Fork oil question........ - SV650.org

21-07-06, 12:41 PM

This topic has probably been thrashed about loads in the past but I'm after a bit of quick information. Basically, as some of you know (cheers for the help so far Jambo

), the front end of my SV is feeling rather spongy to say the least. I've got uprated springs and currently running 10w fork oil. Would it be advisable to put in 20w oil instead, or is that a bit OTT? I weight 13 stone without kit if that helps.

Cheers,

Paul

Viney · 21-07-06, 01:01 PM

Im 15stone and running 15w oil which i find far far better than the 10w 45000miles fishy smelling water/oil that was in there.

22-07-06, 10:38 PM

x2 for the 15wt oil.

If the finances allow and you are still not happy after going to thicker oil see if you can get some emulators. Short of a front end swap that's all you can do.

22-07-06, 10:43 PM

After having read most of the suspension threads ever on this forum to look for information for my own bike, i'd third the 15W

Sid Squid · 23-07-06, 09:27 AM

I think the SV probably benefits from 15W oil as far as handling goes, but with one drawback - if you do a lot of town riding and the roads where you live are as crap as London roads, the 15W oil made the front end a bit 'choppy' and reduced comfort by a noticable degree.
Depends on the use to you which mainly you put your bike of course.

25-07-06, 12:52 PM

Went round to Jambo and Sam's place on Sunday, and after a bit of tinkering we found out that I've got progressive springs

, but one of them had been put in upsidedown by the mechanic who worked on the bike last

. After putting it in the correct way there was little difference, so we put some 20w fork oil in leaving an air gap of 104mm. The bike now handles brilliantly and I had a grin on my face all the way home. I'm going to look at getting heavier springs as Jambo suggested as and when the budget allows.

Sweet!!

TSM · 25-07-06, 01:07 PM

Is it right that if I decrease the air gap the forks will compress exponentially slower near the end of its compression travel.. Will this help from the forks on heavy braking form using their full travel too quickly?

jambo · 25-07-06, 01:24 PM

Paul: Glad you're happy with it, you did the work anyway

TSM: As I understand it the smaller the airgap the greater the compression ratio of the air at the end of the travel. This means a smaller airgap should provide a greater "air spring" effect at the very end of their travel, but if you go too far you can end up with all sorts of issues. Remember that the oil level is measured before you add springs, spacers, washers and caps, all of which use up some of that airgap.

Please feel free to correct the above

Sid Squid · 25-07-06, 01:43 PM

Quote:

Originally Posted by TSM

Is it right that if I decrease the air gap the forks will compress exponentially slower near the end of its compression travel.. Will this help from the forks on heavy braking form using their full travel too quickly?

Not exactly. It would be more accurate to say simply that the apparent spring rate, (ie that of the curly bit of wire added to that of the air 'spring'), will be higher the greater the forks are compressed, the issue of speed is due the damping afforded by the oil weight/settings etc, which doesn't change with oil level, this means that for a given load, the fork will compress less with a higher oil level.

21-07-06, 12:41 PM	#1
Davies Guest Posts: n/a	Fork oil question........ This topic has probably been thrashed about loads in the past but I'm after a bit of quick information. Basically, as some of you know (cheers for the help so far Jambo ), the front end of my SV is feeling rather spongy to say the least. I've got uprated springs and currently running 10w fork oil. Would it be advisable to put in 20w oil instead, or is that a bit OTT? I weight 13 stone without kit if that helps. Cheers, Paul

23-07-06, 09:27 AM	#5
Sid Squid No, I don't lend tools. Mega Poster Join Date: Jul 2003 Location: Skunk Works, Nth London Posts: 8,680	I think the SV probably benefits from 15W oil as far as handling goes, but with one drawback - if you do a lot of town riding and the roads where you live are as crap as London roads, the 15W oil made the front end a bit 'choppy' and reduced comfort by a noticable degree. Depends on the use to you which mainly you put your bike of course. __________________ If an SV650 has a flat tyre in the forest and no-one is there to blow it up, how long will it be 'til someone posts that the reg/rec is duff and the world will end unless a CBR unit is fitted? A little bit of knowledge = a dangerous thing. "a deathless anthem of nuclear-strength romantic angst"

25-07-06, 01:07 PM	#7
TSM The Sick Man Mega Poster Join Date: Nov 2004 Location: Peckham.SE.LDN Posts: 4,768	Is it right that if I decrease the air gap the forks will compress exponentially slower near the end of its compression travel.. Will this help from the forks on heavy braking form using their full travel too quickly? __________________ OTR: KTM 690 Duke R 2015 Full Akro SIDELINE: Kwak ZX636 A1P 2002, Red, R&G's, Yoshi, Double Bubble Screen GONE: Kwak ZX-7R P1, Full Akro, Undertray, Screen GONE: SV650S K2 Very Bruised & Without Fairing, Motovation Frame Sliders, R&G Ally Sprocket Toe Protector, HEL 2 Line Setup, GSXR K1 600 RWU Forks, Barnett Clutch & Springs, Penske 8981 Shock, Gilles Ti Rearsets, Steel Barends, Scottoiler, AFAM Chain & Sprockets, Twin FIAMM Horns, Skidmarx Bellypan, Full Micron Zeta Steel System, Cut down undertay. Forum Problems & Information / Site Suggestions

25-07-06, 01:24 PM	#8
jambo Member Mega Poster Join Date: Aug 2003 Location: Croydonia Posts: 5,376	Paul: Glad you're happy with it, you did the work anyway TSM: As I understand it the smaller the airgap the greater the compression ratio of the air at the end of the travel. This means a smaller airgap should provide a greater "air spring" effect at the very end of their travel, but if you go too far you can end up with all sorts of issues. Remember that the oil level is measured before you add springs, spacers, washers and caps, all of which use up some of that airgap. Please feel free to correct the above __________________ Modern motorcycles are bloody brilliant, enjoy it while we can

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21-07-06, 01:01 PM	#2
Viney Member Mega Poster Join Date: Jul 2003 Location: In the shadows to the left Posts: 7,700	Im 15stone and running 15w oil which i find far far better than the 10w 45000miles fishy smelling water/oil that was in there.

22-07-06, 10:38 PM	#3
PeterM Guest Posts: n/a	x2 for the 15wt oil. If the finances allow and you are still not happy after going to thicker oil see if you can get some emulators. Short of a front end swap that's all you can do.

22-07-06, 10:43 PM	#4
MattTheLoony Guest Posts: n/a	After having read most of the suspension threads ever on this forum to look for information for my own bike, i'd third the 15W

25-07-06, 12:52 PM	#6
Davies Guest Posts: n/a	Went round to Jambo and Sam's place on Sunday, and after a bit of tinkering we found out that I've got progressive springs , but one of them had been put in upsidedown by the mechanic who worked on the bike last . After putting it in the correct way there was little difference, so we put some 20w fork oil in leaving an air gap of 104mm. The bike now handles brilliantly and I had a grin on my face all the way home. I'm going to look at getting heavier springs as Jambo suggested as and when the budget allows. Sweet!!