R26.R R26 better lower control arms - Chapter 1

Hello everybody,

Why?
While I was refurbishing the suspension on my car, I was struck how bad they designed the lower arms on our car. Maybe they behave well in a 1.6 16V family Megane, but not in our Ring ripper. While we were contemplating the weak arms, we managed to make them bent just by turning the wheels from left to right fast. That was the moment when we realized that we need to build some better arms.
The second reason was the stupid price Renault is asking for the original arms (and you cannot find them any place else) and also the stupid price Vibratechnics is asking for the uprated bushes for the arms.
So, we started thinking about solutions for this.

How?
I'm a fan of simple solutions, so I first looked for the same solution like for the Clio 172/182 - some weldable plates to put in the original arms. But the design of our arms doesn't allows us to do this properly, so this solution was dumped fast.
Next idea: to build some new arms from scratch. So we went for a solution we tried in the past in our drift cars, we knew it is stiff enough and we can fabricate until the first track day of 2015. They will be made from 10 mm thick steel, weighting somewhere around 6kg each, so not a very big weight penalty either. They will come with uprated bushes all around.

So, during the Christmas holiday, we managed to come with the first design. It is a replica of the normal arm.

What now?
Once we got to this point, we started thinking what other features we should implement. During this entire process, we also realized what are the weak points of our suspension geometry that we need to address. So maybe you can help by giving your input on the situation.

Questions:
My questions for all of you are:

- is anyone interested in this kind of product. If not, I will build a one off set for my car. If people are genuine interested, I would like to understand how many of you would be.
- what do you think we should run in terms of camber/caster on our cars? Are they ok from the factory? We want more of any of them? How much? (please, when you answer the question, also explain the reason behind, not just that "i know I need to run 3 deg of camber because...internet")
- can you please post some wheel alignment sheets from your cars (doesn't matter how old they are). I need to see what is the average camber / caster angles and how big the differences can be left vs right wheel.

I hope this will turn into a technical discussion. Thank you.

S.

 

Jamie, do you have any wheel alignment sheet from your car? I want to check something. I believe the 225 has around 5 deg of caster stock and 250 has around 7 deg. I want to check if this is true. So posting a sheet or the numbers on the sheet, will help me.
Golf GTI Mk 6 has almost 8 deg of caster.

So, I aim for something like 7-8 deg. Anyone different numbers or ideas?

S.

 

Ok, it seems I'm not the only one concerned about roll center with lowered springs. I plan to address this issue too, after I see what space is available with the new arms.
The arms will have only one adjustment freedom - the camber, but increased castor from the basic design.
And if everything works well, I want to do also some adjustable strut mounts to fine tune everything, but let see.

S.

 

Can you put the pictures in a different place or anything because I don't have a username for that forum and it seems they want a lot of things to do until you manage to see a picture. And I don't like this kind of intrusive forums.

S.

 

To make things clear for everyone.
On the 225/R26 you cannot set nothing on suspension. The rear is completely fixed and in the front, you can just correct for toe.

Let's not forget this is a tricked up version of the 1.5dci/1.6 16v Megane.

S.

 

Hello,

I managed to source some "uprated bushes" for the rear part of the arm. I'm still waiting to get the durometer and be able to compare rubber from various bushes based on the Shore scale and see what is better. But I think I made my mind on a set. Nice part is, there will be some poly bushes available as well, so you can choose if you want the street friendly rubber version or the track-orientated poly version.

I moved slower than expected because of some unprepared business trips, but I still hope I will have a prototype in the next weeks to test fitted in a car. I know I'm moving pretty slow...

S.

 

First of all, we need to understand how are bushes working. They obviously dampen the movement of the inner and outer cases. But there are 2 types of bushes.

Some of them work by twisting the inner metal part against the outer part. So, in order to be effective at least the inner part needs to be bonded to the rubber part.

The other type works by squeezing the rubber between the 2 cases. Here, there is no need to have them bonded.

Now let's go to the poly bushes and the fact that people usually complain they will squeak. This happens because people use the wrong bush in the wrong spot only because it is coloured. It is impossible to put a poly bushes without the bonded inner case where you have the first type of rubber bush (twisting kind). That bush will squeak like hell.

Poly-bush work good when you put them in a place where you squeeze like the case of our lower arm. And they will never squeak!!!

The bushes are not made by me. They are powerflex and I hope they will behave well, but I cannot say anything until we test them. And even if they break, the replacement parts are cheap enough not to count.

S.

 

http://www.rsmegane.com/showthread.php?6386-R26-better-lower-control-arms-chapter-2

Finally we managed to finish the design of the arm. What do you think?

S.