LOUD screaching from rear wheel on Cervelo P2

Yes, this happened to me when I first got my P2. If the skewer clamp isn't tight enough you can suck the wheel into the frame.

There's a few things I learned.

1. Cervelo designed that frame to use a certain profile tire, some tires, are higher profile and may rub on the frame. Such as Continental tires.

2. You can strip the threads in the dropout for the wheel stop screws if the skewer clamp isn't tight enough.

3. you can get bigger screws to extend the stop for higher profile tires (but I don't use the stops)

The guy at the shop just backed the screws away a bit. I'll find out on my next ride if it was enough.  I have stock everything down there so I would've thought it would be good to go with the space. But I probably weigh a bit more than the average triathlete(~200 lbs) and i was applying a good bit of power. Given how little space the leave in there I guess it's not too surprising that it happened. Just glad it happened while training cause my first race coming up has a vicious 2.2 mile climb so it would've been a real bummer to have discovered this then.

when I first found out, I wrote Cervelo, and they sent me longer adjuster screws.

However I found that if I made sure the skewer was tight enough, the problem didn't occur.

Those adjuster screws are not to prevent the problem BTW they are just place holders.

I agree.  Have to check the spacing every time you replace tires, swap wheels, etc...  Also make sure wheel is all the way in the dropouts.

Many times you don't know it unless you are doing a big out of the saddle effort which twists the frame just enough to get the tire to rub.

I didn't realize that. So you're really supposed to place the wheel in as deep/shallow as you want without pushing it into those screws?

Stop Bike.

Check for Cat.

Cant' stress how important that bold statement is above.

I was shocked at how not well known this crucial point was when I bought my P2c in 2008. Had the same problem you did, and here and on ST, lots of folks were talking about those little screws, replacements, etc. 

However, the wheel is held in place by the TIGHT QR skewer. Give it a good amount of force to lock it down. If it's loose, the wheel gets sucked forward and you'll strip those little screws. Those screws are simply there to help center the wheel BEFORE you lock down the skewer.

You can't put the wheel too shallow as the brake pads will hit the tire and erode it (happened to me). THe wheel should pretty much be nearly all the way in, with only a small gap (like 5mm) beteween the frame and the wheel. And have that QR clamped down hard.

+1 on that.

the screws are there to help center the back wheel and ensure that it is straight. you still need to clamp down the QR tightly to keep things from moving around.

This has happened to me as well.  I found that I don't even rest the bike against the screws anymore, I get the wheel in the right position (not against the back of the frame and not against the side of the frame) and then make sure the skewer is all the way tight and the wheel doesn't move.  

A trick my LBS taught me is using one hand "pull" both sides of the frame together (you'll need to hold one part of the frame with your thumb, reach your fingers through the spokes and then pull the other side of the frame with your fingers) as you tighten the skewer.  This allows you to tighten it a bit more and prevent the wheel shifting from happening. 

If it makes you feel better, the first time this happened was when i rented a set of Zipp 808s for my first HIM.  I got off the bike to look at the back wheel at least 3x in the first few miles before I figured out what was happening.   

Not always. Some tri bikes have horizontal dropouts, some have vertical ones, just like road bikes.