ok my system.
windows 10x64bits gigabyte x99 udm5
i7 5820K sound card
 rme aio and focurite forte
cakewalk VS-100
Got reaper 5.0 and protools hd10 monitoring Adam 8X Mic neumann tlm103 
 
Imac 2012 i7 with logic x 10.10
 
 

i don't have the problem on reaper protools or logic X
 
 

My Mobo have 4 month  I change it because i think it was too old  caus the problem 
sonar platinium fresh install 
!!!
 
 

I go on my set up and see I rec in 24bits depth
 
 

Does the forte/rme have mixer software? If it does, maybe that is where the problem is. Open the forte/rme mixer and make sure the levels are set correctly.

ok but on rme or vs-100 is the same way
 

ampfixer
So that sounds like you can set the inputs so hot that the signal distorts, but what you record is very quiet and distorted. Sounds like a set up problem in Sonar. 

 
Sorry John, but I think you're missing the point.
 
The only way to control the input level going into Sonar(and hence to disc) is via your interface/mixer/pre-amp
 
As John rightly points out, if the signal is clipping at your converters, you can lower the fader all you want in sonar but the signal will still be clipped.
Sonar CANNOT know what's going on "outside the box" which is why it's extremely important to set your gain staging correctly right at the beginning of the chain - in this case microphone & pre-amp/interface gain.
 
During recording, the track level indicators in Sonar are for monitoring only - hence the need to keep them at unity to show exactly what level you can expect after recording. Adjusting this fader up or down makes no difference to the recorded signal but will make it impossible to accurately monitor what's being recorded. The same applies to the input gain (trim) at the top of the channel.

Have to agree with Bristol and John here.
Your record levels are set at your audio interface. Everything else is monitoring.

Is it even possible to change the monitoring level behaviour in Sonar?  As soon as you arm a track for recording, the meter shows whatever's coming in through the interface, no matter where the fader is set.  There's no "set to unity" as far as I know.

Set to Unity simply means setting the track fader at 0dB and the Gain at 0 prior to engaging record.
 
The track level meter will then tell you what level your incoming signal will be recorded at whilst you play/sing/hum/fart into the mic.
 
You should be aiming at a level of anywhere between -15dB and -6dB on all of your tracks.