RB6 rear arms to RB5
 

Having seen Kev Lee running RB5 (UM566) rear arms on his RB6 on Tuesday I thought I would give them a go too.

Not sure why as my car is fine but I like to fiddle:p

So I ordered some arms only to find they come with 1 front arm and 1 rear:blush: Fail LOL, and they dont look the same as what a seen on Kevs LOL.

Any way my question is whats the difference between UM566 rear arms and UM521-1 rear arms ?

Kev Lee = UM566
Atsushi Hara = UM5211

They look the same to me?

Hi mate,

The different part number is more to do with what front wishbone comes in the pack.

UM566 comes with the RB5 WC front wishbones
UM521-1 is the older RB5 front wishbones.

You could also get LA272 which come with 4wd fronts.

All the rear wishbones are the same geometry.

Hope that helps
Kev

I noticed you ran you wish bones back to front too (compared to Hara)

and I noticed your rear arms looked machined for extra holes?

NCG arms from the ZX5fs NCG conversion.

Yeah, there was another set of wishbones that I didn't mention - the ones I'm running. As simon mentioned they are the ncg ones which have a machined edge to accept the alloy drop down on the lazer. It makes no difference to the geometry. I'm only using them as I had them spare.

I have drilled an addition shock mount hole on the inside to move the shocks in. It was pretty standard practice on the rb5 vega so I carried it over from there.

I'm not sure how Hara has his but I have them on the standard way. I think flipping them may give shorter wheelbase but would have to check.

Kev , Simon thank you for your answers.

I just need to order another rear arm now LMAO:woot:

Sooo....
What is the handling difference when you run flat RB5 arms Vs gullwing RB6 arms?

Althought I have never tried them (will do this Sunday at our track Gayo), I was told less chassis roll, flatter car on turns.

We run rear motor on an "almost" dirt track last week and the car running the flat wishbones was ace. Considering Kev is running them on our kind of track (big up for all the help my friend :thumbsup:), I have to try.

Looking for a sharper car overall as I'm already quite slow :drool:

I'm interested in he mounting differences between Kev's and Tebo's mounting of the wishbones.

Imagine makes the wheelbase is shorter? Hope to test both ways

I've tried both, the first thing with RB6 arms is more rotation in the corner and the rear collapses more so you need stiffer rear springs to compensate, which combined together give a lot more overall steering, there seems to be a lot less roll stiffness. Personally I have gone back to the 521-1 arms. Those of you running RM RB5's may benefit from the newer RB6 arms, if i remember correctly it was always a little 'pushy'.

UM521-1 arms have 1 lower shock mounting hole that between the positions of the 2 holes on the UM521 / LA272 / LAW43 / UM566 rear arms

Reversing the wishbones gives 3.5mm reduction in wheelbase (so essentially 1.5mm shorter than running the UM713 wishbones with the inner hingepin spacer behind the wishbone for those that already do that).

As stated the LAW43 / UM713 rear arms (with the shock mounting position lower than the line between the hingepin holes) will give more natural rotation.
This really helps the ZX5-FS platform carry high corner speeds and gives the 'tuck in' effect the RB6 has as the speed comes off into a tight corner.

To go to the UM521/UM566/LA272 type arms you will need to use a shorter rod end on the shock shaft, I believe it is the the next size down (so if you currently run long then go to medium, if running medium go to short).

Hope that helps.

3.5mm, quite a bit. Certainly imterested to know how all these options translate to the track.

Turning the arms and shortening the wheelbase will give you more forward and braking traction, imagine that you are basically hanging more weight out of the back a la' Rear motor. You may also gain a little more steering and a bit more of the 'Pendulum' effect mid corner.

Yup cheers for info, same as what I read.

I think question for myself is how does it feel on track for me.


Will try all three options at TORCH in the coming weeks.