Rake probelm

[akb]

I have an R400 with std setup - CR500 on 13 in rims, adjustable platform. I am trying to set the lower wishbones parallel to the floor which give approx 70mm under the gearbox protection bar but can not get less than 25 mm of rake. The rear shocks are on the lowest circlip and as low as they will go.

 

What am I doing wrong or is it not possible to get 15mm on 13 in rims? If it is not possible which is better to have a higher front or a larger rake assuming all suspension geometry will be adjusted once the rake change is made?

 

Thanks

 

Andy

[Stationary M25 Traveller]

Are you setting it up with the equivalent of your weight in the drivers seat ?

[shn7]

You mention rear shocks on lowest circlip. Do you not have adjustable platforms on the rear as well as front?

[akb]

Adjustable all round

 

Nothing in the drivers seat.

[Stationary M25 Traveller]

You should put the required weight in the seat (or both seats if you normally drive two up).

 

Surprised you can't get it low enough ... I had the opposite problem and got extra grooves machined.

 

Where are you measuring the heights front and rear ?

[akb]

Chassis rail under rear mount point or front arm and rail under rear arb

[Stationary M25 Traveller]

Front .... under chassis rail in line with rear of cycle wings.

 

Rear .... under chassis rail at front of rear wings.

[6speedmanual]

What vintage is this car?

I understood proper spec R400 superlight had adjustable platforms all round.

As mentioned above, set to normal operating loads.

Watts linkage set up less rake critical.

Peter

[akb]

2009 R400

 

I will try adding driver to the seat. If I can't get the rake down to 15mm is it better to have higher rake and a low front or a higher front? What are the relative merits? Thx

[chris perry 1]

Hello,

 

I had this when i set up my 2010 academy car.

 

The adjustable spring seats are made up of two large ali threaded washers. I got the shoulder machined off the bottom of the two so it could then sit lower on the damper, this brings the back of the car down.

 

I can email you a pic if you like?

 

25mm rake is quiet a lot, if i was you i would set the rear as low as possible and then raise the front so it is about 10-15mm lower with you in the car. More sump clearance the better.

 

It might be easier to take your car to a race team to have it flat floored, they will set the camber and tracking etc. McMillan motorsport are very good.

 

Chris Perry

[elie boone]

Rake depends on the type of spring, for the Imperial chassis it was 15mm for linear springs and 35 for progressive springs.

[akb]

Ah it now makes more sense. I guess I have the progressive springs. I have a metric chassis. The springs have a smaller gap at the top. So they will be the progressive ones.

 

I understand that raising the rear relative to the front will raise the rear roll centre with respect to the front but how does that affect the over/under steer handling?

 

 

[Shad]

In my experience, the rake is quite critical to the overall balance of the car. Not enough and the car won't want to turn-in very crisply, especially at speed - understeer. Too much and it will want to swap ends before you reach the apex - oversteer.

[myothercarsa2cv]

It might not need to be 15mm... Drive it, see what you think, then adjust, drive, repeat. Nice excuse for a day of blatting 😬