TRX250R.ORG
Riding Styles => MX => Topic started by: rablack21 on November 14, 2013, 09:48:55 AM
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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.
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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
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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
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^^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
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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?
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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
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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!!
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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.
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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
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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.
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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.
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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.
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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?
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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.
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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.
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I race both my 4 stroke and 2 stroke every weekend. I race the same guys in both production and Open class. I run my R in the open class and my can am in the production class. The other guys use the same bikes. Im here to tell you that it will never be easy on a 2 stroke. but you can make it easier like i have by gearing up.
If you gear down, you will be shifting much much more often.
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If you gear down, yes your 4th gear will match there 3rd gear, but... your 2nd and 3rd gears will be much much shorter and when your in those gears and you stab the throttle, you will fly through them so quickly you will be continiously shifting up and down very quickly. Which will also create issues in corners and mis shifts.
Gearing up allows you to increase speed in each gear but also increase the rev range in each gear. Essentially slowing the revs of the motor so that your blasting through the gears as fast. Mind you are still accelerating at the same rate, but your using tq instead of HP.. You have to have a very good motor to race this way, but its essentally what 4 strokes are doing now with the longer gears.
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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
These numbers are from an 88/89 trans, never checked an older trans.
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.
Yes, I think you're getting what I'm talking about.
I race both my 4 stroke and 2 stroke every weekend. I race the same guys in both production and Open class. I run my R in the open class and my can am in the production class. The other guys use the same bikes. Im here to tell you that it will never be easy on a 2 stroke. but you can make it easier like i have by gearing up.
If you gear down, you will be shifting much much more often.
True, you would have to shift more often. However, I'm don't think you can pull those gears without a large big bore. I tried 15-38 once on my quad and it has some goods and bad. It was a short track though and didn't seem to work out very well. In honesty, I didn't give it a full thorough testing.
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i agree that you need alot of motor to pull those gears. I sometimes contemplate droping back a little gear.... One thing i have to train myself is that i can do some of the jumps in 3rd gear now because of the gearing but i still try to grab 4th and i do it to early and bog the motor. Its all about getting used to it. You deff dont ride it like a small bore motor. I would say you need to be in the 60hp neighborhood to pull those gears on a MX track.
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If you gear down, yes your 4th gear will match there 3rd gear, but... your 2nd and 3rd gears will be much much shorter and when your in those gears and you stab the throttle, you will fly through them so quickly you will be continiously shifting up and down very quickly. Which will also create issues in corners and mis shifts.
Gearing up allows you to increase speed in each gear but also increase the rev range in each gear. Essentially slowing the revs of the motor so that your blasting through the gears as fast. Mind you are still accelerating at the same rate, but your using tq instead of HP.. You have to have a very good motor to race this way, but its essentally what 4 strokes are doing now with the longer gears.
I agree with what you are saying, but I would think that you wouldn't necessarily need 2nd anymore since your 3rd gear would be lower. For example, a section on the track that you usually use 2nd and 3rd gear with a high gear ratio maxed out, maybe your could use 3rd and 4th with a low gear ratio not maxed out. I don't know this to be completely true, just curious if you couldn't do this, especially if your motor can pull the supper tall gears.
I agree, it takes a strong motor to pull the really high gears.
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i agree that you need alot of motor to pull those gears. I sometimes contemplate droping back a little gear.... One thing i have to train myself is that i can do some of the jumps in 3rd gear now because of the gearing but i still try to grab 4th and i do it to early and bog the motor. Its all about getting used to it. You deff dont ride it like a small bore motor. I would say you need to be in the 60hp neighborhood to pull those gears on a MX track.
Agreed^^^. So, if you don't have a motor than can pull the really high gear, what is your next best option? This is the question I keep asking myself.
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Your mindset is correct, but i dont think its going to pull/ feel like you want it to. As far as comparing power to a 4 poke.
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So what do you do to beat them then? When I go to the track to race, I have to assume that the other guys have studied the track, prepped their quads, and have them dialed in just like I do, and have the stamina to finish the race. So what do I do differently to beat them then? Cause the transmission ratios say that they are faster than me gear per gear, if everything else is equal. So, if I don't stay a gear ahead, how can I beat them?
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So what do you do to beat them then?
If you cant beat them, join them!!...ahhhahhaaaha
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So what do you do to beat them then? When I go to the track to race, I have to assume that the other guys have studied the track, prepped their quads, and have them dialed in just like I do, and have the stamina to finish the race. So what do I do differently to beat them then? Cause the transmission ratios say that they are faster than me gear per gear, if everything else is equal. So, if I don't stay a gear ahead, how can I beat them?
Be better than them. Have your shocks dialed in better, on the off season practice going in and coming out of the corners and do cardio training. I have a friend, Robbie Horton who was a pro motorcross racer right out of high school, he was pro-am in high school and rode for Kawasaki. I rode with him many days on his practice track and he spent most of his time practicing coming into and leaving the corners.
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So what do you do to beat them then? When I go to the track to race, I have to assume that the other guys have studied the track, prepped their quads, and have them dialed in just like I do, and have the stamina to finish the race. So what do I do differently to beat them then? Cause the transmission ratios say that they are faster than me gear per gear, if everything else is equal. So, if I don't stay a gear ahead, how can I beat them?
Get your technique as close to perfect as you can, study and practice the tracks you frequent
...and get a BB motor
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Get your technique as close to perfect as you can, study and practice the tracks you frequent
...and get a BB motor
I think the last part of your comment, Tbone, may be what the inevitable outcome is.
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Get your technique as close to perfect as you can, study and practice the tracks you frequent
...and get a BB motor
Pretty much this.... I have been working on the perfect forumula to make my bike 4 stroke like and i have it very close. but at the end of the day you still dont have the low end power they do. I have gained a ton of low end over any other 250R engine i have ever ridden, but its still not as strong as low as a 4 stroke.
You have to be a better rider, and make less mistakes. What really kills you on a 2 stroke is the unforgiving of the motor. If you make a mistake it will cost you much more on a 2 stroke than a four stroke. Putting in a ton of practice time on your bike will help you perfect you technique. I lay down virtually identical lap times on my can am and honda. Thats because im very good at switching back and forth between bikes and i know how to ride each of them differently.
But you will never make the bike as easy to ride as a 4 stroke. thats why there are so many good riders these days. 4 strokes have made it easier for an average rider to be good. I had a buddy of mine who is the current atva 450 national champion on my 250R and he looked like he was learning to ride for the first time. He is a much faster rider than I am on his 450, but he wouldnt have a chance even after a month of riding my R at keeping up with me on it.
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Thanks to everyone for their input.
Pretty much this.... I have been working on the perfect forumula to make my bike 4 stroke like and i have it very close. but at the end of the day you still dont have the low end power they do. I have gained a ton of low end over any other 250R engine i have ever ridden, but its still not as strong as low as a 4 stroke.
You have to be a better rider, and make less mistakes. What really kills you on a 2 stroke is the unforgiving of the motor. If you make a mistake it will cost you much more on a 2 stroke than a four stroke. Putting in a ton of practice time on your bike will help you perfect you technique. I lay down virtually identical lap times on my can am and honda. Thats because im very good at switching back and forth between bikes and i know how to ride each of them differently.
But you will never make the bike as easy to ride as a 4 stroke. thats why there are so many good riders these days. 4 strokes have made it easier for an average rider to be good. I had a buddy of mine who is the current atva 450 national champion on my 250R and he looked like he was learning to ride for the first time. He is a much faster rider than I am on his 450, but he wouldnt have a chance even after a month of riding my R at keeping up with me on it.
I am curious to see how the smart carb may play into this with the low end grunt. When I rode Oldschoolr's R with his billet smart carb, I was amazed at how low the rpms could get and it still have instant throttle response. I will let you know when I get mine in.
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Lol im getting one to if they ever release them. A member on here also offered to send me there 40.5 billet to test for them.
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So in the end we come up with what?? The 4 poke just has us beat at certain things due to design. Thats ok, for me anyway, because when they get their ass handed to them by a machine that is well over 20 years old that can't put the power to the ground, a rider with a grin from ear to ear and the sweet smell of pre mix in the air is worth every bit of ridiing the R. If we lose then we still have a grin from ear to ear and we go slow through the pits so everyone can enjoy race fuel and Castor 927.
Ryan, I think we can do the best we can with the quads we have, no matter what engine size, by riding our asses off and being so comfortable on the machine that we strive for a flawless and fluid lap. Luckly we aren't at the pro level and they/we get tired quickly so lets focus on the fitness side as well.
Or as mentioned lets go get a 4 poke and hit the krispy cream on the way back after McDonalds!! I can't lie though I will someday have a Hybrid as those machines are sick!
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^^^^ Fitness and perfect laps will make the biggest difference on a 2 stroke... No joke. Is till dont think i have gone a perfect 5 lap moto without a mistake on my R.... Frusterates the heck out of me....
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So in the end we come up with what?? The 4 poke just has us beat at certain things due to design. Thats ok, for me anyway, because when they get their ass handed to them by a machine that is well over 20 years old that can't put the power to the ground, a rider with a grin from ear to ear and the sweet smell of pre mix in the air is worth every bit of ridiing the R. If we lose then we still have a grin from ear to ear and we go slow through the pits so everyone can enjoy race fuel and Castor 927.
Ryan, I think we can do the best we can with the quads we have, no matter what engine size, by riding our asses off and being so comfortable on the machine that we strive for a flawless and fluid lap. Luckly we aren't at the pro level and they/we get tired quickly so lets focus on the fitness side as well.
Or as mentioned lets go get a 4 poke and hit the krispy cream on the way back after McDonalds!! I can't lie though I will someday have a Hybrid as those machines are sick!
So right you are, Joe! LOL. Won't stop me from giving them hell either way. If they lose to me, I offer them no solace!
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Let me throw this out there.....do you go big, big bore and run a flywheel weight to be more 4 stroke like power?
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Let me throw this out there.....do you go big, big bore and run a flywheel weight to be more 4 stroke like power?
I have often wondered the same thing.
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a heavier fly wheel wont give you more tq. it will smooth out the power and make the engine rev slower. But it wont give you any more tq to power out of corners with.
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Do the powervalve cylinders give more low end grunt? I know going bigger is the major factor.
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Yea I remember reading the power-valve motors are great until a certain cc then the gains aren't as noticeable. Maybe one of these other guys know the exact size cc that's max for a PV to still be worth is. I thought it was somewhere around 33-350 cc's.
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I had a ESR 330 PV engine. It pulled really well down low but it had such terrible over rev that i couldnt stand hitting big jumps with hit. It seemed that i always would need to shift going up the face of a jump.... Granted my 330 was just a TRX9 port job with a 205 psi compression. So it wasnt a crazy engine, we wont even talk about reliability.
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a heavier fly wheel wont give you more tq. it will smooth out the power and make the engine rev slower. But it wont give you any more tq to power out of corners with.
And help reduce stalling in the corners, one more way to help reduce the mistakes.
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Like everyone has already said it is hard to beat the new 450's. That being said I watched both my brother's over the years beat them every weekend. But they practiced like nuts and worked out alot. Not a ounce of fat of them. And that is when they had 265pv's. One a Duncan...the other a LRD. Then after we got the Duncan 340pv it was easier to beat them and you were not as tired by the end of the race. I ran this quad a couple years and it was a blast. We also have always ran 15/37 gearing with 18" Holeshots.
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And thats the thing, theres so many variables that factor in between. I know I would be faster on a four stroke, but throw an older pro national rider on a two stroke and get schooled..lol
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Like everyone has already said it is hard to beat the new 450's. That being said I watched both my brother's over the years beat them every weekend. But they practiced like nuts and worked out alot. Not a ounce of fat of them. And that is when they had 265pv's. One a Duncan...the other a LRD. Then after we got the Duncan 340pv it was easier to beat them and you were not as tired by the end of the race. I ran this quad a couple years and it was a blast. We also have always ran 15/37 gearing with 18" Holeshots.
You guys ran 15/37 gearing on the 265pv also or just the 340pv?
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You guys ran 15/37 gearing on the 265pv also or just the 340pv?
Just the 340pv. We usually ran 14/37 or 14/38 on the 265's.