No worries - another Bonnie owner with satisfactory fork spring upgrade! :thumbsup:

Going to upgrade my rear shocks over winter with a bit of luck!

Wrenching is always fun, unless it's repairing something that broke in an inconvenient way.

Then it's only sometimes fun.

Tea drinking is obligatory in my shop. For me, beer and wrenching don't mix. Beer after wrenching however - priceless.

 

No more topping out and rattling teeth!
Suspension mod is the most required mod on these bikes.

 

Replacing the springs certainly rates high on the effect/cost rating list for mods.

Out with the pogo springs, in with stability!!

I would really recommend going just one stage further which will give the front end some adjustability.
The fitting of Thruxton preload adjusters.

I did this on my Scram but its just as relevent to the Bonnie.
All detailed here:

http://www.triumphrat.net/twins-tec...net/twins-technical-talk/96404-fork-springs-preload-adjusters-on-the-scram.html

A simple install which can be done without removing the forks again.
Makes the world of difference!


V.

 

I changed out my front fork springs last weekend - took about 2.5 hours but very satisfying. Overall, its a reasonably easy job if you take your time, have the tools at hand and can put the bike up on a stand. I used Progressive springs with a 2 inch PVC pipe spacer and 440 ml of 15w fork oil in each leg.

I also put on a Beringer 4 caliper since I had the wheel off. Once I took the bike for a test ride it became evident that the front rotor was warped which did not show up with the OEM caliper. The Beringer caliper mounted easily and is a significant improvement. now for a new front rotor....

 

fork springs

Friday night I installed a set of Hagon progressive fork springs in my Bonnie, while I was at it I also installed the Thruxton Fork preload caps. Set the preloads to thruxton normal, four rings. I had the opportunity to test my work on Sunday. What a significant difference the progressive springs make in the ride. No more jarring my teeth and fatigued shoulders, the ride is much smoother and consistant. The install was a snap, so thanks to all the contributors to this forum regarding the fork springs, your recommendations have proven to be most satisfying. Craig

 

What weight oil are people using with the progressive springs ?

Mine were fitted about 3 years ago & its time to change the oil - but I can't remember what was used

thanks

 

What weight oil are people using with the progressive springs ?

The Hagon springs, when bought here in UK, come with their recommended 20w oil as part of the package


V.

 

Yes indeed - if you're using progressive brand or Ikons though, they recommend using standard fork oil weight, which is 10W.

 

Thanks both - I have the Hagon's, so will go with the 20w.

 

Okay, so after a few days of riding around the City with it, I think my new suspension is currently too stiff - the whole bike rises and falls with some of the pavement heaves on the city streets, and I feel like I get a little bounce too. I'm guessing this means my spacers are too long? I think we made them 12mm, maybe they should be more like 8mm. I'm guessing it doesn't have to do with oil level, though I could be wrong about that. Ideas what to adjust?

Thanks!

 

A reduction from 12 to 8 mm is a small variation. I installed Progressive front springs and used 50 mm (PVC) spacers. I have a Thruxton and wound up up my preload up to the 2nd line as I felt the forks were too soft around the city, so I guess my 'spacer' is effectively now around 60 mm. Whats your weight? I am around 95 kgs so went with a heavier fork oil (15 w) and 440 cc per leg.

 

You can maybe just try taking the spacer out - stiffness should be all related to the spring. Just make sure that the spring sits up against the top nut when you put it back in - you don't want a loose spring in the fork.

However, if it's over full of oil (shouldn't be - we definitely did yours the same as mine) that could affect things. You could syringe small amounts of oil out - maybe 5 ccs to start with.

Or eat loads of burgers and drink loads of beer - I find the Ikons to be pretty good! But a lot of it depends on what kind of riding you do too.

 

Yeah, good points from you both. I weight just over 200. Feels perfect on the highways, but here in the city the local streets are very bumpy. Immediately reminds me why adjustable preload would be good. Perhaps I'll try taking the spacers out and see what that does.

 

I was thinking about this some on my drive home. I should have been concentrating on my driving, but anyway - if the ehole bike rises and falls - that suggests stiff springs OR maybe overfull fluid?

If the bike is "bouncing" that may be a damping problem - or overfull again.

I am no expert on suspension tuning, so hopefully some others will chip in, but it may be that you actually need a heavier weight fluid, to add extra damping so that you don't "bounce".

The way I see it, the springs compress to take up the bumps, the oil is to stop you boinging all over the place.
Doing a search on "ikon springs" in this forum (twins tech talk) brings up a bunch of threads with good info. This is one I started, which a few folks chimed in on with some stuff. Perhaps also do a search on "static sag", and maybe even consider adjusting the rears.

http://www.triumphrat.net/twins-technical-talk/94019-front-suspension-improvements-2.html

As an additional note - kframe put Ikons in his bike - he must weigh a similar amount to you - and he did not use spacers, or change his oil. So he may have a few CCs less. He is pretty happy with his springs, but of course does not ride around minneapolis.

Anyway - after all that rambling, as a course of action I would suggest:

1. remove the spacer (easy)
2. Remove some oil (quite easy).

then decide from there.

Just let me know if you need different spacers, it's the work of moments to machine a couple.

 

Thread Revived

Well I snagged a pair of IKON Progressive Fork Springs at the Triumph National Rally this past weekend! As I wait for their delivery, I've read through the Haynes manual so I know what I'm getting into. But after reading multiple threads on here, I still have a question about the Fork Oil Weight. The Haynes manual says OEM is 10w but I see a lot of posts for and against 5w or 15w.

Here's what I'm looking for as I know you folks can give me experienced input and I prefer to be one-and-done on this project. I'm 170lbs and my wife rides pillion often (she's 115lbs). We occasionally camp so the canvas saddlebags get lightly packed up for the weekend. I take plenty of spirited runs on the twisties when I ride solo. So I'm looking for slow rebound damping (no bouncing returns); which fork oil weight would you suggest?

 

The heavier the oil the slower the rebound, but also the stiffer the compression damping so it's a trade off. I always start with ATF because it's cheap to try, the additives are good for seals, and it's about 10w. In order to set up your suspension, you need to set sag with your new springs installed. This may require you to change the spacer length a couple of times to get sag right . I use pvc to make spacers, it's cheap and quick. Adjustable caps are helpful but you still need to set sag to suit your weight and use the cap adjustment for fine tune, or adding preload for passengers. After sag is correct you can tinker with oil weight, knowing your preload is right.

 

I upgraded to the Ikon Front Springs and used no spacer. My results were perfect.

 

At 150lbs the stock suspension on my thruxton was much too soft= underscoring
Racetech fixed me up with stronger straight wound front springs and their emulator valves.
Dave Quinn set up a pair of hagons for the bike.
Don't assume the stock suspension is too stiff. It's probably too light and is sitting too low in it's travel

 

Successful Install

This past weekend I enlisted my son to help install the Ikon Progressive Fork Springs in my '08 Bonne T100. I was very proud of his efforts as he did most of the work himself including the torque setting on the Front Axle Nut :wrenchin

The only issue we had was when I tried to push in the modified 34mm Spacer per Ikon recommendation. IMHO I'm a relatively strong individual but could not for the life of me compress the Spring enough to get the Fork Cap threading to catch. Very close but no cigar and I certainly didn't want to cross-thread it! After 20 minutes of failed attempts, I opted for a 2" Spacer per TRAT thread posts but I comically could not get that to catch either. Since the Ikon Spring and Washer left only a 1/2" gap of threading at the top of the Tube's travel, I ended up using a 1" Spacer so there was still a slight pre-load.

After a spirited back road ride into work this morning, I'm extremely happy with the results that I expected to feel! Very little dive on hard braking and cornering along with a smooth dampened rebound on the bumps. The upward decompression during quick acceleration is gone as well. Now the Bonne rides more like the '99 Legend I use to own which had Progressive brand Fork Springs. Next I need to invest in the Ikon 7610 Rear Shocks or an equivalent brand!

 

Just a quick note: non-progressive springs aren't evil, and can be far less fine-tunable in an overall system than the properly-selected-for-load straight-weight forks. I find progressive type springs best used in larger, heavier bikes like cruisers and tourers where adding a second person or luggage periodically is less of an upset to the total gross weight, and prefer straight-weight forks and easily-tunable preload on lighter bikes. Even that means you're changing fork caps to get adjustability, it's worth it. $.02

 

Measure your sag. See if you're close.