New Fork Springs

I want to replace the fork springs in my 850 Mark II.

Any suggestions as to the different springs available?

What about different fork oils to suit different springs?

Also, what options are their for rear shocks. I currently have Hagons.

Frank

Since '99 I've heard any one 180 lbish that's tried the off the shelf progressive spring found they dived too much on braking and bottomed on bumps so I guess were made for light folks that didn't like cobble stone jarring. IIRC I've seen two color springs of different rates but only ridden the red one which are ~35 lb/in single rate. Might be green set at one time but unobtainium now. So must look beyond Norton stuff or make your own spring sections with rates that suit you. Can't really go by fork fluid labeling of weight, so must trail and error up and down till best compromise. Generally strong springs need thicker damper fluid. 3 upgrade kits to consider too.

It is not easy to give a recommendation for the fork. All I know say the original fork is too soft and the progressive spring, which are available in Germany are too hard. I have the original and I think the softness is ok, but it could activate a bit more sensitive. I am 70kg.

Hagons are one of the better.

Ralf

I think you should seriously consider a damper upgrade of some kind.

Springs must be controled by the damper system otherwise the " jocky" will not be in control the horse , slider wear and stiction [due to wear] leads owners to conclude the springs are feeding back bad vibes. cobbles and speed humps are tricky as the forks cannot react quick enough , my Kawasaki knocks when hitting a speed hump with forks that are 50 years newer! But a speed hump is designed to do just that, if cars/bikes could float over them..what whould be the point of them!
They are there to Knock the crap out of bikes about 20 mph! when someone is killed due to one{icy] and a huge claim is made..then they will go!

Front and rear springs need to suit riders weight and preference. I'm about 11 stone and find standard springs with approx. 1/8th" preload a good compromise. Front static sag should be between 5-10mm. Rear 10-20mm. Bushes and sliders are 10,000 miles old and I've put a sleeve extension below the top bush to give proper hydraulic bump stop at full extension and modified the damper tube to give bump stop at full compression.
http://www.members.shaw.ca/randell/nort ... ugrade.htm. Noticed Hobot is mentioned, so I guess this has been posted before. Very good info. I use SAE5 fork oil and they work well. Might get round to fitting Honda CB600RR internals over the winter. Adjustable pre-load and adjustable, variable compression and rebound damping.

Sorry, link isn't working.

http://www.members.shaw.ca/randell/nort ... pgrade.htm

Now it is!

More info please! and some pickys?

Al-otment said:

Front and rear springs need to suit riders weight and preference. I'm about 11 stone and find standard springs with approx. 1/8th" preload a good compromise. Front static sag should be between 5-10mm. Rear 10-20mm. Bushes and sliders are 10,000 miles old and I've put a sleeve extension below the top bush to give proper hydraulic bump stop at full extension and modified the damper tube to give bump stop at full compression. I use SAE5 fork oil and they work well. Might get round to fitting Honda CB600RR internals over the winter. Adjustable pre-load and adjustable, variable compression and rebound damping.

Click to expand...

john robert bould said:

More info please! and some pickys?

Bushes and sliders are 10,000 miles old and I've put a sleeve extension below the top bush to give proper hydraulic bump stop at full extension and modified the damper tube to give bump stop at full compression. I use SAE5 fork oil and they work well. Might get round to fitting Honda CB600RR internals over the winter. Adjustable pre-load and adjustable, variable compression and rebound damping.

Click to expand...

[/quote]

I've added web site where I got the info to previous message. Need to get a digital camera!

lawman said:

I want to replace the fork springs in my 850 Mark II.

Any suggestions as to the different springs available?

What about different fork oils to suit different springs?

Also, what options are their for rear shocks. I currently have Hagons.

Frank

Click to expand...

WHY do you want to replace the springs? What attribute of the fork are you wanting to change/improve?
The oils are... well, like an oil thread. :mrgreen: I've used Kal-Gard Smooth Stroke for 35 years, the moly in it makes stiction go AWAY. Problem is, it's out of production.
Rear shocks.. what are you looking for? More spring rate? More damping?

The springs are bottoming out on the front and I am 98 kilos (215lb).

If I change the front springs then I assume I should also do the same at the rear.

Frank

No off the shelf Roadholder springs I've heard of were stronger than factory and most complaints trying off the shelf progressive were more than annoyed by their brake dive. If ya like the basic spring rate for most road texture but hate the bottoming, the simple way is slice off say 1.5 inches of factory spring and stick in a higher rate spring like a valve spring. Shortening a spring is same as shortening a rod, it gets stiffer. Cut coil end supposed to be bent and then ground flat which is tough home job. Geoff Duke had a batch of progressives with 2 higher rate sections than factory. Peel got the last of them and he would not reveal the rates nor manufacturer to reproduce. 215 lb ain't that heavy on the factory rear shocks to bottom unless speed bumps hit maybe and may give a nice planted feel in turns, but only way anyone knows for sure is trail and error. Worse loaded 850 I saw on old factory shocks/springs had two folks over 200 lb each and bottomed on RR tracks and bigger pole holes i observed in a big parade through town. I've read up on some spring makers but not contacted yet. I found with forks standing a bit taller on stronger springs the lean angle w/o fouling increases nicely and braking more definitive too.

I am same weight as you an I have 30 weight fork oil RGM progressive springs also their convene kit fit. An hagon stainless steel shocks at the back.
So far am happy with them the bike rides will no bounce or diving in fact I don't notice them most of time which to my mind says they are doing their job properly. It also depends on your riding style an type of road you ride on plus wheel an tyres will effect thing to.

I am a cruiser and like to be able to look around and I enjoy being slow on the bike.

I would try thicker fork oil first before a spring change.

Torontonian said:

I would try thicker fork oil first before a spring change.

Click to expand...

+1 and if that dont work go heavier again..

hobot said:

Geoff Duke had a batch of progressives with 2 higher rate sections than factory. Peel got the last of them and he would not reveal the rates nor manufacturer to .

Click to expand...

To calculate spring rates,

Spring Rate (N/mm) = (G x d4)/(8 x n x D3)

Where G = wire spring modulus ( approx 80,000 N/mm2)
d = wire diameter
n = number of active coils
D = mean diameter of coil (centre to centre of wire = OD - d))

d4 = d to the power 4
D3 = D to the power 3
mm2 = millimetre squared

Measure diameters in millimetres. Online conversions available to get from N/mm to lb/in.

olChris said:

Torontonian said:

I would try thicker fork oil first before a spring change.

Click to expand...

+1 and if that dont work go heavier again..

Click to expand...

Or (tongue firmly in cheek) lose weight. Sorry

Cheers, Frank

I apologize. For the last two days, here in the ' Valley of the Sun,' it has been cold, damp and raining! My attitude is shite and I haven't even been out to the shop to take pics of my ' winter project ' so y'all know I don't just make smartish comments. Cheers, Frank

wah64apache said:

olChris said:

Torontonian said:

I would try thicker fork oil first before a spring change.

Click to expand...

+1 and if that dont work go heavier again..

Click to expand...

Or (tongue firmly in cheek) lose weight. Sorry

Cheers, Frank

Click to expand...

Al-a-lot, The school boy math does not include the long spring coil bowing for friction inside of stanchions, though should not be that big a deal to consider in real use with shock vibes speeds over coming binding. RGM did not have progressive springs with higher rates available when I was shopping for Peel, so may solve over 200 lb pilots needs. I do know that if more mass behind the shock mounts than in front its too easy to pull up and hold a wheelie for dozens of yards on balance point. I should measure Peels springs installed in forks with straps, scale and big C-clamp. There are two camps on fork springs, one the elite pavement racer designers that claim a constant rate spring is best and progressive spring just used to cover up design set up faults and 2, the off road runners that mostly try to ride w/o loading fork much but slam down on it from bumps and jumps. If ya can only go as fast around as a road racer then stick with their wisdoms, but if rest of cycle so good forks don't get loaded much, as most of mass on rear from the straight or leaned acceleration, progressives work a treat for me, until no fork load at but for instants of most mass suddenly on and off them.

I've had my feet and hands on front sliders/axle [on modern and Roadholders] feeling EXACTLY what they do on and off road in various conditions, surface texture, power loads and lean angles plus cargo or not. What is being totally missed by road racing world is the forks expand, so the more forks can lengthen in a harsh turn the more front can stay in useful control contact. There is direct relation between rear and front loading, going slow or braking loads forks down and removes rear grip to slip but going faster or accelerating unloads forks to pile up mass on rear patch grip. When one gets near limits of cycle handling on the surface conditions its way more like off road riding needs than going to grocery store in town. For rough road riding its best to have more travel range with couple inches of low spring action to take up the annoyance textures but very hi final inch rate plus soft indefinite hydraulic stop and reversal to avoid hard upsetting fork bottoming slams. Throttle up just before a lump also helps forks handle it but scary method as next instant bike lands on forks and something my be in the way.

If we could find a source of springs of correct ID & OD but short enough with already flattened ends, then could just stack em up for better fork action over rough stuff as well as smooth flying surfaces.