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Old 02-28-2014, 12:14 PM   #13921
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Originally Posted by fredswain View Post
This confuses me. What you are saying is that in order to get more grip on tracks with less traction, you are changing to RM4 from RM3. However then you are not only moving battery weight forwards but also adding weight up front. Why would you do this? It's counterproductive. You want to shift more weight rearwards but then add that weight back up front to counter it. If rear grip gets low, all you need to do in RM3 is to reduce rear antisquat and add a little weight to the rear as necessary. The end goal is to get more rear grip and this accomplishes that. It also does it without the negative problem of losing on power steering.

I don't tune any differently for RM or MM. The technique is all the same and so are the results. The actual tune itself varies though.
I hear what you are saying. We tried all the weight back with RM3: Battery rear, weights on the rear hubs, additional weights using brass hangers. We tried from 3 to 1.5 to 0 antisquat.
More Antisquat is suppose to give you more grip under acceleration. I don't need side grip off-power which is 0. I need to lay down the power straight. Adding weight in the rear and reducing squat will make it swing more in corners while the 0 squat keeps it in check and stop it from sliding, but it doesn't solve on on-power traction. Keep in mind they add soap water to make the track wet. Which makes it slippery.

If traction is low, do you add more weight rear or front?
The extra weight in the rear makes the car rotate too much in the corner on low bite surfaces. So what we did was work around the RM4 config, and develop it. Adding weight to the front and moving the battery to the front offers a better balance on low bite conditions. Also, low bite, means your front tires don't steer either, so you need a well balanced car to have a neutral setup. Hence adding weight to the front. At the end of the day, I don't want the back to SLIDE more to rotate. RM3 is good, but the RM4 gives you more weight transfer during acceleration and deceleration, and you need the weight transfer on a technical track. We have also tested this setup on low and med grip outdoor tracks, and its still a good neutral easy driving setup for any dirt or clay condition which a majority of people race on (except high bite) We don't have those nice smooth sugared tracks here. That track was probably the best clay track in Ontario. We have some outdoor tracks with more craters than the moon, and potholes that swallow your car whole.

I am sure we can talk about theory of suspensions all day till we are blue in the face. Things that work on high bite, doesn't apply to low bite. Our main goal was to get and share a setup for the majority of drivers who race on these low med bite conditions. I have an engineering degree, but I am talking about experiences and track testing that our team has done and I tell you sometimes it doesn't always follow the theories. There is no one setup. I see people at my track quote the Xray setup book like its the bible, but they don't understand how one parameter affects the other. Or that you can adjust multiple things to achieve the same effect. There are more than a number of ways to setup a car to work well.
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Old 02-28-2014, 12:20 PM   #13922
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I'm not insulting you or questioning your intelligence. I'm merely trying to understand the logic for the setup.
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Old 02-28-2014, 12:20 PM   #13923
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Originally Posted by Speedo711 View Post
so for my local wet clay track my mm4 car has great traction and turn in.......but when the track is too wet (slimy mud) or dry (slightly dusty) the car pushes like crazy in the "rear motor" turns like 180's....from what you guys have been saying I think i will try less caster or less trailing? Am i correct?

Another thing i noticed is that the TLR's have the shock on the back of the rear arm in midmotor and in the front for rearmotor....i know this is a possible mod for the durango but i cant find a solid explination of what the benefits/drawbacks are.
Fred can steer you in the right direction for MM. I think you need a more balanced setup which doesn't change handling based upon grip level.

But having the shocks in the rear, is like having more weight in the rear, which helps the car rotate better in high traction, kinda like a pendulum. Having it in the front of the arm, moves the weight forward, less of a pendulum affect.
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Old 02-28-2014, 12:50 PM   #13924
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Originally Posted by Speedo711 View Post
so for my local wet clay track my mm4 car has great traction and turn in.......but when the track is too wet (slimy mud) or dry (slightly dusty) the car pushes like crazy in the "rear motor" turns like 180's....from what you guys have been saying I think i will try less caster or less trailing? Am i correct?
I wish we had tracks here to be able to run mid-motor. The only time we ever get to run mid motor is on carpet, or at the nationals, and choosing a mid-motor is sketchy at best based upon grip levels at our nats.

Thus most of the testing we have done for years is on the RM based car. Traction is key here and trying to find a setting that remains stable in all conditions. I don;t want a car that goes from pushy (understeer) to oversteer as the track dries. I don't want to be changing setup all day. Sure it may not be the most optimal setup for each condition, some have a great wet setup, and others dry, but we wanted something that remains relatively quick in all conditions. The car shouldn't change much based on condition, unless its not balanced. As Fred said, it's getting a right balance with weight, oils and springs and geometry. If your car pushes when wet, maybe you need to relook at the setup or weight distribution.

If your MM is pushing, maybe you need more weight shifted in the rear, if the RM is 180s, you need more weight up shifted to the front to prevent over rotation.
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Old 02-28-2014, 01:29 PM   #13925
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Lookin for some gearing help. Just got this truck and a new killshot 13.5 and was wondering if someone could give me a starting fdr. I run on a tight high grip clay track. I know I will have to tune when I get there just don't know where to start. Thanks!
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Old 02-28-2014, 01:51 PM   #13926
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Lookin for some gearing help. Just got this truck and a new killshot 13.5 and was wondering if someone could give me a starting fdr. I run on a tight high grip clay track. I know I will have to tune when I get there just don't know where to start. Thanks!
DESC210? 25T or 26T assuming you are running the 87T spur.
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Old 02-28-2014, 01:52 PM   #13927
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Originally Posted by K22Hsct View Post
Lookin for some gearing help. Just got this truck and a new killshot 13.5 and was wondering if someone could give me a starting fdr. I run on a tight high grip clay track. I know I will have to tune when I get there just don't know where to start. Thanks!
Whatever you do, don't go too crazy on the timing. The locals here have taken to calling that motor the "Smoke-shot".
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Old 02-28-2014, 01:58 PM   #13928
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If traction is low, do you add more weight rear or front?
Neither. Your entire setup is built up on the foundation of your weight distribution. When you change your weight ditribution, you need to change your entire setup to match. You'll never be successful in tuning by just throwing weight around and hoping it works. Understand how your weight affects your your springs, dampening, and roll centers and you'll do better at using your weight and tuning around it.
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Old 02-28-2014, 02:00 PM   #13929
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I'll buy whatever spur I should run. I'm running blinky. Does it not like endbell or boost timing. It has the high torq rotor
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Old 02-28-2014, 02:04 PM   #13930
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Neither. Your entire setup is built up on the foundation of your weight distribution. When you change your weight ditribution, you need to change your entire setup to match. You'll never be successful in tuning by just throwing weight around and hoping it works. Understand how your weight affects your your springs, dampening, and roll centers and you'll do better at using your weight and tuning around it.
There are times I'll add weight. On a lower grip track I'll run saddle packs. On higher grip I'll run a shorty. I retune according to each.
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Old 02-28-2014, 02:06 PM   #13931
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Originally Posted by Dino_D View Post
If your car pushes when wet, maybe you need to relook at the setup or weight distribution.

If your MM is pushing, maybe you need more weight shifted in the rear, if the RM is 180s, you need more weight up shifted to the front to prevent over rotation.
thanks for the advice.....I worded the parts about 180's horribly. I meant that it pushed in the 180 degree corners that are labeled as "rear motor" turns. The midmotor passes cars on the higher speed corners as expected

i might try moving the shorty back or the shock mod.....i really haven't done much experimenting
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Old 02-28-2014, 04:28 PM   #13932
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I'll buy whatever spur I should run. I'm running blinky. Does it not like endbell or boost timing. It has the high torq rotor
It doesn't like too much end-bell timing. I'd keep it around 30 degrees or below and just gear up.
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Old 02-28-2014, 04:45 PM   #13933
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Man that's a bummer shoulda went d3.5. I'm in the wrong thread Idk how. I have a desc sorry guys thanks for help
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Old 02-28-2014, 05:07 PM   #13934
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Man that's a bummer shoulda went d3.5. I'm in the wrong thread Idk how. I have a desc sorry guys thanks for help
Well the D3.5 is still illegal in a lot of places so the Kill-shot is still a better choice. ROAR may say it's legal until the D4 comes out, but our local tracks outlaw them. The smoke-shot will keep you going hard, and you really don't need more than 30 degrees of timing on a medium track for 17.5. I only use 10 degrees with a Speed Passion 17.5r motor and it still pulled fast laps. It's all in the driving mate :-) That's what I love about stock classes.
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Old 02-28-2014, 10:29 PM   #13935
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Neither. Your entire setup is built up on the foundation of your weight distribution. When you change your weight ditribution, you need to change your entire setup to match. You'll never be successful in tuning by just throwing weight around and hoping it works. Understand how your weight affects your your springs, dampening, and roll centers and you'll do better at using your weight and tuning around it.
Actually I don;t move my weight around, i just added enough so the front doesn't really lift on acceleration with the RM4. approx 42g, and re-tuned my shocks accordingly. Spring test first, then actually 8 different settings on the rear oil and piston combos to get it right, and the front took me 5 different combinations before i settled on the right combo. This is by checking to ensure I get 3/4 of the stoke or more without bottoming, if it packs up at 1/2 or bottoms, I will redo. When the car lands on a drop test, the car compresses and rebounds evenly. It it doesn't I redo another combo until it is balanced. Having the car sag back first or front first is not going to make the car handle right. This process takes hours... and i prefer not to do it on a race day.

I don't change to saddle for low grip or shorty if the grip rises during a race day. But I can understand on a MM car, its different as you may need the extra weight for grip, while RM are not affected by it as much. I don't move the battery or weights after the iniital setup. I rather have a consistent car the whole day at the races than having to figure out how the car will react and adjust my driving accordingly on the first few laps. Cause those extra few seconds on the opening laps is the difference between making the A or not.
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