Meradin

iTrader: (19)

So all this talk of thicker gear diff has me wonder. What would I look for handling-wise in a car to make me want to run a thicker fluid. I have my car pretty dialed for me but I am always looking to gain the extra advantage. I am using 1000 in the rear and 500,000 in the front. What does a too loose of a rear diff feel like? We have a decent level of traction but since I have nothing to judge by i have no idea if it is high or medium.

Team_Krusty

iTrader: (3)

Thicker oil in the rear diff will give the car more rear drive and will increase on power rotation. If you find you have to wait till the very end of the corner before you can get on the gas due to the car wanting to push then try a heavier oil in the rear diff.

It's a good tuning aid and something worth trying just to experience the effect it has on your car.

Regards,

Simon

grippgoat

iTrader: (8)

My understanding (based on experience with other cars) is:

Thinner Rear = More corner entry rotation, and more rotation around the apex, especially hairpins. Less on-power steering.

Thicker Rear = A bit more settled on corner entry, potentially sluggish rotation through the corner. More on-power steering.

Front Diff = Harder dive into the corner. More mid-corner steering. More wheel spin on power, leading to slower corner exit, and possibly weird front-end behavior when getting into the throttle.

Thicker Front = More like a spool.

Spool Front = Fastest in 17.5 or faster on a tight track, due to increased corner exit traction.

-Mike

fabrc68

hi all, i'd like to know if someone else has tried, on the T4, this setup "trick" that i've been suggested to try, but still haven't : a driver told me to make a "mix" of composite suspension holder... that's to say, use standard (0 mm roll center) suspension holder in the forward lines of both front and rear arms, and to use the lowered (-0.75mm, longer) suspension holder in the backword lines of front and rear arms.... but he cannot explained, or i didn't get, what such a setup change would accomplish... besides, would't such a change alter the caster (incresing it, 'cause now the arms are a little backword-inclined)....

any hint/suggestion/technical explanation would be useful, thanks

Fab

Adam B

I think that is explained in the T3 setup book which you can download from the X-ray site. Here is a PDF of the 2 pages that explain it.

Skiddins

Almost sounds like having the wishbones at that angle at both ends cancel each other out.

As far as I can tell, it would only be beneficial if the track was very bumpy.

Skiddins

fabrc68

thx Adam, that was exactly what i needed..... i owe you one...

now, i understand that the configuration my friend suggested me is kickup(pro-dive) and anti-squat....anyone cares to comment on what practical effect this combination would have (in comparison to standard position) ? keep in mind that my track is outdoor asphalt, medium grip, mixed (couple of 40mt straights, 2 chicacanes, 2 turnbacks, 2 hairpins, 2 slow curves), and i run in mod class - 4.5t

Fab

erchn

iTrader: (7)

There are many factors that would skew how those adjustments change a car, and I certainly haven't tested them all. I've not used pro-dive, but it "should" make the car pitch to the front faster, though not necessarily give you more steering. In fact, it'll probably make the front-end feel lazier. You'll likely find more information on anti-dive, the effects should more or less be reversed.

Anti-squat I have run, and it tends to lock the rear of the car in more on power, making it square up quickly. It shouldn't have much effect on roll, but I thought it made the car a little inconsistent since you have suspension bind slowing the squat and springs doing that work, I think you generally would run a bit softer spring or lean the rear shocks in when running this.

Both of these settings are used regularly in off-road, so maybe you could talk with some local offroaders about how changing those settings effects their car.

CristianTabush

iTrader: (13)

To add to what Ethan said, basically pro-dive, or "kick up" helps in bumpy track conditions. It effectively adds caster to the car, which will reduce initial turn in, but increases middle and corner exit steering. It also helps to gain high speed steering. The effect of kick up is much like adding more caster at the knuckle, however it is commonly observed that a car with 2 degrees of kick up and 2 degrees of caster at the knuckle, for a total of 4 degrees does not steer quite as much going into the corner as a car with Zero kick up and 4 degrees of caster at the knuckle. From my experience, it makes the car a little less responsive.

Anti Squat is hardly ever used in on-road, but it should make the rear suspension stiffer under acceleration which is supposed to aid in harder acceleration. It tends to make the rear end a little bit loose coming into the corner and hook up more on exit and much like what Ethan says above, it allows the car to square up more.

fabrc68

thanks Erchn & CristianTabush, your interventios are greatly appreciated. i'l give this a try and report my considerations....

in the meantime, i have another question on the T4, altough the problem in generalized, so i try to see if the willingness to help others is still on... i race with foam tires, and i have huge problems keeping the droop to the value i want... 'cause setting the downstop (let's see to "box" values of 6 front and 5 back) alone isn't enough to set the droop... the ride height, and consequently the springs precharge, has a direct hit also...
let's say that i set the downstop to 6/5, and i set a ride height of 5/5 mm with new foam tires (65 mm)... usually that is accomplished by setting a very low spring precharge.... after some runs, the tyres wear off, let's say to 63mm, that means 1mm less ride height... if i compensate the spring precharge, increasing it a bit, to restore the 5mm ride height, the droop value lowers, cause the arms are closer to the chassis...how the hell am i supposed to measure the droop in order to keep it constant ? i don't even know where to start... i have the droop gauge to measure the downstop, but i don't have anything, but eyeball, to measure the effective droop....

someone at the track says that he sets up the downstop (6/5) with new tyres (65mm) and, in order not to have to continuosly change the downstop to adjust the droop, the set a compromise of an initial ride height of about 7mm / 7.5mm..... so they don't change it until the tyres are quite completly worn out...

my consideration on this "compromise" is that you get the "full" setup only towards the end of the tyres usage, when ride height is close to the optimal measure of about 5/5......

also, the setup book (and the various setup sheets that you can find on the net) all specify downstop values, but they never report the droop values.... where do i look to find out the "correct", initial front/back droop value for an outdoor, medium grip, mixed, asphalt track ?

sorry for the long post, but i'm sure that this issue is common for novice foam racers like me, and pro-advice would be very useful.

Fab

erchn

iTrader: (7)

<full disclosure>I've never run foam tires, take this as a mostly uneducated guess.</full disclosure>

I think with foam tires you face at least two problems, related to droop. 1) How to properly measure droop. 2) How to maintain the proper arm angle so that your roll center is consistent at the start of each run.

For #1, I would measure droop over ride height. See this post, for a method of measuring this way. There are other methods, but this should work in general, or give you ideas on other ways.

For #2, I think you'll want to find your desired roll center, at a given tire height. So with full tires you might need the +.75 arm holders. As the tires get smaller start removing shims or go to lower arm holders. The goal would be to maintain the same arm angle, even though the tires of gotten smaller.

When on the bench, I think you'd want to do #2 first, based on tire height. Then set your ride height, then set your droop with #1.

I believe you'll also face upper camber link issues with camber gain as well, but #2 probably applies in the same way. I think another possible, and probably simpler, answer is to have taller and shorter front and rear hubs, which would leave all suspension pretty much the same. The height changing between the outer hinge pin and the axle.

All of this said, I'm probably wrong. I would honestly head over to the Paul Lemieux thread, I'm pretty sure he's going to have a more thorough and informed answer.

Ethan

fabrc68

thx again Ethan... those are good points and i'll think about them...

Xpress

iTrader: (3)

When we used to run foams here (US) I would true 4 or 5 sets of tires at a time all to the same size. Run them a couple times and then put them in a bag and switch to one of the other sets. After all 5 sets had been run I'd find the smallest tire and skim all the tires to match and start the process over again. When the tires started getting too small to maintain traction for the entire run I'd put them away until I was at a race where the traction was high enough that I needed to run the small tires.

Chrissy C

iTrader: (1)

Hi,

If i put the track width spacers shown in the T4 manual (i.e. RR 0.75mm each side front 0mm) on my T3'12 chassis, will the trackwidth be the same...or is the T4 chassis drilled differently?

Does anyone know what the centre of the pin to centre pin measurements are RR and FR on the T4?

And lastly...

Is the trackwidth of the kit T4 the same as the Hagberg mod that a lot of people did on the T3'12?

Cheers guys, i'm just getting myslef confused and need some help lol!

Best,
Chris

Mikkel_R

The Rear track width of the T4 is 0.75 narrower than the T3'12 the front is the same.

Cant remember but in think the Hagberg mod is 1mm narrower on a standard T3'12 so that makes the T4 0.25mm wider than a T3'12 Hagberg car.

Hope that makes sense.