held off on switching to non-RFTs because I've seen this mentioned in several threads now. It seems the Mercedes standard for RFTs might be a nice compromise.

Also, after a couple thousand miles driven, I've grown to love this setup as is with base M Sport suspension + 18". My brain seems to have stopped registering the "crashes".

mj41 · 11-20-2020, 07:33 AM

Thanks for starting this thread. Could use some help with the same type of deal. I am really considering pulling the trigger on a '21 M550 with summers on 20s. I am going out of my 430GC lease and i have a set of 18s with Blizzaks that I'd like to use up. I am no wheel tire expert but wanted to see if anyone had any guidance on this.

I have 18x8 square set up Rial X10 rims with 30mm offset. I'm sure its gonna look a bit weird coming from the 20's but for the winter i don't care. I also have 12mm spacers from my old F80 M3 that i could also use to push the smaller (square) set up closer to fender if need be. Thoughts?

Edit- Answered my own question- They won't fit as the bolt pattern is 5 x 120 on old wheels, new bolt pattern is 5 x 112 on the M550....bummer

cg217 · 03-17-2021, 09:14 PM

So I went in the opposite direction. while mine is a standard 530i and it came with the stock style 634 with the goodyear. it felt so soft, way to soft for me. I am sure the M sport suspension helps but the stock set up felt so floaty and when I turned it, thought it was the titanic. totally understand the plush feeling they were going for but changed the out for 19" 635's with continentals. huge difference, so glad that I changed it. felt way more connected. I almost went to 20" instead and very glad that I didn't. the 19' seems to be the sweet spot. you feel what's going on with the road but it still doesnt beat you up like you're talking about. have the 634 style with tmps, center caps for sale

turbobeagle · 03-17-2021, 09:45 PM

Coincidentally I just reinstalled my 20s a couple days ago to see what it's like in comparison. I will quickly be moving back to the 18s.

Glad the 19s are working out for you. I do think the M Sport suspension makes a big difference so we're comparing apples and oranges to some extent. Sounds like we both bought the wrong suspension

10-26-2020, 04:23 PM	#1
turbobeagle Lieutenant 399 Rep 417 Posts Drives: 2020 540i M Sport Join Date: Oct 2020 Location: SF Bay Area iTrader: (0)	Downsized to 18 inch wheels Just wanted to post another data point for folks that are considering wheel size changes. I switched from OEM 20" w/ RFT to OEM 18" w/ RFT on my 540i M Sport (no DHP/DDC). I couldn't decide whether to go with RFT, but felt I wanted the security of being able to drive a bit further upon getting a flat, particularly since I have my children in the car. My goal was to improve comfort, and while there is definitely a noticeable difference, it's not a simple home run. It seems to help in some cases, and have marginal benefit in others. For small bumps, it definitely makes things smoother. There's a certain set of bumps that I don't think I even feel anymore. For large bumps, it seems to still crash a bit in a way that I wish I could tune out. I'm really curious to know if non-RFTs would solve that. Road noise is improved significantly on certain surfaces. On the highway, it's not a big difference, but in 40MPH driving on rough pavement, it's much quieter. Handling seems fine. I did get the tires to squeal, which never happened before. So I definitely lost some capability there, but I'm ok with that. I assume that's more about switching from Summer to All-Season rubber compound rather than size. I'm really tempted to swap the 18" OEM RFT (Goodyear Eagle Sport) with something like a Conti DWS 06 to see how it feels. I figure I can throw one of the 20" front wheels into the trunk as a full size spare. But honestly, the car feels so good already. In fact, it felt great even with the 20s. If anything, it's remarkable how good the sport suspension is with the barely-there sidewall of the 20s. So it's hard to justify further expense. Just love tweaking
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10-26-2020, 06:06 PM	#3
turbobeagle Lieutenant 399 Rep 417 Posts Drives: 2020 540i M Sport Join Date: Oct 2020 Location: SF Bay Area iTrader: (0)	I normally custom order, but this time I had time requirements that forced me to go with something on the lot. I knew ahead of time that I didn't want 20s, but the dealer really wanted to do the deal and discounted it further (took off the price of the wheels) to make it worthwhile. Once I had a choice of any wheel size, I figured I'd go for more sidewall.
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11-17-2020, 09:19 AM	#4
LuvMyE92 Occasionally frequent poster 2999 Rep 2,744 Posts Drives: CT5V-Blackwing Join Date: Jan 2008 Location: RTP NC, USA iTrader: (0)	My car has the 19" and I would have preferred the 18" for the better ride quality, but I was working a good deal and decided not to wait. I immediately took off the runflats and replaced them with Pirelli all seasons. RFTs have gotten much better than they used to be, and the difference was not as noticeable as before (I do this with nearly every car I buy). The conventional tire does remove that "crashing" feel that the OP describes, as big bumps are absorbed better by the softer sidewalls. I suspect that the difference in road noise that he noticed is largely due to going from summer to all season. Less aggressive tread means a quieter ride, typically. Half of my rationale for doing this was that the car is a lease, so at turn-in time, I figured I could just put the original tires back on and all would be good. I did not figure on Covid and me working from home for 4 months, plus no travel, means that I'll be turning in this car (if I decide not to keep it) with about half of the expected mileage on it. __________________ Current inventory: F22 & G05 Cadillac CT5-V Blackwing w/3 pedals Past: E24,E28(3),E34,E36,E37,E38(2),E39(4),E46,E89,E92 (obviously),F01,F06,F10,F30,F87,G12,G30(2),G82(2)
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11-20-2020, 07:33 AM	#6
mj41 Private First Class 71 Rep 131 Posts Drives: '19 GC '16 X3 Join Date: Sep 2006 Location: Hudson Valley, NY iTrader: (0)	Thanks for starting this thread. Could use some help with the same type of deal. I am really considering pulling the trigger on a '21 M550 with summers on 20s. I am going out of my 430GC lease and i have a set of 18s with Blizzaks that I'd like to use up. I am no wheel tire expert but wanted to see if anyone had any guidance on this. I have 18x8 square set up Rial X10 rims with 30mm offset. I'm sure its gonna look a bit weird coming from the 20's but for the winter i don't care. I also have 12mm spacers from my old F80 M3 that i could also use to push the smaller (square) set up closer to fender if need be. Thoughts? Edit- Answered my own question- They won't fit as the bolt pattern is 5 x 120 on old wheels, new bolt pattern is 5 x 112 on the M550....bummer Last edited by mj41; 11-20-2020 at 09:34 AM..
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03-17-2021, 09:14 PM	#7
cg217 New Member 0 Rep 5 Posts Drives: BMW 530I Join Date: Dec 2020 Location: PHX iTrader: (0) Garage List 2017 BMW530i [0.00]	So I went in the opposite direction. while mine is a standard 530i and it came with the stock style 634 with the goodyear. it felt so soft, way to soft for me. I am sure the M sport suspension helps but the stock set up felt so floaty and when I turned it, thought it was the titanic. totally understand the plush feeling they were going for but changed the out for 19" 635's with continentals. huge difference, so glad that I changed it. felt way more connected. I almost went to 20" instead and very glad that I didn't. the 19' seems to be the sweet spot. you feel what's going on with the road but it still doesnt beat you up like you're talking about. have the 634 style with tmps, center caps for sale
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03-17-2021, 09:45 PM	#8
turbobeagle Lieutenant 399 Rep 417 Posts Drives: 2020 540i M Sport Join Date: Oct 2020 Location: SF Bay Area iTrader: (0)	Coincidentally I just reinstalled my 20s a couple days ago to see what it's like in comparison. I will quickly be moving back to the 18s. Glad the 19s are working out for you. I do think the M Sport suspension makes a big difference so we're comparing apples and oranges to some extent. Sounds like we both bought the wrong suspension
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