Board index Flathead Power-Technical Questions, Answers, and Suggestions Morthodites-"Non Factory" Another non stock front brake

Another non stock front brake

Built something weird, one-off or want to? Ask or tell us about it here.

Moderators: Curt!, Pa

Post Sat Apr 19, 2008 7:05 am

Posts: 1660
Location: Interlaken, NY USA

Here's a link to a front brake setup I'm working on for my Flattie Chopper. The brake is mostly done, I posted over on John's site some info to help George, thought I might as well put the site up here as well. I've tested this caliper on my Bobber last Fall, it has at least the stopping power of the older '74 Sporty caliper I had been using. Mostly I liked the way this one tucks in behind the girder leg. Just satisfies my sense mechanical beauty.
DD
Image

Here's the link to more pics
http://www.freewebs.com/dicky_linn/chopperbrake.htm

Post Sat Apr 19, 2008 11:05 am

Posts: 587
Location: Crewe, Great Britain

Hi Frankie,

Yes, a right mix of parts!!!

That's the beauty with H-Ds, anything can be made to work with whatever else!!!

If you were to want the caliper on the other side of the forks, the 74/76 one will be on the back as well...

Patrick

Post Sat Apr 19, 2008 11:11 pm

Posts: 1634
do you find any particular effect on the handling, having the caliper behind the leg? I don't know much about these raked geometries and I would guess that the greater weight of the girder fork reduces the effect anyway, because of the relative weights of the components, but it would be interesting to know
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Mon May 05, 2008 12:01 pm

Posts: 923
Location: South Provence of FRANCE

...i don't think there are any differences with the front brake of a stock 883 sportsters ...
same place ( behind )
only one disc ...
and IMHO ; a girder's work is the same as a telescopic ...

Post Mon May 05, 2008 12:55 pm

Posts: 1634
no, the relative sprung and unsprung weights are very different and the travel and damping of the girder fork is much less than ( most ) telescopic forks. A girder fork will skid and patter under braking long before a telescopic with the same wheel and caliper set-up

I would guess that the girder is less affected by the placement of the caliper because it is a smaller percentage of the unsprung weight, and that having the caliper behind the leg tends to increase the self-centre ( castor ) effect; but the raked fork angle tends to increase this anyway so again, the effect is less than a telescopic and less than on a stock fork angle

but I've never tried it so i'd be interested to know
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Mon May 05, 2008 3:14 pm

Posts: 1660
Location: Interlaken, NY USA

Well, it's been a long while since I rode an extended girder, and it had no real brake. So, I'm interested to see what this setup does also. My thought was that the frontend won't load under braking as much as stock rake/length, so it just might want to skid more easily. especially with a 3.00x21 on front. I've never bought into placement of the caliper having an effect on handling, to date. It always seemed to me that the force exerted on the fork leg was the same, whether the link pulled to exert it or pushed. However, you indicate it's the placement of the unsprung weight that has an effect. Elucidate please, I'm open to learning, even at this late stage of decrepitude. :lol:
DD

Post Mon May 05, 2008 3:25 pm

Posts: 1634
well, I'm not 100% on the maths, ( meaning I have never troubled myself to find out ), but the principle is easily demonstrated.

block up the front end and take out the wheel. Now, turn the bars. With the caliper above the axis ( in front of the leg ), the weight of the caliper will tend to swing the leg to the stop. With the caliper behind the leg, it will act as a pendulum and tend to centre the fork again. The heavier the fork leg relative to the caliper, the less the effect is, obviously. Likewise, the shallower the fork angle, the less the effect; a vertical leg will not react one way or the other.

there are a whole range of variables, the weight of the fork assembly is one, the weight of the wheel assembly, the fork angle, you get the idea anyway. Triumph and Ducati did a lot of work on this in the 70s. Most 70s production bikes had the caliper in front of the fork because it's easier to assemble and service, but if you have a quick flick around in Google images you will see that behind the leg is now usual, and this is the reason, ie handling.

I've never much liked 3.00 x 21" wheels on Big Twins, I think they are inadequate in terms of tyre contact patch for the weight of the machine, so I expect you are right about the wheel tending to skid under braking
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Tue May 06, 2008 12:21 am

Posts: 923
Location: South Provence of FRANCE

Ouch !
too complicated for me ! :oops:
but Okay guys ! ....keep'on !

Post Tue May 06, 2008 1:11 am

Posts: 1634
's easy really .. if you stand a grandfather clock upside down, it stops working....
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Tue May 20, 2008 10:55 am

Posts: 148
Location: Dorothy, NJ. USA

so, How does that effect the timing? :roll:

Post Tue May 20, 2008 3:44 pm

Posts: 1634
stops it dead.... isn't that what good brakes are for?
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Thu May 22, 2008 8:24 am

Posts: 148
Location: Dorothy, NJ. USA

I always liked a 21 or a 16 Frontrunner for runnin in South Jersey sand. The larger diameter seems to make it easier to climb over the rut. On the road aluminum rims on a 18 or 19 are just fine. Honest


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