Fork Oil Questions

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I have no doubt this is the wrong place to put this thread, but if so, someone will move it.

I bought some 5 wt Honda fork oil (SS-7) at a dealership this morning. It was $6.00 a pint. Everywhere else that I looked (googled Fork Oil) it (not necessarily Honda brand) was costing up to around 30 or $40 a quart. The dealership did not have a sale going on, and they quoted me standard list prices for another part. What gives? Is Honda brand fork oil cheap?

Are all fork oils created equal? What do you get in so called premium fork oils? OK, guys, from my pov, if any one of two dozen mc oils can be used long term in a bike without significant wear problems then they are equal. If garbage grade store brand oil meeting industry specs can be used and causes no wear, then I am hard pressed to acknowledge that it is less good than the premium, top of the line, name brand oil costing 4 times as much (I admit, I never use the former, and usually pick a name brand in the middle of the pack).

Do premium fork oils last longer? Are some all synthetic, blends, or dino based?

Are fork oil threads as contentious as standard oil, filter, and battery threads?

Have you seen this chart (why did they not include all of Honda's oils when I wanted that info)?: Fork Oil Chart


 
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Unless a "premium" fork oil is synthetic, I doubt there is anything better about it. I've chosen to go with Motul synthetic fork oil, just as I also use synthetic oils in the engine and final drive, since synthetic is proven to be a superior product.
 
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I like to change the fork oil in my bikes at about 35K. Usually upgrade to Honda's 10 wt. However, at about 70K on my ST1100 I ran low on the 10 wt & mixed it 50-50 with the 5wt and was mildly surprised by the result. I have done one other oil change since & now have 169K & have no complaints. Then again, I went with a medium wt fork oil from AMSOIL for my VFR. I did not like the result at all. Too stiff. Removed a few cc's per side & live'd with it the last 15K. Next time the VFR gets the same mix as the ST1100. I hope this helps but we are talking alchemy & a dark science.
 
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I like to change the fork oil in my bikes at about 35K. Usually upgrade to Honda's 10 wt. However, at about 70K on my ST1100 I ran low on the 10 wt & mixed it 50-50 with the 5wt and was mildly surprised by the result. I have done one other oil change since & now have 169K & have no complaints. Then again, I went with a medium wt fork oil from AMSOIL for my VFR. I did not like the result at all. Too stiff. Removed a few cc's per side & live'd with it the last 15K. Next time the VFR gets the same mix as the ST1100. I hope this helps but we are talking alchemy & a dark science.
Not sure if the 1300 fork internals are similar to the 1100's, but the 1100 forks are each different and there is an improvement in performance by using different weight oils in each. This was explained to me by a m/c suspension specialist and basically, cartridge and damping rod style forks have differing oil orifices and different flow rates, so using the same weight oil in both does not produce ideal results. On the damping rod side (these differ between ABS and non ABS 1100's), I use a 7W synthetic and the other side gets a 10W-15W synthetic. Seems to work very well in my bike.
 

dduelin

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Any one of two dozen fork oils probably has different objective qualities and performance from Honda SS-8. In many threads on the subject it has been covered many times that weight is not a good way to chose fork oil. The chart is a good way to compare fluid qualities even though it's fairly dated.

The Honda branded fork oils are not cheap as in poor performing rather they could just be considered a good value in a field full of over priced oils.
 
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I bought some 5 wt Honda fork oil (SS-7) at a dealership this morning. It was $6.00 a pint. Everywhere else that I looked (googled Fork Oil) it (not necessarily Honda brand) was costing up to around 30 or $40 a quart. The dealership did not have a sale going on, and they quoted me standard list prices for another part. What gives? Is Honda brand fork oil cheap?
I went to revzilla and all the usual suspects were there for $10-20 a quart, so what did you find in the $30-40 range? Based on my recent search, and lots of prior experience, the Honda oil @ $12/qt. is in the normal price range for fork oil.
 

MajorTom

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$12 a quart? :lol: Here at my local Canadian Honda shop Bel Ray fork oil is $24.95 for a litre (1.05 qt.) bottle. The Honda SS-7/SS-8 is $18 for 500 ml, so practically $36 a quart. I'm trying out the Bel Ray 7 wt. in my next fork oil change. Also will be switching to flat rate springs as a suspension upgrade, so I won't be able to compare the SS-8 that's in there now with the Bel Ray 7 wt.
 

Kevcules

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$12 a quart? :lol: Here at my local Canadian Honda shop Bel Ray fork oil is $24.95 for a litre (1.05 qt.) bottle. The Honda SS-7/SS-8 is $18 for 500 ml, so practically $36 a quart. I'm trying out the Bel Ray 7 wt. in my next fork oil change. Also will be switching to flat rate springs as a suspension upgrade, so I won't be able to compare the SS-8 that's in there now with the Bel Ray 7 wt.
Why may I ask are you going to switch to a flat rate spring on your bike? I'm going through a suspension game of trying to get a smoother response from my front shocks detailed in this thread.https://www.st-owners.com/forums/showthread.php?155408-Front-shocks-removal&highlight=

I'm going to try the suggestions given to me first, but certainly would like to try the other springs if necessary.
 

MajorTom

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Unfortunately, at 210 lb. I weight a few pounds more than your reported weight, :) so adding more preload to my front forks isn't going to be enough. Simply put, the bike is undersprung for my weight, with a (reported) 0.85 kg/mm stock spring. So I started to look around at spring options and came up with Hyperpro, Sonic and Race Tech here on the ST1300 suspension forum.

Hyperpro's offering is a progressive spring, but the other two offer flat rate springs and I'm persuaded by the info on their websites and by discussions on this site that while either will work, dialing in the sag will be much easier with a flat-rate spring. To avoid guessing my total cost due to currency exchange fees, brokerage fees, customs fees, etc. I'd prefer to buy from a Canadian distributor, but I've only found one vendor for bike springs in Canada, fortnine.ca, who carry Race Tech springs for the ST1300 for $166 with free shipping. Sonic springs would come close to that with shipping/currency exchange, but for the extra $10-20 I'd rather order from a Canadian distributor. It will be quicker not having to go through customs and if there's any problem, easier to fix without dealing with international shipping.

Of course nothing's that simple. Once I made the decision yesterday I went onto fortnine's website to order the 0.95 kg/mm spring (as spec'ed from Race Tech's website for my weight) only to find they don't have that size listed. 0.90 kg/mm? Sure. 1.00 kg/mm? No problem. 0.95 kg/mm? Nowhere in sight. :) So now I'm waiting for them to open on Monday so I can call and inquire about the availability of 0.95 kg/mm springs. If they don't carry them I'll either order them from Race Tech, who don't quote shipping costs during their order process, making the total cost from them a mystery, or order the cheaper Sonic springs. For some reason Sonic's online calculator gives me a 1.1 kg/mm spring for my weight and the ST's 700 lb. weight. I'll need to discuss that with them if I decide to go that route.

Lots of choices and lots of info here from people who've tried all three of these options (four if you count adding preload and changing fork oil weight). You makes your choice and you takes your chances. :) Good luck with your journey. I'll certainly post my results when i get done, although that likely won't be until the fall, what with camping and other vacation pursuits filling my time until mid-September.
 
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Once I made the decision yesterday I went onto fortnine's website to order the 0.95 kg/mm spring (as spec'ed from Race Tech's website for my weight) only to find they don't have that size listed. 0.90 kg/mm? Sure. 1.00 kg/mm? No problem. 0.95 kg/mm? Nowhere in sight. :)
Since the forks are mechanically constrained to work together as a pair, you could put a 0.90 in one leg and a 1.00 in the other for a net result of 0.95.
 

dduelin

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Or use .90 and have room for a little preload to hit the sag target.
 
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Since the forks are mechanically constrained to work together as a pair, you could put a 0.90 in one leg and a 1.00 in the other for a net result of 0.95.
Is this a good idea? I have no idea of the rigidity of the fork assembly, but using different weight springs in each shock will induce a torque. I also wonder about rebound dampening on one fork and compression dampening on the other. I suppose if we can cantilever bridges w/ appropriate engineering, my questions are moot - but look what happened at Falling Water. Stuff happens.
 
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Not sure if the 1300 fork internals are similar to the 1100's, but the 1100 forks are each different and there is an improvement in performance by using different weight oils in each. This was explained to me by a m/c suspension specialist and basically, cartridge and damping rod style forks have differing oil orifices and different flow rates, so using the same weight oil in both does not produce ideal results. On the damping rod side (these differ between ABS and non ABS 1100's), I use a 7W synthetic and the other side gets a 10W-15W synthetic. Seems to work very well in my bike.
Funny you mention that. My Aprilia 500 scooter has one fork that is for rebound. Didn't think about using different oil in each fork. Good point!

Why may I ask are you going to switch to a flat rate spring on your bike? I'm going through a suspension game of trying to get a smoother response from my front shocks detailed in this thread.https://www.st-owners.com/forums/showthread.php?155408-Front-shocks-removal&highlight=

I'm going to try the suggestions given to me first, but certainly would like to try the other springs if necessary.
Sometimes you can achieve some good results using a progressive spring that might be a little stiffer than a stock. Going to a straight rate as we call it, it will give your bike a constant spring rate but I think sometimes the drawback is not having the right valving to go with it may do more harm than good. Straight rate will over ride the rebound of stock springs and you'll have less dive, but the quicker rebound might make the bumps harsher. Oil can help, but only so much. Then you have to deal with the compression side. I don't think there is a real good answer. Trial and error sometimes.

Unfortunately, at 210 lb. I weight a few pounds more than your reported weight, :) so adding more preload to my front forks isn't going to be enough. Simply put, the bike is undersprung for my weight, with a (reported) 0.85 kg/mm stock spring. So I started to look around at spring options and came up with Hyperpro, Sonic and Race Tech here on the ST1300 suspension forum.

Hyperpro's offering is a progressive spring, but the other two offer flat rate springs and I'm persuaded by the info on their websites and by discussions on this site that while either will work, dialing in the sag will be much easier with a flat-rate spring. To avoid guessing my total cost due to currency exchange fees, brokerage fees, customs fees, etc. I'd prefer to buy from a Canadian distributor, but I've only found one vendor for bike springs in Canada, fortnine.ca, who carry Race Tech springs for the ST1300 for $166 with free shipping. Sonic springs would come close to that with shipping/currency exchange, but for the extra $10-20 I'd rather order from a Canadian distributor. It will be quicker not having to go through customs and if there's any problem, easier to fix without dealing with international shipping.

Of course nothing's that simple. Once I made the decision yesterday I went onto fortnine's website to order the 0.95 kg/mm spring (as spec'ed from Race Tech's website for my weight) only to find they don't have that size listed. 0.90 kg/mm? Sure. 1.00 kg/mm? No problem. 0.95 kg/mm? Nowhere in sight. :) So now I'm waiting for them to open on Monday so I can call and inquire about the availability of 0.95 kg/mm springs. If they don't carry them I'll either order them from Race Tech, who don't quote shipping costs during their order process, making the total cost from them a mystery, or order the cheaper Sonic springs. For some reason Sonic's online calculator gives me a 1.1 kg/mm spring for my weight and the ST's 700 lb. weight. I'll need to discuss that with them if I decide to go that route.

Lots of choices and lots of info here from people who've tried all three of these options (four if you count adding preload and changing fork oil weight). You makes your choice and you takes your chances. :) Good luck with your journey. I'll certainly post my results when i get done, although that likely won't be until the fall, what with camping and other vacation pursuits filling my time until mid-September.
Since the forks are mechanically constrained to work together as a pair, you could put a 0.90 in one leg and a 1.00 in the other for a net result of 0.95.
I'm about 215+ in gear and I don't feel like the bike is under sprung. I can ride aggressively around here, and unless I'm trying to see how deep I can get to the apex of a turn and nail the brakes, it feels fine. One question, is the fork oil fill in your forks now, up to 66mm from the top? (fork tube down and spring out) or something like that? Correct me peeps if I have that wrong. After reading the posts on suspension, seems if you go to a straight rate spring, you drop the oil lever considerably. That air space can make a nice difference on the diving of the forks. Weak springs and less oil would send it into a dive allot easier. Now with all that said, and I don't seem to have an issue with my 1300, the old owner may have replaced the springs and I don't know it, but I did notice that the oil lever was comparable to the stock fill level. Going back to the straight rate springs, be careful on your judgement call. I bought what RT told me for my 636. It was like a pogo stick. So what I had to do was pull out one side and put the old Hyper Pro progressive in one side to get it to bounce a little. No I didn't send the springs back to RT, I should have. Preload all the way off was only about 25mm of sage, static sag was almost nothing. So using different springs to achieve results isn't a bad idea:) I flip my tires on the bikes to. Done it for the race track along with around here. Left side catches heck around here. About a 1/3 of the way into the wear, I go through the hassle of doing it, but I'll throw in that I haven't done it with the ST....yet. Wear seemed a little more even because I get more hwy time on it. I stay away from the rain as much as possible to :D
 
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I'll throw in one more thing. Since on the ST you can reach down and adjust the preload in the rear on the fly, I noticed the other morning that the bike felt a little sluggish, which for me, some of my bikes are like that on a cool morning until I get several miles on it or the day warms up. On top of that, the rear tire is getting worn and you know they get a little flat and it can affect the turn ins. I reached back to lessen the preload and the turning was much better and smoother. Next time you're all out, give it a try if you some twisties to try it out on. I may have left it a little too stiff cause I had the wif (pillion as you all call it) on a few days before, and I wing it when I back off of it.

Going back to the oil, I've used Wal-Mart tranny fluid if I got in a pinch and it did alright. Don't forget to change out the bushings and or rotate the tube 180, as posted before. Seals, well, I've used the same ones for years in the bikes. I have fork seal grease I got from RT. One tiny jar will last a life time. :D
 
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MajorTom

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Since the forks are mechanically constrained to work together as a pair, you could put a 0.90 in one leg and a 1.00 in the other for a net result of 0.95.
But I'd have to buy two sets of springs to do that and then find a home for the other pair, but thanks for the logical, but impractical, suggestion. :)

Or use .90 and have room for a little preload to hit the sag target.
Ok, but then I lose some fork travel before I bottom out, so again not an optimal solution.

I'm about 215+ in gear and I don't feel like the bike is under sprung. I can ride aggressively around here, and unless I'm trying to see how deep I can get to the apex of a turn and nail the brakes, it feels fine. One question, is the fork oil fill in your forks now, up to 66mm from the top? (fork tube down and spring out) or something like that? Correct me peeps if I have that wrong. After reading the posts on suspension, seems if you go to a straight rate spring, you drop the oil lever considerably. That air space can make a nice difference on the diving of the forks. Weak springs and less oil would send it into a dive allot easier. Now with all that said, and I don't seem to have an issue with my 1300, the old owner may have replaced the springs and I don't know it, but I did notice that the oil lever was comparable to the stock fill level. Going back to the straight rate springs, be careful on your judgement call. I bought what RT told me for my 636. It was like a pogo stick. So what I had to do was pull out one side and put the old Hyper Pro progressive in one side to get it to bounce a little. No I didn't send the springs back to RT, I should have. Preload all the way off was only about 25mm of sage, static sag was almost nothing. So using different springs to achieve results isn't a bad idea ...
Where to begin... First, I'm no fork tuning expert. I'm just trying to implement concepts I've learned from these forums and from reading on the interweb. Having said that, I believe the bike is undersprung for my weight because it dives rather extremely under hard braking. I also tour with my wife, which only exacerbates the problem. So this upgrade is as much about safety as how it handles solo in the twisties. I've been very happy with normal handling since I had the rear shock rebuilt with a heavier spring and the Race Tech valving.

Yes, the fork fluid level was set to the specified level using a syringe and tubing marked to the correct depth from the top of the shock. My understanding of how the air space in the fork contributes is that it provides some progressive action to how the fork works as air will compress, but fork fluid won't. I agree that weak springs and lower oil level will result in more dive under braking, but I believe the fork spring is primarily responsible.

Finally, and here I'm interpreting concepts I've only read about, regarding your pogoing 636, if I understand what you mean by that term (the bike bounces up and down in response to bumps in the road) if the spring rate was appropriate for the combined weight of you and the bike (which it seemed to be according to your sag numbers), I believe that behaviour is due to insufficient compression and rebound damping, not spring rate. Therefore it could be modified by changing the weight and amount of fork oil, or if that wasn't enough, by changing the valving in the shock by using something like Race Tech's gold valve system.
 
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dduelin

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....... Ok, but then I lose some fork travel before I bottom out, so again not an optimal solution.
That is a common misconception but not true. Preload, within reason, sets ride height within available travel.......but it does not reduce travel. An adjustable fork cap to set preload does the same thing as a longer spacer just much easier. They usually allow 15-20 mm of adjustment.

+X amount of preload presses down on the spring +X and the spring presses down on the cartridge seat with the same force so the fork extends +X amount under the same weight of bike and rider as before preload. Result is higher ride height, less sag, optimal.



Dynamic travel, that used during riding, stays the same. If you start with 50 mm of sag you have 58 left. With correct preload you start at 36 and have 72 mm left. Then adjust oil level to fine tune to 10mm or so of bottoming. You get more stroke and no bottoming.
 
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Is this a good idea? I have no idea of the rigidity of the fork assembly, but using different weight springs in each shock will induce a torque. I also wonder about rebound dampening on one fork and compression dampening on the other. I suppose if we can cantilever bridges w/ appropriate engineering, my questions are moot - but look what happened at Falling Water. Stuff happens.
The forks are bolted together at three points, the axle, and the upper and lower triple clamp, they move together or not at all. I've been adjusting sag on mine for 20 years using just the left fork spacer because the one on the right is too much of a pain to change out.
 
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But I'd have to buy two sets of springs to do that and then find a home for the other pair, but thanks for the logical, but impractical, suggestion. :)
Sorry, wasn't aware that you had to buy them in pairs, but now that I think of it I've never seen them sold as single units.
 

MajorTom

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I don't see how that works given there's a limited space the spring occupies within the fork. If the spacer takes up more space there's less space for the spring. Doesn't adding preload close the distance between the coils in the spring? Take this to the extreme and the spring is totally compressed by the spacer and the fork travel is zero. In our real world with a fork spring that's close to the right rate for the application, preload would have little effect on the distance between the coils, but even adding a small amount of preload should reduce the space between the coils and therefore the distance the fork can compress.
 
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I don't see how that works given there's a limited space the spring occupies within the fork. If the spacer takes up more space there's less space for the spring. Doesn't adding preload close the distance between the coils in the spring?
No. The spring compresses based on one factor, the weight of the bike plus rider, so its the same regardless of preload. By adding preload you simply change the relative location of the spring in the tube. With more preload, the less the lower slider needs to move before the spring resistance equals the supported weight. The spring is compressed the same amount in either case, the difference is how far the lower slider moves to achieve the necessary spring compression.
 
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