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Advanced Suspension, Chassis, and Braking Talk about suspension geometry, advanced handling/chassis setup, custom brakes, etc. NOT your basic brake pads and "best drop" Information.

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Old 07-12-2006, 12:41 PM   #1
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Drag Racing Suspension Discusion

I haven't had my Maxima for a while and might be out of touch with the technology, but I was talking with my friend Neal (Nealoc187) recently about how to cut better 60' times because I want to see him in the 11's. He can cut low 1.9's on ET Streets, but I feel the car is capable of much more. My purpose for creating this thread is to brainstorm ideas and exchange proven methods for cutting good 60's in regards to suspension and tire technolgy. I've discussed a few ideas with Neal and I'll briefly describe them below. Please feel free to add input!

1. Adjust Camber: You want to be as close to 0 as possible to get the maximum contact patch. Camber is probably near OEM specs on Neal's car, which I have no clue what that is.

2. Coilovers: Neal purchased K-Sports last night with 7/6 kg/mm springs. Our idea was to jack the rear coilovers up and lower the fronts a bit at the track. Set the rear shocks to full firm. This should help control weight transfer, which is the problem with FWD cars.

3. Spring Isolators or Air Bags: I told Neal about these and am not sure if he has tested them thoroughly. Pontiac GTO's come with spring isolators from the factory during shipping. When the car is prepped, they are thrown out. Head over to your local Pontiac dealer and they will most likely give you them for free. Again, this will prevent the rear coils from compressing, thus preventing weight transfer to the rear.

Another idea I had was Air Bags in the rear, similar to these:
http://www.hotchkis.net/cgi-bin/EDCs...atalogno=31750

RWD guys use these in the right rear to help prevent the spring from compressing. If the diameter fits Maxima coils, this might work.

4. Tires: Neal is running 26x10.5-15 ET Streets, which works out to 265mm wide. What is the widest tire you can run up front, track use only? ET Drags would probably hook better and playing with sizes might help.

5. Chassis Stiffening: The Maxima chassis isn't the stiffest and you want to have your suspension in place putting the power down. SFC's, FSTB, and Lower Tie Bar might help??

Again, if anyone has any ideas or answers to the above discussion, feel free to add. I think a high 1.6 or low 1.7 isn't out of the question with the right setup and good track prep.
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Old 07-12-2006, 02:08 PM   #2
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I'd agree with all of your points, though I'm not much of a drag expert...The LTB would most definitely help, as it really reduces wheelhop in all situations. If one could find a 5th gen version of JClaw's "traction bars" they would be helpful as well.
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Old 07-12-2006, 02:57 PM   #3
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I have a certain modification coming out too that will reduce your wheel hop and there help put more power to the ground. Still need to get around to finishing it for testing.

Also, setting the rear shocks to full still will only aid in the initial dampening, but may not off set the weight transfer at launch (in my humble opinion). You'd really need a spring setup for the drag strip, something like 6kg front / 12kg rear
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Old 07-13-2006, 07:57 AM   #4
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#1: I'm not so sure you want to have 0 camber set on the car. You want it to be 0 at the moment of launch, but with the front end lifting it won't be. I have set mine up at -2 right now, and I think it has helped on the launch as perhaps I get closer to ideal upon front lift, but I can't prove it.

#2: Coilovers are a must at minimum for good FWD drag launches. I have 9/6 K-Sports on my car and on the street I run almost no preload but for the track I am planning to crank the rear preload way up and see what it does. I think you want the rear as stiff as possible, in fact immovable or solid is probably ideal, but doing that introduces more work and the need to swap the rears for track/street. Fabricating a solid rear setup is my next step after trying a high preload.

#3: Spring isolators, air bags, blocks etc could all be used to stiffen the rear but I think I want to fabricate something that is 100% stiff, ie no compression and hence weight transfer at all. I have a few ideas in mind, but as I said above first I'm going to try just adjusting the preload to see how much of an effect it has. Also rake can be increased... I'm currently 3/4" higher in the back but I will be increasing that.

#4: Tires are definitely an area we need to have more experimentation with. Guys have traditionally been running the same rim and slick sizes for the most part (from what I can gather). Mardi is now going to a 10" rim and 26x10 slicks so I'll be really curious to see how he does, as I'm considering doing it also. I think people have fitted 10's or even 11.5's on 7 or 8" rims before, but I'm inclined to think that to put down the maximum contact patch the rim width should not be that much smaller than the tire width. Also a taller tire with more sidewall may help, but gearing has to be considered with taller tires too.

#5: Chassis stiffening-- seam welding is something I intend to do in the near future. I think it will provide quite a bit of stiffening at minimal weight penalty unlike SFC or foaming etc. I'm not so sure that for drag racing a FSTB or tie bar will make much difference for the weight they add (well the tie bar anyways).


As far as wheel hop goes, IMO it is not an issue if the car is set up properly. In fact I don't think traction bars are necessary any more. I have had zero wheel hop problems this year without bars and I'm consistently pulling mid-high 1.7 60's on slicks. I have also not had wheel hop problems on the street, on both all-seasons and drag radials. The key for me was overhauling the front end. I replaced all my bushings with poly ES bushings (I already had ES motor mounts), and I changed the LCA's (and new ball joints) and front wheel bearings. I think many have overlooked these areas, and have had wheel hop problems because of it. I mean most of our cars are 6-10 years old now, and if you haven't changed the sloppy rubber bushings under there chances are they are torn to shreds or at best are squished into shapes that aren't effective at absorbing loads without allowing significant movement/play.


At the end of the day I do think VERY low 1.7's or even 1.6's are possible on our cars (on a good track). I have hit a 1.76 best so far and I still have a lot of room to improve my rear suspension and front rim/tire setup. And furthermore that's with a 3L, without the extra torque of the 3.5. So it *should* be possible.
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1/4 mile stats (all N/A VQ30):
Best 60': 1.73
Best ET & trap: 12.61, 108.98 mph


Click to see the video. More videos also here.
Mods list and dyno here (as of May 9/08).
My EU writeup can be found at VQ Power.
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Old 07-13-2006, 08:57 AM   #5
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would installing a roll cage be easier and more cost effective than seam welding?
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Old 07-13-2006, 10:02 AM   #6
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Quote:
Originally Posted by Larrio Motors
would installing a roll cage be easier and more cost effective than seam welding?
Not easier IMO. If you pull the interior out yourself the welding could be done in a couple hours and you don't have to measure, cut, bend and fabricate anything. And if you know someone who can weld it's free, or almost free. The cage will add weight also, and inconvenience for street driving etc. At this point for a street car I would not really want to put in a cage unless I had to as per NHRA regulations (ie if you're fast enough like Mardi, mid 11's).

Now having said that the cage might add a higher level of stiffness than seam welding but I'm not sure about that, ...it is only attached at a few points, albeit usually good ones. Is a cage's function more to ensure safety in a crash/roll over rather than providing complete stiffening of the chassis (unless you attached it at a higher number of points)? I'd imagine the seam welding would improve things quite a bit because the shell/unibody would become much more of a solid unit then instead of a few different stamped pieces spot welded/glued together at selected points. I'm no expert in this stuff though, I'm just speculating at this point.
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1998. 3L. 5-spd. Sterling Mist. SE. (fun car)

1/4 mile stats (all N/A VQ30):
Best 60': 1.73
Best ET & trap: 12.61, 108.98 mph


Click to see the video. More videos also here.
Mods list and dyno here (as of May 9/08).
My EU writeup can be found at VQ Power.
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Old 07-13-2006, 11:50 AM   #7
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That's true, I didn't take into consideration all the fab work required for the roll cage.

However it seems to me as if almost a bare chassis is needed to properly seam weld the entire car.
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Old 07-13-2006, 12:25 PM   #8
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Quote:
Originally Posted by Larrio Motors
That's true, I didn't take into consideration all the fab work required for the roll cage.

However it seems to me as if almost a bare chassis is needed to properly seam weld the entire car.
It's not that hard to get the interior completely out....

Just did most of it a couple months ago to remove the sound deadening.
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2000. 3L. 5-spd. Black on black. SE. (DD)
1998. 3L. 5-spd. Sterling Mist. SE. (fun car)

1/4 mile stats (all N/A VQ30):
Best 60': 1.73
Best ET & trap: 12.61, 108.98 mph


Click to see the video. More videos also here.
Mods list and dyno here (as of May 9/08).
My EU writeup can be found at VQ Power.
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Old 07-13-2006, 02:14 PM   #9
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Old 07-13-2006, 02:54 PM   #10
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Quote:
Originally Posted by DandyMax
#1: I'm not so sure you want to have 0 camber set on the car. You want it to be 0 at the moment of launch, but with the front end lifting it won't be. I have set mine up at -2 right now, and I think it has helped on the launch as perhaps I get closer to ideal upon front lift, but I can't prove it.

#2: Coilovers are a must at minimum for good FWD drag launches. I have 9/6 K-Sports on my car and on the street I run almost no preload but for the track I am planning to crank the rear preload way up and see what it does. I think you want the rear as stiff as possible, in fact immovable or solid is probably ideal, but doing that introduces more work and the need to swap the rears for track/street. Fabricating a solid rear setup is my next step after trying a high preload.

#3: Spring isolators, air bags, blocks etc could all be used to stiffen the rear but I think I want to fabricate something that is 100% stiff, ie no compression and hence weight transfer at all. I have a few ideas in mind, but as I said above first I'm going to try just adjusting the preload to see how much of an effect it has. Also rake can be increased... I'm currently 3/4" higher in the back but I will be increasing that.

#4: Tires are definitely an area we need to have more experimentation with. Guys have traditionally been running the same rim and slick sizes for the most part (from what I can gather). Mardi is now going to a 10" rim and 26x10 slicks so I'll be really curious to see how he does, as I'm considering doing it also. I think people have fitted 10's or even 11.5's on 7 or 8" rims before, but I'm inclined to think that to put down the maximum contact patch the rim width should not be that much smaller than the tire width. Also a taller tire with more sidewall may help, but gearing has to be considered with taller tires too.

#5: Chassis stiffening-- seam welding is something I intend to do in the near future. I think it will provide quite a bit of stiffening at minimal weight penalty unlike SFC or foaming etc. I'm not so sure that for drag racing a FSTB or tie bar will make much difference for the weight they add (well the tie bar anyways).


As far as wheel hop goes, IMO it is not an issue if the car is set up properly. In fact I don't think traction bars are necessary any more. I have had zero wheel hop problems this year without bars and I'm consistently pulling mid-high 1.7 60's on slicks. I have also not had wheel hop problems on the street, on both all-seasons and drag radials. The key for me was overhauling the front end. I replaced all my bushings with poly ES bushings (I already had ES motor mounts), and I changed the LCA's (and new ball joints) and front wheel bearings. I think many have overlooked these areas, and have had wheel hop problems because of it. I mean most of our cars are 6-10 years old now, and if you haven't changed the sloppy rubber bushings under there chances are they are torn to shreds or at best are squished into shapes that aren't effective at absorbing loads without allowing significant movement/play.


At the end of the day I do think VERY low 1.7's or even 1.6's are possible on our cars (on a good track). I have hit a 1.76 best so far and I still have a lot of room to improve my rear suspension and front rim/tire setup. And furthermore that's with a 3L, without the extra torque of the 3.5. So it *should* be possible.
Dandy,
I am not positive on the camber, but it's something to research. Maybe the SRT4 guys or FWD DSM crowd can answer that question. I know on RWD cars you want ideally the camber set at 0. I do think that Coilovers are a must. A stiff rear spring will help aid weight transfer as well as raking the suspension. I think the biggest gains though will be with trial and error of slicks. Guys like Neal and Mardi might actually benefit from a taller tire. The added power that their cars make will offset the reduction in gear ratio. I am anxious to see what the coilovers and ES bushings do for Neal's 60'. I've always said that his car is capable of low 1.7's. Now I just need to s***up my game and get forced induction on my!
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Old 07-13-2006, 08:43 PM   #11
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Quote:
Originally Posted by MAX2000JP
Dandy,
I am not positive on the camber, but it's something to research. Maybe the SRT4 guys or FWD DSM crowd can answer that question. I know on RWD cars you want ideally the camber set at 0. I do think that Coilovers are a must. A stiff rear spring will help aid weight transfer as well as raking the suspension. I think the biggest gains though will be with trial and error of slicks. Guys like Neal and Mardi might actually benefit from a taller tire. The added power that their cars make will offset the reduction in gear ratio. I am anxious to see what the coilovers and ES bushings do for Neal's 60'. I've always said that his car is capable of low 1.7's. Now I just need to s***up my game and get forced induction on my!
Yeah I know RWD you don't want camber but it's a little different because a typical rear axle is not like a FWD control arm that can pull the wheels into positive camber when the front end lifts up (ie hence the reason to start a little negative maybe?)

And yes that's why I'm saying we (the Maxima community) haven't experimented enough with rims and slick sizes. Heck I'm still spinning off the line even, pulling mid-high 1.7's N/A, so I could potentially benefit from a fatter sidewall or wider rim and tire perhaps. And if I can then higher powered guys like Mardi and Neal definitely should be able to.
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2000. 3L. 5-spd. Black on black. SE. (DD)
1998. 3L. 5-spd. Sterling Mist. SE. (fun car)

1/4 mile stats (all N/A VQ30):
Best 60': 1.73
Best ET & trap: 12.61, 108.98 mph


Click to see the video. More videos also here.
Mods list and dyno here (as of May 9/08).
My EU writeup can be found at VQ Power.
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Old 07-14-2006, 03:41 AM   #12
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Quote:
Again, this will prevent the rear coils from compressing, thus preventing weight transfer to the rear.
Preventing rear coil spring compression only reduces/eliminates the visible evidence of rearward load transfer. Not the load transfer itself, which would occur even if the suspensions were welded solid.

Quote:
RWD guys use these in the right rear to help prevent the spring from compressing. If the diameter fits Maxima coils, this might work.
Actually, the main reason for air bags in RWD "stick axle" cars is to preload the right rear tire. Torque reactions within the axle itself tend to plant the LR and lighten the RR, and the bags are intended to compensate for this.

If your corner weights were not optimum for the dragstrip, you might be able to jack some weight around such that your front tires would be more equally loaded, in which case you'd gain a little.


Actually, I don't think that allowing the rear of a FWD car to drop on acceleration is necessarily a bad thing, as that tends to lower the CG height. Rearward load transfer then also tends to drop. I'm thinking shorter bump stops with a softer initial rate, springs only stiff enough to keep you off the stops after the launch, and some shock development to control the rate of rear suspension motion. Controlling the maximum amount of downward rear suspension travel with a particular detail internal to the shocks might be possible as well. Again, this is somewhat different from a RWD stick axle car, where rear end "squatting" implies load taken off the drive wheels in reaction.

Get as large a percentage of your weight as far forward and as low as possible. Even moving the front passenger seat all the way forward and folding its seatback and the rear seatbacks down - tie them down if you must - will help a little. Run with as little gas in the tank as you can get away without starving the pump.


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Old 07-14-2006, 03:41 AM
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