When you lower the mixer to use, it lowers too much causing beaters to rub on bottom of bowl. I have to manually hold up slightly when in use.

Get a copy of the Repair Part List for your model at Kitchenaid.com
Download the following Kitchenaid Service Manual:
http://www.kitchenaidparts.be/centers/servicemanual/mixer.pdf

It covers several models including yours.
1. Check/Adjust the Flat Beater to Bowl Clearance:

Turn screw (A) SLIGHTLY counter clockwise (left) to raise the flat

beater or clockwise (right) to lower the flat beater
2. Check the Beater Shaft (Agitator Shaft) making sure the Retaining ring
is flushed with the surface of the Planetary Assembly
Constant Pulling and Removal of the beaters can cause the Agitator shaft to move
3. If the above two still don't solve your problem, follow the service manual
directions to disassemble the Planetary Assembly and check for loose screws

1. Unplug stand mixer.
2. Place bowl lift handle in down position.
3. Attach flat beater.
4. Adjust so flat beater just clears bottom surface of bowl
when in lifted position by turning screw
(A) Counterclockwise to lower the bowl.
5. Just a slight turn 90 degrees in either direction.
Place bowl lift handle in up position to check clearance.
6. Repeat Steps 4 and 5 if necessary.
I hope I helped you.

Hi ARADAM, you don’t provide the model number or say if you have a ‘tilt-head’ or a ‘bowl-lift' mixer, which would helpful, but you can easily download a PDF version of your Owners Manual from the KA website at: (http://www.kitchenaid.com/flash.cmd?/#/page/home).
Click on Customer Care>Locate Manuals& Guides> and enter the 6 character model number and select a file listed under Owners Manuals and save that file to your PC. You’ll need to have Adobe Reader to be able to open it. Turn to Page 11 and you will find the instructions for adjusting the mixer head height. I have extracted the instructions below:
Beater to Bowl Clearance
Your mixer is adjusted at the factory so that the flat beater just clears the bottom of the bowl. If for any reason, the flat beater hits the bottom of the bowl or is too far away from the bowl, clearance.
Tilt-Head models
• Unplug mixer.
• Lift motor head.

• Turn screw (A) SLIGHTLY counter clockwise (left) to raise flat beater or clockwise (right) to lower flat beater.
• Make adjustment with flat beater, so it just clears surface of bowl.
If you over adjust the screw, the bowl lock lever may not lock into place.

Bowl-Lift models
• Unplug mixer.
• Place bowl lift handle in down position.


• Turn screw (B) SLIGHTLY counter clockwise (left) to raise flat beater and clockwise (right) to lower flat beater.
•Make adjustments with flat beater, so it just clears surface of bowl.
If you find the adjustment screw missing, you’ll need to replace it. But now you’ll need
I hope this helps! –Howard, Burke, VA
If this solution has helped you, please rate it, thanks! - hslincoln

Hi LEDAVETTORI, you don’t provide the model number or say if you have a ‘tilt-head’ or a ‘bowl-lift' mixer, which would helpful, but you can easily download a PDF version of your Owners Manual from the KA website at: (http://www.kitchenaid.com/flash.cmd?/#/page/home).
Click on Customer Care>Locate Manuals& Guides> and enter the 6 character model number and select a file listed under Owners Manuals and save that file to your PC. You’ll need to have Adobe Reader to be able to open it. Turn to Page 11 and you will find the instructions for adjusting the mixer head height. I have extracted the instructions below:
Beater to Bowl Clearance
Your mixer is adjusted at the factory so that the flat beater just clears the bottom of the bowl. If for any reason, the flat beater hits the bottom of the bowl or is too far away from the bowl, clearance.
Tilt-Head models
• Unplug mixer.
• Lift motor head.
• Turn screw (A) SLIGHTLY counter clockwise (left) to raise flat beater or clockwise (right) to lower flat beater.
• Make adjustment with flat beater, so it just clears surface of bowl.
If you over adjust the screw, the bowl lock lever may not lock into place.

Bowl-Lift models
• Unplug mixer.
• Place bowl lift handle in down position.

• Turn screw (B) SLIGHTLY counter clockwise (left) to raise flat beater and clockwise (right) to lower flat beater. •Make adjustments with flat beater, so it just clears surface of bowl.
If you find the adjustment screw missing, you’ll need to replace it. But now you’ll need
I hope this helps! –Howard, Burke, VA
If this solution has helped you, please rate it, thanks! - hslincoln

Hi LEDAVETORI, you don’t provide the model number or say if you have a ‘tilt-head’ or a ‘bowl-lift' mixer, which would helpful, but you can easily download a PDF version of your Owners Manual from the KA website at: (http://www.kitchenaid.com/flash.cmd?/#/page/home).
Click on Customer Care>Locate Manuals& Guides> and enter the 6 character model number and select a file listed under Owners Manuals and save that file to your PC. You’ll need to have Adobe Reader to be able to open it. Turn to Page 11 and you will find the instructions for adjusting the mixer head height. I have extracted the instructions below:
Beater to Bowl Clearance
Your mixer is adjusted at the factory so that the flat beater just clears the bottom of the bowl. If for any reason, the flat beater hits the bottom of the bowl or is too far away from the bowl, clearance.
Tilt-Head models
• Unplug mixer.
• Lift motor head.

• Turn screw (A) SLIGHTLY counter clockwise (left) to raise flat beater or clockwise (right) to lower flat beater.
• Make adjustment with flat beater, so it just clears surface of bowl.
If you over adjust the screw, the bowl lock lever may not lock into place.

Bowl-Lift models
• Unplug mixer.
• Place bowl lift handle in down position.

• Turn screw (B) SLIGHTLY counter clockwise (left) to raise flat beater and clockwise (right) to lower flat beater.
•Make adjustments with flat beater, so it just clears surface of bowl.
If you find the adjustment screw missing, you’ll need to replace it. But now you’ll need
I hope this helps! –Howard, Burke, VA
If this solution has helped you, please rate it, thanks! - hslincoln

Hi, JAKELEGJEETE, You don’t say if you have a ‘tilt-head’ or a ‘bowl-lift' mixer, but you can easily download a PDF version of your Owners Manual from the KA website at: (http://www.kitchenaid.com/flash.cmd?/#/page/home).
Click on Customer Care>Locate Manuals& Guides> and enter the 6 character model number (in your case, use KSM5PS)and select the last file listed that appear under Owners Manuals: and save that file to your PC. You’ll need to have Adobe Reader to be able to open it. Turn to Page 11 and you will find the instructions for adjusting the Beater to Bowl Clearance. I have extracted the instructions below:
Beater to Bowl Clearance
Your mixer is adjusted at the factory so that the flat beater just clears the bottom of the bowl. If for any reason, the flat beater hits the bottom of the bowl or is too far away from the bowl, clearance.
Tilt-Head models
• Unplug mixer.
• Lift motor head.

• Turn screw (A) SLIGHTLY counter clockwise (left) to raise flat beater or clockwise (right) to lower flat beater.
• Make adjustment with flat beater, so it just clears surface of bowl.
If you over adjust the screw, the bowl lock lever may not lock into place.

Bowl-Lift models
• Unplug mixer.
• Place bowl lift handle in down position.

• Turn screw (B) SLIGHTLY counter clockwise (left) to raise flat beater and clockwise (right) to lower flat beater.
•Make adjustments with flat beater, so it just clears surface of bowl.
If you find the adjustment screw missing, you’ll need to replace it. But now you’ll need
I hope this helps! –Howard, Burke, VA
If this solution has helped you, please rate it, thanks! - hslincoln

Hi, KLOEHR, your beater will not lengthen by losing a screw. However, if you lost your Beater to Bowl Clearance adjustment screw, then it might appear that your beater had ‘grown’ because now the beater may be touching the bottom of your mixing bowl, where previously it had not. Simply said, the beater didn’t grow the mixer head drooped.
You don’t say if you have a ‘tilt-head’ or a ‘bowl-lift' mixer, but you can easily download a PDF version of your Owners Manual from the KA website at: (http://www.kitchenaid.com/flash.cmd?/#/page/home).
Click on Customer Care>Locate Manuals& Guides> and enter the 6 character model number (in your case, use KSM5PS)and select the last file listed that appear under Owners Manuals: KSM5PSWW0.pdf (2930.74 KB) and save that file to your PC. You’ll need to have Adobe Reader to be able to open it. Turn to Page 11 and you will find the instructions for adjusting the mixer head height. I have extracted the instructions below:
Beater to Bowl Clearance
Your mixer is adjusted at the factory so that the flat beater just clears the bottom of the bowl. If for any reason, the flat beater hits the bottom of the bowl or is too far away from the bowl, clearance.
Tilt-Head models
• Unplug mixer.
• Lift motor head.

• Turn screw (A) SLIGHTLY counter clockwise (left) to raise flat beater or clockwise (right) to lower flat beater.
• Make adjustment with flat beater, so it just clears surface of bowl.
If you over adjust the screw, the bowl lock lever may not lock into place.

Bowl-Lift models
• Unplug mixer.
• Place bowl lift handle in down position.

• Turn screw (B) SLIGHTLY counter clockwise (left) to raise flat beater and clockwise (right) to lower flat beater.
•Make adjustments with flat beater, so it just clears surface of bowl.
If you find the adjustment screw missing, you’ll need to replace it. But now you’ll need
I hope this helps! –Howard, Burke, VA
If this solution has helped you, please rate it, thanks! - hslincoln

Hi, LAHR, by the symptoms you describe it appears that it’s time to adjust your mixer’s "Beater to Bowl Clearance" adjustment screw, which should be a pretty easy to do by yourself.
The instructions for adjusting your beater to bowl clearance are located in your Owners Manual. If you don’t have the original manual you can easily download a PDF version of it from the KA website: (http://www.kitchenaid.com/flash.cmd?/#/page/home).
Click on Customer Care>Locate Manuals& Guides> and enter the 6 character model number, in your case KSM150 and select the file listed for your model that appears under Owners Manuals (66) KSM150PSER1.pdf (732.33 KB) and save that file to your PC. Turn to Page 14 and you will find the instructions for adjusting the mixer head height.
But to save you some time, I have extracted the instructions below:
Beater to Bowl Clearance
Your mixer is adjusted at the factory so that the flat beater just clears the bottom of the bowl. If for any reason, the flat beater hits the bottom of the bowl or is too far away from the bowl, clearance
Tilt-Head models
• Unplug mixer.
• Lift motor head.

• Turn screw (A) SLIGHTLY counter clockwise (left) to raise flat beater or clockwise (right) to lower flat beater.
• Make adjustment with flat beater, so it just clears surface of bowl.
If you over adjust the screw, the bowl lock lever may not lock into place.
I hope this helps! – Howard, Burke, VA
If this solution has helped you, please rate it, thanks! - hslincoln

JOE:You don’t say if you have a ‘tilt-head’or a ‘bowl-lift' mixer, but you can easily download a PDF version of your Owners Manual from the KA website (http://www.kitchenaid.com/flash.cmd?/#/page/home).Click on Customer Care>Locate Manuals& Guides> and enter the 6 character model number (in your case, use KSM90P)and select the last file listed that appear under Owners Manuals:KSM90PSWW0.pdf (2930.74 KB)and save that file to your PC.You’ll need to have Adobe Reader to be able to open it. Turn to Page 11 and you will find the instructions for adjusting the mixer head height.I have extracted the instructions below:
Beater to Bowl Clearance
Your mixer is adjusted at the factory so that the flat beaterjust clears the bottom of the bowl. If for any reason, the flat beater hits thebottom of the bowl or is too far away from the bowl, clearance

Tilt-Head models
• Unplug mixer.
• Lift motor head.

• Turn screw (A) SLIGHTLY counter clockwise (left) to raise flat beater or clockwise (right) to lower flat beater.
• Make adjustment with flat beater, so it just clears surface of bowl.
If you over adjust the screw, the bowl lock lever may not lock into place.


Bowl-Lift models
• Unplug mixer.
• Place bowl lift handle in down position.

• Turn screw (B) SLIGHTLY counter clockwise (left) to raise flat beater and clockwise (right) to lower flat beater.
•Make adjustments with flat beater, so it just clears surface of bowl.

I hope this helps! –Howard, Burke, VA
If this solution has helped you, please rate it, thanks!.hslincoln

when you lower the bowl, there is a screw just above the mounting plate. Adjust this very very slightly. Lift bowl with beater attached with out turning on the machine to test first, after you have adjusted.