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Programmers
2010.03.11, 05:19 PM
Hi folks,
I've recently built an AWD mod car. Using odd spares and a couple of other bits, I've replicated my stock car. However, the added speed makes it a little less unbalanced in the rear.

I need some advice.

My current rear end is as follows:
Toe: +1.5
Camber: +2
Springs: Softer than the front

Diff settings are about 70/30 - rear/front.

The back end is completely stock plastic too.

It's fast at the moment and doesn't handle badly. I just need to clean up that last bit of slop.

Any help at all would be great!

Cheers folks,
Tom.

Programmers
2010.03.13, 04:08 PM
Bump... :o

EMU
2010.03.13, 05:18 PM
What grease are you using to dampen the knuckles? This makes a huge difference on modified cars...

I usually use a thicker grease on the front, and lighter but grease 3 locations on the rear (kingpins and where the knuckle meets the tie-rod). On the front I only grease the knuckle kingpins (top and bottom).

The grease, as well as gluing the tires reduces a lot of chatter. Rear tires should be glued to the wheel, front tire sidewalls should be glued up...

Felix2010
2010.03.13, 05:45 PM
Hello,

What is the problem you are having exactly with the rear-end of your car? I now you said it is unruly a bit.

Programmers
2010.03.14, 06:54 AM
What grease are you using to dampen the knuckles? This makes a huge difference on modified cars...
I don't use any. Eek. I never thought about that before.

What is the problem you are having exactly with the rear-end of your car? I now you said it is unruly a bit.It has the tendancy to kick out on the tighter corners which really upsets the balance. :/

mk2kompressor
2010.03.14, 08:56 AM
set your diffs the opposite to what they are 30r 70f.
the rear set for more slip than the front will help control the back end under power when exiting the corner;)

Felix2010
2010.03.14, 09:22 AM
set your diffs the opposite to what they are 30r 70f.
the rear set for more slip than the front will help control the back end under power when exiting the corner;)

MK2 is right, I always run more slip in the rear than in the front. Some guys don't like this and would rather run more slip in the front. But running more slippage in the rear will help prevent oversteer on the AWD.

EMU is right also. Using differential lube/grease on the knuckle kingpins has become popular in AWD racing (And 015/02/03 racing recently). It will help damp the suspension and keep the tires planted.

If this still doesn't do the job to your liking:

-> You could go a little stiffer on the front suspension to lessen oversteer;
-> You could go with harder front tires and/or softer rear tires (And make sure to glue the rear tires to the rims);
-> If you run a low body, you might want to make sure the underside of the body like the bottom of the rear quarter-panels & the undersides of the side rocker panels are not rubbing the track under hard turning. This is something I have been working on for a while now - Trying to find the "Sweet Spot" of ride-height so the body and chassis don't rub the track under hard corning and acceleration, but also keep the overall ride height low-down enough to cut as much air from underneath the car as possible.
I started a thread about "How Low is Too Low" a while back here, under the "Setups" section I think.

Hope this helps Tom:)

EMU
2010.03.14, 04:17 PM
Is it kicking out off or on throttle. In general with AWD, you slow down before the corner, then turn in on throttle. You dont want to drive AWD off throttle in the corners. They dont behave well that way.

I run my diffs very tight in the rear, and loose in front. This allows the car to drive more similar to a RWD, but still get the power on the exit. With the rear diff loose, you really cannot get the power down as hard on the exit, the rear diff (where weight transfers) slips. Which causes the front diff to work overtime. It already performs most of the deceleration, and having it tight reduces the turn in drastically.

My rear diff is very tight, almost more than I would tighten an MR02. I want the car to accelerate as fast as I can without any slip in the diff. AWD in general, has the tendency to push, so you need to try to make it oversteer. You could possibly be using a front tire with too much grip. Make sure your car is well balanced with tires before you assume your problem is elsewhere.

Programmers
2010.03.15, 06:55 AM
Matt, Felix and Emu! Some great advice! I'm going to print your replies and take 'em to a track later this week for some thorough testing! :D

I'll post conclusions, etc, later this week.

Again, thanks for your time fellas. :)

dvsstrike
2010.03.18, 07:22 AM
tom
make sure your diffs are working properly also no binding and some what fresh. i rebuild my diffs every two race days to be consistant. i have rebuilt mine to the point i need new diffs. also put grease on knuckles and remove some plastic where the diffs sit. have you ever had a tc3? everyone use to ream the gear boxs out where the diffs set in there loosely. that what i do wwhen i run plastic everywhere. i can crank down on all gear box covers and diffs spin extemely free.also when setting the diffs make the front slightly tighter than ther rear.

EMU
2010.03.18, 12:04 PM
I used to have my rear diff looser than my front, and now I drive it the opposite. Rear much tighter than the front. It drives much better in and out of the corners. I guess it is better for higher grip situations. In general, it makes the car have more steering without using a very high grip front tire and causing the car to traction roll more.

On carpet or very low grip, you may want more stability on the setup. So a looser rear diff may be the better option. The tight rear diff was recommended to me from Cristian, and I tried it, at first I didnt like it. But after changing the tires, the car was ballistic and set the 5min qualify track record on a layout that was down for more than 2 months. I felt very comfortable placing the car in the corners, which is very important to me. If the car is not consistant in its handling, I cannot push it hard through the corners and know exactly where the car will be after exiting the corner and entering the next.

I use Kyosho differentials. Best diffs, especially with RR delrin outdrives ;)

I also use a similar setting when setting up my virtual AWD cars in Forza3 for the Xbox360, and it works very well :)

JuniorWKR
2010.03.18, 12:15 PM
EMU is correct... you wanna try to set the front diff to where if you hold the car in your hand and rock the front tires back and forth it almost wants to engae the rear tires to spin... if the rear tires spin too the front diff is too tight..

i run my rear diff just tight enough to where is wont slip on the track... any tight and you will lose rotation...

what i have come to find with the front diff if is you set it like i just said you can start to make very small adjustments from there which will actually give you the ability to time when the front diff kicks in... almost makes the car look like a two stroke when hitting the straight away... also with the front diff loose it will make the car feel more like an 02...

but be careful cause too loose and it will start to walk on you...

try running the rear tires slightly large in diameter then the front... on the long straight it will cause it rear to overdrive the front and disengage tohe front diff which will help you set up better for the first turn as when you come off power it will kick back in allowing you to gain more top end speed on the straight and dive in harder on the first turn...

also try running your rear

Programmers
2010.03.22, 04:40 AM
Hey folks,
I spent yesterday messing with my car following the advice from this thread. I didn't get around to using grease or altering the springs because after altering the diff rate from 30f/70r to 70f/30r it made a world of difference!

I also spent a good 30 minutes re-shimming parts of the car and tightening things up and it was magic!

I think shimming makes such a difference! I used to be quite cinical about it, thinking it was a bit pointless. But it really does make a such a difference!

Again, thanks everyone! Really appreciate the top-notch advice.

EMU
2010.03.22, 12:13 PM
Whatever works best for your driving and track layout is what is important. On high speed layouts, we all run nearly the same setups, with slight difference in camber and tire combination, but almost all of the fast guys here have loose front/tight rear diffs.

Shimming makes a huge difference. Now, get out there and give Matt a run for his money ;)

mk2kompressor
2010.03.22, 01:00 PM
ill need to stop giving him advice soon:p

Programmers
2010.03.23, 05:07 PM
Whatever works best for your driving and track layout is what is important. On high speed layouts, we all run nearly the same setups, with slight difference in camber and tire combination, but almost all of the fast guys here have loose front/tight rear diffs.

Shimming makes a huge difference. Now, get out there and give Matt a run for his money ;)
I run 30f/70r on my HFAY car. Reversing it has softened the effects of the tweak I have on my car. I need a new chassis it seems...

As for Matt - I have to let him win because he owns a Mini Z shop n' all. If I beat him, he'd look bad and I don't want to embarress him.

Not because his car is twice as fast and his driving skills are twice as good lol... Nothing to do with that at alll.... :rolleyes: