Racing 450's discussion

[rablack21]

So, I have been doing some number crunching this morning and determined that a 250R can't keep up with a 450 gear for gear due to the ratio difference of the two transmissions regardless of running gear ratio(that is normally used by racers). I am using a quad gear ratio and speed calculator available by Maul tech atv. In summary, a 450 has a faster top speed in 2nd than a 250r. Same for 3rd and 4th, and 5th gear can go either way depending on the ratio sprockets you are using. This info is based on 2 machines set up for mx with 18" tires.

So my first question is for the people that have both a 250r and a 450: Does this info seem to line up with your experience?
It seems to line up with my experience out of the track, so I thought I would ask others.

So, if this information is true and understood, then I think I have been going about trying to beat them the wrong way. I have been trying to gear my 250R to match their speed gear for gear. I can get close, but they still pull more top speed per gear in the gears mostly used on the track. Plus, I noticed the engine doesn't like to pull those high of gears out of corners and in thick loamy dirt.

So now my thinking is this. Due to the ratios of the transmissions, my 3rd gear should match closer but faster to their 2nd gear, My 4th gear over their 3rd gear, my 5th over their 4th. This works out in the numbers and seems to match what I have at time experience on the tracks.

So next question is: Those who have raced both or own both, is this also your experience?

This all seems to make sense in my head, so I thought I would get some feedback from others. This is a discussion so feel free to post your thoughts and experiences.

[Tbone07]

I mean the math makes sense I guess. If the ratios in the transmission are different, and assuming same sprocket ratio and tire size, then the 450 is geared taller (internally) because it has the extra torque and HP to pull those ratios.

Yes the 450's I've ridden have much more "luggability" than any 2-stroke I've ridden (outside of a KTM 300XC). The KTM could pull the same gearing as the CRF450 I had.

Now I've never ridden a 250r above 275CC (my PC2000), and it has great torque and mid-range for a little 275, but not as much as the 450's. Gear selection is much more crucial to maintain speed. I'm eagerly awaiting my 350 Sphynx so I can compare the two

Basically we are stuck with transmission ratios that are optimized for a 250cc engine

[C-Leigh Racing]

4 poke has more weight, so more power to the ground = speed
4 poke has a larger bore engine, so more power to the ground = speed.

250R, is lighter, so power is lost from tires spinning & loosing ground to the 4 poke.
Bore size & weight on the rear tires, is key to a 2 stroke running with todays 4 pokers.
That heavier 4 poke tires digging in & pulling makes the difference, so you got to work on that on the 2 stroke.
If you build a 250R with high compression, like 220~240 lbs compression where that engine will grunt & pull low rpms & learn where to shift gears to keep the engine in the meat of the power output, you can pull them 4 pokers, but that 250Rs got to dig in & pull, not sit on top of the dirt & spin.
Rooster tails look good "sometimes" but you aint going no where.

Ok, now did you understand anything I listed ?.
To put it more easy to understand, watch a tractor pull sometime.
Neil

[05450r]

^^This!.. Pulling out of the corners the 4 stroke shines, and with less rider effort. So to take what Ra said and throw in a few other factors. You will have to work harder on a two stroke, more shifting, clutching, braking, etc. Im sure the two stroke bore and stroke will have a factor as well. Big bore stroke, more torque than small bore, type of porting, pipe, etc. Another factor,4 strokes have engine braking so depending on the track they may not need to brake as much making the transition from braking into the corner to pulling out of the corner alot easier with less tire spin. Suspension setup, depending on what arms and shocks, as well as rear shock, this could be a huge factor! Some of the new 450r front ends with Ltr geometry handle amazing!! I honestly prefer the 450's, however if the turned like a 250r it would be even better, and thats what the Ltr geo does. If it was me I would consider the total package, thats why I got a hybrid, best of both....Hahahha

[rablack21]

4 poke has more weight, so more power to the ground = speed
4 poke has a larger bore engine, so more power to the ground = speed.

250R, is lighter, so power is lost from tires spinning & loosing ground to the 4 poke.
Bore size & weight on the rear tires, is key to a 2 stroke running with todays 4 pokers.
That heavier 4 poke tires digging in & pulling makes the difference, so you got to work on that on the 2 stroke.
If you build a 250R with high compression, like 220~240 lbs compression where that engine will grunt & pull low rpms & learn where to shift gears to keep the engine in the meat of the power output, you can pull them 4 pokers, but that 250Rs got to dig in & pull, not sit on top of the dirt & spin.
Rooster tails look good "sometimes" but you aint going no where.

Ok, now did you understand anything I listed ?.
To put it more easy to understand, watch a tractor pull sometime.
Neil

Neil, Thanks for weighing in. Everything that you listed makes sense. I guess I should have mentioned that this scenario is of course in an ideal world. For example, the numbers that I came up with assume equal traction and don't take into account acceleration. These numbers are just purely top speed capabilities due to transmission ratios. Here's an example:

The calculator says an 04 450 with factory sprockets (13-38) with 18" tires turning 9,000 rpms goes:
2nd gear- 37mph
3rd gear- 45.2
4th gear- 53.7
5th gear- 62.5

Comparison: 250r with 14-39 gearing with 18" tires @ 9,000 rpms goes:
2nd gear- 31.6 mph
3rd gear- 39.1
4th gear- 48.9
5th gear- 60.0

Now, a 450 will almost never use 5th gear on a track so it can somewhat be dismissed. Let's assume both quads are racing, just came out of a corner neck and neck, both are turning 9,000 rpms in 3rd gear and have equal traction. The numbers say (all other conditions being equal), the 450r has a higher top speed in that gear than the 250r.

Therefore in this scenario, I'm thinking in order to compensate for this, I wonder if it would be better to gear the 250r low enough to reach 4th gear in this section of the track instead of using 3rd.  Is any of this making sense?

[C-Leigh Racing]

I see what your saying.
Now if the 2 stroke has more hp, high compression hp, the gears could be shifted sooner than the 4 poke & pull it like that.

The ratios your using, what year trans ?. If 88/89, try the old 85/86 ratios & see what you come up with.
The old 85/86 gears, we used those on the big bore few years back & when shift to 3rd off the gate, would pull off & leave the rest of the field.
Neil

[05450r]

Ra, your too smart and putting too much thought into it(lol), grab a stack of sprockets (front and rear) and hit the track, see what works best for that track. Tracks and weather change from week to week, grab a buddy on a 450 and go rip it up!!

[89Longrod]

You are comparing apples to oranges its never gonna equal out for you...For example you listed 9,000 rpm for the 450...But it is still making power till around 10,500-11,500 depending on the motor work and the ECU etc so why wouldn't you take that into account? Also like everyone else has mentioned you ride each machine entirely different from the other...2 strokes are about being smooth and flowing lines... 4 strokes are about being lazy and knowing you can clear any jump on the track with 10 feet of run in. This is one of the biggest arguments on the VitalMX forums what it comes down to is the 2 stroke rider needs to be a better rider to begin with and do everything right the entire race and pick to correct lines to even have a chance.

[atvmxr]

So now my thinking is this. Due to the ratios of the transmissions, my 3rd gear should match closer but faster to their 2nd gear, My 4th gear over their 3rd gear, my 5th over their 4th. This works out in the numbers and seems to match what I have at time experience on the tracks.

^^^this

250r has a 6th gear, 450 dont.  my 05 450 was geared stupid high from the factory, dropped the front sprocket one tooth.  still stalled in corners all the time.  the 450 was fun to play around on, but I never felt comfortable with it for any serious MX jumps

[Burns363R]

This is what i have been saying all along.  Thats why i run 15-37 gearing with my sphynx 363.   It allows me to shift my bike just like my can am.  i ride them very close to the same way.  The extra power of the 363 is able to pull the tall gearing and give me the speed i need in the gears i need to make it run like a 4stroke.

[rablack21]

You are comparing apples to oranges its never gonna equal out for you...For example you listed 9,000 rpm for the 450...But it is still making power till around 10,500-11,500 depending on the motor work and the ECU etc so why wouldn't you take that into account? Also like everyone else has mentioned you ride each machine entirely different from the other...2 strokes are about being smooth and flowing lines... 4 strokes are about being lazy and knowing you can clear any jump on the track with 10 feet of run in. This is one of the biggest arguments on the VitalMX forums what it comes down to is the 2 stroke rider needs to be a better rider to begin with and do everything right the entire race and pick to correct lines to even have a chance.

I was using the 9,000 rpms as an example. The outcome is still the same with the numbers of the 450 at 10,000rpm. The 450 is always faster gear for gear until you gear to the last gears, which I am purposely discounting because you don't race mx in the top gear. I realize you guys are taking into account rider smoothness and his lines choice and whatnot, but I am trying to exclude that as well. We can assume that these riders are of the same caliber and both perfect at what they do.I do realize thought that you guys have many valid points about human skill.  I am really just comparing machine to machine here.

[chrisr]

One thing to remember also is you can have all the horse power in the world but if your suspension isn't setup right you'll never see the checkered flag.  I've never raced quads but have rode for 30+ years........damn I'm old.  I did however grow up around dirt tracks and working on dirt cars.  I've seen many "underdogs" with way less horse power than the rest of the field take the win because they understood their suspension and experimented non stop with adjustments and different components.  I do understand there is quite a difference between a dirt car and a quad but a slight edge can be found in suspension setups.  Like Neil said above getting those rear tires to dig and bite is a big thing.

[rablack21]

Ra, your too smart and putting too much thought into it(lol), grab a stack of sprockets (front and rear) and hit the track, see what works best for that track. Tracks and weather change from week to week, grab a buddy on a 450 and go rip it up!!

lol. Just thinking about it from a machine to machine comparison here. I am even excluding track conditions. I do realize they account for something as well though. I am assuming that both guys have come prepared to race a specific track, both have their machine prepped perfectly, both have perfect riding skill for their machine. Now, if it were under those conditions, machine vs machine, how would a 250r beat a 450r?

[Burns363R]

I think ryan is saying that the suspension is negligible... basically its a 2 stroke vs 4 stroke debate for gear selection going in and coming out of corners and hitting jumps.  On a 2 stroke your shifting a lot more and typically have less forgiveness than a 4 stroke.

[rablack21]

This is what i have been saying all along.  Thats why i run 15-37 gearing with my sphynx 363.   It allows me to shift my bike just like my can am.  i ride them very close to the same way.  The extra power of the 363 is able to pull the tall gearing and give me the speed i need in the gears i need to make it run like a 4stroke.

You make a good point Kyle. And actually, at 15-37 is where a 250r gear speeds basically match a 450 at their peak powers.