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Inboard disk brakes?

Discussion in 'Technical' started by TEG, Jun 14, 2007.

  1. TEG

    TEG TMC Moderator

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    Good idea or not? Less unsprung weight!

    Inboard%20Disc%20Brakes_tif.jpg
    4WD_with_DS_suspension_6.jpg
    [​IMG]
    [​IMG]

    Used on some Jaguar, Citroen, Rover, Alfa Romeo, custom hotrods, race cars, etc.
     
  2. danny

    danny Administrator

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    I don't get it, don't the discs still turn like on normal car? If so how would there be less unsprung weight?
     
  3. WarpedOne

    WarpedOne Mainecoon Butler

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    In configuration on the last picture there realy is not much less unsprung weight but in the configuration on the first there is.
    Brake disks are located near differential which is fixed to the chassies. They do not go up and down with wheels.
     
  4. TEG

    TEG TMC Moderator

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    Yes they turn so the rotating mass is the same, but they don't have to move with up and down wheel motion (as WarpedOne said) so it is easier for the wheels to bounce up and down quickly without transmitting as much motion to the rest of the vehicle.

    Personally I think they seem like a good idea, but I don't understand why they haven't been more popular. Perhaps the intrusion into cabin space is too much of a downside.
     
  5. danny

    danny Administrator

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    Another downside is that it would be harder to check your brake pads.
    Also in terms of looks, many love to see the brake calipers and disks ;D
     
  6. TEG

    TEG TMC Moderator

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    But no brake dust on your nice shiny wheels!

    Also it is probably nice to the tires to keep those red hot discs further away.
     
  7. Takumi

    Takumi Member

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    Yes, cars that have been "upgraded" to 22" wheels, but retain stock brakes do look funny to me. Looks like something's missing.
     
  8. AGR

    AGR Member

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    Front inboard brakes 1972 Tyrrel F1, notice the driveshaft from the front wheel to the brake disc, and the ductwork to direct air to the disc.
     
  9. AGR

    AGR Member

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    1972 Tyrrell F1 rear inboard brakes
     
  10. AGR

    AGR Member

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    Modern F1 brakes with ceramic discs - notice the CF (carbon fibre) suspension arms, and CF air ducts to cool the brakes.
     
  11. Kardax

    Kardax Member

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    I think the reason they're not more popular is due to cost, complexity, and space concerns.

    Cost - Any non-driving wheels will need another CV joint and bearing to hold the brake. Cooling ducts will probably be necessary, impacting the design of the whole vehicle.
    Complexity - The above parts aren't free.
    Space concerns - Two of the brakes are going to take space away from the engine compartment, which is usually cramped already.

    The result does lower unsprung weight (improving grip), but also raises overall weight (reducing acceleration) and may hurt aerodynamics for the cooling ducts (reducing acceleration, top speed, and efficiency).

    Everyone loves low unsprung weight but one has to ask if all the consequences of this particular technique are worth it.

    -Ryan / Kardax
     
  12. TEG

    TEG TMC Moderator

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    Yeah - I had mentioned the joints & half shafts and space issues in other postings before.

    So, yes, for non-driven wheels it adds extra weight, cost and complexity.

    *But* for driven wheels where you already need a half-shaft and something inboard (e.g.: motor or differential) then why not put the discs inboard as well?

    The Alfetta GT where I first encountered inboard brakes had inboard discs on the driven rear wheels only. The front wheels used in-wheel discs so there were no half shafts in front.
     
  13. AGR

    AGR Member

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    Ceramic discs is the HOT set up, similar to carbon fibre. There isn't a single F1 car that uses inboard brakes, and if there is a car that is very sensative to weight, its an F1 car. They all have outboard mounted ceramic discs.
     

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