wombat
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| posted on 30/6/11 at 08:18 AM |
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Bike Brakes on front?
Having read lots of threads about over braking (solid disks vs vented etc) has anyone fitted bike brakes to the front as an alternative ??
Wombat
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cliftyhanger
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| posted on 30/6/11 at 08:51 AM |
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I would have thought a bad idea. Besides, don't bikes just have a single caliper?
Vented discs do not increase braking in the slighted, just means they don't get as hot. A good thing at the expense of weight.
Plenty of smaller discs/calipers available, if you want less braking ability  or just use cheap pads!
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mcerd1
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| posted on 30/6/11 at 09:17 AM |
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^^ I think he might be thinking about the bigger sport/super bike brakes - most of them have 2 decent size discs on the front 
I think you might find them a bit small, but I know alot of the formula student cars use bike calipers
[Edited on 30/6/2011 by mcerd1]
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MikeCapon
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| posted on 30/6/11 at 09:27 AM |
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Motorcycle calipers are a good choice IMO. The discs though are too thin (4-5mm) to accept the extra heat generated by stopping 4-500 kgs of car.
In the past I have modified CBR900 4 piston calipers by adding sandwich plates to open up the caliper's internal width. These were then run with
car discs on road rally sidecars which are 350-400 kgs plus driver and passenger. Of course there is only one front brake stopping that lot and we had
no problems.
The bike calipers are very light and bloody well made. You wiil find all sorts of bike caliper from single piston sliding calipers up to 6 piston
calipers on some Hayabusas for example. There are heaps of good 4 piston calipers about like the CBR900s.
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matt_gsxr
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| posted on 30/6/11 at 10:12 AM |
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One other problem that you might find is that on the bike they don't have any practical radial restriction on space.
When you put these inside a car wheel you do have a restriction (the inside of the wheel).
If you care enough to fit bike callipers to lower the weight, then you will already be running 13inch wheels, and so the problem is compounded.
You would want to run some sums on pad area, line pressure, etc. they do look a bit small.
Matt
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MikeRJ
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| posted on 30/6/11 at 12:42 PM |
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The discs on a modern 1 litre+ sports bike will be too large (320+mm) unless you are running massive wheels. You'd also have to use a custom
hub design to mount them, and after all that I suspect they wouldn't be up to the job of stopping something that weighs 2.5-3 times the weight
especially as the discs would be inside the wheel, out of the airflow.
Might be suitable for use as inboard rear brakes though.
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hughpinder
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| posted on 30/6/11 at 02:24 PM |
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I suspect that they would actually be ok, as long as you split the caliper, insert a spacer and put in a slightly thicker disk.
On the ability to absorb the kinetic energy, dont forget the pads as well as the disks have less mass.
If there are 2 disks on the bike front, thats only the same as on the car, where there will be one each side of the car!
Bike pads are more expensive(the ones I've seen anyway).
Weight shift during braking: A decent bike can brake so hard all the weight is on the front wheel and the rear lifts off the ground - I haven't
seen a car do this yet! This is not the optimum stopping method though.
When calculating the relative masses, don't forget to allow for the rider/driver -
bike ~ 190kg+85 for driver, car 525+85kg(say)
So that bike that can stop from 190 would be equivalent to a car from 125mph, all other things being equal.
Cars are able carry more speed in the bends, (to brake less relatively, than a bike) to get round the corners.
You will still need to calculate piston area/disk diameter required.
Not sure I'd do it though!
Regards
Hugh
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