Mercedes-Benz Forum banner

1 - 11 of 11 Posts

·
Registered
U140 , U900 , 419 SEE
Joined
·
1,088 Posts
Discussion Starter #1
Hi Everyone,

I recently found the rear driver caliper has a leak, and haven't found the location yet, but found that I had two new calipers that belong on the front. Without looking too closely yet, i wondered if one of the front calipers was the same as a rear caliper in order to swap it out completely with a new one. I realize this would be too easy, and figure it won't fit, or may be smaller, etc, but doesn't hurt to ask.

Thanks for looking and enjoy your weekend.

ACUF
 

·
Registered
1990 Unimog 1300L, 2004 ML350, 1999 SLK 230,
Joined
·
579 Posts
It looks like both front calipers have different part numbers than the rear ones, so I guess they aren't interchangeable. (According to the EPC)
 

·
Unimog Moderator
250GD Wolf
Joined
·
13,266 Posts
Steve @ Eurotruck sells a caliper repair kit, its cheap, that might be the way to go, just crack it open do the repair, and call it good. Also, document it for when I have to do it please :D
 

·
Registered
'76 1300L,HE351CW,H15P Winches,Konis,Hydraulics,All Gears,10mm Plungers,Aftercooler,Lots of Littles
Joined
·
2,674 Posts
Front and rear are totally different, but rebuild of either is a cakewalk.

C.
 

·
Registered
U140 , U900 , 419 SEE
Joined
·
1,088 Posts
Discussion Starter #5
Ok, sounds logical. I figured as much. I can document the repair. Thanks for the speedy feedback.

ACUF
 

·
BenzWorld UNIMOG statesman
Unimog 404.1 Diesel (sold :( )1995 LMTV 1078
Joined
·
5,857 Posts
is their a Brake proportioning/biasing valve in the 4x6 models? Reason I ask is cause in the 404 their was not either. The break cyclinders etc. were of different sizes on front than back so proportioning was built into the system. Maybe that concept followed into the 4x6 models with the brake piston size in the calipers negating the need for proportioning valve in them too?
 

·
Registered
2015 Rubicon Unlimited (Let the shame be upon me!)
Joined
·
3,827 Posts
Well I suppose it would depend on if the second axle is driven or not. On the 406/416 model 4x6 trucks that we've seen pictures of, it appears that the second rear is just a tag axle and is used for load distribution where as in the 2540L38, the axle is live.

Edit.

Well this is what I get for reading this stuff way to early in the morning.

So yes you were referring to the 4x6 tag axle setups. I would think that becasue the axles are not driven they would most likely also be not braked becasue there is no "push" from the drive system and would thus react much faster and might lock up really quickly in challenging situations.

The other way to look at it is hydraulics is governed by the concept that F = P * A, force of action equal to pressure applied to fluid divided by area fluid acts upon. So in basic numbers if the master cylinder outputs 100psi per port and each piston cup has a face 1 inch square then each brake caliper acts with 100 pounds of force. Simple and fairly easy to calculate changes. So the 404 uses different brake piston areas to change the force, say 2" areas in the rear for a force of only 50 pounds and 1/2" in the front for 200 pounds. Again, any way you slice it, F=PA.

To put 6 brake units on the 4x6 truck may require some different units all together, dividing the brake force down to avoid lock up as the mass pitches forward. This is complicated with the increase in theoretic GVW granted by the extra axle by also increase in dead weight by having to haul it around. The cycle goes on and on.

I don't like calculating for brake systems becasue if you don't do it as a common task it is ease to just turn to the internet and suddenly have one of three things: under built, just right or over built and have no idea which one is the one you built.

Master cylinder geometry affects pressure development, line diameter and layout effects transmission, caliper design governs delivery and pad & rotor or drum & shoe swept areas and materials have effects from pedal feel to thermal performance and ultimately the big question: Will It Stop and When?!

So, ACUF: buy the caliper rebuild kits and never look back. Buy one kit for every caliper you own and then when one fails you can swap it out for an on the shelf spare, then rebuild the failed unit. I'd even recommend finding a way to get a set of spare rears so you can always have what you need. Toys and hobby trucks can sit and drip if they have to, working trucks need to roll to make money.
 

·
Registered
U-406/416
Joined
·
688 Posts
What are you guys talking about, Yes, the front calipers fit on the rear axles, Only the internal components are not matching. I'm runing front calipers on the rear, they actully seem to work a bit better. Front calipers are required if you want to run flat faced rims in the rear, I do miss my e-brakes though.
 

·
Registered
U1550L/37 Doka, U1700L/38, Merc 1017A
Joined
·
1,563 Posts
the front caliper do bolt up to the back as the portal boxes are identical but that does not mean the calliepers are the same. not sure but i think the front callipers have a bigger bore size too.
 

·
Registered
U140 , U900 , 419 SEE
Joined
·
1,088 Posts
Discussion Starter #11
Hmmm.. I wondered if the unimind thought deeply enough, it would generate another answer!! Well, at least we know now. I think the rebuild sounds like the best route. Thank you all for the feedback.

ACUF
 
1 - 11 of 11 Posts
Top