Sonic Springs upgrade

[circa1968]

This is going to be the next upgrade to my Venture as the front really dives when braking hard.  I've been reading through various postings & trying to get my head all the way around the project to make sure I'm comfortable doing this on my own.  I'm feeling confident (dangerous) enough at this point, but two things I can't quite get a good understanding of and wondering if anyone could shed some light:

1)  How much oil to put in after draining out the old oil?  Do I follow spec of 553cc or am I supposed to measure it from the top? 

2) Preload spacers.  I've read that Sonic will ship some pvc pipe for this and to cut it to length.  I can't find any specific directions on Sonic's website on what length they should be cut to.

Any advice?

Thanks!

[TheMasterMike]

Progressive are reasonable and worked for me

[BlueSky]

Heavy duty springs probably will displace more oil and raise the level if you use the same amount as before.  Safest method would be to measure from the top I would think.  

[circa1968]

So y'all got me doing more research on progressive vs linear rate springs and now I'm just more confused than ever.   But, my layman's take on it is that linear springs are best for racing so that you have a consistent feel through the fork compression, making it more predictable.  I see that being of value in running this beast through twisties.  On the other hand, progressive will give a more comfortable ride soaking up smaller bumps on the road and give more resistance to bottoming on a hard hit.

Why did you chose progressive springs over linear?  Do you still get front end dive on hard braking, or at least less dive than stock?  That's my main goal. 

If I can get other benefits of better twisties handling, that's great but not my main goal as that would just make me want to go faster and do something stupider.

[saddlebum]

The idea behind progressives is to still give you a smooth comfortable ride while stiffening up as the load on the  front forks increase such as in hard braking or adding weight to the bike. Linear do not have a variable spring rate in the same sense and tend to ride harder.

[BlueSky]

Progressive spring explanation from the manufacturer

FORK SPRING KIT

The 'Original' Progressive Rate Fork Springs soak up the small road bumps, yet are firm enough to absorb the molar-rattling ones. Spring rates have been chosen to reduce front end "dive" during braking, yet still provide excellent ride comfort. Better yet, we warranty our fork springs for life! Progressive Rate Fork Springs have several advantages over straight rate springs. A Progressive Rate Spring has the advantage of a rising rate resistance to compression. The benefit of this is that the spring can be soft enough at the start of the travel to offer a "plush" ride, yet be firm enough at the end of the travel to soak up the big bumps

[circa1968]

19 hours ago, TheMasterMike said:

Progressive are reasonable and worked for me

Thanks guys!  I'm starting to lean towards the progressives.

[ragtop69gs]

Can't speak to the progressive springs. I know the Sonic straight rate springs have worked for me, I'm pleased with the upgrade.

[sldunker]

I put Sonic springs in my 2007 when I had it. Made it a real good handling bike in the twistes. I had progressives in my 84 venture royal- it was a huge improvement on that bike.

[circa1968]

So, after making two changes in my bike's setup, I'm going to leave it as-is for a while.  So far I think I've solved my main issue of nosediving during a relatively quick stop.

#1, added 6psi to the front forks.

#2, replaced stock front calipers with a set of R6 4-piston calipers (thoroughly cleaned, painted silver and rebuilt w/ new seals, just waiting on new ebc HH pads, using what they came with for now).

I'm not sure which of the two makes the bigger difference for me, but with the stock brakes, never felt like I had good feel or modulation (terminology?) of them.  It was either not enough brake power or stabbing them hard, causing the nosedive.

And in retrospect, I had not changed the fluid since I bought the bike, so that might have been part of the issue as it was a bit on the brown side.

In any case, I now have brakes that have good feel and I can modulate the pressure better.  Will see how she handles with a few more rides, but between the brake upgrade, increased fork pressure and lowering the front end 1/2", it really feels like a different (better) bike and I love her even more!

[BlueSky]

The front brake on my 07 takes more hand pressure than I like but I can make the front tire howl when stopping quickly which is probably good enough. I'm sure the brakes have the OE pads.  Perhaps for a rider with my below expert skills, it is safer than more sensitve brakes especially on wet roads.  

[circa1968]

40 minutes ago, BlueSky said:

The front brake on my 07 takes more hand pressure than I like but I can make the front tire howl when stopping quickly which is probably good enough. I'm sure the brakes have the OE pads.  Perhaps for a rider with my below expert skills, it is safer than more sensitve brakes especially on wet roads.  

Agree on the more hand pressure than I like and yes, squeeze hard enough and you get results.

To me, the increased braking power of the R6 brakes makes them less sensitive.  Again, I may be using the wrong terminology here, but with the stock brakes I was going from squeezing hard to squeezing harder in order to come to a controlled stop.  There always seemed to be little little range between the squeeze hard & harder.

Now it feels like the braking force is more linear to the pressure I apply to the lever.  I can go from a light squeeze for light braking with a linear feel from there all the way to a hard squeeze.

I didn't necessarily feel like I need more braking power, just more linear range in the squeeze and the R6 brakes seem to give me that.