M owners Brakes How do you like them Track?

[swamp2]

Originally Posted by ArtPE

1 not really...for a given speed it would be ~ the same...
but braking would take longer for the same pedal force because the tire is not perpendicular to the road...friction decreases...you would have a bit more to get rid of due to the elevation change (potential energy) Ep ~ m g delta h

2 not much...the cars mass would remain the same
distance would ~ the same...
although heat dissipation would improve due to larger thermal mass

Disagree.

On point 1 he asked about work performed by the brakes. The total work performed by the brakes would be larger for a stop from any given speed. Kinetic energy and potential energy both must be converted to heat by the brakes. I agree that lower friction will affect braking distance and that will be a small effect for most normal road grades.

On point 2 braking performance would suffer. Maybe not by a lot but the brakes must convert all of a vehicles kinetic energy to heat. "Converting" non rotating mass to rotating mass increases the systems total kinetic energy (translational + rotational) for a given tranlational speed. More energy is always negative for brake performance. This would be mitigated by the much larger thermal mass of the rotors which might even reduce braking temperatures.

[swamp2]

Originally Posted by earlyapex

One of the reasons for multi-piston calipers is feel, not braking distances recorded on milimeter accurate gps-accelerometers. You missed the point of my post.

Agree for sure about braking distance not being improved by multiple pistons. I am interested to hear more about these measurements. Slightly off topic but why use gps "acclerometers" to get (or try to get) mm accuracy? Wouldn't a traditional accel be better?

[TLud]

I'm not the genius that my old man with a PhD in physics is, so I'm sure he would and you will point out that everything I'm about to say is dead wrong, but here goes...

Originally Posted by Irb Digital

1. Since gravity has a significant impact on V (uphill and downhill) and changes the amount of work needed from the brakes, a down hill braking section would require more work from the brakes, correct?

Originally Posted by ArtPE

1. not really...for a given speed it would be ~ the same...
but braking would take longer for the same pedal force because the tire is not perpendicular to the road...friction decreases...you would have a bit more to get rid of due to the elevation change (potential energy) Ep ~ m g delta h

Originally Posted by Irb Digital

1. In regards to your answer to my first question. IMHO the tire is still perpendicular to the road, the vehicle's center of gravity is what changes. If a vehicle is braking on a downhill more weight would be sitting on the front tires. Wouldn't this increase friction as well as contact patch? You answered not really but looking at the last sentence it seems that there is a direct relation between (E ~ pE) and the elevation change, due to gravity.

Art, not to nitpick, but I think you somewhat confused Irb with the bolded language. The tire remains perpendicular to the road at all times unless the car leaves the ground. The more correct way of stating it would be to say that the force of gravity on the tire is not normal (perpendicular) to the road.

Wouldn't the gravitational force be designated as mg * sin(a), where a is the gradient?

Also, on a downward slope, I don't understand how decreased friction caused by changing slope (as opposed to changing surface) is really different from what Irb meant by gravitational force having more of an effect on forward acceleration. Either way you look at it, the mg changes from pulling the car straight down to pulling the car forward, shifting the center of gravity more over the front wheels, decreasing the friction between the rear wheels and the ground, increasing the friction between the front wheels and the ground, and thereby (1) increasing the force necessary to stop the vehicle, and (2) increasing the work the front brakes must do to the extent the rear wheels are traction-limited. Of course, all of this assumes constant slope. Increasing or decreasing slope adds a slew of other factors.

[earlyapex]

Originally Posted by swamp2

Slightly off topic but why use gps "acclerometers" to get (or try to get) mm accuracy? Wouldn't a traditional accel be better?

I was just trying to be funny. Guess I missed.

[Radiation Joe]

130+ at Watkins Glen on street tires
140+ at Road America on street tires
120+ at Laguna Seca
130+ at Thunderhill

150+ at Brainerd in the RS6 with those 8 piston Brembos that were good for about 4 laps.

[earlyapex]

Art,

This is an argument over a fairly subtle point. I'm just pointing out the fact that fixed calipers (which require multiple pistons, duh!) are marginally better at the edge. The real argument over brakes should work, roughly in descending order more or less, like this:
1) tires
2) weight
3) pad temp resistance
4 - tied) weight distribution
4 - tied) brake mass for heat absorption and fade resistance
6) brake design (caliper stiffness, pistons, etc.)

We are spending all out time at the bottom of the list. My point is that a fixed caliper is less flexible and easier to modulate. You think that isn't important because the M3 performed so well in some Car and Driver test from 100 to zero (which doesn't come close to replicating track braking).

I say it is important based on 10 years of experience with multiple different cars in actual club racing at many different tracks, but it's still a subtlety like changing from 1/16 to 1/32 of overall toe-out. Can I feel the difference? Yes. Could 99% of the population without experience at 10/10ths in racing? No way because they are going to miss the braking pionts by dozens of feet anyway.

Is it going to make a big difference in overall objective performance? No

Do more pistons sound good to balding stockbrokers? Absolutely, but so does a multi-cam high-revving V8...

Originally Posted by ArtPE

any of us trying to out smart 20 PhD's at BMW (actually Conti/Teves) is laughable...

Ok, I'm going to be a bit of a smart*ss here, so just try to laugh along.

I guess Porsche, ferrari, viper, z06, gtr, lotus, aston martin, Sti, Evo, lamborghini, audi, etc. (basically EVERY SINGLE performance car manufacturer in the world other than BMW) should fire all their blithering idiot engineers for using those stupid fixed calipers and hire the geniuses at BMW (who are in the process of converting to fixed calipers thermselves starting with Brembos on the 1 series, so they better hire them quickly as they are fast becoming fellow idiots).

If BMW engineers are so concerned with making sure they don't over-engineer things, why did they use a ridiculously complicated and expensive high-rev V-8, when the REGULAR (not Z06) chevy corvette engine has more horsepower and significantly more torque while using signficantly less fuel?

The point is that all these guys have to factor in marketing (sounds good but doesn't make that much difference - ie big red brembos), actual performance (more horsepower/more expensive and stickier tires) and economics (those stickier tires don't last as long, those multi-piston fixed calipers won't make a hoot of difference for 99.9% of drivers).

Are fixed calipers better? Yes. Are they "better enough" to justify the economics? Probably not, but then neither is that fancy V8.

Originally Posted by ArtPE

the M3 will never exceed 110 on most tracks...and the lowest speeds are 40 or so, so the 100-0 is a much more demanding test than most realize...a 2 minute lap may have 6 braking zones...1 per 20 sec...

OK, here I have to flat disagree completely. That's not even close to accurate (and may explain why you are ignoring the subtleties which become more important the faster you go). The M3 will exceed 130 on most tracks and 135 on many. The reduction in kinetic energy from 135 to 50mph (like Turn10a at Road Atlanta) is 163% more than 110 to 50. (which, admittedly, has nothing to do with caliper stiffness (or pistons for that matter)).

But it's harder to hit the braking points perfectly and maximize braking at 135 than 110. The harder it is to do, the more accurate you want the system to be.

You are also ignoring the fact that most track sessions are at least 30 minutes. Using your math, that's 90 back to back maximum braking efforts. The brakes aren't going to come close to cooling completely in the 20 seconds in between, and as they get hotter and hotter, the subtleties matter more and more.

Originally Posted by ArtPE

it's ALL about E = 1/2 m v^2...the fact that the M3 weighs 300-400 lbs less than the RS4/ISF/C63 has a lot to do with it's braking efficiency, as does tire size...

Actually (as you are pointing out), tire friction and weight are far more important than pistons and calipers . See list at start of post.

Originally Posted by ArtPE

99.9% think we are good drivers...0.1% are...and a good driver will make either systeme work, and out-brake 99.9% of us with the 'lesser' system...

Is driver skill more important than system ability? absolutely.

But the more skill you have, the more you are going to recognize, appreciate and utilize the subtleties of things like a finely tuned alignment and more sublte brake modulation.

Originally Posted by ArtPE

wanna brake better? practice and take some schooling...it's a street car
all differences are so minute they are masked by driver skill levels...

For the masses, yes. But for those that can appreciate the subtleties? Well, that's theoretically why you would buy a BMW or porsche, right? They've got to design the car for those that can tell the difference because that translates to all the people who can't through word of mouth, magazine articles, internet forums, etc.

I've just ordered some pagids and am taking the 3000 mile M3 to sebring on October 5th, so I'll have an actual anecdotal report on real brake experience with good pads.

[earlyapex]

The OP point is still a good question. This car has an incrediblely complicated/advanced/expensive engine design, perhaps the most sophisticated and flexible chassis/suspension setup of any car, and brakes that don't meet the standards established by the rest of the car. Why?

The answer? Probably some combination of economics and supplier relationships. At least they didn't stick us with a non-dry-sump leaking mass market toyota engine like porsche does with the 911.

[footie]

Heat in it's many forms are the only real issues with taking a car to the track, that is as long as the braking power is up to the job in the first place. Pad temperature, fluid temperature and disc temperature are the thing to concentrate on.

Getting a good air flow around the disc and calipers will aid the first two points, upgrade the fluid and fit braided pipes should help improve pedal feel and reduce the amount of travel over prolonged periods on the track.

The actual design isn't as important, not from trackdays.

Feel free to disagree.

P.S.
Porsche conduct consecutive braking tests from up to 150mph when designing their systems, that might explain why their brakes are regarded the best manufacturer systems in the business.

[lucid]

Originally Posted by earlyapex

If BMW engineers are so concerned with making sure they don't over-engineer things, why did they use a ridiculously complicated and expensive high-rev V-8, when the REGULAR (not Z06) chevy corvette engine has more horsepower and significantly more torque while using signficantly less fuel?

Although I agree with some of your points, the above point is unsubstantiated. We discussed that at some length, and there is no evidence to support it that I am aware of. Take the engines out and strap them onto a testbed. Run them steady at say, 100hp, 200hp, 300hp, 400hp, outputs and measure consumption. Then we have some data to evaluate the claim. One can argue that high revs can results in higher fuel consumption, but compression ratio is the major factor in efficiency. 10.7 vs 12.0. Obviously, there are other factors as well. Comparing efficiency numbers of the entire package is a different story (there is a 500lb weight difference to begin with).

[ace996]

Originally Posted by earlyapex

Art,

This is an argument over a fairly subtle point. I'm just pointing out the fact that fixed calipers (which require multiple pistons, duh!) are marginally better at the edge. The real argument over brakes should work, roughly in descending order more or less, like this:
1) tires
2) weight
3) pad temp resistance
4 - tied) weight distribution
4 - tied) brake mass for heat absorption and fade resistance
6) brake design (caliper stiffness, pistons, etc.)

We are spending all out time at the bottom of the list. My point is that a fixed caliper is less flexible and easier to modulate. You think that isn't important because the M3 performed so well in some Car and Driver test from 100 to zero (which doesn't come close to replicating track braking).

I say it is important based on 10 years of experience with multiple different cars in actual club racing at many different tracks, but it's still a subtlety like changing from 1/16 to 1/32 of overall toe-out. Can I feel the difference? Yes. Could 99% of the population without experience at 10/10ths in racing? No way because they are going to miss the braking pionts by dozens of feet anyway.

Is it going to make a big difference in overall objective performance? No

Do more pistons sound good to balding stockbrokers? Absolutely, but so does a multi-cam high-revving V8...




Ok, I'm going to be a bit of a smart*ss here, so just try to laugh along.

I guess Porsche, ferrari, viper, z06, gtr, lotus, aston martin, Sti, Evo, lamborghini, audi, etc. (basically EVERY SINGLE performance car manufacturer in the world other than BMW) should fire all their blithering idiot engineers for using those stupid fixed calipers and hire the geniuses at BMW (who are in the process of converting to fixed calipers thermselves starting with Brembos on the 1 series, so they better hire them quickly as they are fast becoming fellow idiots).

If BMW engineers are so concerned with making sure they don't over-engineer things, why did they use a ridiculously complicated and expensive high-rev V-8, when the REGULAR (not Z06) chevy corvette engine has more horsepower and significantly more torque while using signficantly less fuel?

The point is that all these guys have to factor in marketing (sounds good but doesn't make that much difference - ie big red brembos), actual performance (more horsepower/more expensive and stickier tires) and economics (those stickier tires don't last as long, those multi-piston fixed calipers won't make a hoot of difference for 99.9% of drivers).

Are fixed calipers better? Yes. Are they "better enough" to justify the economics? Probably not, but then neither is that fancy V8.




OK, here I have to flat disagree completely. That's not even close to accurate (and may explain why you are ignoring the subtleties which become more important the faster you go). The M3 will exceed 130 on most tracks and 135 on many. The reduction in kinetic energy from 135 to 50mph (like Turn10a at Road Atlanta) is 163% more than 110 to 50. (which, admittedly, has nothing to do with caliper stiffness (or pistons for that matter)).

But it's harder to hit the braking points perfectly and maximize braking at 135 than 110. The harder it is to do, the more accurate you want the system to be.

You are also ignoring the fact that most track sessions are at least 30 minutes. Using your math, that's 90 back to back maximum braking efforts. The brakes aren't going to come close to cooling completely in the 20 seconds in between, and as they get hotter and hotter, the subtleties matter more and more.




Actually (as you are pointing out), tire friction and weight are far more important than pistons and calipers . See list at start of post.




Is driver skill more important than system ability? absolutely.

But the more skill you have, the more you are going to recognize, appreciate and utilize the subtleties of things like a finely tuned alignment and more sublte brake modulation.



For the masses, yes. But for those that can appreciate the subtleties? Well, that's theoretically why you would buy a BMW or porsche, right? They've got to design the car for those that can tell the difference because that translates to all the people who can't through word of mouth, magazine articles, internet forums, etc.

I've just ordered some pagids and am taking the 3000 mile M3 to sebring on October 5th, so I'll have an actual anecdotal report on real brake experience with good pads.

phenomenal post, really. That just about says it all, but some will still debate just for the sake of debate.
Be good,
TomK

[earlyapex]

Originally Posted by lucid

Although I agree with some of your points, the above point is unsubstantiated. We discussed that at some length, and there is no evidence to support it that I am aware of. Take the engines out and strap them onto a testbed. Run them steady at say, 100hp, 200hp, 300hp, 400hp, outputs and measure consumption. Then we have some data to evaluate the claim. One can argue that high revs can results in higher fuel consumption, but compression ratio is the major factor in efficiency. 10.7 vs 12.0. Obviously, there are other factors as well. Comparing efficiency numbers of the entire package is a different story (there is a 500lb weight difference to begin with).

Fair enough, no scientific test with a control for the placebo effect () but that doesn't mean there isn't a modicum of truth. I can't get 27mpg in sixth gear at 50mph on cruise control in my M3 (i've tried, it's 26mpg BTW).

The basic problem for the M3 is terrible gearing for mileage (and a plain thirsty engine).

Anyway, the vette engine has more power and torque with dramatically less cost and complication, so in terms of the "only as complicated as it has to be" argument in favor of the M3's brake calipers; the M3 engine loses the same argument dramatically.

I'd rather have a badass engine than brake calipers any day, but that doesn't change the fact that some corners were cut and the M3 nuts can't/won't admit it.

Not to mention, the pointlessness of the OP question of, basically, why doesn't the M3 have as good a brakes as my car that costs more than twice as much?

Well, that question pales in comparison to "why doesn't the a brand new $100k 911S come with a dry sump?" I can buy better brakes than a GT3 for $3,500 for my M3 and it would cost the porsche guys more than 10x that to get an engine as trackable as mine.

What corner would you rather have cut?

[lucid]

Originally Posted by earlyapex

Anyway, the vette engine has more power and torque with dramatically less cost and complication, so in terms of the "only as complicated as it has to be" argument in favor of the M3's brake calipers; the M3 engine loses the same argument dramatically.

I'd rather have a badass engine than brake calipers any day, but that doesn't change the fact that some corners were cut and the M3 nuts can't/won't admit it.

Not to mention, the pointlessness of the OP question of, basically, why doesn't the M3 have as good a brakes as my car that costs more than twice as much?

Well, that question pales in comparison to "why doesn't the a brand new $100k 911S come with a dry sump?" I can buy better brakes than a GT3 for $3,500 for my M3 and it would cost the porsche guys more than 10x that to get an engine as trackable as mine.

What corner would you rather have cut?

I actually pretty much agreed with all of that, and expressed similar views earlier in this thread (post #29). I just wouldn't call it "corner cutting", but would rather use design languages such as "trade-off". I am sure the M3 could have been shipped with a better brake system as there is always a better system to be designed/had. But, as I've said earlier, and as you're saying here, probably more than 99.9% of the folks on this forum, including myself, wouldn't really be able to utilize it fully even on a track. The stock system is pretty solid (but does seem to require some minor mods for track work; I'm tired of my brake fluid boiling and will have it flushed this weekend, and might replace lines and pads soon as well) and you get it for a base price of $56k. What else can one ask for? RED calipers I guess...

[Radiation Joe]

Originally Posted by lucid

Although I agree with some of your points, the above point is unsubstantiated. We discussed that at some length, and there is no evidence to support it that I am aware of. Take the engines out and strap them onto a testbed. Run them steady at say, 100hp, 200hp, 300hp, 400hp, outputs and measure consumption. Then we have some data to evaluate the claim. One can argue that high revs can results in higher fuel consumption, but compression ratio is the major factor in efficiency. 10.7 vs 12.0. Obviously, there are other factors as well. Comparing efficiency numbers of the entire package is a different story (there is a 500lb weight difference to begin with).

Don't forget that the Corvette final drive ends up with something less than 2000 rpm at 70 mph. Put that gearing in an M3 and you'll get 28 mpg also. Honestly, I don't understand why BMW doesn't do that with the final gear (6th with MT and 7th with DCT). You can probably hit the speed limiter in the next lower gear anyway.

[Stunnerable]

Good point.. but why can't they use the same gears and ratios from the DCT in the Manual.. I wouldn't mind shifting more.

[lucid]

Originally Posted by Radiation Joe

Don't forget that the Corvette final drive ends up with something less than 2000 rpm at 70 mph. Put that gearing in an M3 and you'll get 28 mpg also. Honestly, I don't understand why BMW doesn't do that with the final gear (6th with MT and 7th with DCT). You can probably hit the speed limiter in the next lower gear anyway.

Yep, that would be included in the packaged to packaged comparison I mentioned. With regards to the M3 gearing, if they won't make 6th taller in MT, why not make 3rd, 4th and 5th shorter?

[lucid]

Originally Posted by Stunnerable

Good point.. but why can't they use the same gears and ratios from the DCT in the Manual.. I wouldn't mind shifting more.

I posted before seeing this post. Agreed.

[DJ9]

Originally Posted by earlyapex

Art,

This is an argument over a fairly subtle point. I'm just pointing out the fact that fixed calipers (which require multiple pistons, duh!) are marginally better at the edge. The real argument over brakes should work, roughly in descending order more or less, like this:
1) tires
2) weight
3) pad temp resistance
4 - tied) weight distribution
4 - tied) brake mass for heat absorption and fade resistance
6) brake design (caliper stiffness, pistons, etc.)

We are spending all out time at the bottom of the list. My point is that a fixed caliper is less flexible and easier to modulate. You think that isn't important because the M3 performed so well in some Car and Driver test from 100 to zero (which doesn't come close to replicating track braking).

I say it is important based on 10 years of experience with multiple different cars in actual club racing at many different tracks, but it's still a subtlety like changing from 1/16 to 1/32 of overall toe-out. Can I feel the difference? Yes. Could 99% of the population without experience at 10/10ths in racing? No way because they are going to miss the braking pionts by dozens of feet anyway.

Is it going to make a big difference in overall objective performance? No

Do more pistons sound good to balding stockbrokers? Absolutely, but so does a multi-cam high-revving V8...




Ok, I'm going to be a bit of a smart*ss here, so just try to laugh along.

I guess Porsche, ferrari, viper, z06, gtr, lotus, aston martin, Sti, Evo, lamborghini, audi, etc. (basically EVERY SINGLE performance car manufacturer in the world other than BMW) should fire all their blithering idiot engineers for using those stupid fixed calipers and hire the geniuses at BMW (who are in the process of converting to fixed calipers thermselves starting with Brembos on the 1 series, so they better hire them quickly as they are fast becoming fellow idiots).

If BMW engineers are so concerned with making sure they don't over-engineer things, why did they use a ridiculously complicated and expensive high-rev V-8, when the REGULAR (not Z06) chevy corvette engine has more horsepower and significantly more torque while using signficantly less fuel?

The point is that all these guys have to factor in marketing (sounds good but doesn't make that much difference - ie big red brembos), actual performance (more horsepower/more expensive and stickier tires) and economics (those stickier tires don't last as long, those multi-piston fixed calipers won't make a hoot of difference for 99.9% of drivers).

Are fixed calipers better? Yes. Are they "better enough" to justify the economics? Probably not, but then neither is that fancy V8.




OK, here I have to flat disagree completely. That's not even close to accurate (and may explain why you are ignoring the subtleties which become more important the faster you go). The M3 will exceed 130 on most tracks and 135 on many. The reduction in kinetic energy from 135 to 50mph (like Turn10a at Road Atlanta) is 163% more than 110 to 50. (which, admittedly, has nothing to do with caliper stiffness (or pistons for that matter)).

But it's harder to hit the braking points perfectly and maximize braking at 135 than 110. The harder it is to do, the more accurate you want the system to be.

You are also ignoring the fact that most track sessions are at least 30 minutes. Using your math, that's 90 back to back maximum braking efforts. The brakes aren't going to come close to cooling completely in the 20 seconds in between, and as they get hotter and hotter, the subtleties matter more and more.




Actually (as you are pointing out), tire friction and weight are far more important than pistons and calipers . See list at start of post.




Is driver skill more important than system ability? absolutely.

But the more skill you have, the more you are going to recognize, appreciate and utilize the subtleties of things like a finely tuned alignment and more sublte brake modulation.



For the masses, yes. But for those that can appreciate the subtleties? Well, that's theoretically why you would buy a BMW or porsche, right? They've got to design the car for those that can tell the difference because that translates to all the people who can't through word of mouth, magazine articles, internet forums, etc.

I've just ordered some pagids and am taking the 3000 mile M3 to sebring on October 5th, so I'll have an actual anecdotal report on real brake experience with good pads.

Very good response!

[Irb Digital]

I just want to say thanks to all for posting. It seems that this thread went to hell and back, and turned out to be extremely informative, mature thread with some awesome arguments for/against BMW's choice on brakes and a lot of other gee whiz info that I enjoy learning, or RELEARNING from my high school and college years.

I stated earlier that I know I wouldn't see the difference, I just like to know I have the best technology available(within reason) of a $70k luxury sports car. It's not a deal breaker, but certainly something I take into consideration when buying a vehicle of this caliber. One thing for sure is upgrading lines and pads would do more for your dollar than any BBK. I never thought that this car should match the track prowess that is in a GT series 911, but it is nice to know if you could extract the max performance of a car, you've got the best equipment available.

I still haven't decided on which vehicle I will purchase, but its pretty much down to the M3 sedan and IS-F. My first choice is the M3, but thats mostly on paper, as I've yet to test drive one. I'm going against my long time preference of a manual, but I can't help but to be extremely impressed and intrigued of these new automated manuals. It will probably come down to money, and the BMW is significantly more expensive once similarly equipped, but if I can get an 09 for a good discount, I'll be finally in one of my long time dream cars. When I was younger there were a few cars I vowed to own:

S2000 : Being a long time F1 fan, everyone raved that this was the closest thing to a poor man's F1 that one could buy. I did get the joy of owning one and haven't driven a better performance car since. The Z I currently own is a better touring car. I bought it because it was more comfortable with my 6ft2in frame, and my convertible days were numbered. The Z just doesn't have the soul or appeal to my senses the way the S2000 did.

Any M series BMW : If they have the balls to call it the "Ultimate Driving Machine", I've got to experience it. Plus, I need to experience what causes all the C&D editors to treat the M3 as God's own chariot. If it happens she's in Alpine White(homage to the F1 team), red interior (homage to the red in the ///M logo).

Ferrari : Explanation not needed

Thanks again for everyone's input

[Radiation Joe]

Originally Posted by lucid

Yep, that would be included in the packaged to packaged comparison I mentioned. With regards to the M3 gearing, if they won't make 6th taller in MT, why not make 3rd, 4th and 5th shorter?

5th is 1:1 and as such is fixed. The other gears have to be adjusted relative to 5th. That's why it's not as simple as changing the final drive.

[MarksM]

Originally Posted by Radiation Joe

5th is 1:1 and as such is fixed. The other gears have to be adjusted relative to 5th. That's why it's not as simple as changing the final drive.

Here try this for gear calculations I think it is correct.

Gear Calculations

[Radiation Joe]

Originally Posted by MarksM

Here try this for gear calculations I think it is correct.

Gear Calculations

Very nice.

I have one on my work computer called "speed in gears.xls" Your data sheets look better than mine, though.

[lucid]

Originally Posted by Radiation Joe

5th is 1:1 and as such is fixed. The other gears have to be adjusted relative to 5th. That's why it's not as simple as changing the final drive.

I wasn't suggesting they change the final drive. Why can't they change some of the intermediate ratios? Why can't the 5th gear ratio be changed as there is nothing specific about the 1:1 ratio I am aware of that requires it to be fixed? Is this about shaft spacing?