Front suspension

I'm thinking of upgrading my forks soon. I'll definately be changing the fork oil, but I'm wondering whether to go up to 15w oil to increase damping a little. I'm also considering fitting progressive springs and topping off with adjustable preload caps. I never use the bike on track, but I'm starting to get a little quicker on the road. JHS have the springs at £70 and the preload caps at £44 + £18 for spacers and shims. Is it worth it?

JHS - Top quality kit.

The front end on my last sv was so stiff, it was great, constant feedback and had the top adjusters too. Recommended by me.

[Biker Biggles]

Yes to springs and oil.
The preload adjusters are not essential IMHO as you should find that if you set the preload/sag correctly with the spacers you will not need further adjustment for road use.

[northwind]

The top adjusters are a luxury, like Biker Biggles says... JHS just sells the K2 parts, since they fit perfectly, no sense in making a custom bit which'd be more. When I got mine, my local dealers were marginally cheaper, but not enough to actually bother me much.

The springs... I think, though can't say for sure, that JHS sells progressive rather than linear springs. Now that's totally a matter of opinion, but one thing you'll find is that if you look around places like Racetech, Ktech, Traxxion, Twin Works, SV Race Shop, Sonic Springs... They'll all recommend linear. Hagon, on the other hand, would recommend them I think. AS, obviously, would JHS

Personally I've never ridden on progressives, so I don't have an opinion of my own, just thought it might be worth mentioning the alternatives.

I appreciate the input, thanks.

I was thinking progressive springs to smooth out commuting journeys, and increasing to 15w oil to help firm the damping up a little. I realise that I don't need adjustable preload on the front, but not wanting to experiment with spacers incase I mess them up, I'd rather have the adjustable type, plus I take pillion quite regularly, and it might be nice to wind it up a notch or two to help with diving.

when I bought my progressive springs they gave me a formular to work out what length of spacer I reqired, The kit came with plastic tube to use as a spacer but I decided to cut the OM ones!!!

It needs doing, the SV has crap front suspension. The fork oil should have been changed by now if you have a curvey. Every 2 years I do mine, any bike.

[northwind]

Originally Posted by Fuzz

I appreciate the input, thanks.

I was thinking progressive springs to smooth out commuting journeys

I think the usual rationale is that sports bike forks are too short for a progressive to really work as it should. The idea's obviously great, mind. Bit of soft, bit of hard, best of both worlds.

[johnnyrod]

I think as you will have a range of weights on the bike, progressive is probably a good compromise. Proper sports bikes would have linear springs which are the right weight for the rider - not very helpful if the weight isn't constant. Get the preload adjusters, with these springs it only takes a few turns to go from just right to too hard or soft.

Originally Posted by northwind

I think the usual rationale is that sports bike forks are too short for a progressive to really work as it should. The idea's obviously great, mind. Bit of soft, bit of hard, best of both worlds.

Arent SV stock springs progressive?

Anyway, the reason why sports bike use linear springs...

I like to try and understand these things so I've run it though my head and the conclusion I've come to is that for sports bikes, or any bike with decent suspension, linear springs are better. Because why would you want to stiffen the suspension and make it less compliant under braking as the front dives?!

This of course must mean there's another reason for having progressive springs, and I think it's due to the damping rods.

Because damping rods have a fixed appature to force oil though, they provide progressive damping - the higher the speed of the fluid though the appature, the higher the damping. This means that for situations requiring high speed damping, like going over bumps, there's alot of damping and the ride feels harsh. While at the same time providing little damping in situations where low speed damping is required, such as weight transfer, resulting in lots of fork dive under braking. Hence why the SV feels both too stiff and too soft all at the same time.

The only other way other than reworking the damping to slow fork dive would be to fit a stiffer spring to counter this, but that would make bumps even more unpleasant. So you want the front to stiffen as it dives, which is what a progressive spring does. Of course this is a fugde, and why it doesnt entirely cure the problem.

Thats how I figure it anyway