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View Full Version : Just How Important The RearEnd Really Is


MagicMan
2006.04.04, 03:48 PM
By now you guys are getting familiar with my threads and hopefuly finding them useful and helpful.

Disc Damper Systems are a MUST on RCP Track material. Anyone with just a TOP shock, is just gonna hop around, now if you find yourself hopping (Rear) around WITH a DDS then you have another issue. OR it's your front that's hopping and you don't realize it.
Also be aware of how you run your WIRES around your DDS. If one wire is pinched after you throw your body on, and it is dis-allowing it to flow in a certain direction, you will find yourself oversteering badly. So be careful.
Springs in the disc damper are slightly important too. If you are running a large track where your turns transition from left to right slowly, you can get away with using hard springs in the DDS. If you run a medium to small track where the turn transition is rapid. You man want medium to soft springs.

H/T-Plates are slightly important as well. If you want good carry speed throughout a turn, you want to stick with a hard H plate. And the advice on this secion actually is the same as the lower portion of the DDS section above. However, remember that if your too flexable on the rear, on a turn, you may lift one of your front tires and be riding with three wheels on turns and not realize it. So tune wisely.

Differentials are fairly important. As for my opinion; I tend to leave a gear differential on stock board cars because you really need no tuning on the differentiating of the rear end. But once you go modified, you may want to go Atomic or Kyosho on the diff, (or the cheap way out -Iwaver). Because with such power, you will need to tune the diff. The benefits of a gear diff is that it's WAY lighter, however, they DO make Titanium shafts for ball diffs that make the weight come close. Also another benefit of the gear diff is absolutely no power loss. There is no slippage. Loosening your diff on a ball diff will sometimes make you feel like you are peeling out or burning rubber, when in fact the spur gear of the diff is spinning but not spinning the plages to spin your wheels. However, if you overtighten, when you approach turns, you may notice you slow down too much, or once you give throttle, there isn't enough differentiating throughout the turn to make a good cutting turn (understeer).
A good rule of thumb on a gear diff: hold your wheels (rear) and punch the gas. If your spur gear spins freely without serious strain, the diff is too lose.

Motor mounts are a luxury. It's not necessary, but it sometimes makes life easier. I find the ML lighter than the MM Pn mounts, so if you run a MM car, and want to run a alloy mount, grab the ML and set it to run at the MM wheelbase setting.

Weight means so much, it is so under-rated. Say a Mini-Z's weight was 3lbs with batteries (just an example): Now a real car would weigh roughly 2500-3500 lbs. So we'll average that to 3000lbs. Therefore.. every pound in a Mini-Z will scale out to 1000 scale lbs in real life. So if you shave off a hair of weight that you think will do nothing... and now your Mini-Z weighs 2 and a half pounds, that's like doing a 500lb weight reduction in a real car. And if anyone knows about racing in real life, we should all know how much weight reducing is done in race cars. Weight is the ONE and ONLY thing you can do to a car that will increase the following three things at the same time: Braking, Handling, and Accelaration/Power. So do NOT underestimate the power of using plastic in your Mini-Z as oppose to Alloy. And don't forget to replace whatever metal you can, with Titanium.


LET THE FEEDBACK BEGIN!!!!! :D

arch2b
2006.04.04, 08:01 PM
well, this thread is just as good as the others :p

i have atomic disc dampers on just about all my cars agree with your sentiments :cool:

tweak diff settings can be a real tricky task and i find many newcommers asking which way to go for what results, i.e.; what does tight do vs. loose. this and the other threads will certainly be very well referenced :)

hobbycar
2006.04.04, 09:14 PM
Another point in relation to weight for spinning parts like a diff is that heavier means harder to start spinning (affecting your car's acceleration) and harder to stop spinning (meaning harder to slow your car down).

-hobbycar

MagicMan
2006.04.04, 09:46 PM
Another point in relation to weight for spinning parts like a diff is that heavier means harder to start spinning (affecting your car's acceleration) and harder to stop spinning (meaning harder to slow your car down).

-hobbycar


Right, meaning that if you have a ball diff, they make Titanium shafts for them. I believe I mentioned this earlier. This will make the spin up less strainful. I wonder if they make Ti for stock gear diffs.

EMU
2006.04.05, 02:09 AM
Right, meaning that if you have a ball diff, they make Titanium shafts for them. I believe I mentioned this earlier. This will make the spin up less strainful. I wonder if they make Ti for stock gear diffs.
Ive been looking for a stock Ti shaft for some time :rolleyes:

As far as weight is concerned. Removing weight is important, but WHERE it is removed from is more important. Generally, the body should be reduced the most. The window section of the body is generally the highest point on the body, and I usually will remove all sections of the window that are not visable from the outside. Then you want to feel how the car handles with a good chassis setup. If there is too much steering, you may want to remove a little weight from the front of the chassis/body. Too much understeer, you may want to reduce weight from the rear... In general, weight balance is more important that total weight, especially for modified cars.

Setting up for a race event like a PN race that has a minimum weight, you want to reduce the weight as much as you can then add weight in specific locations to meet the weigh in requirements. This way you will have the car handle exactly as you want it to.

I believe that a stock diff weighs almost 6g, while a Kyosho ball diff weighs almost 11g. A Ti-shaft ball diff weighs about 8g... So acceleration is best with a stock diff, and on RCP where you have alot of grip, there is not really an advantage to a ball diff except for a modified car, since there isnt enough torque from the motor on the stock cars (using X-Speed or Speedy 05BB).

With disc dampers, if you use a hard spring on the bottom, and a softer spring on top you will have more power on steering, since the rear will sag less under acceleration, and more % of the mass will be on the front wheels.

I have noticed that the PN ML motormount is about the same mass as the stock MM mount (dont know about the RM mount). So that would give the 98mm setups a little more rear grip than when using a stock MM pod... I prefer the PN ML mount to the PN MM mount. And prefer PN mounts to Atomic ones. The Atomic ones are heavier than the PN mounts. Although the features that Atomic has included in the VIII 94mm mount are quite nice with the ride height adjustment and ability to use a standard motor that does not have the drilled holes...

stepchild
2006.04.18, 05:10 PM
now if you find yourself hopping (Rear) around WITH a DDS then you have another issue.
What would that other issue be and what's the fix?

hobbycar
2006.04.18, 06:20 PM
What would that other issue be and what's the fix?

I'm not sure if this is the case 100% of the time but when I had hopping issues in the rear I fixed it by doing 2 things:

1) put on newer rear tires (the ones I had on it were worn down alot)
and
2) put on a softer H-Plate for the rear suspension (in fact I went all the way back to using the stock H-Plate)

-hobbycar

stepchild
2006.04.18, 06:40 PM
I'm not sure if this is the case 100% of the time but when I had hopping issues in the rear I fixed it by doing 2 things:

1) put on newer rear tires (the ones I had on it were worn down alot)
and
2) put on a softer H-Plate for the rear suspension (in fact I went all the way back to using the stock H-Plate)

-hobbycar
My rear tires are in pretty good shape and I'm running med H-plate. I have a med spring on bottom of dds and soft on top. Med soft springs up front. This is on a RM chassic.

It only hopes during power turning, but not to bad. I would just like to get rid of it all togather.

EMU
2006.04.18, 09:04 PM
Try running a soft spring on the bottom of the dds, then try running a hard bottom medium top and see how it feels. Do you have an adjustable height damper post mount on your motormount. If so try adjusting it higher and lower and see which gives the least hop under power. I have noticed a decent amount of hop on my F40 under power, off power it is very smooth. I am currently running a medium t-plate on it, but if I go softer it has too much body roll and the inside front tire lifts under throttle and steer. I havent done much work on that car as far as the rear suspension is in that setup, I have been working on the cars that I have been racing, which that car would not be suitable on a large track. I have it setup to do tight track racing, which is does well.

What damper are you using on the RM setup?

stepchild
2006.04.18, 09:23 PM
Try running a soft spring on the bottom of the dds, then try running a hard bottom medium top and see how it feels. Do you have an adjustable height damper post mount on your motormount. If so try adjusting it higher and lower and see which gives the least hop under power. I have noticed a decent amount of hop on my F40 under power, off power it is very smooth. I am currently running a medium t-plate on it, but if I go softer it has too much body roll and the inside front tire lifts under throttle and steer. I havent done much work on that car as far as the rear suspension is in that setup, I have been working on the cars that I have been racing, which that car would not be suitable on a large track. I have it setup to do tight track racing, which is does well.

What damper are you using on the RM setup?
I'm using the stock motor mount, so I don't think it's adjustable. Mind is very smooth off power. It's just when on power that I get the hop. My damper is an atomic. Off the top of my head I think it's the AR33, but not sure. I'll try out your suggestions and see what it does.

MagicMan
2006.04.19, 02:02 AM
I'm using the stock motor mount, so I don't think it's adjustable. Mind is very smooth off power. It's just when on power that I get the hop. My damper is an atomic. Off the top of my head I think it's the AR33, but not sure. I'll try out your suggestions and see what it does.

Is this hop coming from your rear end? or your front tires skipping. Rear mount generally isn't the easiest thing in the world to set-up. What kind of damper are you using. and do not go to a soft H plate on a RM. You'll get too much flex, and end up on 3 wheels in a turn and not even know it. Matter of fact, I recommend Hard.

Get back to me when you can.

stepchild
2006.04.19, 06:43 PM
Is this hop coming from your rear end? or your front tires skipping. Rear mount generally isn't the easiest thing in the world to set-up. What kind of damper are you using. and do not go to a soft H plate on a RM. You'll get too much flex, and end up on 3 wheels in a turn and not even know it. Matter of fact, I recommend Hard.

Get back to me when you can.
I tried what EMU suggested. Putting a hard spring on bottom of DDS and med on top. It seemed to work just fine after doing that. In fact it seems to handle very well...at least for my driving skill.

EMU
2006.04.19, 11:45 PM
I tried what EMU suggested. Putting a hard spring on bottom of DDS and med on top. It seemed to work just fine after doing that. In fact it seems to handle very well...at least for my driving skill.
Good to hear :D I tried my F40 in the main tonight, but one of the rear bumper screw mounts broke, and the bumper was dragging on the rear right wheel... I liked the feel much better than any of my MM cars on the track (less grip on this specific track). I didnt know until after the race was over that the bumper was cracked, and was wondering why it was handling poorly.

I am going to try changing the springs in my dds as well to the hard/medium combo and see how it feels.

stepchild
2006.04.20, 09:08 AM
Good to hear :D I tried my F40 in the main tonight, but one of the rear bumper screw mounts broke, and the bumper was dragging on the rear right wheel... I liked the feel much better than any of my MM cars on the track (less grip on this specific track). I didnt know until after the race was over that the bumper was cracked, and was wondering why it was handling poorly.

I am going to try changing the springs in my dds as well to the hard/medium combo and see how it feels.
Sorry to here about your car breaking. But good to know why it wasn't handling very good. I broke a knuckle the other day and had no glue as to why it wouldn't turn. Finally noticed the knuckle, which was a relief.

I agree RM feels better then MM to me also. Not sure why, but it does.

locwan
2006.07.28, 11:08 PM
Is this hop coming from your rear end? or your front tires skipping. Rear mount generally isn't the easiest thing in the world to set-up. What kind of damper are you using. and do not go to a soft H plate on a RM. You'll get too much flex, and end up on 3 wheels in a turn and not even know it. Matter of fact, I recommend Hard.

Get back to me when you can.

I ran a RM w/ ATM DDS and a hard T plate in the past, on a home made track with tar paper surface. The track is very narrow and has many tight and rapid turns to make it more technical. I found that w/ a hard T plate setup, my car spun fairly fequently under power on turn-exit.

I've since replaced the T plate w/ the softest one I could find. The car behaves better under power now during turn-exit, exhibiting more control and I'm able to power-slide out of the turns without spinning out.. however, during straight line sprints, the car is definitely hoping more (surface isn't perfectly bump-free) That being said.. I'm not quite sure that I understand why this is happening, (save the hoping in the straight away) any explainations would be welcomed. :)

Further more, is it so bad to have only 3 wheels make contact during the turn? Doesn't the extra weight transfer to the outside wheels make turning easier, especially on a tight track?

Digisane
2006.08.05, 08:58 PM
By now you guys are getting familiar with my threads and hopefuly finding them useful and helpful.

LET THE FEEDBACK BEGIN!!!!! :D

Hey Magicman,

Very helpful tips there.. I particularly like the one about weight, as that makes a whole lot of difference! I used to run my body with the window 'glass', and just that alone made the car faster in everyway! Of course, by doing that you create a dust problem.... :D

Digisane
2006.08.05, 10:39 PM
I used to run my body with the window 'glass',

Hmm. I meant without... :mad:

can't seem to edit own posts anymore?

jaeneke
2006.08.06, 05:12 AM
i love to drive with alloy wheels !! the extra weight of those wheels keep the wheels themselves better to the ground !

the only disadvantage is that the motor needs more power to get the wheels 'going' but on a track like in our club you only have to accalerate from 0 once(if you don't crash :D ).

another dis/advantage is the braking distance when you turn the throttle to "0" its slightly longer then plastic wheels...

TED
2013.03.18, 10:35 AM
Top shock or not looking at some MR-02 some with and some with out I'm running with a DPS. if I use a top shock what type and what oil?

imxlr8ed
2013.03.18, 11:57 AM
Ahhh!!! Run!!! It's a 6 year old thread!!!!

http://members.modernvespa.com/dullivan/uploads/zombie_thread_210.jpg

Traveler
2013.03.18, 12:11 PM
Closer to 7 years! :eek:

cowboysir
2013.03.18, 01:07 PM
But seriously though...:rolleyes:

I have a couple cars with kyosho top shock with a light/medium oil mix. It does seem to help keep the rear planted but other cars without top shock also drive pretty well.

I guess the answer that most would give you is experiment...get your car running well without top shock and then see if you get improvements with one installed.