In search of lower unsprung weight

[ChrisC]

Now some clever person at Jaguar though that it would be a great idea to put the rear brakes inboard right next to the diff.

Nice you might say, it saves a load of unsprung weight and also allows for larger discs (16 inch wheels only remember).

However look at this photo and see if you can spy the the brake pads. Now imagine how dificult it is to change them when this unit is installed under the car.

http://en.wikipedia.org/wiki/File:Jaguar_E-Type_Series_3_rear_subframe.jpg

Now I know this because even minor replacement work costs a small fortune and ends up with large percentages of the car in pieces on the garage floor!

Ah the joys of jaguar! (FYI, they gave up the search in 1991 and moved to conventional outboard brakes like everybody else)

[Harsh]

i've often thought (possibly because of my non engineering background) that brakes are the least engineered part of a modern car.

Surely with modern technology and materials there has to be a better way of stopping all four wheels?

the inboard brake concept should work much better, improving unsprung weight makes sense but instead of conventional brakes why no use a radical design that applies a braking force to the drive shafts themselves.

just random musings of course.

[TheStoat]

Yep, very pleased that my Cobra hasn't needed the rear pads or discs fettling in the last ~28,000 miles - lovely Jag running gear too :)

Bachi - the further from the centre of rotation you are, the more moment you can exert against the rotating object. Hence discs getting bigger on sporty cars and no desperate shaft grasping action in motorsports ;) Well I think anyway. TBH I'm pushing the limits of my GCSE Physics here...

[ChrisC]

Harsh, You could stop the shaft directly but there is an issue you may not enough friction to do it as The stoat says if you are too close to the center or rotation. Though you could go all radical and make the brakes electric, that could be scaled up to work easily even close to the centere of rotation. Is that radical enough?

On the other hand you could make your discs and pads lighter, the caliper is always going to be heavy, the jag only has 4 pot front an 2 pot rear but the rears are still about 5-6 kg each. Thing is you can only ever do it on the rear as the front has to be at the wheel unless you are fwd or 4wd.

Just as a bit of a laugh, ask the next boy racer with 19 inch rims on a citreon how much weight he has added to each his wheel. Replacing air with metal, that will make me go faster and handle better surely!

[Redex R]

Inboard discs now theres a novelty , quite popular on some old motors , Rover P6s as I recall , must be cheaper than the Porsche Ceramic discs £30k I believe , speeds just a question of money , and so is stopping quickly apparently !