Quote:
Originally Posted by Evan135
I agree they will match the rear axle ratio to match engines. I have been through several gear ratio verses speed calculations for many manual transmission BMW's. I am a little obsessed with gearing as it is as important as the engine with how a car feels to drive.....to me anyway
All Bmw's I have run numbers on have the car hit 62 mph in second gear. There may be exceptions, but I am not aware of them. The 1M is using a 265/35/19 tire that is about 6% taller than the stock 245/35/18 135i tire. The 1M engine has about 500 rpm more useful rpm the the stock N54, or about a 7% wider power band. My guess is that BMW might use a 3.46 to cover those 2 differences.
Don't shoot me if I am wrong, but it would match what they have done elsewhere. They might use something a little lower like a 3.23 if the 1M is getting too close to the M3.
I am glad this has come up. One of the reasons M cars are always quicker and feel better is that they are geared for performance not mileage and they usually get all the gear they can use to make it to 62mph in second.
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I ran some numbers using the M3 gearbox with the larger tires of the 1M.
Here's what I got on the 1M with the 3.85 FD. Gear-top speed at 7k rpm.
1st- 35.05
2nd- 59.3
3rd- 90.07
4th- 119.59
5th- 142.32
6th- 163.58
I would think that BMW would want to go a bit taller on 2nd to get it to 60mph, if they are concerned about advertising that all important number.
Drop in the 2.32 second gear ratio from the 135i MT, and mph goes up to 61.34mph.
Better selling number with only 1 manual shift instead of 2.
What numbers did you get?
The calculator I am using is acting funny.
Here's the 1M with the 135i MT gear ratio's and the M's 3.85 FD.
1st- 34.63
2nd- 61.34
3rd- 92.41
4th- 120.61
5th- 142.32
6th- 167.43
If these numbers are right, then it might be better to use the 135i's MT gear ratios with the M's FD LSD.
I don't recall the 1M engine having any more revs though.
Some reviews said that the engine felt like it pulled stronger all the way to red line, some didn't.
But, I think red line is still 7k.
Have you seen it at 7500rpm for red line?