Fork Springs - Best source?

Stupidly, I left my Norton tied down in the back of my truck, wonder of wonders, the springs sacked out.

Now I find that my head pipes drag and scrape when I get frisky.

So I can look at catalogues without dissassembly first, what are the stock spring's specifications - ID, OD, length and rate?

Anyone have recommendations re vendor, brand, rate?

I have a spare used set leftover when I did my external springs. Make a fair offer and they are yours. SHipping is from 53132.

If satisfied with the factory one rate fits all then take the offer and ride on. The off the shelf progressive springs are commonly reported too soft for riders over 180 lbs. on brake dive and bottoming. Its possible to brew your own by mix-match of a 2" inch section of spring spacer with 2" cut out of factory spring. Clean up stanchion insides as that's where most the fork friction occurs. Move the bottom damper holes up above tapper if not done already, for silent bottoming.

Thanks Bwolfie. May take you up on your offer.

In researching, I find that the springs are dimensionally similar to many '70s and '80s bikes - SR500, XR500s, RD 350s-400s, XS650s, and even Laverdas and Guzzis, so I should be able to get some at the local MC junk yard.

That said, I'm looking for something stiffer than stock, more rate, and I'd like to do my shopping before I dissassemble the front end.

So, does anyone on here know what the stock spring rate is?

xbacksideslider said:

Thanks Bwolfie. May take you up on your offer.

In researching, I find that the springs are dimensionally similar to many '70s and '80s bikes - SR500, XR500s, RD 350s-400s, XS650s, and even Laverdas and Guzzis, so I should be able to get some at the local MC junk yard.

That said, I'm looking for something stiffer than stock, more rate, and I'd like to do my shopping before I dissassemble the front end.

So, does anyone on here know what the stock spring rate is?

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Total Fork Travel
6 in.
Fork Leg Oil Capacity
150 cc in each leg
Springs
75 1/2 Coils
18.687 in. free length
36.5 lb./ in

Thank you, drones76

Assembled with factory innards- Roadholder fork travel is only a bit over 4" d/t both spring coil bind to close up any more and damper rod too short to open more. Sounds like a lot of effort to shuffle through bone yard to extract springs if not knowing what's inside first. Would be a good thing to know for others if you do find spring joy by jumping Norton fence.

Clubman Racing has heavy duty progressive springs @ 35-50 lb.
http://www.clubmanracing.com/suspensionforksnorton.php

Thanks, I saw that. How much stiffer are those compared to stock?

Generally, I think progressive springs are unnecessary, no for us I'll go farther - a bad idea, since the "progressive" part is taken up by the sag as soon as you sit on the bike. If you have lots of travel, say at least 6" or more, then, yeah, progressivity is an OK idea since it presumably will allow better wheel/road contact when you're wheel is only lightly weighted, when it is launched or floating over the lee side of up bumps, as opposed to heavily weighted while it dives into the bottom of swales or holes.

IMO, when you have limited travel, like we do, you can't afford to give up more than 20% to sag and unless your progressive spring has a high rate, that's what it's gonna do, right off.

I am 200 lbs and have never been able to make a progressive fork spring work in a Norton that is ridden in a sporting manner. The only place I have made them work was on the rear of a bike with plenty of travel- like off road with 12 inch plus. Jim

If you have lots of travel, say at least 6" or more, then, yeah, progressivity is an OK idea since it presumably will allow better wheel/road contact when you're wheel is only lightly weighted, when it is launched or floating over the lee side of up bumps, as opposed to heavily weighted while it dives into the bottom of swales or holes.

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I got it both ways in spades so what you state only applies to factory Roadholders w/o longer damper rod and extra spring. Still even with only 4" travel like other moderns I've rid, they work pretty good so why not short travel Roadholders too?

Can cut the factory spring down which stiffens it up some, but not much, so then put in a valve spring or other to take up slack and the harsh stuff yet sags to same level as factory. Jim this would likely please your poor forks too.

Ms Peel has 6.12" fork travel with settable sag by a couple of ways one via change-able progressive 2" spring spacer. Does cause issues trying to foul something as takes rather more leaning. Valve springs are a good fit and progressive from finger squeeze to almost solid. Ms Peel's factory length main spring was last of its kind in a batch by Paul Geoff. I pestered him on the 3 rates chosen but he said for him to know and me to find out. With enough requests he might do up another batch. http://www.norbsa02.freeuk.com/

Might contact Greg Summerton ? <gregss@bigpond.com>
he has built custom springs for external spring Road holders.

I got a set of external springs listed for a BSA or something british off of Ebay cheap. I had to cut them down a little to fit with my Hyde fork brace. I did some maths and so far sitting on the bike they seem to be the same if not a little stiffer than the original internals. Real road testing will tell but so far so good. Plus no stiction from binding up on the inside of the fork tubes. And they look the business!

External springs work very well but they eat up the chrome pretty fast.

The best I have found for stock forks is:
1. oem Norton springs. Quite soft.
2. Aftermarket straight weight springs for Yamaha RD350. They drop right in but will be too soft for most riders. They tend to drag less inside the tube. {not real sure why]
3. Big guys can use aftermarket springs for Honda SOHC 750. They are pretty firm.

I like to install RD350 springs and check the laden and unladen sag. You want about 1/8th inch unladen and 1 1/8 inch laden sag. If you use PVC tubing and preload them for 1/8th inch unladen you will probably find too much sag when laden. To correct this cut 1 inch from the spring, grind the end flat and replace the 1 inch with PVC tubing. This will make the spring rate higher and the laden sag will decrease. You may end up cutting off more spring before you get the laden sag correct. I removed around 1 1/2 inch of spring to make it work for me. Add PVC spacers to maintain the unladen sag at around 1/8th and maybe up to 1/4 inch.

Get the spring rate right and the sag correct to keep the steering geometry correct. Now you can adjust the oil level to make the fork softer or harder. If the fork is too hard as it compresses then remove a bit of oil. If it is too soft add a little oil. The air chamber above the oil is your adjustable progressive spring -use it. It works much better than a progressive spring.

I do not recommend adding travel to the Norton fork by using longer damping rods. This takes away from the fork overlap and increases "sticktion". It also places dangerous loads on the aluminum fork lower tube and may cause failure. I cracked one of my own and have seen others broken because of this.

To keep the fork from clacking when it tops out I use a 1/8th inch thick teflon washer on top of the piston -inside the cartridge. It steals very little travel.

Check the fit of the damping rod in the top cartridge cap. If it is loose, rusty or pitted you will have very little rebound damping. Replace whatever is needed to get a good fit and then polish the rod. Now fill the fork with the correct amount of [dare I say it] Mobil 1, 0w-20 synthetic motor oil. It is the slickest stuff I have ever used in a Norton fork.

You can actually end up with a fork that works pretty well. With a straight weight spring you will have a fork that is capable of using all of its travel and feels lively. Jim

I do not recommend adding travel to the Norton fork by using longer damping rods. This takes away from the fork overlap and increases "sticktion". It also places dangerous loads on the aluminum fork lower tube and may cause failure. I cracked one of my own and have seen others broken because of this.

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Sorry Jim but that's an old wive's tale I've proven wrong in spades on Ms Peel. I'm talking earth busting shear loads 50+ mph not mere road lumps and roots. You simply can not load forks to bind once fully extended as there's no spring loading then and compress immediately to plenty over lap on any light force, no binding no damage no nothing but soft silent landings, except for pilot teeth when helmet chin bottoms on bars or headlight. About only striction that matters in forks is the spring sliding in stanchions. Sure bent stanchions and too tight or out of round bushes may bind to matter but thats not the fault of the basic design.

Air pocket pumps down so its effect decreases within 1/4 mile off road and 1/2 mile normal road use. Its safe to use up to 175 ml but not more I found out. Varying the oil grade made more damping effect to me than fluid level within 150-175 ml amounts. Switch the plastic pipe for a heavier spring and see why I like it so much. I'm not the only one with my mods that hunts weird surfaces for shear fun of not hardly noticing it.

Jim, than you so very much for taking the time to make that post. Exacgtly the kind of information I was seeking. I'll be looking for some CB750 springs and adopting your other tips as well.

I already have the longer damper rods but I think I'll stay with them since their "picking up" the front end was a great improvement in ground clearance, gave me more travel, and slowed the steering some. On the other hand, maybe I ought to be looking for some longer stanchion tubes. Isn't there someone who does that? Was it Forking by Frank?

Steve, I'm with Jim on progressive springs. If you don't have luxury of long travel, then they just waste precioius stroke.

Jim, than you so very much for taking the time to make that post. Exactly the kind of information I was seeking; another example of why this site is so good - the people on it. I'll be looking for some CB750 springs and adopting your other tips as well.

But . . . . I already have the longer damper rods/Ford spring and for now I think I'll stay with them since their "picking up" the front end was a great improvement in ground clearance, gave me more travel, and slowed the steering some - all plusses IMO. On the other hand, your point about cracking is well taken and I ought to be looking for some longer stanchion tubes. Isn't there someone who does that? Was it Forking by Frank?

Steve, I'm with Jim on progressive springs. If you don't have luxury of long travel, then they just waste precioius stroke.

Yes, Frank has longer tubes.

Raising the front end will increase the trail and slow the steering. Suspension and steering geometry is a very personal thing. What one person likes the next person hates.

You do need to be careful about changing the trail to the point where instability sets in and causes high speed wobble. Too much or too little can do it. It is also influenced by the rear ride height and the particular frame you are using. They can vary quite a bit from one frame to the next.

Kind of like everything else on a Norton- one size does not fit all. Jim

Steve, I'm with Jim on progressive springs. If you don't have luxury of long travel, then they just waste precioius stroke.

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I'm just frustrated and scared for what yoose guys are missing out on with safer securer road joys by just putting in your own tougher spring spacer to suit the factory limited travel fork or 2" extra hobot mod. Most road lumps only need couple inches of soft travel to float over but need serious spike in last ~2" spring resistance for hitting edges of pot holes, 2x4's, frost heaves, cement road seams and panic brake grabs. Progressive springs don't have to be smoothly progressive or even a single spring like the off the shelf let downs every beefy Cdo pilot complains about. Speed Bumps don't hit progressively but sharply so extra heavy 2" or so spring just takes it up smoothly instead of almost or fully bottoming. My extra 2" extension really helps front stay in traction when leaned on power on lumpy surfaces yet agree not really needed unless trying to out run the moderns in turns, but un-tamed isolastics won't allow that even with best forks.

Someday might try Greg Fauth's fork kit and see what ya might be missing out on, 6" travel, highly progressive spring rates as well as progressive damping rates but in mean time can get some relief by just slicing dicing spring sections.
On 6" travel forks, to retain stock sag plus the extra strong 2" spring cushion would require taking out like 4" of factory spring to fill in with weak 2" spring plus a 2" stronger one. On Peel I set sag at 2" so 2 extra inches of bump absorbing and 2 extra inches of rebound action that stays in effective traction control.

Hobot,
I tried the long damper rod conversion many years ago on my N15 [with Commando forks] . It only lasted a couple months before I split the RH lower and squirted oil all over the place. Luckily I was only going at walking speed or it could have been bad. I will stay with 4 inches of travel and spring it so I can use all of it- thank You, Jim

Yes and you also got stuck with poor grade of Castwell tank seal too while Wes and my tanks holding up. I am not out to mislead anyone nor pump me up but I can't tell ya how harsh I've treated Peel on purpose then even worse by accident crashing through goopher holes or landing on nose stopped short on my helmet leaping a 5 ft bank to catch air but landing at top in a ft deep wash out rut tall grass hid. Forks survived perfectly, much to my own horrified amazement. Peel forks disappeared miles of wash boards and crap on THE Gravel that jars and chatters regular roadholders and Race Teched Suzuki forks so I sit back to unload wrists on their forks while still gripping almost white knucked to prevent constant snatch outs. Liked Peel's forks better than MX bikes I was lent so gave up on the dirt bikes in more pleased amazement. Maybe its our weight difference? Regardless of fork travel support, still suggest you try a strong spring spacer some day. I've kept Trixie bone stock on purpose and found she just ain't up to the off road flings or hwy sports games nor keeping her tire down on squeal braking. I've also got the feed back from Greg Fauth & customers too, so ain't just me thank goodness. I am definitely stifled in my cornering hobby till money/time enough to get Peel going again.