Great info!!!!

Overdrive
 

ok so i finally got one after haveing a mtx3 for a while i decided to UPGRADE there is a wealth of info on here but i cant seem to find much about the side pullys like what affect the 25 has opposed to the 24 i dont know a whole lot about overdrive ratios i do understand the 1.1 means front and rear rotate at the same speed, but if i measure my tires and come out with say .996 with the 24 tooth does that meen that the front is spinnig faster or the rear is spinning faster?

Any help would be wonderful

Thanks Dustin

Look at overdrive charts for MTX3 or MTX4.

Anything above 1.0000 means OVER DRIVE ( front tires rotating FASTER than rear tires ). Examples : 1.0351 means 1.0000 - 1.0351 = 0.0351 x 100 = 3.51 %. Therefore, front tires is rotating 3.51% FASTER than rear tires.

Anything below 1.0000 means UNDER DRIVE ( front tires rotating SLOWER than rear tires ). Examples : 0.9152 means 1.0000 - 0.9152 = 0.0848 x 100 = 8.48 %. Therefore, front tires is rotating 8.48% SLOWER than rear tires.

Equal to 1.000 means FULL TIME 4WD.

However, since rear tires's diameter are wearing out at faster rate than front tires, we need to give some tire split by shaving front tires diameter before race. Most split range from 2mm to 3mm. Examples, front tires diameter before race : 62mm and rear tires before race : 64mm. Thus 2mm split.

Why tire split ? Because we can't drive very well when front tires have bigger diameter than rear tires ( I feel like I want to shoot the car ). ..... this is true for racing on long mains. We want driveable car for the whole mains. Another trick to slowdown rear tires wearing out faster than front is using 1 or 2 grade harder compound for rear tires. Examples, 35 shore for front, 40 shore for rear.

For MTX3. I find the nicest setup by going underdrive. Replace the rear side pulley 19T with 18T, and keep using 24T side pulley.

For MTX4. I also prefer underdrive with 25T side pulley.

Anyway, people may have different opinion and driving taste on these...... so please don't take my preferences without further testing on your own.

Overdrive is not only about rotational speed, but about ROLLOUT (distance travelled per each clutchbell revolution).

2-2.5mm tire split is used not because of the wear issues, but because it is required with 24t pulley to get 1:1 overdrive. Since with 24t pulley the fronts rotate faster, they have to be smaller to get the same rollout as the rears have.
Equal size tires with 24t pulley would result in terrible overdrive.

The reason we use smaller fronts and 24t pulley instead of equals and 25t is handling. Basically, smaller tires offer less lateral (=sideways) grip, but are more consistant. Also the suspension geometry changes with smaller tires (arms/axles sit lower, this gives higher front roll centre). This just feels better most of the time.
The only time I use the 25t pulley (and equal size tires that this requires) is when it rains and I'm running Pit rubbers or when it looks like it will be raining 10 minutes into the final :D Although I have tried the 25t side and equal size foams on a dry loose track and found it quite usable, I like the consistency of smaller fronts more.

Dustin,

I have an excel spreadsheet that I created and it is set-up so that if you put the # of teeth on each pulley into it, the sheet will determine front to rear drive ratio based on tire diameter. This can be used for any 200mm or 1/8 car. The tire diameters are in a table so that you can quickly determine what size tire will give you the OD ratio you are seeking.

email me at [email protected] and I will send you a copy.

Lee

Hey guys I decided to leave elec touring and come back to nitro and my friend has a mtx-4r and it is perfect at my track but the thing is people are stopping selling them so I was wondering if there is a new one coming out or should I just go ahead and buy one

thanks for all the great info guys :nod:

Check this thread: http://www.rctech.net/forum/nitro-ro...tx-5-a-26.html. However; an MTX4 ran 2nd in the worlds last year.

Kindest regards,
Lars.

Sometimes I'm just wondering why people reply to 2 years old threads... but I'm not sure I really want to know:weird:

Thanks for the advice. I'll check the dates of the posts from now; I don't understand why this thread came up as updated on my subscribed threads?

Kindest regards,
Lars.

:lol::lol:

You are certainly not the first one nor the last that have that happened to them...

mugen clutch shoes
 

Which one is made from harder material :

grey clutch or yellow clutch ?

what is the main difference between the grey and yellow ?

I forgot oredi ...... :cry:

anyone in need of a MR4r AND a MRX4x roller plus LOTS of parts? I got what ya'll need :)