front disc brake tie bar length and angle, please help :)

[tonydevon]

Hi, I am new to scooters as you might know, but I have basic understanding of engineering etc

my problem is thus

I have just one job left before my build is off to powdercoat etc, I am trying to sort out the front brake tie bar

now my common sense and logic says that it should be the same length eye to eye as the axle to pivot holes on the links

it should also run parrallel to the straight line thru the axle and pivot holes on the link

to achieve that its really not going to look how I want it

I have looked around online and various pages etc, seen some done what I class as properly, and others with tiebars short and at different angles

can anyone on here please offer advice, I thought this best place to ask as theres some proper builders on here

thanks

[tonydevon]

heres a scootrs one, so I assume that running it shorter and different angle is fine, if a professional company do it? or do peple modify them?

and it appears that Mr Frank Sanderson does something similar, so maybe Im wrong with my theory?

[soulsurfer]

.

[jason frost]

Which disc are you fitting ?

[tonydevon]

Scratch build. 220mm wavey disc.
Caliper carrier is made and done. Just this linkage to sort.

[tonydevon]

Im gonna go with the easy mounting route, worst case scenario is that it doesnt feel right, not the end of the world to drop the shock off, cut mount, move it and spray it, can get them re powdercoated easy enough

the last scooter I rode didnt even had dampers so Im figuring that this has to be an improvement, no matter how bad it is

[Minority]

Im gonna go with the easy mounting route, worst case scenario is that it doesnt feel right, not the end of the world to drop the shock off, cut mount, move it and spray it, can get them re powdercoated easy enough

the last scooter I rode didnt even had dampers so Im figuring that this has to be an improvement, no matter how bad it is

My take on the subject (FWIW). Think the main thing is to ensure that the caliper mounting bracket is free to rotate around the axle and the tie rod is free to rotate at each mounting point (hence my use of rose joints, which also makes the length of the tie bar easily adjustable).

"Just before we lost some of the posts on the change over, there was a thread about antidive brakes.
It included some discussion about where to position the link to the fork and the theory behind it, which included some fancy diagrams of parrallelograms.
My theory is much simpler and goes along these lines:
As the caliper mounting bracket is now free to rotate around the axle, when you apply the brake, the forces generated on the caliper mounting bracket are rotational about the axle.
Therefore the tie rod should be mounted so that the opposite force to resist the rotational force, is at 90 degrees to the tie rod caliper mounting point/axle axis.
This would provide maximum anti dive effect with no tendancy to either "dive" or "rise" under braking loads.
Suspension movement would have a slight effect of course and you could adjust the effect you want - angle greater than 90 degrees = tendency to rise under brakes, angle less than 90 degrees = tendency to dive under brakes.
This is just my personal theory and please feel free to shoot me down in flames.



"

Still loving your build by the way Tony

[tonydevon]

ok thats cool, thanks I can understand that

I think my biggest problem with these setups is that in theory you should end up with juddering, as the unequal lengths actually try and move the caliper and pads across the disc, maybe the amount of movement on scooter front ends is so minimal that this doesnt occur, maybe Im wrong completely

but what I like is that you have explained your setup, as much as I appreciate advice from people I really love it when they explain why its like that, the theory and understanding behind it, I had an old workshop teacher that taught my engineering course, he was one of them old boys that was a font of knowledge, he wouldnt accept you just telling him something wouldnt work, go away and proove it doesnt work LOL, I learnt more from prooving that things wouldnt work, than I ever did being shown how things did work.

thanks for comment about my build, powdercoaters booked, hes going to let me drop it all off Friday 7am, really great guy, I been sandblasting and wet flatting the alloy bits, trying to get rid of as many blemishes as possible

the last job is this brake anchor rod, Im going to get the caliper in place, and go for it with your method

I also am using rod ends, M10 as I had them laying around LOL, rear brake has M8 rod ends for the linkage, again as I had them laying around, dont like spending money

hope is that I have it all back friday 4th, if not then I have to wait till friday 11th that will hurt my time schedule a bit.

[Darrell Taylor]

if you weld a bracket to the fork leg make it a long one with 3 holes in it bottom hole 90 degree to fork leg then 2 above which the top one will be 90 degree to the top caliper bracket mounting point
i used the top caliper bolt to fix the tie rod to ,i just replaced it with a longer high tensile bolt to save drilling another hole/adding yet another bolt
this way you,ll not need to strip and reweld and will give you the oppurtunity to test the 3 positions to find which suits your own personal taste
your next challenge is getting wheel in the centre,although if you have made the set up yourself u probably have engineered it already,
lovely build!

[jason frost]

I use a short arm mounted just above paralel. http://scooterotica.org/forum/viewtopic ... 12&t=29814