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Discussion Starter · #1 ·
so i guess it's time to replace the front fork springs with some sort of progressive spring, but i have a few questions first before jui commit to doing it...

1. which brand of progressive-style spring do you recommend and why?

2. what weight fork oil do you recommend and why?

3. how difficult is it to replace the springs? do i also have to change out the fork seals? is it a difficult job for some one to perform who has never done it before, as i have no experience with tinkering with front suspension at all, but have done every repair and mod on my bike so far by myself, including replacing brakes, clutch springs, carbset-ups, replacing the master cylinder after a wreck, removing the triple tree to tap out a bolt that had it's head sheared off in a wreck, etc. and feel confident enough to do my own valve checks and adjustments onece i hit the 12k mark.)

4. what is a spacer? what is it's purpose/function, and is there a stock size that is recommended, and do some spring kits come with pre-fabbed spacers or do you manufacture your own, and if so, out of what material?

5. is it worth it to go through all the trouble of repalcing just the springs and not install emulators as well? what do the emulators do? i ask because at this time i am on a bit of a budget (major back surgery in december after severely herniating 2 discs and finding out i have spinal stenosis after a nasty jiu jitsu injury, and was out of work for the last 3 months and have some medical bills i have to pay off!)

a little bit about me, which may help in suggesting what type of spring/stiffnes...i am 6'2, currently 175lbs (but will be back to 185 soon, was down to 163 after surgery and am trying to gain the weight back!) ride fairly spirited in the twisties / fairly aggressive but not ridiculous, and ride the bike like it's stolen everywhere else, lots of engine breaking and accelerating between twisty turns!

(sorry for the long post, but i just want to be as educated as possible before doing this mod!)
 

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1. Ikons - because they are fairly stiff and I'm heavy. Good price - quality mix, and recommended by many folks. And having fitted them - they are GREAT! Any of the others will be good too.

2. 10W - because that's what it said in the instructions - I have a bit of "bounce" at low speed on smooth surfaces, so 15W may be better to properly damp

3. It's very straightforward. You do NOT have to replace the fork seals. Do one leg at a time - pull the front wheel and fender. Slacken the top bolt in the top triple tree. Slacken the top cap. Slacken the bolt in the lower triple tree, remove fork, undo cap, slide out innards, empty oil, fill to recommended level with new oil, install new spring, refit leg, repeat on other side.

You did your own ARK and all that - you can easily handle this, especially if you have a workshop manual (recommended).

4. The spacer is just used to preload the spring correctly. If the spring is below the level of the top of the fork, then it will bounce around. A londer spacer will put more pre load on the spring.

5. I don't know anything about emulators, but if you just do a simple Ikon / progressives / hagon / works brand spring install, you will curse yourself for not having done it sooner. I could not believe the difference.

Hope this helps.

Do it! I was impressed with just doing the front, now I have done both front and rear suspension, the way my bike handles is UNBELIEVABLE, I am so happy with it!
 

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The Hagon springs are a straight drop-in replacement with the stock spacer. I have them, big improvement.

I used new 10W oil because opinion seems divided about going to heavier or lighter oil, so I just stayed with the stock weight and replaced it.

The one thing I'm not sure of is what the height of the oil should be. I made it the same as the Triumph spec, for lack of knowing what else to do.

I installed gaiters while I had it apart.
 

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Based on blacktiger's recommendation I changed the Scrambler's fork oil to 7 weight, 140mm from the top of the compressed fork. Less oil means a larger air chamber and slightly softer spring rate.

IMHO, the stock spring rate works well, but the damping is far to harsh. The lighter oil matches the spring rate very well. This has made an incredible difference. I no longer cringe when I see a pot hole coming, the bike handles irregularities in the road like a champ.

The highest compliment I can pay is that I no longer think about the fork action at all. they have become "invisible" in their function.
 

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I no longer cringe when I see a pot hole coming, the bike handles irregularities in the road like a champ.
The highest compliment I can pay is that I no longer think about the fork action at all.
Man, I've got to do that. I cringe when I see the slightest irregularity looming ahead of me because of the all too certain "whump" that's to follow.
I am on a low bike budget now, so maybe I'll just do the fork suspension.
I owe to myself for safety, don't I? :D
 

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Discussion Starter · #6 ·
i've done the rear suspension with the lower end Ikon's and am very pleased for the money i spent on them. obviously the more expensive rear shocks would be even sweter, but like i said, dollar for dollar the Ikon's were worth every penny, and way better than stock, now i just want to get the front forks dialed in!
 

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SB, Ikons are great on the rear end of my o4 Thrux.

I went with the Progressive brand front springs and used 455cc per leg - 15 w oil. I weigh 95 kg. I went with a 2 inch spacer and then later decided on a 2.5 inch spacer. I have wound the preload all the way in for a firm ride. Its very planted on the curves around the bay area although a little rough on the poor quality streets in SF. Its a relatively easy job with a motorcycle lift - about 2.5hours of taking my time. This site has some great hints how to do it. A very worthwhile mod...
 

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Discussion Starter · #8 ·
so what springs does everyone recommend for a 185lb/84kg rider?
 

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I did the racetech springs - they are a constant spring rate, not progressive (I don't like the feel of the progressive springs). Also the emulators.... Totally different bike now. Used a "7wt synthetic", which was about the same viscosity ratings as a 10wt honda fluid.... a tiny bit harsh - it would be better with 5wt in the same brand. Still better than stock (I'm just super picky)

racetech FAQ section

From what I remember, the front springs are already a progressive rate... you're just going to a different set of rates is all. Lots of people seem to like the different aftermarket spring rates for progressive type springs.

others (like me) prefer the constant rate springs.

they run around $110.

Not sure if that's pricey compared to these other options. They'll suggest a good rate based on rider weight... for you they say around 0.950kg/mm (stock is 0.750kg/mm).

Bikebits has great advice - a lot of what people can do for free really fixes a lot of things.... a lot of "harshness" is the weight of the fluid used - and the air gap, which is part of the progressiveness of the suspension as it nears the bottom of the travel. Might give that a shot before dropping a wad of cashola...

Another good reason for this - I'm not sure there was enough oil in mine from the factory... I didn't do it by volume, I did it by the amount of air space in mm.... when I took the stock springs out and compressed the fork - it was a bit low - yes, some comes out with the spring, but not that much! So swapping out with fresh fluid, at the correct height, might make enough of a difference. Worth a shot.
 

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so what springs does everyone recommend for a 185lb/84kg rider?
I think you ought to either use 15wt or blend 10 and 15 wt to get 12.5 wt. Like all these guys said it's a very straightforward process. Pull out the old, stick in the new, doneski.

Also, if you don't want to take the forks off the bike to dump the oil out you can use a vacuum pump to suck out the old fork oil. I have a $40 (or less, can't remember) Mity-Vac I bought from Auto Zone. It's great for all kinds of stuff! You'll be amazed how nasty the old fork oil looks. It looks like raw sewage, seriously!

Another tip: take all the old parts out of the forks (springs, spacers, etc) and lay them down on the floor (use rags so you don't make a mess of the floor), and lay the new parts next to the old parts to compare the length to see if you need to trim the spacers etc. Like others said, you can use longer-than-stock spacers to increase the preload, or just use the preload adjusters on your fork caps.

One more tip: Make sure your socket is long enough (deep enough) to go past the preload adjusters and bite good onto the top of the fork cap. If not it will damage the cap. You can turn the preload all the way down (tight) to help with the depth. Watch out though, the caps will *pop* off a bit when they come loose.

You will enjoy that new front end a lot!!!
 

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Discussion Starter · #11 ·
yeah, i remember the caps 'popping' off a bit when i removed them to take off the top triple tree when i had to tap out that bolt that the bolt head sheared off of.
 

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Discussion Starter · #12 · (Edited)
just throwing this out there...if the stock springs are some kind of progressive spring, and i just checked out the racetech site and the springs they recommend for the thruxton have the same spring rate as the stock springs that come on the bike from the factory, why wouldnt i just buy emulators and new fork oil (possible like prop mentioned and combine 10w and 15w wo get 12.5w) and just use the factory springs?

EDIT: misread the site, and after checking the spring rate calculator the spring that is recommended for my weight is different than stock.
 

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Discussion Starter · #13 ·
well, i just spoke to a buddy and his take was to replace the fork oil with the stock weight, keep the stock springs, and install race tech emulators. he said that when you are really hitting turns hard you want the front end to dive a bit, and too stiff of oil will hinder or prevent that, but if you keep the same weight oil and put in emulators the emulators will control the rate of the dive.
 

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I'm afraid I have no experience of the emulators so I can't comment, but that little wimpy stock spring just doesn't do it for me - but there it is, I'm not a suspension expert, all I can say is my bike handles WAY better than it did before - and inexpensive and totally retrogradeable...er....upgrade. :D
 

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Just the thread I was looking for!

I was going to wait until this weekend to swap out my stock springs for progressives...but it sounds like I could do the swap after work in a couple of hours before it gets dark outside where I'll be working.

Question - I need to pick up some PVC on the way home in case I need to make a spacer adjustment, and I forgot to take a width measurement this morning.

Does anyone happen to know what width PVC I should buy?

THANKS
 

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If you've never riden a Bonnie with emulators fitted you don't know what you're missing. A far plusher ride than without. If you go with Race Tech, fit the recomended springs as well other wise it's like fitting the 904 BB without the raise in compression.
 

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...
Question - I need to pick up some PVC on the way home in case I need to make a spacer adjustment, and I forgot to take a width measurement this morning. Does anyone happen to know what width PVC I should buy?...
The PVC pipe marked 1" Schedule 40.
The ID is 1".
The OD is 1&5/16".
A little file work will clean up the saw cut.

Cheap & easy :D
 

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Just wondering..... can the fork springs be changed without remmoving the tubes?

I've got a set of springs from Works Performance waiting to be installed, did W P shocks two weeks ago, As for the proper spring rate, either straight or progressive, the primary factor is the weight of the rider in full riding gear. Stock springs may be fine for some and not so good for others. Most manufacturers will spring on the soft side for a 170 lb. rider.

I purchased directly from W P and they were very helpful in helping select the proper components for my bike, weight, and riding style. Give them a call ......
 

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1. Ikons - progressively wound springs that are well made and don't cost a bundle - also readily available.

2. 5W - because that's what a few of the heavier guys recommended and it has worked out really well. Much more supple ride.

3. other guys have covered it....

4. I cut down the original spacer with a hacksaw. Took 10 minutes for both...

5. I don't have an educated opinion on emulators.
 
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