dmayhew25

iTrader: (14)

Dave, car looks good!

How much does the car weigh in at with 3700's? Did you do anything to help lighten it up?

Dave Bowser

iTrader: (51)

lol..........whats up espo you coming down for the nats?

Dave Bowser

iTrader: (51)

no i did not do anything to lighten it up i know with the IB 3800's its 54oz's but with 3700's i don't know

raving-monkey

well you never know with me..i always have bodge jobs up my sleeve..you should know me well enough by now to know that

teamgp

BDR,

At the time that I wrote the post, I had not thought about the other affects of using shims for rear in-board toe-in and therefore I didn't comment on them then. My point today is more around emphasizing the use of out-board rear toe-in to ensure that a driver is only changing one area of the chassis' dynamic as opposed to the multiple areas of change that come with using in-board rear toe-in (track width, roll center, camber gain, etc.)

As far as the camber gain is concerned, the focus of what I found with out-board rear toe-in is more around the arms downward travel for the inside rear wheels tire contact patch. At the time I tested this, my rear arms were sloping downward from the outside in towards the chassis centerline when the suspension was at rest. The wheelbase was at maximum, and therefore the upper links plane between pivot its points was not lined up at the same angle as the lower arms plane because of the fixed length of the aluminum roll center holders. Now with the rear part of the arm being shimmed out, it actually swung more away from the chassis centerline as the arm moved downward and flattened out. In effect the difference between the lower arms length in relation to the upper links length between their respective pivot points increases (the same effect as if you shortened the upper link) and therefore more camber is gained at the rear inside wheel in a corner as its arm moves downward and flattens out. This would happen the more the arm moves downward until it passes the point of being level with the chassis and then the camber gain would start to decrease. Since the tires start with negative camber, more negative camber gain means a smaller tire contact patch and also less stability since the affect of rear toe is reduced as well. Although I don't believe I included it in the post, I also observed that as the outside rear arm swung upward, its negative camber gain decreased slightly which would confirm the difference in both arms pivoting planes.

With out-board rear toe-in the difference between the rear lower arm length and the upper link length stays at a consistent distance in relation to each other and therefore there will be less camber gain on the rear inside wheel in a corner than if you used in-board rear toe-in. But the best way for anyone to see this is to use the corner simulation test on a setup station.

Of course I agree that there are some big differences between running rubbers and foams, as I found out at the C when I had a problem with my rear tires coming up to temp for effective grip. Their are several differences.

But there are also several areas of chassis tuning that pretty much give the same affect in handling. Though the affect may be delayed, short lived, or slightly limited by the differences in the two types of tires grip and how it changes due to different sidewall effects, temperature changes, elasticity, & reaction to traction compound to name a few.

You'll notice that I'm pretty articulate on what I "suggest" might work and what I "state" has worked "for me" particularly. And I don't think anyone would argue that I don't provide enough detail as to the overall environment and controls that need to be factored into the results that I've found. One of the first things I'll ask anyone who is seeking advice is, "what type, brand and compound of tire are you running?" Rest assured though I may be green in the area of rubber tire RC racing, I do have a lot of past experience in the area of rubber tire "scale" racing which has similarities, tire pressure notwithstanding.

But I'll make sure to be more clear in the future when giving advice to drivers running rubber tires.

I don't believe your response was negative in its motive. But I'll add this for the benefit of all those who have recently made, and will quite possibly continue to make, derogatory remarks concerning my advice, motives, methods, intelligence and even character now that I am a sponsored driver (of which I have been truly blessed with this "privelege" from someone who is very well respected and has a proven track record of success in the RC business):

I may be a little too detailed at times and seem to be saying that my way is the right way, but if this is anyone's perception then they have totally missed the point on why I spend a lot of my time responding in the forums. I'm still very much learning this craft and will be the first to admit so. However, I put a lot of effort into helping others here (my motive) because I became very tired of the normal responses given by a lot of the truly experienced drivers on this forum who don't take the time to give enough information for others (like myself) to start thinking for themselves. And then those same people seem to get perturbed when they see the same question asked in only a short amount of time and they proceed to make short, rude and plain disrepectful comments to those who simply don't know where to start, or let alone ask the right question.

Rather than tear each other down and lift up our own credentials (of which I have very little), why not focus on actually helping others so that this hobby, and dare I say SPORT, can grow beyond the capacity of what the rctech.net forum servers can handle today.

BigDogRacing

iTrader: (12)

Guy- great response. Thanks for taking the time to type all that.

I feel the same way as you about derogatory remarks. I'm embarrassed to admit that I have flamed persons in the past, and to be honest, I don't like the guys who get on here and don't know as much as they think they do (which really isn't a problem) and then they start giving wrong advice to others. For instance, pertaining to batteyr Q's- I've seen guys give advice that I know for a fact will cause poor charging and negative results. That irritates me!

Anyway, since we're on the subject of camber rise and rubber/foam differences, it's a good time to make the observation that camber, camber link location, and most aspacts pertaining to them are quite different from foams to rubber.

I'm at work and catching a run, have to come back to this later.

alb

iTrader: (20)

NOW my head hurts.

FLCL

Dave Bowser

Nice looking Xray..many fans though???too hot where you run??? also do you go to Clevleand??? (my first year in USA going to Cleveland)

TeamGP

Thank you for posting your thoughts on rear toe in at the hubs. this has been a topic that we talk about. mostly inboard vs out board. and then how much. (foam tires) interested in your thoughts on weight transfer, forward bite/angle of toe in, effects on cornering. between inboard toe in and out board toe in. my first year with a Xray car (05) want to learn all that I can about suspensions

dado11g

iTrader: (1)

what is the minimum weight limit?

tonyv

iTrader: (1)

Interesting remark. While I agree on the basic principle the key thing here is why is it different? In fact the physics are exactly the same, they are laws of nature after all. The reason some things appear to work opposite is because of the basic starting point. Rubber tyres on carpet give generally (much) lower grip than foam tyres on carpet.

Contrary to what many believe it is too easy to make statements like: "if you lack rear end grip run softer springs". There are many things wrong with such a generic statement. Depending on the cause of the oversteer this statement would be in response to the statement may be right or wrong. For instance the rear tyres might give insufficient grip to cope with initial centrifugal forces when entering a corner which generally translates to snap oversteer. Then making the rear softer will normally help. This in fact reduces the maximum grip but allows the suspension to absorb more of the centrifugal force so the force working at the tyres is reduced too. This solves snap oversteer.

BUT you also might have too much grip. In this case your springs may actually be too soft allowing the chassis to roll too much causing the grip the two tyres give to actually be lower. This results in the car slowly entering an oversteer situation which makes the car's speed to drop noticeably during cornering but the car is usually still controlable. In this case running harder springs is the right answer.

Note that I did not mention foam tyres or rubber tyres at all. The above holds true for both. It's the level of grip that counts. Since foam tyres generally give more grip it is more likely that your problem will be that you are running too soft springs than too hard springs. For rubber tyres grip is lower so you will more likely be on the other end of the scale.

The key notion here is that most setup options are not lineair in their workings. Just imagine how much grip the car will have (i.e. corner speed) if you run 1Lb springs compared to running concrete springs. With 1Lb the car may still run but it will be floating all over the place instead of going where it is supposed to go, especially at speed. In the second case the car will slide out as soon as you try and hit a corner at any kind of speed.

BigDogRacing

iTrader: (12)

OK Tony, I see your point, but here's mine:

Given car- say mine for example; on foam/carpet assuming the car is "in the ballpark" on setup, I need more steering- do I soften the front springs or go stiffer first? Well, considering 3 out of 4 times when you go to a stiffer spring on carpet/foam you get more traction on that end of the car, I'm going to go harder. Many times I've been carpet racing and as the bite comes up I try to siffen the rear of the car to get more steering by increasing the traction balance to the front of the car and instead of getting looser, it tightens up. Go back and put one softer and the car picks up steering- either that or go one stiffer on the front spring... same difference.

OK, my car again on a medium or good (not super high like indoor asphalt) asphalt track; The car is fast and again I'm close but need a hair more steering- do I stiffen the front spring or soften the rear spring first? Nope, because 90% of the time the opposite is true on asphalt- you need to soften the end that needs more traction.

Dangit- another run. I'll be back

kewdawg

iTrader: (3)

Sounds like your confusing steering with reaction time (how fast the car reacts to input)? Stifffening the front end does not increase traction on carpet or asphalt - using foam or rubber. It does, however cure the car's slow / sluggish behavior when transitioning from left to right (chassis) and vertical (suspension). To increase steering, you would indeed, need to soften one the suspension variables such as the shock's angle, spring, oil, piston, etc..

brians11

iTrader: (40)

I ran my 05 for the first time this weekend, with ib3800's it was 1468 grams... i had to add about 75 grams to make legal weight.. my biggest change from kit setup was the 2mm chassis... so the car is very light out of the box

Core Creations

iTrader: (108)

Do I remember others saying the thrust assembly is rather weak on the FK'05s? Anyways, my question is this: When I had an RDX the fix for some of their crappy thrusts were the Xray assemblies...They fit perfect. Now I have an 05, and the stock assemblies are crumbling. I am going to replace them, but saw the carbide versions are almost $20 a piece, and the better tougher version for the RDX chassis are like 7 bux...??? Should these be okay? I bought my 05 second hand and now looking back I'd bet the diffs never had grease applied to the thrust setup

hpipro321

u should just spend the money and get the right parts i broke my thrust assembly because i didnt take the right care of my diff in the begining of assembly