Britax Marathon installation woes -HELP!!

two bricks shy

New member
We bought a Britax Marathon to replace a Graco Comfort Sport that just wasn't meeting our needs.

We are trying to install it in the Passenger side outboard position with a lap-shoulder belt combo in a 1996 Chevy Blazer. My only choices are outboard positions.

We've run into a few problems and after 3 hours of trying to install the silly thing I am at my wits end. I am really hoping for some advice...

This is the biggest issue:
- using the lock off clips as directed (furthest away from the buckle), we either can not close them or when we finally get them closed with a loud "positive" click they pop back open when we try to check the seat for stability and proper tightness they pop back open, if they last that long. I've tried using the one closest to the buckle and even tried only using the lap portion of the belt furthest away from the clip. The only thing that seemed to work was using the metal locking clip from our Graco, but according to the Britax site that is not advised.

I am having a few problems with leveling of the car seat in general which we are fixing with rolled towels and also lining the belt up so we can get it in the lock off clips.

I know there are other Blazer users out there that use this carseat. What am I doing wrong????

Thanks in advance!


Well-known member
Your Blazer's seatbelts do lock, Chevy uses locking latchplates (that's why the make end of the buckle is huge.) You do not need to use the lockoffs or a locking clip.

Now, based on your post I'll assume the MA is RF:

For the recline, are you using the RF tether? What do you mean by "leveling"?

be back later, have to tend to baby...

two bricks shy

New member
Thanks for your reply!

I am trying to use the RF tether on the passenger side seatbelt anchor on the floorboard. Without the tether the top of the MA is super wobbly while the base is snug as can be. Getting the recline is harder too without. I would really like to use the tether for added stability to the top of the MA.

On leveling, there is a sticker on the side of the base with a red line and a warning to keep the line level with the ground when rearfacing. I'm having trouble not dropping that line towards the front of the car. I currently have a rolled towel in the crease of vehicle seat to help the MA be more stable in that area. Trying the MA with out it has proved difficult to get full base of the chair contact with the seat. Maybe try it without the towel and tether it down to see what happens?
I've also had a little trouble with side to side leveling with the MA itself, but I can usually fix that with tether adjustments.


Admin - CPS Technician
Yeah, take out the towel and only use the tether for recline, it should be fairly straightforward if you have the lightweight locking latchplates and a good place to top tether (a little tip to the seat is fine as long as the lapbelt is twanging tight and the base is level).
More upright than 45 degrees is fine, too...just never ever go more reclined than 45.

two bricks shy

New member

Thank you so much!!!

After following all your advice, it took a whole 10 minutes to get it installed securely and correctly. :D

We went for our first ride this evening and it was excellent. It is entirely too wonderful having a kiddo comfy in their seat (that will last them a good while) and not having their head jackknife over/fwd when they fall asleep. if I can just find one in my size ;)


Admin - CPS Technician
Glad to hear the good news! Yeah, why can't they make the grownup version of that seat that would just replace the rear seats altogether? Rip out the second row and clamp down some adult sized Marathons, lol.


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