RPMs at 80 mph in 6th (manual) 135i. Anybody???

[GT3]

Originally Posted by Katera

Ok, I get it. It's why I asked the question, I really didn't know. /shrug No dumb questions and all that....:iono:

Sorry man, didn't mean to come off as if I was busting your balls.

I think I remember seeing your posts over at Cayman Club if I recall correctly. Glad you eventually found a car that meets your needs. :smile:

[cracka]

Originally Posted by Balls

2800 to be precise. I set the cruise at 80 today (which happened to be the speed limit of that Autobahn section--130 Km/h).

2800 RPM here too. And as I'm in the US, I had to break the law to find out for you. :wink:

[JCtx]

Thanks a lot to both of you:w00t:.
Since no manuals are available to test-drive, will have to somewhat extrapolate the experience by driving a 135i the way I want it but auto, and a 328i manual (only manual available).

Hey, does the 328i have the same CDV deal? Thx.
JC

[SlickShift]

It's "RPM" not "RPMs" by the way. :wink:

[wnta135]

JT asked for the speed chart for the 128 so ...
As pointed out by others, these are based strictly on tire size, gear ratio and final drive ratio. Let the flames begin on how much HP it takes to get there.

[imported_Katera]

Originally Posted by GT3

Sorry man, didn't mean to come off as if I was busting your balls.

I think I remember seeing your posts over at Cayman Club if I recall correctly. Glad you eventually found a car that meets your needs. :smile:

Yea, I posted over there for a long time. I still LOVE the Porsche Cayman and Club Cayman is a incredible website for Croc drivers. Honestly, I really do love Porsche and most of the guys over there remind me a ton of the guys here on 1addicts. For example when I posted over there that I had chosen the 135i Vert over the Cayman, and wished them all well? Overwhelmingly positive response from those guys. 9/10 wished me well and pointed out what a great car the 1 was. Of course it's hard to be jealous when you drive the best looking car on the planet...the Cayman. Passionate, dedicated and a tight family just like here on 1addicts. I had my own reasons for choosing the 1, but I will still haunt there from time to time.

[tommyb13662]

Well i can say stock with just a tune it will hit 160 it felt rather effortless.

[Matticus91]

Originally Posted by tommyb13662

Well i can say stock with just a tune it will hit 160 it felt rather effortless.

Might want to check the date on a post before you drag it from the depths of hellllllll

[Tenspeed]

I find it interesting that a 135i with an overdriven 6th gear is 81 mph at 3000 RPM when my E88/N55 135i with a 1:1 7th gear is running 90 mph at 3000 RPM. Every 1000 RPM is 30 mph for my car in 7th gear.

[Cavpilot2k]

And yes, this is one hell of a zombie thread. Back from the dead!!

Okay, so the OP has a big problem with his assumptions,.

"the 135i has slightly smaller tires (245s vs 255s), so it has to turn slightly more rpms at the same speed"

That measurement is tire WIDTH, not DIAMETER. Tire width has almost nothing to do with how many revolutions it has to make at a given speed (if you want to get really advanced, yes a wider tire will be pulled out a very small amount into a wider radius by centrifugal force, like you see on top fuel dragsters when they spin out, but the effect too small to have any effect at the RPMs we are traveling at).

Tire diameter (17" vs 18") will have an effect on how many RPM it has to make at a given speed, as the circumference of a 17" tire is slightly less than the circumference of an 18" tire, thereby necessitating more RPM to cover the same distance in the same span of time (MPH).

So look at tire diameter as a variable, not tire width. Some 135s come with 17", some with 18" (sport and M-Sport). Same with 328's and 335's.

All that said, my MT 135 with 18" tires does 80 MPH at about 2800 RPM.

[Gunslinger1971]

Originally Posted by Cavpilot2k

Tire diameter (17" vs 18") will have an effect on how many RPM it has to make at a given speed, as the circumference of a 17" tire is slightly less than the circumference of an 18" tire, thereby necessitating more RPM to cover the same distance in the same span of time (MPH).

So look at tire diameter as a variable, not tire width. Some 135s come with 17", some with 18" (sport and M-Sport). Same with 328's and 335's.

All that said, my MT 135 with 18" tires does 80 MPH at about 2800 RPM.

The dimensions your referring to here are wheel diameter. They have little to do with you rpms at cruising speed. I believe what you need to look at is tire height/diameter.
When you look at tire measurement the second number will indicate your sidewall height.
My 328xi has 225/45/17 tires on it. They are 225mm wide, sidewall height is 45% of width, and they are made for 17" wheels.
I am simplifying this but let's say I want to put 19" wheels on my car but want to maintain the same 3000rpm at 80mph with my manual transmission. I would need to mount a tire (that would fit obviously) that would have the same 24" height as the ones I'm taking off. Maybe a 245/35/19 for example.

I've used tire calculators online that can tell you tire height when you input a size. This is what you need to be looking at.

[Dackelone]

I think your gonna need to take speedo error into account. Also tire size/brand bc every tire will have a different overall diameter. Also tachometers can be off.


For my 2010 US spec 135i with 6 speed manual trans... with Michelin PS3's in 225/255's on the factory 18" wheels... here is my speedo on the (electronic)V-Max limiter. Now even though the speedo says 155 mph, my GPS said I was "only" traveling at 240 kph or 148.148 mph.

So that's 27.435 mph for every 1,000 rpm. or... at 80 mph that would be 2,915 rpm's in 6th gear.




PS: the fastest I have ever seen via my GPS is a speed of 285 kph on the Autobahn.

[Cavpilot2k]

Originally Posted by Gunslinger1971

The dimensions your referring to here are wheel diameter. They have little to do with you rpms at cruising speed. I believe what you need to look at is tire height/diameter.
When you look at tire measurement the second number will indicate your sidewall height.
My 328xi has 225/45/17 tires on it. They are 225mm wide, sidewall height is 45% of width, and they are made for 17" wheels.
I am simplifying this but let's say I want to put 19" wheels on my car but want to maintain the same 3000rpm at 80mph with my manual transmission. I would need to mount a tire (that would fit obviously) that would have the same 24" height as the ones I'm taking off. Maybe a 245/35/19 for example.

I've used tire calculators online that can tell you tire height when you input a size. This is what you need to be looking at.

You are correct, for the most part in that the tire diameter has little (but not nothing) to do with RPM. Yes, you 17" wheels are mounted with 45mm high tires, and if you put 18" wheels on, you would likely use 35mm high tires, but while they are close, the diameter of those two circles would not be the same, and would therefore result in a slight change in RPM. (17"+45mm+45mm does not = 18"+35mm+35mm)

My whole point was that the OP mentioned tire width as a factor, and width is most definitely not a factor.

[Gunslinger1971]

Originally Posted by Cavpilot2k

You are correct, for the most part in that the tire diameter has little (but not nothing) to do with RPM. Yes, you 17" wheels are mounted with 45mm high tires, and if you put 18" wheels on, you would likely use 35mm high tires, but while they are close, the diameter of those two circles would not be the same, and would therefore result in a slight change in RPM. (17"+45mm+45mm does not = 18"+35mm+35mm)

My whole point was that the OP mentioned tire width as a factor, and width is most definitely not a factor.

I think we are getting our wires crossed here and I apologize for that.

I stated that wheel diameter has little to do with RPM but tire diameter does. The tire height/diameter directly affects your RPM at any speed.
Also, I was generalizing a bit In my comparisons but just to be clear the second number in a tire size (225/45/17) does not refer to an actual measurement but an aspect ratio of the first number. So in the above case the sidewall height is 45% of the width (225mm).

[TheCaptain]

Originally Posted by Cavpilot2k

You are correct, for the most part in that the tire diameter has little (but not nothing) to do with RPM. Yes, you 17" wheels are mounted with 45mm high tires, and if you put 18" wheels on, you would likely use 35mm high tires, but while they are close, the diameter of those two circles would not be the same, and would therefore result in a slight change in RPM. (17"+45mm+45mm does not = 18"+35mm+35mm)

My whole point was that the OP mentioned tire width as a factor, and width is most definitely not a factor.

I think there might be a misunderstanding about the middle number in the tire size. The middle number is not the height in mm like the first number, it's the percent of the width. So a tire that is 245/35/18 has a sidewall of 85.8mm (35% of 245mm), not a sidewall of 35mm.

[Cavpilot2k]

Originally Posted by TheCaptain

I think there might be a misunderstanding about the middle number in the tire size. The middle number is not the height in mm like the first number, it's the percent of the width. So a tire that is 245/35/18 has a sidewall of 85.8mm (35% of 245mm), not a sidewall of 35mm.

Yes, you are correct (both of you).
I didn't bother to do the calculations (didn't see any reason to), so I just sub'd the number in as a measurement placeholder/arbitrary figure.
The point is that wheel/tire diameter can play a small part in RPM, but tire width, as stated by the OP, does not.

[Vigilante375]

The gearing is the major factor for RPMs.

Tire height of a tire will cause the speedo and RPMs to be off by a little. Granted you're only going up or down a few inches/mm's.

But this is a very outdated thread so no need to continue on when the OP has, more than likely, moved on.

[germ]

1. Definitely go with 6 MT
2. You are confused on what the tire spec numbers mean
3. But it doesn't matter. RPM in 6th gear@80 mph is just below 3k
4. I have to ask why you care. What does a difference of a few hundred RPM do to you? RPM do not relate directly to mileage
5. I don't know if the shifter is the same as 328i, but the 135i shifter is pretty good, though not exceptional as, say, a Honda S2000. Some people feel the need to do the clutch valve mod. I am not one of them.
6. You will get ~20 mpg if you don't hold back

[6MT_Addict]

Originally Posted by germ

1. Definitely go with 6 MT
2. You are confused on what the tire spec numbers mean
3. But it doesn't matter. RPM in 6th gear@80 mph is just below 3k
4. I have to ask why you care. What does a difference of a few hundred RPM do to you? RPM do not relate directly to mileage
5. I don't know if the shifter is the same as 328i, but the 135i shifter is pretty good, though not exceptional as, say, a Honda S2000. Some people feel the need to do the clutch valve mod. I am not one of them.
6. You will get ~20 mpg if you don't hold back

Check the date and comments before responding pls. OP posted 8 years ago

[suspenceful]

I have trapped 157mph (GPS confirmed) in the 1/2 mile. The speedo was pegged at 160mph for those runs and I was in 5th gear. The car still pulls like a freight train and I'm sure I've hit actual speeds of 165-170mph before. I have no doubts that it would continue to pull to almost 200mph in 6th gear. I'm still on stock turbos.


1/2 Mile NoFlyZone Trap Speed by Jacob Spence, on Flickr

Watch my speedo in the first run. It was one of my slower runs (1st run).