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Discussion Starter · #1 ·
I bought a set of Progressive fork springs for the Thruxton about 2 months ago and just have been too lazy, um I mean busy to install them. I decided to do it today and also install the rubber fork gaitors.

I pulled the front wheel, slid the legs out and drained the old oil... it was a filthy gray color...pretty gross. As I pulled the stock springs out, I was also surprised to see how short they are. Looks like about a 7-8" difference compared to the new Progressives. The shorter length OEM springs Triumph made up the difference with a long tubular spacer. The stock springs are constant rate...all the coils spaced evenly. Progressive (and others) are tightly spaced coils at one end, gradually going to a wider spacing for the remainder.

I reassembled the forks with the original washers, the new springs, and using the chart and PVC spacer material provided in the box, cut the new spacer to 2.5". I refilled the legs with new BelRay 15W fork oil (the same amount I drained by measure) and put the adjusting caps back in, with them screwed all the way out.

After the legs and front wheel were back in I went for a little ride on my favorite twisty road. All I can say is WOW! Even pulling out of my driveway and rolling down my street, I could feel an immediately 'softer' feel over small bumps, but with much improved rebound damping that really reduces front to rear pitching and wallowing. Stock fork setup is basically a pair of pogo sticks!

After I got on to the higher speed twisty road (that I know very well) I went into the first couple of turns a little slower than usual just to get the feel. It felt firmly planted, so I bumped the speed up as I rode, and soon found that I was able to take most of the turns at a faster speed than was comfortable before. I glanced at my speedometer at one point and I was going through a marked 30 mph curve at 65 mph. I don't think I was able to do this before without the front discouraging you by wallowing and chattering.

All I can say... this is the best handling and overall ride improvement that you can do for such a minimal cost. Still, the OEM tires are the weak point, and if I push it to the limit they still slide a bit, but it's nowhere near as scary as it was before.

Guess I should have put these springs and oil in right after I got the bike. I've been suffering with the stock setup for 4500 miles. Anyone out there that's on the fence, jump off and do it!

Also, my new IKON rears are very nice. I got the chrome bodies with black springs. Messed a bit with the adjustments, and feels the best to me on the lowest spring pre-load and position #2 on rebound damping. Fairly plush, but controlled ride over rough roads.

That's my experience for today... just wanted to pass it along.

Cheers,
BLIGHT
 

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Progressive fork springs..R3

:) Found the same result myself when I replaced my Rocket III fork springs with the Progressives...Also put Progressive 412's on the rear for an improvement there as well
 

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I've said it before, and there's a better than average chance I'll say it again - upgrading the suspension on these bikes does WONDERS for them.

Nice one Blight!
 

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Nice job Blight. Seems to be a chorus of praise for those springs and how it transforms ride and handling. A question about oil fill volume. A thought is...placing the same amount of oil back in the fork tubes may not be the best approach if you had short stock springs and long spacers before. I would think with now a long spring and shorter spacer you have effectively more volume inside the fork tube. Perhaps this is all moot because the springs are designed to only have a certain level of displacement which is similar to stock.
Can anybody comment on how much oil should be used when replacing with the longer progressive springs with shorter spacer?
Congrats Blight,
George
 

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I thought the same thing, but when I put Ikons in my Bonneville, and Progressive brand in my Ninja, both kits recommended that the fork oil be filled to the stock recommended level, which is done by measuring from the top of the fork tube to the top of the oil, with the fork fully compressed and upright, and no spring in.

Both worked great.
 

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Prop...when you fill to say 135mm from the top of the fork tube...is this without a spring AND without the spacer? The disconnect in terms of volume delta seems to me would be the stock config has a long spacer. Are the spacers hollow?
Thanks,
George
 

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That is correct, the oil level is measured without spring, spacer or any washers associated. The spacers are indeed tubes, as you say.
 

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Makes more sense then why adhering to the 135mm level would work. Since the spacers are hollow tubes, their volume would correspond to change in spring length so net volume of spring and tube would be close in either stock or new combination.
Thanks,
George
 

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Discussion Starter · #9 ·
Nice job Blight. Seems to be a chorus of praise for those springs and how it transforms ride and handling. A question about oil fill volume. A thought is...placing the same amount of oil back in the fork tubes may not be the best approach if you had short stock springs and long spacers before. I would think with now a long spring and shorter spacer you have effectively more volume inside the fork tube. Perhaps this is all moot because the springs are designed to only have a certain level of displacement which is similar to stock. Can anybody comment on how much oil should be used when replacing with the longer progressive springs with shorter spacer?
Congrats Blight,
George
Hi George, I used the fill-specs on the included chart for the Thruxton, and I too wondered about the same amount of oil being displaced by the longer springs, but filling it to the specs equaled the same amount I drained (I measured it in a plastic cup and made a mark)

It seems there is enough room in the tubes for the slight difference in oil height after the springs are installed. I didn't measure the old and new coil OD's or wire OD's but I bet they have carefully engineered these to be a direct drop in replacement. The new recommended spacer length of 2.5" was perfect in terms of easily replacing the top cap pre-load adjusters. I have them on full-soft for now and may tighten them up a just a hair. I have to spend more seat time, and also measure sag with this new setup to see if it needs any further adjustment.

BTW, I also feel the 15W fork oil (others here have recommended it) especially with stock damper tubes is just the ticket to correct the secondary rebound 'bounce' by adding a little more rebound damping. Doesn't seem to affect the compression damping as much, which keeps the ride smooth over bumps.

I'm goin' for a ride now... it's a comfy 85 deg F here this afternoon! I gonna try to wear out my tires so I can get some good ones!

Cheers,
BLIGHT
 

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Guys, keep in mind that when it comes to fork oil the weights are relative, & not absolute. Unlike motor oil there is no "universal" standard to verify that Mfg. A's 15 wt. is the same viscosity as Mfg. B's 15 wt. If that has changed please enlighten me.
 

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That's not how I understood it - but I have no specific reference to point to on that.
 

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blight -- what brand springs did you get? And did you get the standard height springs, or lowered?

BTW, I just installed Ikons on the rear, and the improvement just highlights how bad the stock fronts springs are in comparison.
 

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Discussion Starter · #14 ·
blight -- what brand springs did you get? And did you get the standard height springs, or lowered? BTW, I just installed Ikons on the rear, and the improvement just highlights how bad the stock fronts springs are in comparison.
Hi Oldretrorider... I bought the 'Progressive Suspension' brand. I know it's a little confusing when there are other brands like IKON selling 'progressive' fork springs. I just went with the brand I know. They are all good, so go with whatever is the best deal for you.

I got the standard height, because I have raised the tubes up about 1" in the triples so I could mount the Thruxton clip-ons up above the upper triple clamp. It's much more comfortable to ride, and it sharpens the steering up by dropping the front end and decreasing rake angle a tad. It gives the bike a much more aggressive stance too, visually.

Today, I measured the F/R sag and saw that the front was dropping a bit more than the rears (IKONs back there on minimal preload and #2 dampening) so I tightened up the front 5 full turns (360 deg) I took a ride today and felt it was still very compliant and comfortable, but very confidence-inspiring and a little more business-like.

To address the other questions about oil viscosity... I asked my shop guy (who races too) and he recommended Bel-Ray 15W Fork Oil. So, that's what I bought... it's a little pricey, about $12 a quart or so, but don't go cheap on your fork oil!

By the way, I agree... the new IKON rear shocks ('progressive springs' there too...hehehe) are great and they just pointed out how bad things were in the front before I did the fork work. It only took about 1 day's worth of riding to come to that conclusion!

Cheers,
BLIGHT
 

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By the way, I agree... the new IKON rear shocks ('progressive springs' there too...hehehe) are great and they just pointed out how bad things were in the front before I did the fork work. It only took about 1 day's worth of riding to come to that conclusion!

I'm having the same realization i reverse. THe only thing I hated about the stock shocks was the severe dive on braking, so I figured I'd save myself some coin and just do the front. My Ikon front springs (with the sweet Thruxton adjusters!) are making it really obvious how bad the rears are so I guess I'll be getting some Ikon rears soon...
 

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Discussion Starter · #16 ·
I'm having the same realization i reverse. THe only thing I hated about the stock shocks was the severe dive on braking, so I figured I'd save myself some coin and just do the front. My Ikon front springs (with the sweet Thruxton adjusters!) are making it really obvious how bad the rears are so I guess I'll be getting some Ikon rears soon...
The IKON rears are a very good value. You can spend a whole lot more on rear shocks, but there has to be a point where there is a diminishing value for the price paid. I'm quite happy with the way these shocks work, and they look really great too.

Interesting that you had an 'inverse epiphany' on which end to fix first! Funny thing is, the stock rear shocks didn't feel that bad to me from day one, but the front end felt really wimpy, bouncy and under-damped.

I went for the rears first really to gain some adjustability on rebound damping and also to get black springs. That's when the fork's weaknesses reared their ugly heads.

What's silly is that I had the box of new fork springs and Bel-Ray 15W fork oil just sitting on the floor next to the bike for several weeks and never even installed them!

Hope you enjoy your new suspension pairing... as I said earlier... I can't wait to try the new setup with some better tires someday. Look out CBR's GSXR's Ninjas...etc!!!!!

Cheers,
BLIGHT:motorbike:
 

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Thanks Blight, I have just received a set of Progressive brand fork springs for my T100. Can anyone assist me with the recommended quantity of oil. I think I will start with 15w BelRay. I have put on a set of Ikon's at the rear which made was a big improvement.

Thanks, Dave
 

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What set and where did you purchase the gaiters from?

Hi blight,

I too have the progressive front springs and rear shocks, made a big difference for sure; I have yet to change the oil but was thinking of getting the gaiters and will then change the oil at that time. What set and where did you purchase the gaiters from?

Regards,

Joe
 
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