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View Full Version : How Low is Too-Low? >Chassis height with & without body


Felix2010
2009.07.10, 01:02 AM
Hey guys,

I would like to ask how low y'all run your MR02s when running on RCP? (I'ma worry about MA010 chassis clearance later:))

I never thought too much about it. Just always wanted it nice n' low. But lately I am looking at my MR02s and when I am pushing-down on the chassis to test the suspension & clearance, I am wondering if under cornering-load the middle-rear of the chassis bottom isn't rubbing the track? -> And the same goes for the body. For example, on the 2007 350z Super-GT: When I first got one, I shaved the rear and front lip/spoiler for proper track clearance, using pics of Reflex's 2008 PNWC Team cars as models. The front & rear have plenty of ground clearance; The bottom-middle "rocker-panel" section is what I wonder about.

I just measured the chassis ground-clearance on my MR02 and have 2mm (Maybe 2.1mm) directly in the middle of the chassis, and this is perfectly even from front to back. With the 2007 Z Super-GT body on, the side-bottom body clearance is around 1.7mm. From what I always see in pics from the PN events and what not, everyone's MR02s look to be sitting comparably very low. My question is, does my ground/track(RCP) clearance sound adequate?

Also, is there a difference in you guy's Stock/Mod cars' ground clearance for races?

Thanks for the help in advance. :D

JuniorWKR
2009.07.10, 10:59 AM
as long as you arent rubbing when racing i guess its never too low... but i feel that the lower you run your car the less body roll you have which will take away rotation and may flat line your suspension... some travel is good... in both mod and stock i run my mr02 at stock height and have no problems... you also need to have a little bit of droop in the front and rear to have a properally working suspension and im unsure if you can achieve that but running the car so low...

marc
2009.07.10, 11:01 AM
As I always say, a picture of your question will help us provide a better answer.
If your track is perfectly clean, and all gaps are perfectly smooth than I don't see too much a problem with having it down low. However, I'm not an experienced racer, only raced a couple of times. I bet EMU or some of the other more experienced drivers can tell you. I think if you go too low, the car will not handle well. Low is good, but too low can be bad. Again, please take a picture of your car where we can see it's ground clearance, or lack-of.

ianc
2009.07.10, 12:14 PM
Hi Felix,

I think that the actual suspension deflection on these cars (depending on the stiffness of course) is actually very small - on the order of 1 mm or so, so if you're worried about dragging at 2 mm, you're probably fine (given a well-groomed track). You could test this by making marks with a colored magic marker on the underside of the body\chassis where you suspect rubbing, then run a few laps. If the magic marker has worn off, then you may have a problem.

That said, I find that when cars are too low, they tend to be too darty and twitchy. I've actually recently been experimenting with raising my LM slightly with good results so far.

I know EMU has long been a proponent of the 015 as compared to the 02 because the higher roll center allows more weight transfer, and this seems to make sense to me. My Frankenstein GT40 is using an 01 chassis with an 02MM motor mount, and it is one of the most stable, predictable cars I have right now. I also have a twitchy 934 that I'm running on an 02 chassis which I'm thinking of converting over to an 015 as an experiment in this vein.

Good question!

ianc

ruf
2009.07.10, 03:53 PM
We've lost world championship races due to mounting the body too low (thought we were being smart by installing the side clips higher). Rear of the sideskirt would ground under acceleration out of a corner. Didn't happen in practice and qualifying. Only showed up in the LCQ and mains as the traction came up and the cars started rolling and squatting more in mod class. Couldn't figure out why we suddenly weren't getting traction on exit. Total newbie pointed out the paint worn off the bottom edge when we got home a week later. I'll use a sharpie to mark the bottom edge of the body to check for wear.

lfisminiz
2009.07.10, 06:39 PM
Very good question and feedback so far.

Felix2010
2009.07.10, 11:27 PM
The track I run on is in my home and very clean and very-well cared for. It is medium in size I would say, probably 2 and a half Wide-L kits worth of RCP. So I can get going pretty good. Most of the time I run Mod motors because I just get bored running slower motors when practicing.:)

Junior & ianc - The chassis height I have posted is with droop, sitting static on the track (forgot to mention that:o). I totally understand what you guys are talking about when it comes to suspension droop and suspension-weight transfer and how important they are in proper setup. I too have followed EMU's MR015 development and it's very interesting.
I have checked for rubbing using different methods including the magic-marker method and from my tests the chassis does not rub unless I run semi out-of-control, or when my tires begin to where thin. On my 2007 305z Super-GT body the side-skirts in front of the rear wheel-well do "glaze" the track on occasion, not so much I lose traction though. I think I'm going to either raise the body about 0.5mm, or an easier thing to do would to shave that much off the bottom side-skirts to gain the extra clearance. 0.5mm-0.8mm I think wouldn't be too noticeable. Before I go and raise the chassis though, I am trying to get an idea of how high the top racers have their chassis' set up for racing on RCP - The "sweet spot" of track clearance: Low-CG (Enough to cut the airflow from underneath the MR02's chassis) but with proper weight transfer capability.

ruf - Exactly why I figured I'd post this question.:D It's one of those things where it may not present itself immediately but can pose a major issue with a car's setup. Sorry to hear it cost you WCs!:eek: I am wondering though, when you have your MR02's on the bench, what do your chassis height & body side-skirt ride height numbers run between (millimeters)?
Thanks for the feedback guys.:)

A simple ride-height in millimeters of the chassis is what I'm looking for marc. Figures are what I'm wondering about, not pictures of people's rides. You don't judge a properly inflated tire by "looks", do you?;)

color01
2009.07.11, 05:48 AM
1.7mm clearance on the side skirts should be enough... I ran the Super GT Z 2007 too and I left the front bumper and side skirts approx. 1.5mm from the ground. Car ran fine. ;)

For what it's worth, some more ride height info: My front ride height (chassis front edge) is usually less than 1.5mm, and rear ride height between 2-2.5mm depending on tire size. I don't know if this seems like a lot of chassis rake to you, but I rather like it. The car's quite planted with plenty of steering. A little less than 0.25mm front droop btw, that's about how much the springs compress when the car's sitting still.

Felix2010
2009.07.11, 11:22 AM
Thank you for the info color0. Much appreciated:D

I also need to decide whether or not to go with a harder rear oil-shock spring. I am running 98mm WB with Reflex's Side Damper System. Even with a Kyosho Hard carbon H-plate this system is super smooth and quite soft.

I will try more rake for sure as it is this rear side-skirt area (Directly in front of the rear wheel-wells) that I am concerned with the most.

Thanks again!

Rune
2009.07.13, 12:46 PM
Thank you for the info color0. Much appreciated:D

I also need to decide whether or not to go with a harder rear oil-shock spring. I am running 98mm WB with Reflex's Side Damper System. Even with a Kyosho Hard carbon H-plate this system is super smooth and quite soft.

I will try more rake for sure as it is this rear side-skirt area (Directly in front of the rear wheel-wells) that I am concerned with the most.

Thanks again!

A little OT, but you should try out the 3Racing H-plates. Medium and hard are harder than Kyosho & PN hard. They work really well with the side damper setup. For me this si the only plates I use with RR side damper.

ianc
2009.07.13, 01:10 PM
A little OT, but you should try out the 3Racing H-plates

Going a little further OT, I would not recommend these at all. I tried a couple sets of them, but they (at least the ones I got) are poorly manufactured in the area of the attachment point to the chassis so that they do not hold firmly in one place, but rotate, inducing tweak. I would never use them again. I have had much better luck with Atomic and PN's, as they are a much tighter fit. YMMV...

ianc

Rune
2009.07.13, 01:29 PM
Going a little further OT, I would not recommend these at all. I tried a couple sets of them, but they (at least the ones I got) are poorly manufactured in the area of the attachment point to the chassis so that they do not hold firmly in one place, but rotate, inducing tweak. I would never use them again. I have had much better luck with Atomic and PN's, as they are a much tighter fit. YMMV...

ianc
:)Strange. I have used these for the last 6 months and have never had any issues with them. I use the High clamp force PN mount.

They are very consistent from plate to plate, and are a good fit. Could be that it has been a bad batch out there? Also they are very cheap, and you can buy them separately witch I think is a really good thing.

I always use a caliper when I mount a H-bar, and check alignment after a few runs.

ianc
2009.07.13, 01:43 PM
I use the High clamp force PN mount.

That may help. The possibility of a bad batch could be there. I found that the little slots in the side of the H-plate where it mounts to the chassis was just too large for the corresponding tabs on the chassis. I tightened the mounting screws to the point where I was afraid of stripping out the chassis holes, but they would not stay straight under heavy cornering. Sounds like the PN mount would cure this problem. Unless you use it, I wouldn't recommend them though. The Atomic and PN plates are a much tighter fit, almost too tight to press in by hand initially, but when the mounting screws are tightened down, they give a nice solid fit...

ianc

Rune
2009.07.13, 02:25 PM
That may help. The possibility of a bad batch could be there. I found that the little slots in the side of the H-plate where it mounts to the chassis was just too large for the corresponding tabs on the chassis. I tightened the mounting screws to the point where I was afraid of stripping out the chassis holes, but they would not stay straight under heavy cornering. Sounds like the PN mount would cure this problem. Unless you use it, I wouldn't recommend them though. The Atomic and PN plates are a much tighter fit, almost too tight to press in by hand initially, but when the mounting screws are tightened down, they give a nice solid fit...

ianc

The main reason I dont use PN or Kyosho are that they are not as stiff as the 3R, and that works better for me. Especially on the RR side damper system. This system really works well with very hard H-Plates.

ianc
2009.07.13, 04:02 PM
The main reason I dont use PN or Kyosho are that they are not as stiff as the 3Racing

I too like a lot of spring rate in the rear of my MM's. Atomic makes a very hard SSG plate which I've been using with excellent results. Look for AR041.

ianc

Felix2010
2009.07.13, 10:15 PM
I might pick up a 3R H-Plate to try. I had been thinking about trying one since on Reflex's site they mention the 3R H-plates are harder than the K H-plates. Atomic's Ultra-Hard H-plate is another thing that I just keep editing out of my cart whenever I buy stuff.

I really like the Kyosho carbon H-plates though. They are so perfectly cut and great quality.

Rune
2009.07.14, 12:45 PM
I might pick up a 3R H-Plate to try. I had been thinking about trying one since on Reflex's site they mention the 3R H-plates are harder than the K H-plates. Atomic's Ultra-Hard H-plate is another thing that I just keep editing out of my cart whenever I buy stuff.

I really like the Kyosho carbon H-plates though. They are so perfectly cut and great quality.

I have tested the ATM Extra hard plate, but I dont like the shape of it where it mounts to the chassis. These dont fit in either ATM or PN H-Bar mounts.

The kyosho plates are really good quality, but regarding how they work, I think the PN and 3Racing are just as good. The bad thing about kyosho and PN are that you have to buy the set. I am sure I have given away and thrown 10 - 15 soft H plates. I have never had the need to use them.

The RR side damper setup really comes alive with harder H-plates.