Busy front end after spring change

[HaulinAshe]

If we all had unlimited funds, we would have no issues.

Sorry, but I totally disagree. I've seen huge $$$ spent on suspension that was completely wrong for the rider. Typically it's people getting exactly what they asked for instead of listening to the advice of an experienced suspension tech that knows that particular bike.

At this point, you have several good people on this forum shooting in the dark. Make the sag measurements like FredW suggested if you want more educated advice before spending more $$$.

 

[UHOH]

I had the forks done at a shop as I am not familiar with their dis-assembly. 5wt oil was used.

...

Any suggestions?

not a suggestion, just an observation. I don't know suspension.

with friend had replaced fork fluid using 5W oil about 45,000.

then last spring at 60,000 re-did it with 10W oil. works better for me.

2004 model, stock suspension still, 175# solo rider.

 

[MCRIDER007]

Fork Springs: FRK SPR 40.0x38.0x310 1.2kg FRSP S4031120

It looks like RT gave you springs that are 49mm longer than stock (310mm vs 261mm) and a spring that is 50 percent stiffer...which means that the spring is only going to compress 67 percent as much as the OEM springs when a load is applied. I think the internal OEM spacer is around 80-85 mm so the RT spacers would have to be very short (about 25-30mm) to give you the same sag. If the RT spacers are more than 40mm then you probably have too much preload and the suspension is not able to fully unload when you are in a negative travel situation (which happens at speed because the front end gets lighter).

I would measure the total sag with the rider on and aim for 45mm with 3 lines showing. If the sag is less than 45mm you need to cut the internal spacers accordingly (its a 1:1 ratio).

 

[azitlies]

Fork Springs: FRK SPR 40.0x38.0x310 1.2kg FRSP S4031120

It looks like RT gave you springs that are 49mm longer than stock (310mm vs 261mm) and a spring that is 50 percent stiffer...which means that the spring is only going to compress 67 percent as much as the OEM springs when a load is applied. I think the internal OEM spacer is around 80-85 mm so the RT spacers would have to be very short (about 25-30mm) to give you the same sag. If the RT spacers are more than 40mm then you probably have too much preload and the suspension is not able to fully unload when you are in a negative travel situation (which happens at speed because the front end gets lighter).

I would measure the total sag with the rider on and aim for 45mm with 3 lines showing. If the sag is less than 45mm you need to cut the internal spacers accordingly (its a 1:1 ratio).

And this coincides with my experience installing 1.2kg sonic springs on my st1300 (yeah, it NEEDS springs that stiff). These type of replacement springs ARE NOT the same length as the OEM springs... thus the pvc spacer HAS TO BE (shorter!) a different length compared to what the original spacer was.

I'd bet yer tech hasn't done this before, and he had a ***** of a time putting the fork caps back on... resulting in exactly what MCRIDER007 is describing.

 

[KennyWiz]

Fork Springs: FRK SPR 40.0x38.0x310 1.2kg FRSP S4031120

It looks like RT gave you springs that are 49mm longer than stock (310mm vs 261mm) and a spring that is 50 percent stiffer...which means that the spring is only going to compress 67 percent as much as the OEM springs when a load is applied. I think the internal OEM spacer is around 80-85 mm so the RT spacers would have to be very short (about 25-30mm) to give you the same sag. If the RT spacers are more than 40mm then you probably have too much preload and the suspension is not able to fully unload when you are in a negative travel situation (which happens at speed because the front end gets lighter).

I would measure the total sag with the rider on and aim for 45mm with 3 lines showing. If the sag is less than 45mm you need to cut the internal spacers accordingly (its a 1:1 ratio).

The RT Springs were actually shorter.

Cutting down the spacers today. Fingers crossed!

 

[KennyWiz]

I would measure the total sag with the rider on and aim for 45mm with 3 lines showing. If the sag is less than 45mm you need to cut the internal spacers accordingly (its a 1:1 ratio).

The RT Springs were actually shorter.

Cutting down the spacers today. Fingers crossed!

Looks like .75" which is 19.05mm

 

[MCRIDER007]

The RT Springs were actually shorter.

Cutting down the spacers today. Fingers crossed!

If the RT Springs were shorter than the OEM springs then RT's invoice info is really suspect...but if your sag is way less than it should be then cutting the spacers should resolve most of your problems. I think RT is an example of a business that has grown a lot faster than its service department and a lot of the info on their site is not accurate, including the spring calculator. I hope the FJR's dampening adjustments can compensate for such a big increase in spring rate or you might have to get some different springs to make everything work the way it should. In any case, cutting the spacers should be a big improvement over what you have now.

 

[azitlies]

I checked the Sonic Springs website and it recommends 1.1 or 1.2 for the feej, depending on the weight of the rider.

Put 1.2 in my st1300 (about 50 or so lbs heavier then the feej), and they were awesome. Absolutely awesome.

good luck to the op, hope this works out for you.

 

[LAF]

I checked the Sonic Springs website and it recommends 1.1 or 1.2 for the feej, depending on the weight of the rider.

Put 1.2 in my st1300 (about 50 or so lbs heavier then the feej), and they were awesome. Absolutely awesome.

good luck to the op, hope this works out for you.

+1

I have 1.1 and go 215 or so in full gear and they are superb! I went through Traxxion and as it came, it went in no issues. No spacer to cut or anything. Also the rear Pensky fit like a glove also and rides very nice no adjustments needed on it either. I told Lee my weight and it came set up same with the front. I even used their oil recommendation to keep it all to their spec so Lee would know if I had issues. Also they called for a much larger air space or much lower oil level (depending how you look at it) recommendation then factory and I stayed close to it. The oil they sent was Maxima Racing Fork Oil 10, with this description on the bottom of the label, Harley Davidson Type E.

 

[KennyWiz]

Chopped off 10mm from the spacer and now suspension is usable in 3-5 lines out for single rider. (Usable meaning the "busy" front end is gone at high speed).

Now that is sorted, I can "feel" the need for a heavier oil. We'll start with a true 7.5 on the oil chart and work from there.

Again, all of your time has been greatly appreciated! Thank you very much!

:clapping:

 

[Fred W]

Chopped off 10mm from the spacer and now suspension is usable in 3-5 lines out for single rider. (Usable meaning the "busy" front end is gone at high speed).

Now that is sorted, I can "feel" the need for a heavier oil. We'll start with a true 7.5 on the oil chart and work from there.

Excellent. So your dynamic sag should now be running at just under 30mm? That is still pretty tight for an ST bike, more in line with a sport bike setup at ~25mm, but at least you are not popping the top stop anymore (assuming that was what was happening).

Before you change the oil, you might as well try clicking in some more dampening and see if that gets you what you need.

The time to change the oil viscosity up a notch is when you can get the low speed dampening to be OK (with the clickers) but the high speed is still under damped.

Don't forget that you can also make small changes in the fork stiffness (during compression) by raising or lowering the oil fill level. So if you think the spring is still a tad too stiff, try lowering the oil level.

 

[MCRIDER007]

Now that is sorted, I can "feel" the need for a heavier oil. We'll start with a true 7.5 on the oil chart and work from there.

I am not too sure what you can "feel" but when you install a heavier spring the usual result is that the system needs less compression dampening and more rebound dampening. Heavier oil increases both the compression and rebound dampening. There isn't any need to go to a heavier oil unless you have run out of adjustment on the rebound dampening.

 

[Fred W]

Now that is sorted, I can "feel" the need for a heavier oil. We'll start with a true 7.5 on the oil chart and work from there.

I am not too sure what you can "feel" but when you install a heavier spring the usual result is that the system needs less compression dampening and more rebound dampening. Heavier oil increases both the compression and rebound dampening. There isn't any need to go to a heavier oil unless you have run out of adjustment on the rebound dampening.

Wow. That's like...

Deja Vu.

All over again.