Increasing preload

[oddnumber]

Right folks, been meaning to do summat about my Dragstars sloppy front end for a while, and read on one of the yank forums that swapping out the stock spring spacers with longer ones (they suggest 2") will stiffen it up. Does that sound right?? Or safe??

Thanks for any help :)

[dubmeister]

Stick an inch of the correct size pipe on top of the springs it's cheaper;)

[devon-tony]

it wont and cant stiffen the front end, but it will jack it up

[Borg]

Look on the Hagon site for progressive fork springs, the come with better oil as well. Phone them though as they have a lot more than listed on the site. they did say it was well out of gate.

I got a set for a Triumph for £55 ish.

http://www.hagon-shocks.co.uk/Main.htm

[oddnumber]

Thanks very much folks. I had a spare hour so gave it a go - the forks seem harder to compress now, but they top out really quickly.

Is this safe? I'm half tempted to lob the stock spacers back in.

[devon-tony]

lack of sag isnt really a good thing

the front cant be stiffer, as you havent actually changed the spring.

[oddnumber]

Rode into work today, front end is definately different, not as mushy. The front end is slightly higher too. I quite like the ride.

One thing occurred to me though - with a longer spacer, there'd be more pressure in the forks, so how likely is it to blow a seal or summat??

[Blackjack]

What a brilliant idea.

Taking advice on suspension from Americans.

:rolleyes:

Take the spacers out.

If it tops out on you in a bend, it's very likely to cause the front wheel to break loose, dumping you on your ass.

[dubmeister]

How does the preload adjuster on the top of a fork work if it doesn't just squash the fork to shorten it the same as a spacer

[devon-tony]

yes it does do that but the forks will be designed to still have suitable static sag even with full preload

and its nowwhere near in the region of 2" of adjustment

[oddnumber]

Fair enough, I see your point. Thanks for your advice everyone :)

Looks like I'll whip the spacers out then. You live and learn I guess :D

Ta very much again.

[matthewmosse]

sidecar crowd use this all the time, my outfit has apparently has 3" preload spacers fitted, Only bad factor, I hope that the fork seals don't go as they'll be a bugger to rebuild. the travel might be a bit limited and there is the risk of the springs becoming 'coilbound' ie the spaces between the coils on the springs are squezed out making the springs effectively a pice of soild pipe. I'd say go for it, It's nice and cheap, then again I'm a tight git:D

[devon-tony]

the key word in that answer is "outift" your not very often cranked over and going round a roundabout are you :)

[shaggy696969]

By far the better way to go is a set of Hyperpro progressive springs. or even using a thicker grade oil but not spacers. I know on your Dragstar if you did have a off it wont be a fast one but I wouldnt be tempting it.

[Blackjack]

the key word in that answer is "outift" your not very often cranked over and going round a roundabout are you :)

Not very often that an outfit weighs that same as the bike the springs were designed for either.

[johnr]

i often use 2 pence coins as spacers to setup preload. theyre cheap enough, and are a uniform thickness, so you can add and remove them till you get it just right. and , hey, theyre 2 pence each. my old suzuki had a pound in each leg, so total cost of the preload, 2 quid!! inmfinately adjustable, and you dont have to faff tryingto cut the tube dead square and the right length!!

[matthewmosse]

nope, I don't crank the outfit over 'often' on roundabouts, but I have, and under much higher loading then a solo bike ever is under and so far I've not been aware of the forks becoming coilbound or bottoming out. For budgett reasons, I've not opted to upgrade the forks with new springs, the bike normally covers over 10,000 miles in a year and preloading works well enough for me, If I rode faster then it might be worth the investment in fancy springs but the issue is really is the springing adequate for the needs of the user. Try and see, I'd say, just don't push a inprovised repair / mod too hard, too soon until you know it's limitations.

[gothtec]

i often use 2 pence coins as spacers to setup preload. theyre cheap enough, and are a uniform thickness, so you can add and remove them till you get it just right. and , hey, theyre 2 pence each. my old suzuki had a pound in each leg, so total cost of the preload, 2 quid!! inmfinately adjustable, and you dont have to faff tryingto cut the tube dead square and the right length!!

Thats the hint I was thinking of... May do it to my own!

Got a website address for making adjustments to dragstars, can seem to find it though...

[Blackjack]

One last time.....

All putting a spacer on top of the springs does is to alter the ride height.

If it isn't bottoming out, it's pointless, and even then it's of limited use due to that whole coil binding thing.

If it makes it top out, it's dangerous.

Sidecar people might like to try lobbing a couple of used valve springs, of similar diameter to the spring, obtained from somewhere that overhauls car engines in there instead. You want manly valve springs from something with two heavy valves per cylinder, not poncy ones from something with 16 feather weight valves.

Brave people might like to combine that with shortening the spring which will actually make it stiffer. Though then you WILL need a spacer and coil binding is likely to be an issue.

Basically, springs are measured in lbs/in (possibly Kgf/mm or something these days) and the force is spread through the whole spring (usually, sometimes they're progressively wound and that alters things a bit).

So....

If a 100lb weight compresses the spring 1", its a 100lb/in spring.

Say it has 50 coils, then 100lbs force compresses each coil by 0.020"

Cut 10% of the coils off, leaving 45, and 100lbs force still compresses each coil by 0.020". But, 45 x 0.020" = 0.9"

Since springs are linear (up to their yield point) adding another 10lbs will compress each coil by 0.002", making for a total compression of 0.99".

So, ballpark figure, lopping off 10% of the length of the 100lbs/in spring made it into a 111lbs/in spring. Neat huh?

Well no, because it may not have as much travel as the forks now....

Which is where using a valve spring as a spacer comes in handy, as long as the valve spring has a higher lbs/in rating than the fork spring.

Whether this makes an improvement or not will depend on quite a lot of things. If you change the length of a spring, you change it's frequency, and you altered the wheel frequency of your bike. You want to know about that, go look it up, be warned, it's confusing.

Springs where the coils are closer together at one end than the other (progressively wound), cut the end with the biggest gap between the coils.

Shaping of the end of the spring is advisable as they're quite hard and the pointy bit is quite capable of wearing a hole through some of the softer bits and escaping. But hey, you cut the spring with a cutting disc on an angle grinder, so swapping a grinding/sanding disc on there and flattening the end isn't going to be a big deal.

If your problem is actually pogoing, then chances are that playing with the fork oil is a better place to start, try replacing whatever is in there with what the manufacturer recommends as a first step. Lot of shops just bung "fork oil" in there without worrying about SAE rating, and if it's never been changed, well it tends to get thinner with age, not thicker.

If that doesn't work, try thicker fork oil. Upping the level of fork oil, means that the air in the fork leg is compressed into a smaller space, so it has some effect on spring rate. Bear in mind that as the spring compresses it's also reducing the space inside the leg, and probably displacing the oil too. Small changes are recommeded here.

Levels and amount have an effect too. So if you take the springs out, what did you do about the oil that came with them?

I'm not suggesting you try any of that (apart from trying valve springs instead of solid spacers if you've already got non standard spacers) but if you do, bear in mind that chopping a spring up is a bit permanent.

[Borg]

£55 for the right springs from Hagon. Isn't your safety worth that much ?

Do the job properly. You only have one life.

[johnr]

the key word in that answer is "outift" your not very often cranked over and going round a roundabout are you :)

but on a solo you dont have 150 kilos of metal and fibre glass hung on the side of the bike. forks on outfits have a considerably harder time than on solos!

[Blackjack]

but on a solo you dont have 150 kilos of metal and fibre glass hung on the side of the bike. forks on outfits have a considerably harder time than on solos!

That's kind of the point John.

Spacers raise the ride height.

150 kilos of side car lowers the ride height.

The Drag Star in question in the original post, doesn't have a sidecar (well not that he mentioned)

[oddnumber]

The Drag Star in question in the original post, doesn't have a sidecar (well not that he mentioned)

You're right, no sidecar.

I've weighed up the info on here and taken the spacers out, reckon its not worth the risk to be honest. I'll go down the route of maybe thicker fork oil though.

Thanks very much for the advice and information, its appreciated :)

[Borg]

Why not do the job properly ?

[Dougie]

Hagons do Progressive spring kits with a litre of their fork oil for just over £60 including postage.They make quite a difference.

[J Top]

I have in the past fitted name, I forget the name, brand progressive front springs to the front of Harleys and they come with a piece of plastic pipe to cut down as adjustment

[Dougie]

Aye,the Hagon kit came with 25mm alloy spacers.

[slim..]

All the preload ajuster on modern forks does is compress the spring & reduce the sag slightly

if you think about it most of these have a max ajustment of around an inch & the japs have spent millions of yen sorting that one out .....so i'd say the max you should look at preloading some fork springs is ........ wait for it .....yes you guessed it an inch :thumbsu:

just my tuppence worth :D