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Old 12-09-2003, 11:22 AM   #46
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Default Re: Re: 16/19 Conversion question

Quote:
Originally posted by InitialD
I guess this depends on the driving style, track layout, track surface and tire shore choosen.

Many have mentioned that at the end of a long main, the split still remains about the same as previously intended. My own experience has told me that I end up with 3 mm split after a long main when I started out with 4.5 mm. So the overdrive you get at the end of the main is not as bad as if you started out with same front and rear tire diameters and with stock internal pulleys which makes the car handling not constant.
My goodness!! you are everywhere!!

just stick to your snake sir..
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Old 10-22-2004, 02:18 PM   #47
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Should I change my gearing to 0.8 mesh ? I have the 16/19 conversion.
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Old 10-22-2004, 03:21 PM   #48
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The .o8 gearing just changes the ratios of the 2 speed, where you may have a drop of XXXX RPM between 1st and 2nd gear, you can change the gears so that there is a smaller RPM drop when changing gears, and there are different ratios available, so the gearing changes are better for the power band of the engine. The 2nd gears will also allow the car to make more top speed on BIG tracks.

It's all about getting the most out of the available/usable power from any specific engine.
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Old 10-22-2004, 03:24 PM   #49
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Thanks theRED5 !

Roger Wilco ....
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Old 10-22-2004, 03:34 PM   #50
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The 16/19 conversion change is better if you run longer mains, and see the handling fall off at the middle and end of the race. If you see that the car is using too much rear tires, that they wear out and get so small that the chassis starts dragging, then you make the change run the rears 4mm bigger, and in the race, you'll find that the car is still handling like it did at the start. Ride hts should be the same as you would for a heat, 5 rear 4 front, although sometimes, in high heat or at a track where there's hi tire wear, I sometimes start a 30 min or more main, with an extra 1/2 to 1 mm of ride height.
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Old 10-22-2004, 04:12 PM   #51
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OK, that's the 4mm I was also wondering about. 60mm and 64mm in the rear.

Well, up here in Montreal, snow is not too far away so I'm basically getting ready for the spring.

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Old 10-22-2004, 04:42 PM   #52
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And what about downstops? Will I have to change them if I use that conversion?
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Old 10-22-2004, 04:47 PM   #53
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just to confuse you more , when you use the conversion you have to re check your droop and adjust accordingly, and you will probably have to unscrew the front shock rod ends to get your droop back,,,,

dont forget with 64 rear and 60 front your ride height in the front would be 2mm higher then with even tires front to rear thus loosing your stock droop settings


also there is no over drive front or rear in a stock mtx-3
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Old 10-27-2004, 07:59 AM   #54
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About the 16/19 conversion,
I have difficulty calculating the ratio

for the stock rear final gear ratio
I take 1 full turn of the rear wheel = 48t gear/19t gear =2.5263158
so the main shaft has to turn 2.5263158 times to have one full rotation of the rear wheel
For the front: main shaft 19t gear /24t= .79166667 multiply by 16t/32t (front one way for one full turn) which is .5 = .395833335

so if I take 2.5263158 (nbr of turn of main shaft) X .395833335 = 1.000000008377193 (pretty close to 1 !)

Here lies my confusion.
If 1full turn of rear wheel = 1 full turn of front wheel
Why the rear wheel wears so much faster than the front wheel.
And by doing the conversion the rear wheel will turn faster than the front wheel.

Can someone help me out , I am totally lost...
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Old 10-27-2004, 09:18 AM   #55
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Here's a good explanation given on the MTX3 thread. Thank you Bivens

Quote:
Originally posted by Bivens
Not to be harsh....but.....there seems to be a LOT of questions concerning the 16/19 conversion that indicate that MANY people do not fully understand the concept.....the above post is not the only one, simply the latest....let's see if this helps....

The stock rear drive ratio from the center shaft to the front and rear wheels is 2.526:1 (SAME front and rear....thus, you must run the same diameter tires to have a non-overdriven condition)

The FRONT drive ratio with the 16/19 conversion is 2.375:1 (while the rear remains unchanged at 2.562:1). With the conversion, the front of the car has a drive ratio that results in the front-tires spinning approximately 6% FASTER than the rear tires....therefore, that 6% difference must be compensated for by tire sizes.

The proper tire size to achieve a non-overdriven condition may be determined by calculating the rollout of the front and rears for each turn of the center shaft and picking the proper tire size to achieve the condition you desire.

To simplify things, here are some example tire combinations that achieve a near-even drive ratio front to rear.....(it is not specifically a constant split...but it's close as you will see)

Front.........Rear.........Overdrive #
50mm.........53mm............1.004
52mm.........55.5mm.........0.997
54mm.........57.5mm.........0.999
56mm.........59.5mm.........1.001
58mm.........61.5mm.........1.003
60mm.........64mm............0.997


As you can see....an approximate 3.5mm split achieves a non-overdriven condition (rollout for front and rear equal) for a large range of tire sizes. (slightly less split for small tires... and more split for larger tires)

The main thing to understand is that this conversion allows you to get more even tire-wear (Fronts and rears wear together...without having to constantly true the front tires down to match the ever-shrinking rears). You also get to run the front of the body lower over the wheels......if you like to SLAM the body to the ground. You get the benefit of having less foam on the front tires......good turn-in without excessive tire flex and traction-roll issues (and they're lighter). Finally, assuming you keep a similar rear tire-size to what you would normally run....the front roll center is changed slightly due to the suspension geometry change of adapting to the small front-tires without compromising ride-height.

One last thing to remember......the overdrive percentage of 1.000 is only one option.....you can use an overdriven condition to alter the handling of the car...especially on low-bite tracks. A number higher than 1.00 means that the front tires tend to "pull" the rear of the car.....a number less than 1.00 means that the rear tires "shove" the front around.......each has a slightly different feel. This is easier to distinguish on low-bite tracks and is not so apparent on high-traction surfaces.

If you do not run SOME split front-to-rear....then you will unnecessarily stress the drive-train and wear out the belts and pulleys faster.........recall from above that there is a 6% overdrive created with the conversion and if the tires are equal-sized front-to-rear then the front tires are trying to pull the rear along 6% faster than it wants to pull itself......

If someone has a place for me to post an image....I can take a screenshot of a chart I have created in excel for ease of tire-size selection......I can send it to anyone in excel or pdf format also. PM me if you'd like a copy. I'd be happy to answer any questions about this post....please PM me.
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Old 10-27-2004, 10:21 AM   #56
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If you run the stock 24/19 pulleys with tires of the same size, you have the same drive ratio front to rear. If you run the 16/19 pulleys and run your fronts 3.5mm smaller than the rears, you basically have the same drive ratio front to rear. How does this keep the rears from wearing out at the same rate they did before. I was under the impression, that having the front overdrive is what actully lowered the rear tire wear. By having a 3.5mm split, you are basically back in the same boat as you were before.
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Old 10-27-2004, 10:32 AM   #57
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With the response, about ratio in Mistercrash post, if front = rear, why does the rear end wears out faster ??

Last edited by sharky; 10-27-2004 at 11:44 AM.
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Old 10-27-2004, 12:51 PM   #58
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You need to remember, with the front one way, the front wheels are doing half the work of the rears. While off power of braking, the fronts are spinning free, while the rears are giving the resistance which slows the car, which equals more wear. I'm sure there are other factors, but this is the easiest to explain. By reducing the front tires in relation to the rear with the 16/19, you have less tire area doing the same amount of work as the rear, which generates more wear in the front. in theory, when using a front diff or solid axle, the tires should wear pretty even with the stock setup. I never tested because my tracks are all permanent and big enough where I only run the One-Way. Hope this helps.
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Old 10-27-2004, 04:34 PM   #59
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Here's a twist ! What if I add a front diff with the 16/19 conersion. Should I maintain the 3.5mm split in tire size ?

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Old 10-27-2004, 05:35 PM   #60
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I'm not sure if it would give you any benefit to run the 16/19 with a front diff. Remember, the only reason we need to true the wheels down is to keep the OD ratio at 1:1. But with the front diff, all four wheels are "live" at all times. So the wear should be even. But try it if you want, let us know how it goes.
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