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I’m currently in Europe and of course checking out all the smart cars. Today I noticed a fortwo with rear disk brakes (I think it was a 451). Is this an option that never made it to the US or an after market conversion?
 

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Chances are, aftermarket parts. As far as I'm aware, the ForTwo was never factory equipped with front and rear disc brakes.

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smart Madness use to carry S-Mann rear disc brake conversion kit. For the little smart car. Imported from the Neatherlands. Maybe that’s what you saw. smart never offered rear disc brakes on the for two. It would have been nice to, improved braking power.
 

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The smart has never had and, doesn't require rear disk brakes as 80% of the braking force is from the front...
That may be true in a full out emergency stop, but under normal braking and especially in performance driving, having a rear brake bias under light to moderate braking is more stable and highly beneficial in helping to place the car on a track and alter grip and handling balance. This is even more true with RWD cars, but then the fortwo was likely never designed with these kind of sporting intentions.
 

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After having owned a 450 for 10 years and 150,000 km's, the rear drum brakes
still had 40% remaining which, tells me they weren't used very much...
 

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After having owned a 450 for 10 years and 150,000 km's, the rear drum brakes
still had 40% remaining which, tells me they weren't used very much...
Exactly, and it can be felt when braking hard and transitioning into a corner. A brake proportioning valve can be of significant help to correct the braking bias.

But the other issue is that drum brakes don't require as much brake fluid movement as drum brakes, so swapping to rear discs without changing the master cylinder can result in little or no braking power. Worse is that some drum systems used a valve to retain some residual pressure in the fluid, and that can cause a disc brake to drag. Remove the valve and braking becomes very weak as the master cylinder can't move enough fluid to pressurized the line and clamp the discs.

It's worse with the ED that I have. Although the braking imbalance is partly made up for by regen, when the yaw sensors experience forces greater than expected in normal driving, it thinks a crash is imminent and then cuts the regen entirely.

With a regular fortwo, a proportioning valve to decrease front bias would seem likely to work well as long as the owner is willing to accept a bit earlier ABS intervention.
 

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The 450, and 451 aren’t exactly performance vehicles. Expensive cars commonly have both discs and drums fitted on the rear wheels. The drums are there just for a parking brake, the discs for normal braking. On most cheap cars, it is cost-effective to just have drums alone on the back where they are not doing as much work and lock ups are less critical. The drums on the back are there to lock up and act as a parking brake, while the discs are the best solution for the front.
 

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Could have been the "cosmetic" (as in fake) rear disc add ons....

I'm with the others who think rear discs on a smart are just overkill; these are road cars, not track beasts. :)
 

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Discs are not needed on our little smarts. Even if you are doing track days or autocross you still shouldn't need them. If you are over powering your car to that point, you may want to look into a better platform to start with.. They just don't have the weight and traction to require anything more.

Now, having said that, I did build myself a rear disc setup for my car. I think cosmetically these cars look silly with their tiny drums. I wanted matching disc on the rear and it was a very simple bolt-on conversion.
 

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Discussion Starter #12
Thank you all for responding. I agree the smart doesn’t need rear disc brakes. It just seems to me that the drum brakes are such old technology and they look cheap. Having said that, I wouldn’t want to go through the difficulties and expense of changing them out, especially since they were never offered from smart as finding replacement parts could be a problem.
 

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rear

According with the dealer,front brakes last 20-23 k miles ,and acording to them the rear last 50k miles in mine the front went at 21k ,I check the rotors for sale in europe they only give a guarrante of 30k kilometers and in europe the rear drums are complete diferents from the ones in USA only in England I saw the drums equal to the ones we have in Usa.
All this for the w453.
 

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I would hope that only the front pads wear in the 20's, but the rotors go until the next pad change. Most cars should be able to get two pads changes out of a set of rotors. Rotors do not have to be changed routinely with every pad change nor do they have to be turned. They only need to be changed when they are at or below the minimum spec or have other issues. I think I recall correctly that some of our members here have gone over 150K miles with their rear brakes.

Len
2014 EV Coupe 16,000 miles
2014 EV Cabriolet 8,000 miles
 

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The need for pad/shoe change is so variable, depending so much on the driver and driving conditions. We have all followed cars where the brakes are almost constantly applied when merely lifting your foot from the gas would suffice. Some folks drive with their left foot resting on the brake pedal, unaware that even the lightest pressure may begin applying the brakes. For me, pads or shoes usually last most of the way toward 100k miles. For my wife, a very cautious driver who uses her brakes much more, less miles.
 
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