Coupe vs Convertible, N54 v N55

[GTi325]

Hey there all--

I'm looking to purchase a used 135i. I've seen some posts on 128 v 135, but I'm looking at coupe vs. convertible. It's going to be a 135i 6-speed manual, period, no budging. Must at least have sport, if not M-sport.

I've owned a Boxster S, and it was a very daily drivable convertible...how about the 1 series? I've driven e46 3 series and current 6 series convertibles, and I couldn't stand the cowl shake and general looseness, but Z4s were rigid enough for my liking. I haven't actually had an opportunity to drive a 1 convertible yet. Thoughts and experiences regarding the convertible's sturdiness? If you have any experience to compare it with a Z4, 986 Boxster, or AP2 S2000, I'd love to hear it.

Also, N55 vs N54. I think I want to keep it N54 based on feel from what I've driven, which means 08-10. I've found some good deals on 2011s in my range, is there a significant argument for an N55 besides the car being a couple years newer?

Anything I should look for besides rattling wastegate actuators and faulty HPFPs?

Thanks!

[135iam]

6 months ago (after looking for 4 months) I purchased an off lease 2010 135i, 6mt, convertible, sport package, space grey with black interior/top.

My previous weekend/track day car was a 2004 Honda S2000 with 21K miles (non- staggarded setup 255's all around), numerous suspension mods, and rollbar/seats/harnesses for track days. next step with the car would have been a full interior gutting, hardtop, and aero....but I never wanted to take the car that far. It was a fun car on track, but too boring on the street unless you really pushed it. I sold it 3 yrs ago when we adopted 2 kids.

So last year I was looking for the fun I had with the S2K with more streetable power and I ended up with the 135i.

Here are my thoughts comparing the two cars (135i sport package and S2000)
1. The S2000 is a much stiffer platform, and its a very noticable difference.
2. Bushings, I consider the rear subframe bushings a "must have" for anyone remotely serious about driving their 1 series hard. hit a bump on a cloverleaf going 60mph in a 35 and the car is jittery and a bit scary.
3. The lack of LSD is annoying (even on the street) for aggressive driving. Straight line accelleration is bearable without the LSD by modulating the gas, but throw the car in a corner 7/10th or harder and try to put on the power exiting and its bothersome.
4. Cowl shake, honestly I dont have much if any of it and there are alot of poor roads by me.
5. my car still has the stock suspension and alignment until the warranty is up (April). The car really needs more front grip. I plan to add:

• dinan fixed camber plates
• rear subframe bushings
• the most aggressive alignment I can get with that
• apex EC7 18x8.5 and 18x9.5 wheels with 255/265 rubber

The next step after that will be the HPA koni coilover conversion with Swift springs. If it still feels like it needs tightened up I will be going with the M3 front and rear arms after that.

if you dont need the back seat like I did, I am thinking you might be happier with a Z4.

Sorry for the long post, its my first one on here so I figured I'd make it a good one

[128Convertibleguy]

The actual chassis on my 128i convertible is quite stiff. The suspension (to be modded) and subframe bushings are a different matter, but it's the same on the coupe.

The only real issue is the 200 pounds or so that was needed to stiffen the chassis.

[GTi325]

Originally Posted by 135iam

6 months ago (after looking for 4 months) I purchased an off lease 2010 135i, 6mt, convertible, sport package, space grey with black interior/top.

...

if you dont need the back seat like I did, I am thinking you might be happier with a Z4.

Sorry for the long post, its my first one on here so I figured I'd make it a good one

Thanks for that. Pretty much what I needed to hear. I'd rather have a 135 coupe vs a Z4. I don't need a drop top, but I seem to be able to find the convertibles in nice shape at great prices. I honestly don't want to have to do much to the car in order to be happy with it. I don't mind modding the car, and probably will down the road, but I have a project car, and I have a certain appreciation for a car that does what it needs to in it's stock form. It may get a golf tee mod and a lower stage chip that can run a stock intake or possibly an intake early on.

Are there any good hardtop options for the convertible for the winter?

Thoughts on twin scrolls vs twins?

[JimD]

The 1M is based upon the n54. The aftermarket also seems greater for the n54. But early n54s also had HPFP issues. There may be more power available in a n54 but it would be hard to say the n55 isn't adequate. And the HPFP has an extended warranty and nobody seems to be having issues with the latest design (based solely on posts, I drive a 128).

I have not driven the convertibles you mention but my 128i vert is not as solid as a Miata but probably is as solid as my old Fiat 124 spyder. It shakes a bit on really rough roads. It also has noticably more noise round big trucks. But on reasonable roads and with normal levels of noise, it is solid and quiet. It has big X-braces under the passengers compartment but still has some twist over big bumps. Windshield is solid, however, it is cited by BMW as strong enough for roll-overs.

I don't see why you would want a hard-top. The soft-top is easy to heat and cool and quiet enough unless you get stuck beside an 18 wheeler on the highway or something. You need the windscreen, however, to minimize buffeting. With it, ladies do not need to put their hair up or use a ball cap. It costs $300-400 so it may be worth checking on used ones or to ask for from a dealer. The windscreen blocks off the back seat, however, so with 4 aboard you have to live with the breeze.

You might want to look at a 1 with the top down to understand why the convertible is best.

[Fifty3bags]

Originally Posted by GTi325

Thanks for that. Pretty much what I needed to hear. I'd rather have a 135 coupe vs a Z4. I don't need a drop top, but I seem to be able to find the convertibles in nice shape at great prices. I honestly don't want to have to do much to the car in order to be happy with it. I don't mind modding the car, and probably will down the road, but I have a project car, and I have a certain appreciation for a car that does what it needs to in it's stock form. It may get a golf tee mod and a lower stage chip that can run a stock intake or possibly an intake early on.

Are there any good hardtop options for the convertible for the winter?

Thoughts on twin scrolls vs twins?

I don't really know the differences in the twin scroll compared to normal turbo. But the n54 with twins is yielding better results from tuning.

[135iam]

Originally Posted by GTi325

Are there any good hardtop options for the convertible for the winter?

Thoughts on twin scrolls vs twins?

As far as I know, there are no hard top options.

I test drove alot of 2011 and 2010 BMWs before I bought mine. 11's with the DCT trans, 2010 autos, 6 speed manuals (N54 and N55). My favorite was the N54 manual. Second favorite was the N55 DCT auto.

After researching the effects of modding each engine, I decided the N54 was a good choice. So I looked for the lowest mileage N54 I could find.

[2012_135i]

A while back one of these coupe vs. 'vert threads resulted in some serious blood letting.

I tested both a convertible 135i and a coupe at the time of purchase. They rode very differently. The 'vert was noticeably harsher on Honolulu streets to the point of being unacceptable for me, whereas the coupe was firm but much more supple. I was surprised at the difference. There would probably be less of a difference on smooth, unrepaired asphalt but there is precious little of that around here.

Stock performance of the n54 and n55 are essentially the same but my understanding is you can do more in the way of tuning with the n54. I'm not a modder so that makes no difference for me although I will probably get a basic tune at some point which will be good enough. I liked the idea of 1 turbo getting the same stock performance as 2 turbos with possibly less things to go wrong.

[RoundelM3]

My wife's car is a 2011 128i M-Sport convertible 6MT, and after updating the wheels and tires to 18" (same as 135i) non-runflats, it rides and handles very nicely. I had an E92 335i with the N54, and it seemed that there were a lot more tuning options for that engine than for the N55. That said, Dinan did come out with both S2 and S3-level tuning software for both engines, although the latter required a bigger intercooler and oil cooler, but the N55 tune produced less power than the comparable N54 tune.

The N55 as applied to the LCI E9x and E8x did have some good tuning options, but like the newest N55 in the F3x, it was tuned more for efficiency than power. That said, there were a few single-turbo upgrades available for the N54 that produced more power than the twins. The twin-scroll turbo is larger, and takes better advantage of power pulses with one scroll per "bank". The only thing to keep in mind is that as you push the power output up, the engine produces more heat and additional oil cooling is highly recommended if you go over 15 lbs. of boost. The N54 intercoolers were not terribly efficient, and a good 5" replacement made a noticeable difference without any other mods. Haven't done this to my N55 F30, but I'm sure the same principle applies.

[128Convertibleguy]

Originally Posted by 2012_135i

A while back one of these coupe vs. 'vert threads resulted in some serious blood letting.

I tested both a convertible 135i and a coupe at the time of purchase. They rode very differently.

I'd be surprised if that wasn't tires or tire pressure. Mind you, I could be wrong and surprised.

But I don't know what else could make the ride "very" different.

[Bob Z.]

I used to have a Porsche Boxster S and find my current 2013 135i convertible (6MT and M-Sport) to be a much better car on a day-to-day basis, and also better than the Mercedes SLK 350 I used to own as well. The softop is one of the best I've experienced - great sound insulation, construction, etc. and I treated mine with 303 Protectant, which will ensure it stays like new.

By the way, mine is still up for sale here in the classifieds but probably deep within the for sale ads since I've not been that serious about selling it lately.

[JimD]

I agree, I don't think there is any major difference. I drove a coupe at PCD, that was all they had, and didn't notice any real difference. My vert has the sport suspension and my wife's does not. Putting non-run flats on mine made it ride essentially the same. No major difference sport versus non. M-sport affects badges, not suspension, it is the same as sport.

But over big discontinuities the vert does "shudder" which might be what the comment is based upon. I would expect less of this in the coupe.

[GTi325]

Originally Posted by 2012_135i

A while back one of these coupe vs. 'vert threads resulted in some serious blood letting.

I tested both a convertible 135i and a coupe at the time of purchase. They rode very differently. The 'vert was noticeably harsher on Honolulu streets to the point of being unacceptable for me, whereas the coupe was firm but much more supple. I was surprised at the difference. There would probably be less of a difference on smooth, unrepaired asphalt but there is precious little of that around here.

Stock performance of the n54 and n55 are essentially the same but my understanding is you can do more in the way of tuning with the n54. I'm not a modder so that makes no difference for me although I will probably get a basic tune at some point which will be good enough. I liked the idea of 1 turbo getting the same stock performance as 2 turbos with possibly less things to go wrong.

I lived on Oahu for a bit, and I don't remember the roads being as bad as they are here, that being said, sounds like the coupe is a little more forgiving. I'm not terribly worried about the tuning market. I would likely do a tune on either car, but I have a car that's faster than a tuned/bolt-on 135, and if I feel that I need to drive faster on a certain day, well, I have options. I was more interested in power delivery. It just seems that the twins would be better on power, while the single may be better in real world fuel economy.

Originally Posted by Bob Z.

I used to have a Porsche Boxster S and find my current 2013 135i convertible (6MT and M-Sport) to be a much better car on a day-to-day basis...

I still have some left over 303, haha. I thought the Boxster was very daily driveable. I don't mind stuff as long as it's graceful over poor road surfaces that occur in everyday driving. I guess noise in a Boxster is just different since the motor is right behind you and it's a beautiful sound.

I took my Boxster to AutoX and then drove my dad's 1M for a fun run and beat my best time in the Boxster by a full second on my first try. I just can't afford a 1M; hence, my search for a 135--I know they're completely different animals, I've driven them both.

Originally Posted by JimD

...
M-sport affects badges, not suspension, it is the same as sport.
...

Are the swaybars, dampers, springs all the same? Brakes? Honestly, I'm a sucker for black headliners in cars, which is one of the stupid reasons why I wanted an M-Sport but it's not a deal breaker.

[135iam]

Originally Posted by GTi325

Are the swaybars, dampers, springs all the same? Brakes? Honestly, I'm a sucker for black headliners in cars, which is one of the stupid reasons why I wanted an M-Sport but it's not a deal breaker.

Yes

[Gray_Panther]

I can attest that the soft top on my parent's 128i is built well. Insulates sound and no flapping or annoyances. Even though it is an automatic, it is still an experience to drive with the top down. My coupe 6MT is just fun in a different sense.

[Gray_Panther]

Post pics of the VW's, please!!!

I grew up in MKII Golfs/GTI's and my uncle still has his G60 red corrado

[2012_135i]

Originally Posted by 128Convertibleguy

I'd be surprised if that wasn't tires or tire pressure. Mind you, I could be wrong and surprised.

But I don't know what else could make the ride "very" different.

It was just my subjective experience that the convertible's ride was harsher when hitting bumps, road patches, and potholes. Both cars were brand new so tires should have been the same, but yeah, if there was an inflation difference that could have had an impact. My understanding is that coupes and convertibles have somewhat different suspension setups because of differences in body rigidity so I chalked it up to that.

[2012_135i]

Originally Posted by GTi325

I lived on Oahu for a bit, and I don't remember the roads being as bad as they are here...

Don't know about Memphis, but Honolulu has some of the worst roads in the country now. Things have been deteriorating for a while and the situation has made the papers on a number of occasions. Road crews are working on the problem but can't seem to make any headway. Kalakaua Ave., one of the main roads in and out of Waikiki, is atrocious.

[granracing]

I owned an 2001 S2000 for several years and sold it this past summer then bought a 135i Convert. ONLY reason I sold the S2k was because we had a second kid. For 5 years, I made it work even with one child in the family.

For S2000s, drive both an AP1 and an AP2. They do feel different; I personally like the AP1s more. I'm sure with mods they become much closer.

The s2k and 135i are just different cars. For back curvy roads, I do miss the s2k. It handles extremely well especially when properly set-up (still stock), feels more sporty and tossable, and the power band is quite usable for back roads.

The 135i is more refined in nature, a more relaxed ride, and for some reason to me doesn't feel as sporty driving. If you have or are planning on kids any time soon, at least the 135i can work with an accomodating wife. The top in the 135i is perfectly fine for winter months.

I like both cars just for different reasons. A tune on the 135i makes it a much more fun car. Keep that in mind if you test drive one.

[ejm3]

2 degrees here this morning and my soft top was fine.
Of course the car was in the garage overnight.

[135iam]

Originally Posted by ejm3

2 degrees here this morning and my soft top was fine.
Of course the car was in the garage overnight.

I have been surprised how many people post about driving 1 series convertibles in the winter. I am thinking about selling off my 3rd vehicle and picking up a set of snow tires for the stock wheels and taking it out next winter.

[ejm3]

Don't use me as an example. I have an RX350 I will drive the other 4 days to work this week.
Today just happened to be sunny and clear (albeit cold) so I took it just to run it.

I still have the stock summer RFTs on it so I have to pick a day here and a day there when I'm absolutely certain there will be no snow and thats pretty much what I do.

This crappy winter thats translated into about 1 day a week i take it.