Disk brakes... have cars ever had inboard disc brakes?
Discussion
drivin_me_nuts said:
... so are there any vehicles around with more than 2 discs on the same axle, or is it completely unneccessary?
Most modern cars have vented discs....where the two surfaces of the disc are separated, which gives some of the main advantage of twin discs, i.e. heat dissipation.I would have thought it's easier (to maintain and engineer) and cheaper (in terms of cost and weight) to have one larger disc then two smaller ones. Unless the vehicle has to have small wheels (too small for adequately sized brakes) for some reason I don't know why you would do it.
My XJ6 has inboard rear disc brakes. The manual says you need to drop the whole rear subframe to change the discs, so it's not ideal...
thanks for the replies.. It was one of those late night thoughts I had on the verge of sleeping... Glad you chaps answered it or I would have there for ages just thinking of the pros and cons of 2 discs or 4 or inboard or discs close to the wheels (not sure if you call the, outboard). Anyway, night all, the dream genie beckons 
Randy Winkman said:
Alfasud - inboard fronts.
My mate proudly pointed his out on his cloverleaf, and promptly 'glued' his fingers to them (he'd just had a 'spirited' drive - oh how we laughed as we applied cold running water and covered our ears from the screams)... they were actually glowing!Man from UNCLE said:
If I remember correctly some Rolls Royce's had a combination of drum & disc brakes on the rear, I think the drums were for hand brake use only though so not sure if that counts.
They are more common than you might think. They are know as driscs in the industry, and the mk3 Astra has them.
drivin_me_nuts said:
Would having discs inboard or otherwise change the braking behaviour of a car?
I see no mechanical reason why. The disc is just on the other end of the drive shaft. I would assume that heat dissipation could be an issue, though, on higher performance applications.
From a cost point of view they are harder to access so maintenance costs would be somewhat higher.
Alfa dumped them when the Sud was replaced by the 33. I assume cost probably played a part in that decision.
Megaflow said:
One of the large car engineering outsourcing houses, TRW IIRC, was playing around with twin discs a few years ago. The problem with the design, and I'm sure all types of twin disc designs, is the discs have to float, and trying to keep them clean and free moving in the environment they live in is very tricky.
It was Delphi who developed that twin disc system. I drove a BMW X5 with the discs installed back in 2004 I think, on one of their ride/drive experiences.drivin_me_nuts said:
Would having discs inboard or otherwise change the braking behaviour of a car?
Only slightly - there is a bit of play between the wheel hub and the inner end of the driveshaft, mainly in the CV joint, but other than that it's pretty much the same.Also note that the Alfasud's handbrake was linked to the front brakes. That whole setup was a right PITA.
drivin_me_nuts said:
Would having discs inboard or otherwise change the braking behaviour of a car?
Main issues are packaging, cooling and appearance.Wheels have got bigger, discs have got bigger, brakes have got more powerful. The combination of space and heat rules them out these days. Also no-one will be able to see your go-faster painted callipers!!
Jacobyte said:
Also note that the Alfasud's handbrake was linked to the front brakes.
Same on pre-'88 Saab 99/900s. I can understand the reasoning behind having a handbrake on the front wheels given the weather conditions in their home market, but what a pain those Girling callipers were... angusc43 said:
Alfa dumped them when the Sud was replaced by the 33. I assume cost probably played a part in that decision.
And the fact that they were a sod to change the pads on, I seem to remember the most efficient way to change the pads was to be hung upside down from an engine hoist over the engine bay to ease access 
Jacobyte said:
drivin_me_nuts said:
Would having discs inboard or otherwise change the braking behaviour of a car?
Only slightly - there is a bit of play between the wheel hub and the inner end of the driveshaft, mainly in the CV joint, but other than that it's pretty much the same.Also note that the Alfasud's handbrake was linked to the front brakes. That whole setup was a right PITA.
On the plus side the inboard discs no doubt helped the handling (as possibly steering feel) no end - very low unsprung weight. At the time I was happy to put up with the hassle of maintenance.
Interesting article about inboard discs here:
http://blog.garritys.org/2009/09/inboard-brakes.ht...
Including a picture of the inboard brakes I remember best (from making the Tamiya kit when I was young), the Lotus 72:
http://blog.garritys.org/2009/09/inboard-brakes.ht...
Including a picture of the inboard brakes I remember best (from making the Tamiya kit when I was young), the Lotus 72:
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