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View Full Version : More Caster Options for the PN Front Suspensions? 02/03 A-Arm, 03 Upper Arm?


Felix2010
2011.06.28, 07:17 AM
I have to say that one of my favorite things PN Racing brought to Mini-Z is adjustable front-end caster:D :

Starting with the MR02, PN released their Alm. Upper Front Tower Bars in 0.5, 1.0, and 1.5 (fixed) caster options. When everyone was putting these onto their MR02's , I read that the 0.5 bar wasn't "0.5 degrees" caster, but instead was "0.5mm caster" - Which basically gave the car 2-degrees of caster per each 0.5 increment. Total caster adjustment max = 6 degrees or thereabouts with the 1.5 bar(At least this is what I heard, please correct me if I am wrong about this).

Then the PN 02 Double A-Arm FS arrived, with adjustable caster, the adjustments via 0.2mm washers: Maximum of 2 washers to give a maximum of 1.8 degrees of caster (0.9 degrees per 0.2mm shim).

Caster adjust is the same for the PN 03 A-Arm FS, and also for the PN 03 Alm. Upper Arms - 1.8-deg max.

Is there any reason why PN limited the max-caster adjust to only 1.8 degrees? Or is this something that could be adjusted more if PN released higher-caster replacement parts for these Suspensions?
Also, if anyone has filed-down the appropriate parts to gain more caster from these PN FS's, I would like to know more about the best way to do this mod (Add more caster).

I actually ran a 0.5mm shim on my A-Arm to get additional 0.1mm/0.5-deg of caster, for a max of ~2.3-degrees. Is there any disadvantages/problems to shaving the front upper tower bar or caster arms to achieve more caster? Somewhere in the range of 4-degress would be great, based on the feedback Reflex's 4-deg caster option Front Suspension has received.

Thanks in advance for your help

yasuji
2011.06.28, 11:51 AM
I have to say that one of my favorite things PN Racing brought to Mini-Z is adjustable front-end caster:D :

Starting with the MR02, PN released their Alm. Upper Front Tower Bars in 0.5, 1.0, and 1.5 (fixed) caster options. When everyone was putting these onto their MR02's , I read that the 0.5 bar wasn't "0.5 degrees" caster, but instead was "0.5mm caster" - Which basically gave the car 2-degrees of caster per each 0.5 increment. Total caster adjustment max = 6 degrees or thereabouts with the 1.5 bar(At least this is what I heard, please correct me if I am wrong about this).

Then the PN 02 Double A-Arm FS arrived, with adjustable caster, the adjustments via 0.2mm washers: Maximum of 2 washers to give a maximum of 1.8 degrees of caster (0.9 degrees per 0.2mm shim).

Caster adjust is the same for the PN 03 A-Arm FS, and also for the PN 03 Alm. Upper Arms - 1.8-deg max.

Is there any reason why PN limited the max-caster adjust to only 1.8 degrees? Or is this something that could be adjusted more if PN released higher-caster replacement parts for these Suspensions?
Also, if anyone has filed-down the appropriate parts to gain more caster from these PN FS's, I would like to know more about the best way to do this mod (Add more caster).

I actually ran a 0.5mm shim on my A-Arm to get additional 0.1mm/0.5-deg of caster, for a max of ~2.3-degrees. Is there any disadvantages/problems to shaving the front upper tower bar or caster arms to achieve more caster? Somewhere in the range of 4-degress would be great, based on the feedback Reflex's 4-deg caster option Front Suspension has received.

Thanks in advance for your help

for me, for modified, i have tried maximum castor on my AA Arm set up for 02 and 03 it makes it feel disconnected like im driving my car off a rubber band...so i run the .2 shim on each side...

color01
2011.06.28, 03:52 PM
Shaving the arms or hinge mounts will marginally weaken the parts, of course, but I don't see why you can't do it. If I remember correctly Davey G also ran a blue shim behind the hinge mount once his double-A-arm system loosened up sufficiently. I just stacked the two steel shims such that the conical faces pointed outwards, that's almost the same thing as a blue shim. ;)

Perhaps it's the way I drive, perhaps it's the places I race, but just like Grant I've never really found a way to use more than 2 degrees of caster. I had the Reflex tower bar on 4deg caster for a time and ended up going back to the 2deg option anyways because it didn't turn in crisply enough for my taste. You might also recall that I even tried 6deg caster at one point by flipping the PN tower bar around, but that just doesn't work at all lol, it's waay too much and destabilizes the car at high speed unless you have some gigantic rear wing to balance it out.

I would never say "don't" do it or that you shouldn't try to get more, but I think the reason PN parts are limited to ~2deg caster is because that's the maximum we've been able to use for most tracks. Now, if we were to go to TQ Racing (gigantic 1/12 Ozite track) then perhaps more caster would be in order, but otherwise I've never successfully deviated from ~2deg.

mugler
2011.06.28, 09:19 PM
Now, if we were to go to TQ Racing (gigantic 1/12 Ozite track) then perhaps more caster would be in order, but otherwise I've never successfully deviated from ~2deg.

Do tell! Being that we race there curious to hear why more castor at a big track like TQ may be beneficial. (BTW it's even more gigantic - it's considered a 10th scale track 90x45 ft :D - ahhh too much fun that track)
PS - good racin @ cruizin rc!

color01
2011.06.29, 02:31 AM
Thanks mugler! As far as I understand and have felt, more caster gives more efficient high-speed cornering at the expense of low-speed cornering. Given that TQ is all high speed, all the time, it would make sense to max out caster and then use a harder front tire to doubly improve cornering efficiency.

Did you see Sai's videos yet from Cruzin? My car gets extremely loose at high speeds, there's just too much high-speed steering and not enough in the infield. This to me would be reason to go from 2deg caster as I have now, back down to 1deg.

mugler
2011.06.30, 12:06 PM
Haven't see the video yet but for sure will look for it later tonight and check it out...I read the race report.

I never associated more caster with high speed cornering since almost all literature link caster to exit speed so good to know and will try it and see how it goes.

What role do harder tire play in high caster/high speed corners?

color01
2011.06.30, 02:34 PM
The wider open the layout, the harder front tires I tend to run because I don't need the extra cornering power up front -- softer front tires tend to increase scrub after all, and we can't have that. :) As you know, caster does have the effect of softening turn-in, since the front end has to force weight transfer against the chassis' will, but it also creates extra camber, which favors high-speed steering over low-speed steering.

High caster/hard front tire should provide the same amount of steering as "normal" caster/standard soft front tire at high speed, except with less scrub and wasted energy. You might even run 0 camber with the high caster setting to get the optimal mid-corner camber from both wheels at the same time, who knows? :)

mugler
2011.06.30, 07:17 PM
I see, will give those settings a try next time @ TQ, which may even be this Sunday:D

didin't find your race video under Sai's YT account, is it posted somewhere else?

EMU
2011.07.01, 12:09 AM
I see, will give those settings a try next time @ TQ, which may even be this Sunday:D

didin't find your race video under Sai's YT account, is it posted somewhere else?

I think Sai had issues uploading the video. Here is a low res video of the race http://www.ustream.tv/recorded/15624529 I pushed as hard as I could from the crash on the start to the end of the race... When I caught Brian, I couldnt find any room to get by. Great driving under pressure, especially since he did not have much wheel time going into the race. Both of us had very little sleep going into the race, so it we were both running solely on adrenaline :D

I completely agree with Brian's comments about caster. Larger layouts, I typically use more caster with harder tires. I try to keep speeds up, and caster will typically give less steering into the corner and more out. On a tight track, I like a much more responsive corner entry, where on a large track I like more stability and more exit steering. On this carpet, I like less caster than RCP. I have not driven on the TQ carpet, so I cannot comment on that surface. The grip characteristics may be different.

mugler
2011.07.01, 10:55 PM
Intense chase race! looks like as much fun as you can have on carpet - running RC cars that is:D
The carpet at TQ raceway is of the Ozite variety which is pretty much standard material for 10th scale carpet tracks, if you get a chance to run on it go for it, you'll have a ball. The one over here is also soaked with traction compound off of other cars, so that come into play as well.