Topic: swaping front end and rear end?

[Ouch]

Retro what front end did you use (year and model) cause i know some one some where will ask you that so you might as well go ahead and post up 

thnks...hopfully this post will answer alot of start out questions other will have

[crazypj]

correct me if I am wrong...not too proud to admitt if i am....

Front fork swap......when dong a front fork swap choose a set up that keeps the rake and trail as close to stock as possible so not to alter the ride unless that is the goal

Rear swing arm...lengthing the swing arm gives greater straight riding stability but takes away from sharp turning and shorting the swing arm takes away from straight riding but adds to turning

 

Correct about fork swap.
 Longer swing arm does nothing to 'slow' steering, it's the latest trend on sport/GP bikes.
 Longer WHEELBASE is what affects steering.
 As I said originally, if you don't know what your doing, keep as close to stock as possible.
 If you DO know what your doing,.................well, .......................you wouldn't be asking the question here 

[Ouch]

correct me if I am wrong...not too proud to admitt if i am....

Front fork swap......when dong a front fork swap choose a set up that keeps the rake and trail as close to stock as possible so not to alter the ride unless that is the goal

Rear swing arm...lengthing the swing arm gives greater straight riding stability but takes away from sharp turning and shorting the swing arm takes away from straight riding but adds to turning

Wait...wouldn't putting a longer swing arm lengthen the wheel base?

 

Correct about fork swap.
 Longer swing arm does nothing to 'slow' steering, it's the latest trend on sport/GP bikes.
 Longer WHEELBASE is what affects steering.
 As I said originally, if you don't know what your doing, keep as close to stock as possible.
 If you DO know what your doing,.................well, .......................you wouldn't be asking the question here 

[Retro Rocket]

Longer swing arm does nothing to 'slow' steering, it's the latest trend on sport/GP bikes.

It doesn't work like that mate, the modern bikes have much smaller engines physically, so their swingarms are mounted a lot further forward, really, they have nothing in common with these old bikes. When they are using longer arms on moto GP bikes they also redesign the frames, usually moving the motor a little further forward to retain a similar wheelbase. Lengthening the arm on an old Honda will add high speed stability but slow down its steering into corners requiring a little more effort to get the bike to turn in. I have noticed in discussions recently about suspension swaps that comparisons are being made with modern bikes, frame geometry has come a long way since our bikes were made, there is virtually no comparison to modern bikes as they are built to a completely different formula, swingarm to steering head numbers are different, swingarm length are different , suspensions over all are different and even the rigidity of the frames dictate what the suspension will do with far more accuracy than our old steeds....

[Ouch]

Longer swing arm does nothing to 'slow' steering, it's the latest trend on sport/GP bikes.

It doesn't work like that mate, the modern bikes have much smaller engines physically, so their swingarms are mounted a lot further forward, really, they have nothing in common with these old bikes. When they are using longer arms on moto GP bikes they also redesign the frames, usually moving the motor a little further forward to retain a similar wheelbase. Lengthening the arm on an old Honda will add high stability but slow down its steering into corners requiring a little more effort to get the bike to turn in. I have noticed in discussions recently about suspension swaps that comparisons are being made with modern bikes, frame geometry has come a long way since our bikes were made, there is virtually no comparison to modern bikes as they are built to a completely different formula, swingarm to steering head numbers are different, swingarm length are different , suspensions over all are different and even the rigidity of the frames dictate what the suspension will do with far more accuracy than our old steeds....

Thanks for the clairity

[crazypj]

Semantics 
I know modern motors are real short, 'stacked' transmissions, mass centralisation, etc
Need to be more specific because some of these threads may come up again several years from now
I've been quoted on things I posted 3~5yrs ago, (or more in some cases)
I had to check thread to find context (I had forgotten the original post)

[Retro Rocket]

Semantics 

 

[crazypj]

I guess we'll just have a conversation and hope the OP can keep up 

[Ouch]

I guess we'll just have a conversation and hope the OP can keep up 

well w're listening 

[kajtek]

for those of you wanting to fit 41mm forks (r6, zx6r etc), check out the modern triumph bonneville/scrambler, they use triple clamps with offsets that look very similar to my 400 4, and have 41mm forks. so you could use sport bike forks without changing the offset. will try and get a measurement (guy at work has a scrambler)

ashley

[FunJimmy]

for those of you wanting to fit 41mm forks (r6, zx6r etc), check out the modern triumph bonneville/scrambler, they use triple clamps with offsets that look very similar to my 400 4, and have 41mm forks. so you could use sport bike forks without changing the offset. will try and get a measurement (guy at work has a scrambler)

ashley

Awesome suggestion Ashley.
Could you also get fork length too?

[kajtek]

sure thing, may take a while as the guy rarely brings his polished 'sunday' (its the flat green steve mcqueen edition i think..) bike to work, if i dont see it soon i can pop in to a triumph dealer and hope they ignore me messing around with a digital caliper on their showroom bikes!

[faux fiddy]

Ahhh!!!  I didn't put that one together.

Offset trees work alright, but you are usually limited to a couple different angles. There are a few machinists out there who have custom made there own offset trees to a desired angle.

The advantage of offset trees is that you can rake the forks without altering the frame.

Just make sure that you understand what your rake and trail measurements are and where you want to them to be, before you go out and slap offset trees on your bike. Don't become one of those statistics that wanted to quickly build a cool, low dollar custom bike, then ended up in either a hospital or morgue.

A friend had a sportster he modded, 3' rake machined into the headset ordered online. Good stuff as far as quality, but increased the stack highth. Added wide glide, and somewhere in his mods he lost an inch of fork travel.

He sold it to a guy that scratched it up at least once within months. Did it again and  limped home and ate pain pills for a couple days while his punctured lung got worse. Never saw the doctors until his employees started wondering where he was.
Too Late.

My bud feels real strange about selling him the bike.  They were kinda buds but he sure didn't want to meet family at a funeral.

[Retro Rocket]

A friend had a sportster he modded, 3' rake machined into the headset ordered online.

Had a friend put the same things on his Harley, nearly killed him, as you turn the bars you could actually see the front end move in an arc, altering the rake and trail as he rode it..... Stupid dangerous.....

[crazypj]

Splitt...thanks..question? what effect will putting a longer swing arm in have on rake, trail, offset, CoG...or is that only a question that will be answered once a different swing arm is in?

 Longer swing arm has zero effect on trail. (or very limited in some cases if you raise or lower rear of bike enough to affect steering angle)
 There are line drawings to explain it but basically, take a line through center of steering stem to ground.
 It will 'contact' ground in front of tyre contact patch.
 Drop a plumb line from axle center
 You can actually make a reasonable measurement by measuring height of axle then removing wheel and mudguard and fixing axle/bike at pre-measured height.
 String through steering stem, mark ground, string off axle, measure distance
The difference (how far back the plumb line touches ground) is the trail
 Usually you'll have around 3.5"~4.5" trail (ignore trials bikes for now )
This is a pretty constant number, no matter what the steering angle of fork offset (if things are done right)
When you move forks 'backwards' by having less offset, you increase trail which increases straight line stability
 That's about as basic as I can make things (already done too much typing )

[popssss]

so with the rear swing arm swap, what did you decide?  I'm trying to decide what to do with the stock KZ650 rear swing arm, and replacing it with a newer mono shock setup, any advice?

[Ouch]

so with the rear swing arm swap, what did you decide?  I'm trying to decide what to do with the stock KZ650 rear swing arm, and replacing it with a newer mono shock setup, any advice?

the only advice i can give is to do the research and math...do it so much that your dreaming about it because your life depends on what you do....i had not chose a set up yet...mainly due to a car wreck a couple of week ago...the O/P was at fault and no insurance....